Friday Oct 24, 2008

Early Access 4 of the Web Services Connector for JMX is out

You can download it from ws-jmx-connector.dev.java.net.

The changes since the early access 3 are detailed in the release notes.

The major improvement is related to the JMX-to-XML mapping of CompositeData and TabularData. We have defined a much more compact representation that makes exchanged messages up to 3 time smaller.

To better address non Java clients we have added a taglet to help you generate the information that a pure WS-Management client would need to interoperate with your JMX application. An example of this taglet usage is provided. It covers all the tasks required to make VBScript to interoperate with an MBean, from MXBean interface development and documentation to VBScript writing.

In addition, a set of new VBScript samples provide some concrete examples of interoperability.

You can send us your feedback on users@ws-jmx-connector.dev.java.net

Regards

Jean-François Denise

Friday Jul 11, 2008

VBScript XML processing to extract JMX content

In a previous post I have presented the details of the VBScript script used to interact with a JMX application in which a Web Services Connector was deployed.

In order to deal with XML namespaces, I wrote a really horrible function based on the knowledge of the namespace prefix name computation. Something that I presented as a very bad way, caused by my lack of expertise in VBScript.

Since this previous post, I have written a bunch of scripts and dived into some VBScript librairies details. I have found the right way to process XML and deal with Namespaces. This is done thanks to XPATH usage. By setting a set of properties on the object returned by CreateObject("Microsoft.XMLDOM"), you can inject prefix/namespace associations. These associations are then usable when selecting XML nodes.

Retrieving the WS-Enumeration enumeration context of an MBean subscription

WS-Man session creation and subscription invocation is detailed in the previous post. The enumeration context must be extracted as follow:
set reply = ...

Dim objXMLDoc
set objXMLDoc = CreateObject("Microsoft.XMLDOM")

' Make the reply to be loaded synchronously
objXMLDoc.async = False

' Load the reply 
objXMLDoc.loadXML(reply)

' Make XPath the selection dialect
objXMLDoc.setProperty "SelectionLanguage", "XPath"

' Associate "wsen" prefix to WS-Enumeration namespace.
objXMLDoc.setProperty "SelectionNamespaces", "xmlns:wsen='http://schemas.xmlsoap.org/ws/2004/09/enumeration'"

' There is a single enumeration node, selectSingleNode returns the first one.
Dim node
set node = objXMLDoc.selectSingleNode("//wsen:EnumerationContext")

' node.text contains the enumeration context value
dim enumContext 
set enumContext = node.text

Retrieving the MBean Notifications pulled from the server

Notification pulling is detailed in the previous post. Extracting all the Messages contained in the list of notifications is done as follow:
set reply = ...
dim replyXml
set replyXml= CreateObject("Microsoft.XMLDOM")
replyXml.async = False
replyXml.loadXML(reply)

' Make XPath the selection dialect
replyXml.setProperty "SelectionLanguage", "XPath"

' Associate "jmx" prefix to JMX Web Services Connector namespace.
replyXml.setProperty "SelectionNamespaces", "xmlns:jmx='http://jsr262.dev.java.net/jmxconnector'"

' Select all the Notification Message nodes text values
set msgList = replyXml.selectNodes("//jmx:TargetedNotification/jmx:Message/text()")

' Display the Messages
for i = 0 To (msgList.length - 1)
    set msg = msgList(i)
    ' Display the notification message
    WScript.echo "Notification : " & msg
next

Conclusion

VBScript API to extract XML content is efficient and simple to use. It is very helpful when extracting values from complex data structures (such as CompositeData or MBeanInfo). Obviously its usage is much wider than JMX interoperability.

Hope this help.

Jean-François

Friday Jun 20, 2008

RESTful is Rastafarian thinking!

I am back from The Server Side Java Symposium (TSSJS) that occurred in Prague. I was invited to speak about JMX, Monitoring, Management and Troubleshooting in the JDK 6 platform. I spoke 1 hour and enjoyed the conference (only 2 days, I had to leave Prague before the end of the conference).

Some people went to me at the end of my talk with questions related to the ability to persist information that Visual VM or JConsole tools are exposing. My next post will cover this topic in details and should come with a Conf Dumper helping you achieve this use case.

TSSJS is a fantastic conference (it was the first time that I participated). Really it is. It is full of excellent talks from free and open minded speakers. It has been a delight to attend (more particularly) Ted Neward and John Davis talks.

I had already planed to leave Prague not before the promising Ted's REST and SOAP: Arch Enemies or BFF? presentation. And I have been well advised to do so...

Ted has simply presented us the Genesis of the Web Services... From the first second to the last one, it has been a flow full of excellent comparisons, well chosen anecdotes, funny paradoxes, well targeted criticisms, technical excellence, hope, joy, anger,...

The paroxysm has been reached when he has compared Restful with the way Rastafarians see human/business relationships. He described such relations as "cool point to point ones, no intermediary (notion that doesn't exist for Rastafari), nothing expected back, simply giving... exactly like an HTTP URL..." I can't re-transcript the demonstration but it was so true...

When he ended his talk by "Questions?", it has been, for me, like your grand father, seated nearby the fire camp, ending counting you his famous frightening story...

Ted had transformed a technical debates onto a Computing Tale...

Furthermore, I fully adhere with his analysis. He summarized the novelty of the REST approach by "the ability to identify values of your software thanks to URL". This is exactly what I have tried to describe in the 2 parts of the RESTful Access to JMX Instrumentation discussions (and more precisely by the notion of Well Known URL).

So to conclude, if one day you have the chance to go to the TSSJS, please do so, you will be not disappointed.

Really not.

Jean-Francois Denise

Tuesday Jun 03, 2008

RESTful Access to JMX Instrumentation, second part

This post is an answer to William Vambenepe who recently wrote an interesting post related to JSR 262 and the REST access to JMX I discussed a few months ago. William shows some interest in the REST adaptor for JMX and asks for the next steps. Here they are...


A bit of context

The REST approach is a possible solution for interaction with JMX agents mostly due to the fact that monitoring and management is increasingly present in our systems at a much higher level than it used to be.

The data exposed tends to be directly understandable. There is no need for complex processing on the client side to understand what is going on. Why is this possible? I think that it comes from the fact that the new trend in Monitoring and Management consoles (consoles such as JConsole or Visual VM), is to display "raw" data.

This raw data is interpreted by only viewing or displaying it graphically. It makes MBean designers think more and more about their MBean interfaces as human-readable APIs. My colleague Daniel Fuchs shows the limits of this approach in a recent blog entry. But I also remember Daniel saying a few years ago that people will soon start to design MBeans to comply with JConsole's capabilities. I think that he was absolutely right. This is what is emerging now.


So it seems an appropriate time to build an HTTP based access, along standardized lines, to allow web designers to benefit from this valuable management information by making it possible to embed it directly in Web pages.


My previous post put in place the foundations of the REST adaptor for JMX agents. This post covers the next features that should be added in the near future. I write “should be added” because I would like to hear your reactions to them before I add them to the current implementation. Please let me know whether or not they will meet any of your requirements, so that we can discuss how to improve them. The adaptor will be much more valid if it answers the needs of the community.


Security

HTTPS and Basic AUTH seem natural choices. Nothing special, simple and safe. They should cover most cases. Is Basic AUTH enough or do we also want to offer “mutual authentication”, to allow the server to authenticate clients based on client certificates? What about access control? We could easily add access control based on JMX permissions as is done today when you provide an access and password file when starting the JVM.


Snapshot of values

Currently we can't retrieve a complex MBean attribute atomically. Say that we want to retrieve all the values contained in the HeapMemoryUsage attribute of the Memory MBean. This attribute is of type CompositeData. The well-known URLs (that point to plain text data) associated to this attribute are the following:


http://curcuma:9999/rest/jmx/java.lang:type=Memory/HeapMemoryUsage/committed

http://curcuma:9999/rest/jmx/java.lang:type=Memory/HeapMemoryUsage/init

http://curcuma:9999/rest/jmx/java.lang:type=Memory/HeapMemoryUsage/max

http://curcuma:9999/rest/jmx/java.lang:type=Memory/HeapMemoryUsage/used


Currently, we can only retrieve committed, init, max and used individually.

If we introduce a new query parameter named capture, we could ask the adaptor to construct a frozen view of an attribute value (or more generally of a sub-tree). We could then retrieve the values located in the snapshot.


In practice:

GET http://curcuma:9999/rest/jmx/java.lang:type=Memory/HeapMemoryUsage?capture=mysnapshot1


Returned resource :

<ul>
<li>http://curcuma:9999/rest/snapshots/mysnapshot1/jmx/java.lang:type=Memory/NonHeapMemoryUsage/commited</li>
<li>http://curcuma:9999/rest/snapshots/mysnapshot1/jmx/java.lang:type=Memory/NonHeapMemoryUsage/init</li>
<li>http://curcuma:9999/rest/snapshots/mysnapshot1/jmx/java.lang:type=Memory/NonHeapMemoryUsage/max</li>
<li>http://curcuma:9999/rest/snapshots/mysnapshot1/jmx/java.lang:type=Memory/NonHeapMemoryUsage/used</li>
</ul>



The returned URLs reference the captured data. We now have the freedom to analyze the values outside the ever-changing real world. This pattern could also be applied higher up in the tree (at the MBean level, for example) to create a snapshot of multiple attributes.


