这篇文章主要介绍“elasticsearch节点间通信的transport启动过程是什么”的相关知识，小编通过实际案例向大家展示操作过程，操作方法简单快捷，实用性强，希望这篇“elasticsearch节点间通信的transport启动过程是什么”文章能帮助大家解决问题。
transport顾名思义是集群通信的基本通道，无论是集群状态信息，还是搜索索引请求信息，都是通过transport传送。elasticsearch定义了tansport，tansportmessage，tansportchannel，tansportrequest，tansportresponse等所需的所有的基础接口。这里将以transport为主，分析过程中会附带介绍其它接口。首先看一下transport节点的定义，如下图所示：
NettyTransport实现了该接口。分析NettyTransport前简单说一下Netty的用法，Netty的使用需要三个模块ServerBootStrap，ClientBootStrap（v3.x）及MessageHandler。ServerBootStrap启动服务器，ClientBootStrap启动客户端并连接服务器，MessageHandler是message处理逻辑所在，也就是业务逻辑。其它详细使用请参考Netty官方文档。
NettyTransport每个在doStart（）方法中启动serverBootStrap，和ClientBootStrap，并绑定ip，代码如下所示：
protected void doStart() throws ElasticsearchException {
clientBootstrap = createClientBootstrap();//根据配置启动客户端
……//省略了无关分代码
createServerBootstrap(name, mergedSettings);//启动server端
bindServerBootstrap(name, mergedSettings);//绑定ip
}每一个节点都需要发送和接收，因此两者都需要启动，client和server的启动分别在相应的方法中，启动过程就是netty的启动过程，有兴趣可以去看相应方法。bindServerBootstrap(name, mergedSettings)将本地ip和断开绑定到netty同时设定好export host（export host的具体作业我也看明白也没有看到相关的绑定，需要进一步研究）。
启动client及server的过程中将messagehandler注入到channelpipeline中。至此启动过程完成，但是client并未连接任何server，连接过程是在节点启动后，才连接到其它节点的。
方法代码如下所示：
public void connectToNode(DiscoveryNode node, boolean light) {
//transport的模块必须要启动
if (!lifecycle.started()) {
throw new ElasticsearchIllegalStateException("can't add nodes to a stopped transport");
}
//获取读锁，每个节点可以和多个节点建立连接，因此这里用读锁
globalLock.readLock().lock();
try {
//以node.id为基础获取一个锁，这保证对于每个node只能建立一次连接
connectionLock.acquire(node.id());
try {
if (!lifecycle.started()) {
throw new ElasticsearchIllegalStateException("can't add nodes to a stopped transport");
}
NodeChannels nodeChannels = connectedNodes.get(node);
if (nodeChannels != null) {
return;
}
try {
if (light) {//这里的light，就是对该节点只获取一个channel，所有类型（5种连接类型下面会说到）都使用者一个channel
nodeChannels = connectToChannelsLight(node);
} else {
nodeChannels = new NodeChannels(new Channel[connectionsPerNodeRecovery], new Channel[connectionsPerNodeBulk], new Channel[connectionsPerNodeReg], new Channel[connectionsPerNodeState], new Channel[connectionsPerNodePing]);
try {
connectToChannels(nodeChannels, node);
} catch (Throwable e) {
logger.trace("failed to connect to [{}], cleaning dangling connections", e, node);
nodeChannels.close();
throw e;
}
}
// we acquire a connection lock, so no way there is an existing connection
connectedNodes.put(node, nodeChannels);
if (logger.isDebugEnabled()) {
logger.debug("connected to node [{}]", node);
}
transportServiceAdapter.raiseNodeConnected(node);
} catch (ConnectTransportException e) {
throw e;
} catch (Exception e) {
throw new ConnectTransportException(node, "general node connection failure", e);
}
} finally {
connectionLock.release(node.id());
}
} finally {
globalLock.readLock().unlock();
}
}如果不是轻连接，每个server和clien之间都有5中连接，着5中连接承担着不同的任务
protected void connectToChannels(NodeChannels nodeChannels, DiscoveryNode node) {
//五种连接方式，不同的连接方式对应不同的集群操作
ChannelFuture[] connectRecovery = new ChannelFuture[nodeChannels.recovery.length];
ChannelFuture[] connectBulk = new ChannelFuture[nodeChannels.bulk.length];
ChannelFuture[] connectReg = new ChannelFuture[nodeChannels.reg.length];
ChannelFuture[] connectState = new ChannelFuture[nodeChannels.state.length];
ChannelFuture[] connectPing = new ChannelFuture[nodeChannels.ping.length];
InetSocketAddress address = ((InetSocketTransportAddress) node.address()).address();
