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Gossip

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.

Usage

Maven

<dependency>
  <groupId>net.lvsq</groupId>
  <artifactId>jgossip</artifactId>
  <version>1.5.0</version>
</dependency>

First you need one or more seed members

List<SeedMember> seedNodes = new ArrayLis<>();
SeedMember seed = new SeedMember();
seed.setCluster(cluster);
seed.setIpAddress(ipAddress);
seed.setPort(port);
seedNodes.add(seed);

Then, instantiation a GossipService object

GossipService gossipService = new GossipService(cluster,ipAddress, port, id, seedNodes, new GossipSettings(), (member, state) -> {
        //Do anything what you want
    });

Run GossipService

gossipService.start();

Stop

gossipService.shutdown();

Get offline nodes

gossipService.getGossipManager().getDeadMembers();

Get online nodes

gossipService.getGossipManager().getLiveMembers();

Settings

  • gossipInterval - How often (in milliseconds) to gossip list of members to other node(s). Default is 1000ms
  • networkDelay - Network delay in ms. Default is 200ms
  • msgService - Which message sync implementation. Default is UDPMsgService.class use UDP protocol to send message, certainly you can extand it.
  • deleteThreshold - Delete the deadth node when the sync message is not received more than [deleteThreshold] times. Default is 3

Event Listener

Currently, jgossip has four events

GossipState.UP;
GossipState.DOWN;
GossipState.JOIN;
GossipState.RCV;

Example

int gossip_port = 60001;
String cluster = "gossip_cluster";

GossipSettings settings = new GossipSettings();
settings.setGossipInterval(1000);

try {
    String myIpAddress = InetAddress.getLocalHost().getHostAddress();
    List<SeedMember> seedNodes = new ArrayList<>();
    SeedMember seed = new SeedMember();
    seed.setCluster(cluster);
    seed.setIpAddress(myIpAddress);
    seed.setPort(60001);
    seedNodes.add(seed);

    gossipService = new GossipService(cluster, myIpAddress, gossip_port, null, seedNodes, settings, (member, state, payload) -> {
        if (state == GossipState.RCV) {
            System.out.println("member:" + member + "  state: " + state + " payload: " + payload);
        }
        if (state == GossipState.DOWN) {
            System.out.println("[[[[[[[[[member:" + member + "  was down!!! ]]]]]]]]]");
        }});
} catch (Exception e) {
    e.printStackTrace();
}
gossipService.start();

Run the above code in each application to create a cluster based on the Gossip protocol. You can provide a meaningful GossipListener as the last parameter of GossipService. When state of a node changes, you can capture this change and make some responses.

Publish Messages

If you want to send messages to gossip cluster:

gossipService.getGossipManager().publish("Hello World");

If a node in cluster received messages, it will trigger the GossipState.RCV event, and handler predefined by GossipListener can consume these messages, such as "Hello World" above.

The type of message is arbitrary, but only if it can be serialized. jgossip will try its best to deliver to every node. By default, messages will stay in memory for a while, and then jgossip will automatically delete them. So the best scenario for this feature is to send some simple messages regularly.

Please pay attention, if you need to send mass messages in a short time, which will consume a lot of resources, this requires you to weigh the actual situation.