Notifications

We could map from JMX Notifications to atom feeds. This could be a good approach. However, here I would like to keep it simple and carry on with the resource-centric approach and try not to break the model. I would like to make the number of required technologies as minimal as possible. Relying on HTTP(S) with a bit of HTML/XML should be the maximum we allow ourselves... ;-)


So, how can we proceed? JMX MBeans are the event sources. Clients generally subscribe to MBean notifications then pull notifications from the MBean server. Pulling seems very appropriate in our web context. Pushing has never really worked.

If you want reliable, zero-loss notifications then you should stop reading this post. You are going to be frightened by what I am about to say. In JMX we generally see notifications as an unreliable way to receive information. You can't count on a high level of reliability. Lost notifications are not common but they can occur. Once you know the context in which notifications are handfed, you can design an event system that copes with it. Making your MBean re-emit notifications until an acknowledgement comes back can be a decent solution.


If we agree with what has been said previously, we can attach a rolling buffer to each MBean resource that contains the last n emitted notifications (10 is a possible default value). This buffer can be pointed to using the URL scheme we have already put in place.

Here is an example URL for retrieving notifications:

http://curcuma:9999/rest/notifications/jmx/java.lang:type=Memory/



If events occur, the list of emitted notifications is returned in the GET response.

<ul>
    <li>
       Notification 1 
    </li>
    <li>
       Notification 2
    </li>
    ...
    <li>
       Notification N
    </li>
</ul>

Representation of notifications

A Notification is a complex type for which we can define a set of well known URLs. By nature, a notification is a snapshot of data, and its URL contains the information that makes it unique. The JMX API doesn't guarantee a unique sequence number. The emission time seems a better identifier.


<ul>
  <li>http://curcuma:9999/rest/notifications/jmx/java.lang:type=Memory/25_12_1970_12_00_00/message</li>
  <li>http://curcuma:9999/rest/notifications/jmx/java.lang:type=Memory/25_12_1970_12_00_00/number</li>
  <li>http://curcuma:9999/rest/notifications/jmx/java.lang:type=Memory/25_12_1970_12_00_00/type</li>
  <li>http://curcuma:9999/rest/notifications/jmx/java.lang:type=Memory/25_12_1970_12_00_00/userdata/<...possible path if complex type></li>
   ... user data URL continue if complex content.
</ul>

Custom notifications

If the emitted notification is custom-built, and some getters are exposed, then the added field is discovered and exposed. For example, the following notification defines a getPriority field:


public class PriorityNotification extends Notification {
  ...
  public int getPriority() {
    ...
  }
}

This will be returned as follows:

<ul>
 <li>http://curcuma:9999/rest/jmx/notifications/java.lang:type=Memory/25_12_1970_12_00_00/priority</li>
 <li>http://curcuma:9999/rest/jmx/notifications/java.lang:type=Memory/25_12_1970_12_00_00/message</li>
 <li>http://curcuma:9999/rest/jmx/notifications/java.lang:type=Memory/25_12_1970_12_00_00/number</li>
 <li>http://curcuma:9999/rest/jmx/notifications/java.lang:type=Memory/25_12_1970_12_00_00/type</li>
 <li>http://curcuma:9999/rest/jmx/notifications/java.lang:type=Memory/25_12_1970_12_00_00/userdata/<...possible path if complex type></li>
</ul>



Filtering based on emission time

You could argue that only keeping 10 notifications is insufficient and that all notifications should be stored. OK, but in this case, we would like to be able to filter out the old ones. That can be done by adding a since query parameter when getting notifications. For example:

http://curcuma:9999/rest/notifications/jmx/java.lang:type=Memory/?since=20_12_1970_00_00

We just need to agree on a date format.

Notification retrieval scope

This approach allows us to express a homogenous "retrieval scope”. By choosing a location in the tree (a URL where we can get notifications), we can retrieve notifications emitted by :

  • MBean servers (all MBeans, and potentially all attributes too, could add a JMX pattern to narrow the scope)

  • MBeans

  • MBean attributes (equivalent to AttributeChange).

  • Information inside an attribute value (namely, is it a real scope, and do we want it?)



Conclusion

It seems that things are still being kept simple here without compromising the JMX technology's philosophy. Or perhaps not, and you think it is already too complicated and I should stop mining this seam... just let me know and I will down tools! ;-)

What do we have on the plate for the next post? Setting attributes and invoking MBean operations. If you have some ideas, please let me know. They are tough ones!

Thanks.

Jean-François Denise

jean-francois.denise@sun.com



Friday May 23, 2008

Use VBScript to cheat at poker with JMX!

This year at JavaOne Eamonn and I presented during our technocal Session, where we stand with respect to JMX. Eamonn covered JMX in general and JMX 2.0, while I covered the Web Services Connector for JMX. At the end of the talk, we performed a demo named “CSPoker, JMX Technology, Java VisualVM and WinRM at the JavaOne Tournament's Final Table”. We linked together a set of JMX related technologies to offer, in an original Online Poker Web Site use case, an interesting setup highlighting the power of JMX (here's a PDF file of the demo architecture) .

At the end of the talk, some people asked me some questions about the WS-Management access to JMX we had just demonstrated. More details on the WS-Management to JMX interoperability can be found in this article.

Here, I am providing some details on the actual script used during the demo. This script automates the Poker Engine monitoring and management tasks. It first registers to listen for JMX Notifications exposed as WS-Eventing notifications. Each time a “Poker table joined” notification is received, it checks that the IP address from which the player joined is not already known to the system. If an IP address is already known, it means that another user already joined from the same host.... which is very bad if you want to avoid the same player using multiple identities....

When such a “bad user” is detected, the script ejects all the players that joined from that machine.

Intialisation of the WS-Management access

dim wsmanObj
set wsmanObj = CreateObject("WSMAN.Automation")
dim objConnectionOptions
set objConnectionOptions = wsmanObj.CreateConnectionOptions
dim iFlags
iFlags = wsmanObj.SessionFlagUseNoAuthentication
dim session
set session = wsmanObj.CreateSession("http://localhost:8080/admin", iFlags)

At this point, you have a WS-Management proxy (the session object), that allows you to interact with a JMX Agent attached to the Web Services Connector.


Subscription to the MBean notifications

The MBean we want to subscribe to is named : cspoker:type=CSPokerControl

Because the WS-Management session doesn't offer a nice API for subscriptions, we need to construct the subscription invocation request using the “all purpose” invoke method :


Dim reply
reply = session.invoke("http://schemas.xmlsoap.org/ws/2004/08/eventing/Subscribe", _
"http://jsr262.dev.java.net/DynamicMBeanResource?ObjectName=cspoker:type=CSPokerControl", _
"<wse:Subscribe xmlns:wse='http://schemas.xmlsoap.org/ws/2004/08/eventing'>"_
& "<wse:Delivery Mode='http://schemas.dmtf.org/wbem/wsman/1/wsman/Pull'/></wse:Subscribe>")

At this point we have sent a WS-Eventing subscription request (in PULL mode, meaning that the client will send a request to pull notifications from the server) and received a response. The response contains the WS-Eventing context to be used to retrieve notifications.

Retrieving the Eventing context

To get the eventing context from the response, we need to make use of the VBScript DOM library : Microsoft.XMLDOM

Warning : Because namespaces are not handled well in this DOM library, we are trying to discover the Namespace prefix based on our knowledge of the way they are declared (ns<i>). I am not a VBScript expert and would be very interested to know if there is an equivalent to getElementsByTagNameNS using VBScript???

Function findElement(elem, tagElem)
' wscript.echo "Finding Element " & tagElem
 for i = 0 to 15
  set findElement = elem.getElementsByTagName("ns"& i &":" & tagElem)
  If findElement.Length > 0 Then Exit For
 next
End Function

Dim objXMLDoc
set objXMLDoc = CreateObject("Microsoft.XMLDOM")
objXMLDoc.async = False
objXMLDoc.loadXML(reply)

' Get the Eventing context to use in the next WS-Eventing Pull request
Dim nodeList
set nodeList = findElement(objXMLDoc.documentElement, "EnumerationContext")
dim context 
context = nodeList(0).text
wscript.echo "Subscription Enumeration Context " & context

At this point, the context variable contains the WS-Eventing context that identifies our subscription. This context is to be used to retrieve notifications.

Retrieving the Notifications

This is done by sending a Pull request to the server and providing it the context. The pull request blocks until some Notifications are emitted or the timeout (1 minute by default) is reached. As for subscribe requests, no Pull API is offered. We need to use the general purpose invoke operation. We have written a pull function that handles pull request timeouts properly. When the timeout occurs, instead of exiting the script, the error is trapped and the script continues. Because we expect multiple notifications, the Notification pulling is done in a loop.