//尝试建立连接
for (int i = 0; i < connectRecovery.length; i++) {
connectRecovery[i] = clientBootstrap.connect(address);
}
for (int i = 0; i < connectBulk.length; i++) {
connectBulk[i] = clientBootstrap.connect(address);
}
for (int i = 0; i < connectReg.length; i++) {
connectReg[i] = clientBootstrap.connect(address);
}
for (int i = 0; i < connectState.length; i++) {
connectState[i] = clientBootstrap.connect(address);
}
for (int i = 0; i < connectPing.length; i++) {
connectPing[i] = clientBootstrap.connect(address);
}
//获取每个连接的channel存入到相应的channels中便于后面使用。
try {
for (int i = 0; i < connectRecovery.length; i++) {
connectRecovery[i].awaitUninterruptibly((long) (connectTimeout.millis() * 1.5));
if (!connectRecovery[i].isSuccess()) {
throw new ConnectTransportException(node, "connect_timeout[" + connectTimeout + "]", connectRecovery[i].getCause());
}
nodeChannels.recovery[i] = connectRecovery[i].getChannel();
nodeChannels.recovery[i].getCloseFuture().addListener(new ChannelCloseListener(node));
}
for (int i = 0; i < connectBulk.length; i++) {
connectBulk[i].awaitUninterruptibly((long) (connectTimeout.millis() * 1.5));
if (!connectBulk[i].isSuccess()) {
throw new ConnectTransportException(node, "connect_timeout[" + connectTimeout + "]", connectBulk[i].getCause());
}
nodeChannels.bulk[i] = connectBulk[i].getChannel();
nodeChannels.bulk[i].getCloseFuture().addListener(new ChannelCloseListener(node));
}
for (int i = 0; i < connectReg.length; i++) {
connectReg[i].awaitUninterruptibly((long) (connectTimeout.millis() * 1.5));
if (!connectReg[i].isSuccess()) {
throw new ConnectTransportException(node, "connect_timeout[" + connectTimeout + "]", connectReg[i].getCause());
}
nodeChannels.reg[i] = connectReg[i].getChannel();
nodeChannels.reg[i].getCloseFuture().addListener(new ChannelCloseListener(node));
}
for (int i = 0; i < connectState.length; i++) {
connectState[i].awaitUninterruptibly((long) (connectTimeout.millis() * 1.5));
if (!connectState[i].isSuccess()) {
throw new ConnectTransportException(node, "connect_timeout[" + connectTimeout + "]", connectState[i].getCause());
}
nodeChannels.state[i] = connectState[i].getChannel();
nodeChannels.state[i].getCloseFuture().addListener(new ChannelCloseListener(node));
}
for (int i = 0; i < connectPing.length; i++) {
connectPing[i].awaitUninterruptibly((long) (connectTimeout.millis() * 1.5));
if (!connectPing[i].isSuccess()) {
throw new ConnectTransportException(node, "connect_timeout[" + connectTimeout + "]", connectPing[i].getCause());
}
nodeChannels.ping[i] = connectPing[i].getChannel();
nodeChannels.ping[i].getCloseFuture().addListener(new ChannelCloseListener(node));
}
if (nodeChannels.recovery.length == 0) {
if (nodeChannels.bulk.length > 0) {
nodeChannels.recovery = nodeChannels.bulk;
} else {
nodeChannels.recovery = nodeChannels.reg;
}
}
if (nodeChannels.bulk.length == 0) {
nodeChannels.bulk = nodeChannels.reg;
}
} catch (RuntimeException e) {
// clean the futures
for (ChannelFuture future : ImmutableList.<ChannelFuture>builder().add(connectRecovery).add(connectBulk).add(connectReg).add(connectState).add(connectPing).build()) {
future.cancel();
if (future.getChannel() != null && future.getChannel().isOpen()) {
try {
future.getChannel().close();
} catch (Exception e1) {
// ignore
}
}
}
throw e;
}
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