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apache / incubator-retired-gossip / c97c5ff81013710688e3518ba1f89a05434d7087
commitc97c5ff81013710688e3518ba1f89a05434d7087[log] [tgz]
authorIan <irstevenson@gmail.com>Sun Jan 31 11:17:34 2016 +1100
committerIan <irstevenson@gmail.com>Sun Jan 31 11:17:34 2016 +1100
treeabc2ef7d79b724075c93789a1af45748f0ed2e49
parent1d064f467633c0db751c28abd18c5095f77697ea [diff]
Added test for `StartupSettings` and documentation of use - in `README.md`.

* Also tweaked the `StartupSettings` so that it now reads in an `id` for the node, rather than just resulting in a blank `id`;
* Moved some logging from stdout to log4j
* Full `maven test` passing

Arguably this would result in a version change, as the settings file format has changed and now requires an id field. However we could make it optional, but it seems odd to have nodes with no ids.
5 files changed
tree: abc2ef7d79b724075c93789a1af45748f0ed2e49
  1. src/
  2. .gitignore
  3. .travis.yml
  4. pom.xml
  5. README.md
README.md

Gossip Build status

Gossip protocol is a method for a group of nodes to discover and check the liveliness of a cluster. More information can be found at http://en.wikipedia.org/wiki/Gossip_protocol.

The original implementation was forked from https://code.google.com/p/java-gossip/. Several bug fixes and changes have already been added.

Usage

To gossip you need one or more seed nodes. Seed is just a list of places to initially connect to.

  GossipSettings settings = new GossipSettings();
  int seedNodes = 3;
  List<GossipMember> startupMembers = new ArrayList<>();
  for (int i = 1; i < seedNodes+1; ++i) {
    startupMembers.add(new RemoteGossipMember("127.0.0." + i, 2000, i + ""));
  }

Here we start five gossip processes and check that they discover each other. (Normally these are on different hosts but here we give each process a distinct local ip.

  List<GossipService> clients = new ArrayList<>();
  int clusterMembers = 5;
  for (int i = 1; i < clusterMembers+1; ++i) {
    GossipService gossipService = new GossipService("127.0.0." + i, 2000, i + "",
      LogLevel.DEBUG, startupMembers, settings, null);
    clients.add(gossipService);
    gossipService.start();
  }

Later we can check that the nodes discover each other

  Thread.sleep(10000);
  for (int i = 0; i < clusterMembers; ++i) {
    Assert.assertEquals(4, clients.get(i).get_gossipManager().getMemberList().size());
  }

Usage with Settings File

For a very simple client setup with a settings file you first need a JSON file such as:

[{
  "id":"419af818-0114-4c7b-8fdb-952915335ce4",
  "port":50001,
  "gossip_interval":1000,
  "cleanup_interval":10000,
  "members":[
    {"host":"127.0.0.1", "port":50000}
  ]
}]

where:

  • id - is a unique id for this node (you can use any string, but above we use a UUID)
  • port - the port to use on the default adapter on the node's machine
  • gossip_interval - how often (in milliseconds) to gossip list of members to other node(s)
  • cleanup_interval - when to remove ‘dead’ nodes (in milliseconds)
  • members - initial seed nodes

Then starting a local node is as simple as:

GossipService gossipService = new GossipService(
  StartupSettings.fromJSONFile( "node_settings.json" )
);
gossipService.start();

And then when all is done, shutdown with:

gossipService.shutdown();

Event Listener

The status can be polled using the getters that return immutable lists.

   List<LocalGossipMember> getMemberList()
   public List<LocalGossipMember> getDeadList()

These can be accessed from the GossipManager on your GossipService, e.g: gossipService.get_gossipManager().getMemberList();

Users can also attach an event listener:

  GossipService gossipService = new GossipService("127.0.0." + i, 2000, i + "", LogLevel.DEBUG,
          startupMembers, settings,
          new GossipListener(){
    @Override
    public void gossipEvent(GossipMember member, GossipState state) {
      System.out.println(member+" "+ state);
    }
  });

Maven

You can get this software from maven central.

  <dependency>
       <groupId>io.teknek</groupId>
      <artifactId>gossip</artifactId>
      <version>${pick_the_latest_version}</version>
  </dependency>