# 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
```xml
<dependency>
<groupId>net.lvsq</groupId>
<artifactId>jgossip</artifactId>
<version>1.5.0</version>
</dependency>
```
#### First you need one or more seed members
```java
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
```java
GossipService gossipService = new GossipService(cluster,ipAddress, port, id, seedNodes, new GossipSettings(), (member, state) -> {
//Do anything what you want
});
```
#### Run `GossipService`
```java
gossipService.start();
```
#### Stop
```java
gossipService.shutdown();
```
#### Get offline nodes
```java
gossipService.getGossipManager().getDeadMembers();
```
#### Get online nodes
```java
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
```java
GossipState.UP;
GossipState.DOWN;
GossipState.JOIN;
GossipState.RCV;
```
# Example
```java
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:
```java
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 <html><span style="color: green">"Hello World"</span><html> 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.
一个 Java 版的 Gossip 协议实现.rar （39个子文件） 
一个 Java 版的 Gossip 协议实现 
新建文本文档.txt 19B jgossip-master 
pom.xml 5KB src test java net lvsq jgossip TestGossipService.java 1KB TestGossipMember.java 907B TestGossipDigestSyncMessage.java 2KB TestAckMessage.java 2KB TestRegularMessage.java 1KB main java net lvsq jgossip handler Ack2MessageHandler.java 1KB SyncMessageHandler.java 4KB MessageHandler.java 954B AckMessageHandler.java 3KB RegularMessageHandler.java 2KB ShutdownMessageHandler.java 1KB net udp UDPMsgService.java 4KB MsgService.java 1KB event GossipListener.java 909B core CustomSerializer.java 1KB GossipSettings.java 3KB MessageManager.java 358B GossipMessageFactory.java 2KB VersionHelper.java 1KB CustomDeserializer.java 1KB GossipService.java 3KB Serializer.java 2KB InMemMessageManager.java 954B GossipManager.java 22KB model CandidateMemberState.java 2KB AckMessage.java 2KB MessageType.java 974B Ack2Message.java 2KB HeartbeatState.java 2KB SyncMessage.java 2KB GossipDigest.java 3KB GossipState.java 896B SeedMember.java 3KB RegularMessage.java 2KB GossipMember.java 3KB LICENSE 11KB README.md 4KB资源评论
