xgossip

Gossip based membership management and failure detection.

Introduction

xgossip is inspired by the paper Epidemic Algorithms for Replicatied Database Maintenance, which maybe the first paper of gossip protocol, to manage members in the cluster. It employs gossip protocol to spread members' change and exchange member list between members using push-pull strategy.

Failure detection, which is based on the algorithm in the paper On Scalable and Efficient Distributed Failure Detectors, will mark member as suspected when ping and proxy ping are failed, or backed when ping response is not timeout. Gossip protocol here is used to broadcast the failure or recover of members and then xgossip will suppress sending rpc to suspected members.

Demonstration

To make a 3 nodes cluster

• localhost:5302
• localhost:5303
• localhost:5304

Start node localhost:5302

$ mvn exec:java -Dexec.mainClass=in.xnnyygn.xgossip.Launcher -Dexec.args=5302

Start node localhost:5303 with seed member localhost:5302

$ mvn exec:java -Dexec.mainClass=in.xnnyygn.xgossip.Launcher -Dexec.args="5303 localhost:5302"

Start node localhost:5304 with seed member localhost:5302

$ mvn exec:java -Dexec.mainClass=in.xnnyygn.xgossip.Launcher -Dexec.args="5304 localhost:5302"

Now you can stop localhost:5304 with Ctrl+C and see what will happen.

localhost:5302 and localhost:5303 should print some message like member localhost:5304 SUSPECTED.

Then restart localhost:5304

$ mvn exec:java -Dexec.mainClass=in.xnnyygn.xgossip.Launcher -Dexec.args="5304 localhost:5302"

localhost:5302 and localhost:5303 should print some message like member localhost:5304 BACKED.

Finally, press enter in the console of member localhost:5303 to shutdown.

You should see something like member localhost:5303 LEAVED.

Example log of localhost:5302

2018-09-08 16:22:58.756 [in.xnnyygn.xgossip.Launcher.main()] INFO  rpc.DefaultTransporter - start udp server at port 5302
member localhost:5302 JOINED, available endpoints [localhost:5302]
2018-09-08 16:23:25.250 [udp-server] INFO  xgossip.MemberManagerImpl - member localhost:5303 joined
member localhost:5303 JOINED, available endpoints [localhost:5303, localhost:5302]
2018-09-08 16:23:49.061 [udp-server] INFO  xgossip.MemberManagerImpl - member localhost:5304 joined
member localhost:5304 JOINED, available endpoints [localhost:5303, localhost:5302, localhost:5304]
2018-09-08 16:24:01.859 [scheduler] INFO  xgossip.FailureDetector - member localhost:5304 suspected
member localhost:5304 SUSPECTED, available endpoints [localhost:5303, localhost:5302]
2018-09-08 16:24:06.259 [udp-server] INFO  xgossip.MemberManagerImpl - member localhost:5304 backed
2018-09-08 16:24:07.872 [udp-server] INFO  xgossip.FailureDetector - member localhost:5304 backed
member localhost:5304 BACKED, available endpoints [localhost:5303, localhost:5302, localhost:5304]
member localhost:5303 LEAVED, available endpoints [localhost:5302, localhost:5304]

How to use

The interface of xgossip is MemberManager.

• initialize()
• join(seedEndpoint: Collection)
• listAvailableEndpoints(): Set
• leave()
• addListener(listener: MemberEventListener)
• shutdown()

Service should call initialize when start and shutdown when stop.

To join the cluster, call join with seed endpoints. Technically, you should provide some seed endpoints unless current member is the first member in the cluster.

When service is running, available endpoints in the cluster can be retrieved by calling listAvailableEndpoints at any time. Listener is also supported with notification of new members, suspected members etc.

Build

xgossip uses maven as the build system.

$ mvn clean compile install

License

This project is licensed under the Apache 2.0 License.