Function pull(session, context)
 On Error Resume Next
Dim pullXml
pullXml = "<wsen:Pull xmlns:wsen='http://schemas.xmlsoap.org/ws/2004/09/enumeration'><wsen:EnumerationContext>" & context & "</wsen:EnumerationContext><wsen:MaxTime>PT1M0.000S</wsen:MaxTime><wsen:MaxElements>1000</wsen:MaxElements></wsen:Pull>"
 pull = session.invoke("http://schemas.xmlsoap.org/ws/2004/09/enumeration/Pull", "http://jsr262.dev.java.net/MBeanNotificationSubscriptionManager", pullXml)
  On Error Goto 0
End Function

' This piece of script is called in an infinite loop

Dim notifs

 notifs = pull(session, context)

At this point, the notifs variable contains (or does not contain, if the timeout occurred) the JMX notifications in an XML format.

Extracting the Notification content and tracking the cheat

We only do this extraction if the list of notifications is not null. The VBScript DOM library is again used to parse the notifications. Because a pull request can return multiple notifications, we must iterate on all TargetedNotification elements contained in the notification list. A TargetedNotification is an XML representation of a JMX Notification defined by the JSR 262 (JSR in which the Web Services Connector is defined).

In our case, the TargetedNotification/Message XML Element contains the Player name. The TargetedNotification/UserData XML Element contains the IP Address as a string (eg:<jmx:String>192.168.0.1</jmx:String>)

To keep the IP <==> Player relationship, we use a Map data structure and array. In VBScript, we use a dictionnary (scripting.dictionary Libray)

' Create a Map
dim dict
set dict = CreateObject("scripting.dictionary")
Dim ipArray(10)
Dim arrayIndex
arrayIndex = 0

if Not(isNull(notifs)) then

  set objXMLNotif = CreateObject("Microsoft.XMLDOM")
  objXMLNotif.async = False
  objXMLNotif.loadXML(notifs)
  set NodeListNotifs = findElement(objXMLNotif.documentElement, "TargetedNotification")
  WScript.echo "Pull returned " & NodeListNotifs.length & " notifications"

  ' Now that we get the list of notifications, extract the content.
  Dim i
  Dim EventType
  Dim msgObj
  ' Loop over the received Notifications
  For i = 0 To NodeListNotifs.length - 1
      Dim listMsg
      set listMsg = findElement(NodeListNotifs(i), "Message")
      Dim eventMessage 
      eventMessage = listMsg(0).text

      Dim listUserData
      set listUserData = findElement(NodeListNotifs(i2), "String")
      ' We have an IP address
      if(listUserData.length > 0) then
           Dim ipAddress
           ipAddress = listUserData(0).text
           wscript.echo eventMessage & " Joined From " & ipAddress
           if dict.exists(ipAddress) then
              Dim prev
              prev = dict.item(ipAddress)
              if Not StrComp(prev,eventMessage) Eqv 0 Then 
                 dim users
                  users = Array(eventMessage, prev)
                  For Each user In users
                    wscript.echo user & " already connected from same host [" & ipAddress &"], will eject him." '"Type return."
                    wscript.echo "Ejecting player " & user
                    ejectPlayer session, user
                    wscript.echo "Player " & user & " ejected"
                  Next
              end if
           else
             dict.add ipAddress, eventMessage
           end if
      else
         wscript.echo eventMessage
      end if
  Next

Ejecting the player

The function ejectPlayer calls the ejectPlayer MBean operation by making use of the general purpose invoke operation.

Function ejectPlayer(session, playerName)
 dim pokerURI
 pokerURI = "http://jsr262.dev.java.net/DynamicMBeanResource?ObjectName=cspoker:type=CSPokerControl"
 dim xmlInvoke
 xmlInvoke = "<jmx:ManagedResourceOperation name=" & Chr(34) & "ejectPlayer" & Chr(34) & " xmlns:jmx=" & Chr(34) & "http://jsr262.dev.java.net/jmxconnector" & Chr(34) & "><jmx:Input><jmx:Param><jmx:String>" & playerName & "</jmx:String></jmx:Param></jmx:Input></jmx:ManagedResourceOperation>"
 session.invoke "http://jsr262.dev.java.net/DynamicMBeanResource/Invoke", pokerURI, xmlInvoke
End Function


Hope that these VBScript extracts helped you understand better how you can use this path to interoperate with JMX.

Thanks.

Jean-François Denise

jfd@sun.com




        
    

Thursday Mar 13, 2008

RESTful Access to JMX Instrumentation, Via URI-fication of MBean Attributes

As you perhaps know from reading my posts, I am involved in the definition of JSR 262, Web Services Connector for JMX Agents. JSR 262 offers an access to Web Services that is very far removed from Representational State Transfer (RESTful) Web Services. So, this blog is not about JSR 262, but instead it describes some of the investigations and development I have performed related to the Java API for RESTful Web Services (JAX-RS API) and the JMX API.

Having simple HTTP-based access to a Java Management Extensions (JMXTM) MBean is an idea that I like a lot and one for which I think that there are thousands of real use cases. For example, when developping a Web application, integrating a piece of information obtained from JMX instrumentation, such as the status of a service, should be as simple as loading an HTML page.

My first attempt was to define and implement a merge of JSR 262 and a RESTful approach... All in vain! The two technologies cannot co-habit, so you are forced to choose between them. You either have to go down the WS-\* path or you have to go down the RESTful path. There's no way to make one leverage the other to offer a tidy solution. In this case, keeping the two parts separate is much better than trying to bundle them together. In this investigation, I have limited the scope just to retrieving information from JMX instrumentation. Setting MBean attributes or invoking operations has not been addressed (yet).

June 2008. UPDATE TO THE ORIGINAL ENTRY. I added description for support of notifications and snapshot of values in this new entry.

If you want to play with this prototype for RESTful access to JMX instrumentation (based on Jersey, which you will need to download) before reading the blog entry, you can jump straight to Running the Adaptor. This RestFul JMX Adaptor is hosted by the OpenDMK java.net project.

But first, let's start with a bit of background. The next sections describe how the information from JMX instrumentation is accessed, and how this information can then be mapped into a format that is acceptable to the RESTful approach.

JMX Instrumentation Information Tree

So, how does JMX instrumentation present its information? First, we have an MBean server in which MBeans are registered. Each MBean contains a set of attributes that represent an actual piece of information. MBean attributes are not always exactly actual pieces of data, though, as this is dependent upon the Java class of the attribute. If the attribute is a primitive type, then yes, the attribute is indeed an actual piece of data. If it is a complex type (or a collection), then it is not. Complex types need to be traversed to discover the actual data.

So, we can represent the whole set of information exposed by the JMX instrumentation as a tree. The root of the tree is the MBean server, the MBeans are the root's child nodes and the attributes are the MBeans' child nodes. Some attributes are terminal nodes (primitive nodes), some other attributes (complex types) are intermediary nodes.

The following figure presents the JMX instrumentation information tree:


In this tree, we can see the data path as leaves.


Here, we can identify three elements:

  1. The leaf node, which is a data container.

  2. The intermediary node, which is a child container.

  3. The data path, which is composed of the set of parent/child relationships from the root to the leaf.

Traversing Complex Types

We just saw that you need to traverse complex types to access the actual data. However, how to deal with every sort of complex type that can be defined is outside the scope of these investigations. So, we have limited ourselves to Array, List, Set and the generic JMX types CompositeData (which is very similar to Map) and TabularData (which is a table of CompositeData).

The above list of types complies with MXBean usage, so we are able to go quite far, even with this limited set. These types are traversed in different ways, as follows:

  • To traverse a List or an Array, you need to iterate the structure.

  • To traverse a CompositeData, you need to find out each key and retrieve the associated value.

  • To traverse a TabularData, you need to iterate the structure and then traverse each CompositeData (as described above).

Mapping the Information Tree to RESTful Web Services

I am not making a revolutionary statement by saying that nodes are resources and data paths are URIs. In our information tree, we have two kinds of resources, container resources that are referenced by other resources, and the content resources. These resources can be identified by URIs, as explained in the next sections.

Resource URIs

The different resources in our information tree are identified by the following URIs:

  • MBean server: http://<host>:<port>/<root context>

  • MBean: http://<host>:<port>/<root context>/<MBean ObjectName>

  • MBean attribute: http://<host>:<port>/<root context>/<MBean ObjectName>/<attributeName>

  • Collection (list or array) element: http://<host>:<port>/<path to complex type>/<index>

  • Map element: http://<host>:<port>/<path to complex type>/<URL encoded(key.toString)>

  • CompositeData entry: http://<host>:<port>/<path to complex type>/<key>

  • TabularData element: http://<host>:<port>/<path to complex type>/<index>

Container Resources

MBean servers, MBeans, arrays, lists, sets, CompositeData entries and TabularData elements are all container resources. A simple XML definition is enough to represent these resource types. To avoid defining a new XML element, we can reuse the XHTML list element (<ul><li></li></ul>).

