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Insights and updates on Java SE and OpenJDK from the Java Platform Group Product Management Team

  • December 18, 2014

Node.js and io.js on Java

The Nashorn JavaScript engine is one of many improvements in JDK 8. Nashorn (German for Rhino) is a faster replacement for the previous JavaScript engine known as Rhino. There is also another noteworthy feature: the ability to run many Node.js and io.js applications in the JVM. These applications can then call back and forth between optimized Java libraries and automatically receive monitoring capabilities through JMX.

In the upcoming JDK 8 update 40, it is planned to improve Nashorn / JavaScript performance even further through optimistic typing.

Java Virtual Machine - More than just Java

The Java Platform offers a way to run different types of applications, even if those applications are not written in the Java programming language. As a result, developers can take advantage of optimizations and stability of the JVM, while system administrators can better control and monitor deployments.

Examples of other languages on the JVM include: JavaScript (Nashorn), Ruby (JRuby), Python (Jython), Scala, Groovy, and many others.

Project Avatar – A JavaScript services layer on the JVM

Avatar.js is a project to bring the node programming model, APIs and module ecosystem to the Java platform. Although written in JavaScript, these applications can take advantage of the Java platform's scalability, manageability, tools, and extensive collection of Java libraries and middleware. After downloading the Avatar.js binaries, developers can then execute their applications. For example, Tim Caswell’s article "Hello Node!" contains basic examples for hello-console.js and hello-http.js that can be used as a basic way for testing Avatar.

Nashorn, The Hidden Weapon of JDK 8 was presented at the Silicon Valley Java User Group meeting in December 2014. The available slides describe the use of Nashorn and Avatar at Netflix and provide additional Nashorn demos.

Avoid rewrites and re-use libraries

One major benefit of running serverside JavaScript applications within the JVM is access to Java libraries. Developers do not have to rewrite major libraries or functionality like SQL or NoSQL drivers, Hadoop clients, encoding libraries, etc. Additional examples are available in a previous post, Nashorn: the rhino in the room, but they are not specific to Node.js.

Niko Köbler has a two-part article about Avatar 2.0 and its Model Store API. By using this model store API, developers can more easily interact with SQL and No-SQL and benefit from many existing optimizations.

  1. Part 1 explains the architecture and threading model.
  2. Part 2 covers the technology behind the Model Store API.

Monitoring Applications on the JVM

All Java processes can be monitored through a mechanism called JMX. System Administrators can enable remote authenticated JMX connections and see inside these running applications, rather than monitoring from the outside coming in.

Additional details about JMX monitoring (both local and remote) can be found in a previous post, Deep Monitoring with JMX.

Monitoring applications with Mission Control / Flight Recorder

Java Flight Recorder is an effective way of monitoring JVM applications in production. Unlike standard development profilers (like the NetBeans profiler), Flight Recorder has negligible performance impact.

The dashboard view in Mission Control provides basic information about CPU and memory resources. Developers may use the Threads tab to better understand system throughput, or if the application is blocking around any particular resources.

To open Mission Control, run the jmc command and connect to your Avatar application. The screenshot below shows Mission Control monitoring a Node.js application identified as com.oracle.avatar.Server.

Monitoring Node.js on Java

Although the Node.js applications are written in JavaScript, Flight Recorder can also perform trigger-based recordings on events, such as a CPU spike. System Administrators and Developers can look back at the recording to see what lead up to the event.

Additional details are available on the Mission Control home page and user guide.

Additional ways of running Node.js on the JVM

Avatar is one of several ways to run Node.js applications on the JVM.

When run on Oracle Java, both projects can be monitored by Flight Recorder / Mission Control as described above. Because this monitoring is provided directly by the Oracle JVM itself, there is no need to make any code changes or apply additional monitoring packages.

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