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.

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