References to a child can either be relative to the current resource or absolute. I chose to make them absolute. Below are some examples of representations of different container resources.

  • MBean server containing two MBeans:

    <ul>
    <li>http://<host>:<port>/<root context>/java.lang:type=Memory</li>
    <li>http://<host>:<port>/<root context>/java.lang:type=Thread</li>
    </ul>
  • MBean with two attributes, NonHeapMemoryUsage and HeapMemoryUsage:

    <ul>
    <li>http://<host>:<port>/<root context>/java.lang:type=Memory/NonHeapMemoryUsage</li>
    <li>http://<host>:<port>/<root context>/java.lang:type=Memory/HeapMemoryUsage</li>
    </ul>
  • CompositeData, composed of commited and init keys:

    <ul>
    <li>http://<host>:<port>/<root context>/java.lang:type=Memory/NonHeapMemoryUsage/commited</li>
    <li>http://<host>:<port>/<root context>/java.lang:type=Memory/NonHeapMemoryUsage/init</li>
    </ul
Note: You will notice that I am not using the HTML link tag (<a href="..."></a>). This is because I am not defining HTML access (such as that provided by the JMX technology's HTML adaptor), but rather XML access.

Container resources like those above are not of particularly great interest to us. They help with navigation when you are having difficulties finding your way through the information tree, but when you know where you want to go, they are almost useless. When you know where you want to go you don't need to navigate at all, you just jump at light speed to the end of the path by providing the full URI.

However, in some cases where the information is dynamic, container resources can be really helpful.

Content Resources

In this prototype, actual data is represented by straightforward plain text. For example, Hello world, is plain text...

A Restful Adaptor for JMX Instrumentation

I have developed a prototypal implementation of the above mapping using the JAX-RS Reference Implementation (a.k.a the Jersey project). The adaptor attaches to the platform MBean server that is located inside any Java Virtual Machine (JVMTM) from Java Development Kit (JDK) version 5.0 or above. The adaptor offers URI-based navigation, and the returned pages are in either HTML or XML format, according to the receiving client's "Accept Headers" setting.

The current prototype covers all the types exposed by the JVM software's MXBean interfaces (used for monitoring memory, threads, classes, etc.). If your MBeans are also MXBeans, they you should be able to navigate to them without problems. I re-used the HTML <ul><li> tags to handle lists in XML. In HTML, the <a href="..."> tag is used in conjonction with the <li> tag in order to make clickable URLs.

The adaptor provides an API (JMXWSMBeanRestResource#setListXMLTags) that allows you to change these list tags and provide your own.

If your MBeans expose unsupported types, you can provide your own resources by calling JMXWSMBeanRestResource#registerResourceHandler. Look at the source code for JMXWSMBeanRestResource.CollectionResource to understand how the adaptor's JAX-RS resources are defined.

JAX-RS Resources

JAX-RS allows you to define “top level” resources that return sub-resources. I defined a top level resource named JMXWSMBeanRestResource, which serves as the JMX adaptor's entry point and handles the MBean server and the MBean resource types. It also delegates the navigation of attribute values to sub-resources. The current sub-resources are the following:

  • PlainResource

  • ArrayResource

  • CollectionResource

  • MapResource

  • CompositeResource

  • TabularResource

Each resource handles a data type and, in turn, delegates it to other sub-resources to reach the leaf (the plain text resource).

The JAX-RS resource / sub-resource pattern allows for very simple tree navigation. Each resource is annotated using JAX-RS annotations. The following ArrayResource shows what a sub-resource actually does:

public class ArrayResource { 

/\*\* Returns the list of URI that point to array items. \*\*/

@GET

@ProduceMime("text/xml")

public Response getXMLItemURIs() throws Exception {

return getURIs();

}

/\*\* Returns the Sub resource pointed by the array index. ResourceFinder is a reference to the JMXWSMBeanRestResource that manages Sub Resources. \*\*/

@Path("collection/{index}")

public Object getItem(@UriParam("index") String index) throws Exception {

int idx = Integer.valueOf(index).intValue();

return resourceFinder.findResource(Array.get(array, idx));

}

...

}

That's about it for the introduction. Now you can see the adaptor in action.

Running the adaptor

  1. You need first to do a CVS checkout of the Restful Adaptor sources from OpenDMK java.net project

    1. export CVSROOT=:pserver:guest@cvs.dev.java.net:/cvs

    2. cvs co opendmk/contributions/rest-adaptor

    3. Open the NetBeans project rest-adaptor/RestAdaptor.

  2. Follow the steps documented in Restful Adaptor readme file.

  3. Run the adaptor (this requires a minimum of JDK version 5.0, although JDK 6 is recommended).

  4. The adaptor will display the URL on which it is bound, as well as some other information, such as the composition of the URIs and the names of the MBeans.

  5. In your browser type the following URL : http://localhost:9999/rest/jmx.

  6. If your browser is set to accept XML headers by default over HTML headers (as is the case for Firefox), you will receive the resources in XML form, which is not really the best form for a browser. However, you can still navigate by copying and pasting the URIs until you reach a leaf. The best thing to do is to change your Firefox settings to accept HTML headers by default over XML headers, as follows:

    1. In your browser, type about:config

    2. Go to network.http.accept.default

    3. Prefix the value with text/html.

    You can now navigate from the root to the leaves.

But, as I said previously, navigation is really not the best way. What you really want to do is to jump to a value using a well-known URL. But where are these well known URLs? They are there already, waiting for you. If you want to see them all, go to the following URI:

http://localhost:9999/rest/jmx/all

This URI references a special resource that lists ALL the leaves of a JMX information tree for a given MBean server. All listed URLs identify an actual piece of data.


This list of URLs (that can be very long) can be filtered by using a URI parameter that contains the following JMX specification ObjectName pattern: http://localhost:9999/rest/jmx/all?pattern={your jmx ObjectName pattern}

Well Known URLs

In a system being managed by JMX instrumentation, the set of exposed MBeans is generally well defined. The set of MBean ObjectName instances is well known and documented so that clients can access the exposed information. We can take advantage of this and select a set of URLs that will never change for a given system. For example, the URIs that identify the commited heap memory of the JVM software from JDK version 5.0 or version 6 will never change, except for the host and port deployment information, as shown below :

http://<host>:<port>/rest/jmx/java.lang:type=Memory/NonHeapMemoryUsage/commited

This file contains the URIs you expect to find in a JVM implementation from JDK version 6, regardless of your context. For monitoring and management of the JDK software, the URLs that change are related to Array and TabularData (i.e. thread IDs, system properties, logger names, etc.) and to memory managers that are not identical as far as the hardware architecture is concerned.

You can easily discover these URLs without navigating through the tree, by starting at index 0 and incrementing by 1 until you reach a 404 error. For example, to retrieve all the thread IDs, you just have to increment the {index} :

http://<host>:<port>/rest/jmx/java.lang:type=Threading/AllThreadIds/{index 0-N}

The example of thread IDs shows up a major limitation of this approach when the information is very dynamic (as threads are). The array size and elements can change in such a way as makes the returned values invalid. In this case we would need a snapshot of the array.

June 2008. UPDATE TO THE ORIGINAL ENTRY. I added description for support of notifications and snapshot of values in this new entry.

Conclusion

This RESTful adaptor provides a possible way of implementing a RESTful access to JMX instrumentation. I have a strong feeling that it could be very helpful when aggregating loosely coupled pieces of information. The current adaptor does not address all data structures (although MXBeans are fully handled), but it is provided in Java source code and offers an API for you to add your resource handlers.

Possible usages:

  • Develop AJAX based dashboads to monitor Java VM and/or your applications.

  • Quickly construct HTML pages to offer human readable access to the internals of your systems.

What are the next steps:

  • Add a support for Notifications.

  • Add a support for POST/PUT.

  • Add a support for snapshot of values.

I would like to thank Paul Sandoz for is great help. REST philisophy is Paul's second nature. Expose him your problem and he will Restify it. Really smart!

I would be very happy to receive any feedback about this approach. Feel free to contact me and thank you for reading.

Regards.

Jean-François Denise

Monday Feb 18, 2008

Web Services Connector for JMX enters Public Review

The JSR 262 has just entered the Public Review phase. The Early Access 3 of the Connector, that implements the Public Review, can be downloaded from http://ws-jmx-connector.dev.java.net.

Specification changes since Early Access 2:

  • PUSH mode supported for notifications. This is specified in the client by including JMXWSDefinitions.JMX_WS_NOTIFICATION_PUSH_MODE_URL in the Map given to JMXConnectorFactory.connect. Some related Map entries on the client and server configure security. A new interface JMXWSCredentialsProvider specifies how the connector server gets the credentials it needs to connect to any given client and push notifications.

