Node.js Helix Participant

Apache Helix is a cluster management framework that is currently being incubated by the Apache Incubator project. The Helix participant is the component of the Helix architecture that hosts the distributed resources.

node-helix-participant is a node.js module that aims to provide a subset of the Helix library necessary to create native node.js Helix participants.

Motivation

The original Helix library is written in Java for the JVM. For node.js applications and services, however, the is no way to directy instantiate a participant. In lieu of this, some interprocess communication must occur between the node.js process and the JVM process hosting the Helix participant. A few poblems emerge from this separation of the true resource owner and the Helix participant that acts as a representative.

The major concern is that there is now inconsistency between actual ownership of the resource and what is known to the participant, meaning the guarantee of atomic region ownership is no longer strictly true. In additon, state transitions may fail due to to either the Helix participant or the application hosting the resource, and because the two exist without shared memory or logic, managing failed transitions becomes a much more difficult task.

Contributing

Code Style

The APIs for these modules are meant to stay consistent with those in the Java-based Helix distribution. However, the APIs will be written in a fashion that is consistent with node.js and JavaScript conventions.

Code style should abide by the following:

• Use strict mode
• Use JSDoc 3 for documenting code
• Always use semicolons
• Indent with two (2) spaces
• Use Unix-style newline characters (single LF)
• End files with new lines

Testing

All significant code changes should be tested. These changes can be manually tested using:

# Less verbose output
vows
# Full spec output
vows --spec # npm test does the same thing

Continuous Integration

All pushes to this repository will be continuously integrated, will all tests being run with each build. The CI dashboard provides information about each each build. Currently, the project is being built against node v.0.10.x, v0.8.x, and v0.6.x.

If your commit does not require a new build to be tested, then put [ci skip] somewhere in your commit message.

Dependencies

• node-zookeeper-client
• async
• async-stacktrace