  • New JMX types supported for MBean operations: NotificationResult, NotificationFilterSupport, AttributeChangeNotificationFilter, MBeanServerNotificationFilter. This allows the JSR 262 connector to support the new Event Service being defined by JSR 255, which has MBean operations that use those types. We also added support for java.lang.Enum and java.util.Set.

  • Connection identifiers supported consistently with the JMX Remote API (JSR 160) specification. This was already alluded to in the Early Draft 2 but is now formalized consistently.

  • Removed the interface JMXWSManResourceHandler. This was a halfway house between the Connector and Adaptor models. The model now is that for a Connector (client sees the JMX Remote API), the protocol is completely specified and invariable.

  • Some minor reshuffling of static final fields between JMXWSConnectorServer and JMXWSDefinitions.

  • The getMBeanInfo operation is now mapped as a Custom Action. Previously the MBeanInfo was a property of the MBean resource, alongside all the attributes of the MBean. This mix of data and metadata was strange.

  • JMXAuthenticator.authenticate method. The passed Object parameter used to be a String[2]. It is now a String[3]. The third element contains a client certificate in case HTTPS Mutual authentication is enabled (null otherwise).

  • XML Element NotificationLost has been removed from the schema. WS-Management already offers such definition by the mean of DroppedEvents XML element. NotificationLost was a redundant redefinition.

  • The schema has been updated, mostly to reflect the changes above, and some minor refactoring.

Implementation changes since Early Access 2:

  • Leverage of the Metro stack components (as detailed in my previous blog entry) in order to increase interoperability and efficiency of the Connector. We are currencly observing a \*3 increase in performance.

  • Rely on the latest JAX-WS 2.1.3 release.

  • Introduction of an adaptor API that allows you to change the way MBeans are exposed in the WS-Management world (javadoc is bundled in the Early Access 3 auto extractible jar under docs directory).

The document that covers interoperability with Microsoft WinRM tooling (winrm command line, VBScript API and Event Viewer support for WS-Management events) has been updated in order to reflect the Public Review changes.

Feedbacks on the specification can be sent to jsr262-spec-comments@sun.com. Feedbacks on the connector implementation can be sent to users@ws-jmx-connector.dev.java.net.

Thanks.

Jean-Francois Denise

Monday Feb 11, 2008

Up the Metro stack to JMX Technology: A Wise Man's Journey

Up the Metro stack to JMX Technology: A Wise Man's Journey


What a long trip... We started by driving on the HTTP highway, slid on SOAP, turned left at the XML crossroads, passed over the WS-Addressing bridge, visited WS-Enumeration, WS-Eventing and WS-Transfer, got a bit lost in WS-Management country, discovered that JMX was not so far off, and finally took a rest (but not a RESTful one) in the Web Services Connector... Did we do all that on our own? No, we did it with a set of friends, the Metros, or the high-performance, extensible, easy-to-use web service stack.


OK, I guess you get it. This little journey lists the set of standards that have been pressed into service to expose JMX MBeans as WS-Management resources. Luckily we didn't have to implement them all. The JAX-WS (a core Metro component) and WiseMan (a WS-Management Java implementation) projects have been of great help.

Now Sun has announced that the WiseMan project is to become part of the Glassfish community. So, it seems to be an appropriate time to look at how the Web Services Connector for JMX Agent RI makes use of WiseMan and Metro.


In this article, I will describe how we changed WiseMan to use part of the Metro stack, what the benefits were, and finally how these technologies are leveraged in the Web Services Connector for JMX Technology

Moving WiseMan to the Stack

In 2007, some significant engineering tasks were undertaken in the WiseMan project to bring the benefits of Metro to WiseMan. This section outlines the steps that were needed to make this move a reality.

The details of this technology switch are of interest to anyone who wants to make their existing applications benefit from Metro's features.

From Servlet to JAX-WS 2.0

WiseMan, was, in its pre-1.0 release, closely coupled with Servlet. At the time, Servlet container was the only way to deploy a WiseMan-based application. We decided to add a JAX-WS Endpoint to the WiseMan project and suddenly we found we could be much more agile. Deployments like the Java SE and Java EE platforms became possible. What a change! For example, being able to base our test suite on the lightweight HTTP server bundled with JAX-WS made our lives much easier...

The JAX-WS Endpoint we developed is a Provider<SOAPMessage>. Simply annotating with @WebService was not possible. WS-Addressing makes intensive use of SOAP headers to convey part of the protocol information. To access to such headers, we need full access to the SOAP Message. After some redesigning of the existing code we extracted a WSManAgent Class that is accessible from a JAX-WS Endpoint or a Servlet.

We took this opportunity to switch to the JAXB release contained in Metro.

So we were happy and impatient to move forward. We already knew that the JAX-WS team was working on adding WS-Addressing support and were waiting for it eagerly.

From JAX-WS 2.0 to JAX-WS 2.1

JAX-WS 2.1 comes with support for WS-Addressing. It's a very smart integration. By just using annotations, your Endpoint becomes addressable thanks to WS-A.

The @Addressing annotation that you can use to tag your Endpoint implies that the WS-Addressing 1.0 release is to be used. However, WS-Management requires the use of another release of the WS-A standard, which is a great pity. We discovered that we were not able to leverage this support. We were afraid this was the end of the road, but the JAX-WS engineering team came back to us showing us the Metro specific API. We were not the first customer with a dependency on a Membership Submission and they defined another “non standard but supported” Annotation to express our requirement : com.sun.xml.ws.developer.MemberSubmissionAddressing

With this annotation added, we removed all the code related to WS-A request-response headers.

So we were happy...but not for long. Our great friends Yves and Sandra of the JMX QA team started to develop some simple stress tests and we started to discover horrible things...

From SOAPMessage to Message

We discovered that 80% of the time spent handling a request was spent in the DOM/SAAJ layer. That's 80% of some big numbers, too...

You remember? Our Endpoint is a Provider<SOAPMessage>. This means that when called, a SOAPMessage object is injected and a SOAPMessage object is expected as the returned value. So we were either stuck, or we had to re-implement the SOAP layer to rely on the STAX API, or we were left with our disapointing figures.

Could the Metro API solve this issue? Yes, the Metro API solved this issue. Once again we were not the first customer, etc., etc., etc. As a solution, an efficient implementation of SAAJ, that is very well integrated with JAXB, is exposed as the Message API (located in the com.sun.xml.ws.api.message package). In order to benefit from its power, you must completely forget all the development you have done on top of SAAJ and rewrite everything on top of this new API. Which is exactly what we did. OK, we re-designed it to make both approaches live together nicely, but we also designed a new API for WiseMan, that was completely isolated from SAAJ. And things started to work much faster (3 to 4 times quicker). The numbers were becoming acceptable, for this kind of XML based processing.


Current WiseMan Architecture




The diagram above shows the different products that are used to build the WiseMan stack on the client and the server. You can see that the WiseMan client stack doesn't rely on Metro, yet. A work-in-progress aims to define and implement such a move, which will greatly improve performance and ease of use.

Improvements for the WiseMan Project

This move helped the project to:

  • Improve deployability

  • Improve alignment and reuse

  • Improve interoperability

  • Improve performance

Deployability, interoperability and performance are the key words of the Web Services Connector for JMX Technology. Based on these new capabilities, WiseMan is becoming the WS-Man implementation of choice for the Web Services Connector for JMX.

When using this connector you are not directly in contact with the stack but you indirectly benefit from the properties you are interested in.


Web Services Connector for JMX Continues Leveraging Metro

This section looks at how the the Web Services Connector for JMX Technology continues leveraging Metro.

Fast Infoset

- "Increase performance!"

- "Increase performance? Hmm..."

Simple, use Fast Infoset! It comes with the stack, it's efficient, it doesn't break interoperability and it's easy to use. We did it and we experienced another big improvement. To enable Fast Infoset in your client API, access the BindingProvider and provide a Fast Infoset key to the request context. For example:

BindingProvider provider = (BindingProvider) port;

Map<String, Object> requestContext = provider.getRequestContext();

requestContext.put("com.sun.xml.ws.client.ContentNegotiation", "pessimistic");

Dispatch<Message> on the client side.

On the client side of the connector, we use the JAX-WS Dispatch class. A Dispatch instance can be seen as an Endpoint proxy that deals with the complete SOAP Message (as opposed to classical JAX-WS proxies that expose a service level API). Since JAX-WS 2.1, Dispatch also handles WS-Addressing. Using Metro specific API, we are creating an efficient Dispatch that is compliant with the WS-Addressing Membership Submission release.

The following code extract shows how to create a Dispatch<Message> for Membership Submission:

Dispatch<Message> port = service.createDispatch(JMXWSConfiguration.JMX_WS_CONNECTOR_PORT, Message.class, Service.Mode.MESSAGE, new MemberSubmissionAddressingFeature(true, true));

Endpoint on the client side

WS-Management defines a way for a WS-Management Agent to deliver its Events in a PUSH mode. This delivery mode implies that the event sink (the client) is itself an Endpoint. We deploy a JAX-WS Endpoint (Provider<Message>) inside our connector client to receive pushed events.

WS-A EndPointReference API

The JMX Web Services Connector RI exposes a non-standard API to customize the mapping of MBeans to WS-Management resources. In this API, we allow customers to hook their customization as low as the WS-Management protocol itself. We needed a WS-Addressing Endpoint reference to expose.

The JAX-WS class javax.xml.ws.EndpointReference offers a standard 1.0 representation that we are internally translating into a Membership Submission via the Metro API (using the class com.sun.xml.ws.developer.MemberSubmissionEndpointReference).

Security

JAX-WS offers support for HTTP Basic Authentication and HTTPS. We are leveraging both.

HTTP Basic Auth

You provide the credentials to a Dispatcher via the request context. The following code extract shows how to provide your credentials.

BindingProvider provider = (BindingProvider) port;

Map<String, Object> requestContext = provider.getRequestContext(); requestContext.put(BindingProvider.USERNAME_PROPERTY, “user); requestContext.put(BindingProvider.PASSWORD_PROPERTY, “password”);

Server Side Security

The way you secure the server side depends on the container in which the Connector is deployed. For more details about how to use the HTTP server bundled in Metro, check the HTTP server API documentation.

Current Web Services Connector Architecture




Interoperability

Based on this architecture, we performed interoperability testing with WinRM (Microsoft's WS-Management based set of tools and API).

This document sums up the scenarios we are testing.

We didn't experience any problems related to interoperability.

Conclusion

Choosing Metro was definitely the right choice. On nearly all levels it has offered the features we were hoping for. When the boundaries of the standards were reached, Metro-specific API entered the scene and offered a solution. Metro really is ahead of the field in terms of improving performance.

So who is the wise man? The ones who defined such long stacks? No, I don't think so....

But Glassfish could be. Its management and monitoring features are based on JMX technology.

So?

So, by deploying the Web Services Connector for JMX (for which the Public Review specification and Early Access 3 RI will be available mid-February) in a Glassfish Server, all the existing MBeans (such as those defined by AMX, by JSR 77, and by you) are automatically exposed as WS-Management resources.

You can imagine the long journey we went through. Would you want to do this on your own, to expose your tiniest resources?

Be wise and use JMX, let us fill in the gaps!

Jean-François Denise

PS: My sincere thanks to Jitendra and Rama from the JAX-WS team for their help. Special thanks to Stuart Clements, my personnal editor and grammar checker.

Friday Dec 07, 2007

JConsole to isolate the Memory leak case

In this blog entry I want to provide you with a tip in order to help you answer to the fact that there is or not a memory leak in your application.

In some cases, where you are instantiating a lot of objects in a very short period of time, you can observe some huge memory consumption making the application to run out of memory. When it happens, we are (too?) quickly identifying this problem as a Memory leak and forget that the application can have reached some badly set JVM memory threshold causing OutOfMemory exception.

In order to distinguish between theses cases, I am using JConsole in a very very simple and quick way.

Steps to follow to isolate the case

1) Keep the JVM activity below the OutOfMemoryException to occur. For example, if your server crashes after 10000 received requests, tune your test case to deal with only 5000 requests. Doing so you will not run out of memory.

2) Start the application you want to monitor.

3) Start JConsole and attach it to your application. If your are using NetBeans, click on the "Run Main Project with Monitoring and Management" toolbar button.

Your project is compiled, run and JConsole automaticaly attached to it.

4) Click on JConsole Memory Tab and call Perform GC button located on the top right corner. The memory consumed during the application startup is released.

5) Start the activity (start a client application that will connect to the server, call a JMX MBean that initiates some activity, ...). Thanks to JConsole you will follow the memory allocation. Some big numbers can be reached there. In the example below, my server is simply serving simple Web Services Request. The memory consumed reaches 200 Megs...

6) Once the activity is stopped, you will notice that the amount of consumed memory is still very high. Call Perform GC multiple time to make sure that the GC is actually freeing the consumed memory.

7) Now you have 2 cases, or the memory consumed number is similar to step 4 and you are not experiencing a memory leak, or it stays high and you found a memory leak. In this example, the memory consumption is high but is not linked to any memory leak. You will notice that the Old Generation Memory pool (last vertical bar on top of Heap label) is cleared. There is no accumulation. In case of memory leak, you would have seen that this pool contains some objects. Mandy Chung wrote a blog entry that describes such case.

You can now take the right action. Or you allocate more memory for your application (use -Xmx JVM option for example), or you start investigate your problem (eg: by using NetBeans Profiler).

Jean-François

Monday Dec 03, 2007

NetBeans 6.0 JMX new features

NetBeans 6.0 is out. You should go experience the new Editor, really amazing... What does it add compared to the previous one? Well... not a lot of things... It simply anticipates your coding, checks your coding and drives you to write better code...no more than that... Kudo to the NetBeans team!

JMX module is part of the game and still downloadable from the stable update center. I am pasting a screenshot of the new update center UI that you now find in NetBeans 6.0.




In this blog entry I am focusing on JDK 6.0 JConsole related new features. You can access to the list of features, latest tutorials, documentation and known issues from this web site : http://management.netbeans.org/jmx.

JConsole to Monitor J2SE Project

If you are used to the JMX module, you will notice that the way to connect JConsole to your J2SE Project has not changed.

Just set your J2SE Project as the “main project”and click on this toolbar button:


Your project will be compiled, run and JConsole will attach to it. The way to setup JConsole and the Monitoring & Management features of your project has changed. The next chapter shows you how to achieve such configuration.

Better integration in J2SE project

Right click on your Project to access the project properties. You will notice a “Monitoring and Management” section. This is your configuration entry point.




From there you can:

  • Enable / Disable JConsole auto attachment.

  • Change JConsole polling period.

  • Use (or not) the project classpath to make JConsole findout your MBean custom handled types. Unselecting this option will show you that you introduced some custom types that imply deployment of these classes on the JMX client application. Having custom types handled by your MBean interfaces is not something that we encourage and this is something that you can simply avoid by using MXBean

  • Lookup the Project Classpath to load JConsole custom plugins. A new JConsole API has been defined in order to allow you to develop custom JConsole tabs and have them added to the list of tabs. The next chapter cover this feature. This article describes JDK 6.0 JConsole plugins new feature.

  • Explicitly add paths to your JConsole plugins jar files or classes.

  • Enable or disable Remote RMI access. By default, remoting is not enabled.

      • You can provide the RMI port the server will listen to. Doing so, you will start a non secure remote access.

      • Or you can provide a path to a management.properties file in which you can configure security.

New Support to load JConsole custom tabs

To do so, simply add JConsole plugins that you downloaded or developed, to the Monitoring and Management Properties Plugins Path list.

In this example, I am adding the JTop plugin that is bundled with JDK 6.0 (<java home>/demo/management/JTop/JTop.jar). This plugin demonstrates the use of the java.lang.management API to obtain the CPU consumption for each thread.

Add the plugin to the Project properties and run your application

In the “Monitoring and Management” Properties :

  1. click on Add Jar/Folder button then provide a path to JTop jar file. The jar file is added to the list.

  2. Close the project properties.

  3. Run your project with by clicking on the JConsole toolbar button.

JConsole is started, JTop tab being loaded and displayed.




Some interesting JConsole plugins


JConsole to Monitor any Java project

If you want to connect JConsole to another kind of Java project (e.g.: Web Application), you can start JConsole and connect it to the application server running your application. To do so click on the following toolbar button to launch JConsole management console:




You can tune the JConsole default Target (default URL to connect to), polling period, plugins path, classpath, arguments or JVM arguments from the NetBeans Options. To do so:

  1. Select Tools | Options from the main menu

  2. Select Miscellaneous tab

  3. Select JConsole tab

The following window is displayed:




Hope to have helped you discover a useful new feature of the JMX tooling.

Regards.



Jean-François Denise

(jean-francois dot denise at sun dot com)

Wednesday Sep 05, 2007

WS-Security to secure JMX Web Services Connector

In a previous post, Securing JMX Web Services Connector, I explained how to enable HTTPS when using the JSR 262 RI. Basic Authentication and HTTPS are the basic building blocks on which you can rely to secure remote WS access to your JMX instrumentation. These technologies are very commonly used and are simple to put in place when you need point-to-point security. For more complex architectures, however, where messages contexts contain multiple nodes, HTTPS is not the best solution.

WS-Security

WS-Security, a Web Services standard defined by OASIS, aims to secure communication at the SOAP message level (as opposed to HTTPS, that secures messages at the transport level) in a unified, flexible and extensible way. WS-Security supports partial message signing and encryption, in case you need to encrypt the SOAP message body element and keep the headers non-encrypted; for example, when encrypting credit card numbers or any XML subtrees.

In addition to confidentiality and authentication (also offered by HTTPS + Basic Authentication), WS-Security offers message integrity, thanks to XML signatures. With XML signatures, you can protect your communication against message-tampering.

Interoperability at the security level

Due to the huge number of alternatives you can use when trying to secure your communications, you will generally run into interoperability problems. WS-Security has been designed to offer interoperability while still allowing you to plug in various technologies. The WSIT project on java.net (JavaOne 2007 Technical Session TS-4865 offers a good introduction to WSIT) offers an interoperable WS-\* stack that, along with a full set of other WS standards, integrates a Java technology implementation of WS-Security. WSIT is the solution I have adopted to plug WS-Security into the Connector.

Plugging WS-Security into the JMX Web Services Connector

Now that we have briefly introduced WS-Security and WSIT, let's go back to what really interests us, namely plugging WS-Security into the Web Services Connector. The XWSS project, that is part of WSIT, offers everything we need to enable WS-Security in our context. How is this achieved? Simply because the JMX Connector is a JAX-WS Web Service (compliant with WS-Management but still a classical JAX-WS Web Service) and XWSS works well with JAX-WS.

So, I started by reading a XWSS article on how to add WS-Security to your Web Services on top of the Java SE 6 platform. I then adapted the XWSS sample application to create a simple JMX client and server. I interacted with Kumar Jayanti from the XWSS team to get our two technologies working well together. We encountered some issues with WSIT Milestone 6 (mainly related to the fact that WS-Policy was still linked to a Java EE platform type of deployment, and the JMX Connector was being deployed on the Java SE platform), but these have been fixed in the latest WSIT builds. The next WSIT FCS Milestone should contain all the necessary fixes. The usage of WS-Policy makes for a transparent usage of WS-Security. If you package your WS-Security configuration files properly, you can enable WS-Security on the client side and on the server side without touching a single line of code (see the next section for full details of how to make this work).
To enable WS-Security you simply need to package your application with the WSIT binaries and the WS-Security configuration file.

Building and Running the JMX WS Connector Sample Secured with WS-Security

  1. Dowload the XWSS sample application.
  2. Unzip it. A directory named src is created.
  3. Download the sample JMX Agent Main.java file.
  4. Copy Main.java into the src/simplejdk6ws/ directory. The ConnectorServer is started on port 8080. In case of conflict, update the Main.java file (be sure to update the client code accordingly, see the next section for the client side).
  5. Download the sample JMX Client SimpleWSClient.java file.
  6. Copy SimpleWSClient.java into the src/simplejdk6ws/ directory. The Connector connects to port 8080. In case of conflict, update the SimpleWSClient.java file (it should follow the value you previously provided when starting the server). This client application is a very simple one, it connects to the server and asks for the Default Management domain (MBeanServerConnection.getDefaultDomain()).
  7. The server side security configuration file is src/META-INF/server_security_config.xml. Any message received and response sent is Authenticated, Signed and Encrypted according to the configuration defined in this configuration file. You don't need to update this file.
  8. The c lient side security configuration file is src/META-INF/client_security_config.xml. Any message sent and response received is Authenticated (user Ron), Signed and Encrypted according to the configuration defined in this configuration file. Again, you don't need to update this file.
  9. Download WSIT (which contains JAX-WS).
  10. Install WSIT with the following command:
    java -jar jax-ws-latest-wsit-installer_nightly.jar
    The jax-ws-latest-wsit directory is created.
  11. Create a directory named endorsed. Move jax-ws-latest-wsit/lib/webservices-api.jar into this directory.
  12. If you have not already done so ;-), download JMX Web Services Connector Early Access 2.
  13. Call the following command:
    java -jar jsr262-ri.jar
    The jsr262-ri directory is created.
  14. To build your sample, go to the src directory and type the following command:
    javac -cp :../endorsed/webservices-api.jar:../jax-ws-latest-wsit/lib/webservices-rt.jar simplejdk6ws/\*.java
  15. Download the Java mail JAR file .
  16. Start your server from the src directory. The command should be something similar to the following:
    java -cp .:../mail-1.4.jar:../jsr262-ri/lib/jmxws.jar:../jsr262-ri/lib/wiseman-core.jar:../jax-ws-latest-wsit/lib/webservices-rt.jar -Djava.endorsed.dirs=../endorsed/ simplejdk6ws.Main
    You should see the following message:
    JSR 262 ConnectorServer is ready to serve on http://localhost:8080/jmxws
  17. Start your client from the src directory. The command should be something similar to the following:
    java -cp .:../mail-1.4.jar:../jsr262-ri/lib/jmxws.jar:../jsr262-ri/lib/wiseman-core.jar:../jax-ws-latest-wsit/lib/webservices-rt.jar -Djava.endorsed.dirs=../endorsed/ simplejdk6ws.SimpleWSClient
    You should observe a very verbose output containing the secured received and sent SOAP messages. You will notice that the user Ron never appears in the messages, because the user name is encrypted. At the end, the Default Management domain will be displayed.
  18. You are done. Not a line of code was written, and all that was needed was some configuration and packaging.

Bridging with Authorization

When a request is received, the JMX WS Connector Server looks for the existence of Principals in order to create a javax.security.auth.Subject that will be used to check the Java platform's permissions. XWSS, after having dealt with Security, creates a Subject that contains all the authenticated principals (X500 certificate, Trusted user, etc.). XWSS makes this Subject accessible thanks to the call SubjectAccessor.getRequesterSubject(context). This call is XWSS-implementation-dependent and other WS-Security implementations are likely to offer their own way. This is why we have added a hook to plug a Subject extractor into the ConnectorServer to retrieve the Subject and make it accessible to the ConnectorServer.

The following XWSSSecuritySubjectExtractor class is an example of such an XWSS-aware SubjectExtractor:

        class XWSSSecuritySubjectExtractor extends JMXWSSubjectExtractor {
            protected Subject getExtraSubject(WebServiceContext context) {
                try {
                    return SubjectAccessor.getRequesterSubject(context);
                } catch (XWSSecurityException ex) {
                    ex.printStackTrace();
                }
                return null;
            }
        }
                        

To pass the extractor instance to the ConnectorServer, use the environment map :

        Map env = new HashMap();
        
        // Provide the extended SubjectExtractor to inject WS-Security Subject
        env.put(JMXWSConfiguration.JMX_WS_SUBJECT_EXTRACTOR, new XWSSSecuritySubjectExtractor());
        
        JMXConnectorServer server =
                JMXConnectorServerFactory.
                newJMXConnectorServer(new JMXServiceURL("service:jmx:ws:" +
                "//localhost:8080/jmxws"), env,
                ManagementFactory.getPlatformMBeanServer());
        server.start();
                                                                    

This is the updated Main.java file that contains the Subject Extractor.

WARNING: You need the updated JMX WS Connector RI jmxws.jar and wiseman-core.jar file to use the SubjectExtractor API. You can download these jars here.
Call java -jar jsr262-patch-ws-security.jar to extract the jmxws.jar and wiseman-core.jar files.
When compiling the agent, add both JAR files to your classpath.

So, if one day you reach the limits of the capabilities of HTTPS + Basic Authentication, you should think about using WS-Security. I hope that I have demonstrated to you that enabling it is straightforward. But you should be aware that enabling WS-Security will significantly impact the performance of the WS Connector. The time needed to check security added to the time needed to create and parse a secured SOAP Message (here is an example of a AUTH+PRIV+SIGN getDefaultDomain response SOAP message) makes for much slower client/server interaction.

Enjoy and have fun.

Jean-Francois

Thursday Aug 16, 2007

Securing JMX Web Services Connector


I have been contacted by a customer of the JSR 262 Early Access 2 who asked me for some material on how to enable HTTPS. I realized that no material was provided. No sample, no blog entry, nothing... Why is there such a lack of documentation? Thinking at it, it appeared that the extreme simplicity of enabling HTTPS for the WS Connector made us forget to provide material for it. This blog entry is trying to correct that and highlight the extreme simplicity enabling HTTPS.

Here, I will present in turn a JDK 5 and a JDK 6 example. The scenario is very common. You have already written a JMX agent and a JMX client. You have already tested that all your JMX MBeans are working well. It is now deployment time! And it is at this precise time that your customer asks you for Security...
You never thought that it could happen to you. You know that security is a complex topic. Encryption, symmetric or asymmetric keys are things that you have heard of but you prefer to stay away from them...
No worries, the JMX WebServices Connector takes charge of all the details. You are just required to configure it. So let's start by securing your ConnectorServer.

Securing the ConnectorServer

Your agent code looks something like :
  JMXConnectorServer server =
                JMXConnectorServerFactory.
                newJMXConnectorServer(new JMXServiceURL("service:jmx:ws:" +
                "//localhost:8080/jmxws"), null,
                ManagementFactory.getPlatformMBeanServer());

  server.start();

Right? This is the very classical way to start a JMX Connector. If this is not the case, if the way you create and start your agent is not similar to this code, please send me a mail (jean-francois dot denise at sun dot com)

So how do you enable HTTPS? Simply by changing the protocol name when creating the JMXServiceURL to be ws-secure instead of ws.

So now your code looks like :
  JMXConnectorServer server =
                JMXConnectorServerFactory.
                newJMXConnectorServer(new JMXServiceURL("service:jmx:ws-secure:" +
                "//localhost:8080/jmxws"), null,
                ManagementFactory.getPlatformMBeanServer());

  server.start();

Are you done? Not yet, you need to provide a KeyStore location and a KeyStore password for SSL to find the certificates. You don't have a KeyStore or a certificate? Not a big deal, use keytool! For example call :

keytool -genkey -keystore jsr262Keystore -keyalg RSA

Answer the questions and provide a KeyStore password. In this blog entry I am using 123456 as the password value. This is something that you should never do in a real context. In this blog entry context, however, is is safe enough.
keytool generates a file named jsr262Keystore. You have now a KeyStore that contains a certificate secured by a password.
If you are running JDK 6, it is enough to actually launch your JMX agent in a secure way. The keyStore and password are provided thanks to two standard Java properties. For example :

java -classpath ... -Djavax.net.ssl.keyStore=jsr262Keystore -Djavax.net.ssl.keyStorePassword=123456 MyJMXAgent

Simple, no? Yes, but what about if I am using JDK 5? Why isn't it so simple?
Simply because JDK 6 has been extended to support a default SSL configuration that relies on the Java properties we previously used (javax.net.ssl.keyStore and javax.net.ssl.keyStorePassword). On JDK 5, you need to provide an instance of javax.net.ssl.SSLContext. Here, I provide you with an SSLContext that reads the standard Java properties in order to compute an SSL configuration. You can use this TestSSLContext Java file that implements the required logic.

How do I pass this SSLContext to the WS ConnectorServer? By using the env map when calling the JMXConnectorServerFactory class.
Your updated source code looks like :
        // Create the SSLContext
         SSLContext ctx = TestSSLContext.getInstance("SSLv3");
        // Create an env map
        Map env = new HashMap(1);
        // Provide the SSLContext
        env.put("jmx.remote.ws.sslcontext", ctx);
        // Create the ConnectorServer providing the env map
        JMXConnectorServer server =
                JMXConnectorServerFactory.
                newJMXConnectorServer(new JMXServiceURL("service:jmx:ws-secure:" +
                "//localhost:8080/jmxws"), env,
                ManagementFactory.getPlatformMBeanServer());
        
        server.start();

You are done, you can start your JMX Agent the same way you did using JDK 6.

java -classpath ... -Djavax.net.ssl.keyStore=jsr262Keystore -Djavax.net.ssl.keyStorePassword=123456 MyJMXAgent

You have now a JMX agent running, waiting for https requests. Let's go secure the client side.

Securing the Connector

This is JDK 5 or 6 independent. You need to replace the ws protocol name with ws-secure as you did on the server side, then provide a TrustStore location and password. The KeyStore named jsr262KeyStore we previously created can be reused by the client.
Your client code looks something like :
 JMXServiceURL url = new JMXServiceURL("service:jmx:ws://localhost:8080/jmxws");
 JMXConnector connector = JMXConnectorFactory.connect(url, null);
 //Get the MBeanServerConnection
 MBeanServerConnection mbsc = connector.getMBeanServerConnection();

Once the JMXServiceURL value has been updated, you code looks like:
 JMXServiceURL url = new JMXServiceURL("service:jmx:ws-secure://localhost:8080/jmxws");
 JMXConnector connector = JMXConnectorFactory.connect(url, null);
 //Get the MBeanServerConnection
 MBeanServerConnection mbsc = connector.getMBeanServerConnection();

When starting the client you provide the TrustStore and password using two standard Java properties. For example :

java -classpath ... -Djavax.net.ssl.trustStore=jsr262Keystore -Djavax.net.ssl.trustStorePassword=123456 MyClient

And... you are done! Extremely simple, no? I hope so, otherwise, let me know ;-).

Some material

Here is all the material I created to write this blog entry. A first NetBeans project containing the source of the agent, the source of TestSSLContext (remember, this is only needed on JDK 5) and the jsr262KeyStore. A second NetBeans project containing the source of the client. You will have to correct some references (mainly JDK, JAX-WS libraries) when opening them but they can help you start securing your app.

Next blog entry to come? Why not use WS-Security (Security applied to the SOAP message) to secure JMX Web Services communication. Stay tuned.

Regards.

Jean-Francois

Tuesday Jun 05, 2007

J2EE Deployment of JMX WS Connector


If you are already evaluating the Early Access 2 of JSR 262, you have perhaps a need to deploy the Connector in your servlet container.
A sample, located in samples/servletdeployment directory, shows you how to achieve such deployment. The provided example shows how to deploy the JSR262 JAX-WS Endpoint com.sun.jmx.remote.ws.wsman.JMXWSManServiceEndpoint inside a JAX-WS compliant servlet container. When created, the endpoint gets a reference to the platform MBeanServer (thanks to java.lang.management.ManagementFactory.getPlatformMBeanServer())
If the MBeans you want to manage are registered inside the platform MBeanServer, you can reuse this sample code. Registering MBeans in the platform MBeanServer is something that we encourage.
If you want to attach the connector to another MBeanServer, then you need to subclass JMXWSManServiceEndpoint and provide your own MBeanServer.

Extending JMXWSManServiceEndpoint JAX-WS endpoint

When extending an annotated class (JMXWSManServiceEndpoint JAX-WS endpoint is annotated), the extended class doesn't inherite from the mother class annotations, you need to re-annotate the extended class.
When deploying in J2EE, no JMXServiceURL is provided to the connector (as opposite to the JMX J2SE way of deploying a Connector). You need to provide to the Connector the URL on which it has been deployed. This is done by calling setURL on JMXWSManServiceEndpoint class. This URL is used when translating from MBean ObjectName to WS-Addressing EPR.

Extended class

The following sample code is a ready to deploy extended class that gets a reference to the first MBeanServer found thanks to the javax.management.MBeanServerFactory class. The URL on which the endpoint has been deployed is hard coded. You can easily externalize it, for example read it from a property file.

import com.sun.jmx.remote.ws.api.JMXWSManDispatcher;
import com.sun.jmx.remote.ws.api.JMXWSManServiceEndpoint;
import javax.xml.ws.WebServiceContext;
import javax.annotation.Resource;
import javax.management.\*;

@javax.xml.ws.WebServiceProvider
@javax.xml.ws.ServiceMode(value=javax.xml.ws.Service.Mode.MESSAGE)
public class ExtendedEndpoint extends JMXWSManServiceEndpoint {
   @Resource
   private WebServiceContext context;

   public ExtendedEndpoint() throws Exception {
       super(new JMXWSManDispatcher(null, 
               (MBeanServer)MBeanServerFactory.findMBeanServer(null).get(0)));
   }

   protected WebServiceContext getWebServiceContext() {
        return context;
   }
}


Packaging the connector

You simply need to update the endpoint implementation in the sun-jaxws.xml file and repackage the extended class in a war file similar to the sample.

sun-jaxws.xml file

<?xml version="1.0" encoding="UTF-8"?>
< endpoints
        xmlns="http://java.sun.com/xml/ns/jax-ws/ri/runtime"
        version="2.0">
        < endpoint
                name="JMXWSManEndpoint"
                implementation="ExtendedEndpoint"
                service="{http://jsr262.dev.java.net/jmxconnector/wsdl}JMXConnectorService"
                port="{http://jsr262.dev.java.net/jmxconnector/wsdl}JMXConnectorPort"
                url-pattern="/jmxws"
                binding="http://www.w3.org/2003/05/soap/bindings/HTTP/">
        </endpoint>
</endpoints>

Conclusion

The simpler way to deploy the Connector is by using the JMXConnectorServerFactory class. This will answer your needs when you want to take benefit of the JAX-WS http server. Direct JAX-WS endpoint deployment is the other way when reusing an existing infrastructure.

Jean-François

Saturday May 05, 2007

JMX Web Services Connector is out, in WS-Man dress.


JMX Web Services Connector (JSR 262) RI is out! You can download it here.

The novelety in comparaison with the previous Early Access is that the Connector protocol is now based on WS-Management (WS-Man). Connector WS-Man implementation is based on the WiseMan project.

Native WS-Man clients can now interact with MBeans. MBeans are no more the exclusivity of JMX clients. Clients such as Windows Remote Manager (WinRM) and openwsman, can retrieve MBean attributes, call MBean operations and subscribe to MBean notifications.

JSR 262 specification defines a mapping between JMX MBeans and WS-Man Managed Resources. More details can be found in the Early Draft 2 specification. Have a look to the spec and send us your feedbacks.

Next Thursday, at JavaOne, during Eamonn and myself Technical Session, we are presenting an interoperability demo that highlights these new JMX interoperation capabilities. Demo is composed of three scenario:
  • HP Open View Operations / JSR 262 (done by Denis Rachal from HP)
  • Microsoft WinRM Scripting for JSR 262
  • Microsoft Vista Event Viewer to subscribe to MBeans
See you there!

Jean-François
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