Lettuce是一个高级的Redis客户端,下面通过对其创建连接过程的源码进行走读
下面看看RedisClient是如何创建单机模式的异步连接的, 首先从RedisClient中的connectAsync看起,在该方法中并没有什么特别的地方,在对RedisURI进行非空校验后就直接调用了内部方法
public <K, V> StatefulRedisConnection<K, V> connect(RedisCodec<K, V> codec, RedisURI redisURI) {
assertNotNull(redisURI);
return connectStandalone(codec, redisURI, redisURI.getTimeout());
}
在内部方法中首先通过一个异步方式创建连接,在从ConnectionFuture中获取连接
/**
* 获取单机连接
*/
private <K, V> StatefulRedisConnection<K, V> connectStandalone(RedisCodec<K, V> codec, RedisURI redisURI, Duration timeout) {
//单机异步连接
ConnectionFuture<StatefulRedisConnection<K, V>> future = connectStandaloneAsync(codec, redisURI, timeout);
//获取连接
return getConnection(future);
}
那么异步创建连接的过程又是什么样子的呢?下面就通过其代码进行分析一下
private <K, V> ConnectionFuture<StatefulRedisConnection<K, V>> connectStandaloneAsync(RedisCodec<K, V> codec,
RedisURI redisURI, Duration timeout) {
//编解码器不能为null
assertNotNull(codec);
//检查URI是否有效
checkValidRedisURI(redisURI);
logger.debug("Trying to get a Redis connection for: " + redisURI);
//创建DefaultEndpoint
DefaultEndpoint endpoint = new DefaultEndpoint(clientOptions);
//创建connection,该connection是一个真正有效的connection其它的都是再此基础上进行增强
StatefulRedisConnectionImpl<K, V> connection = newStatefulRedisConnection(endpoint, codec, timeout);
//异步方式创建连接
ConnectionFuture<StatefulRedisConnection<K, V>> future = connectStatefulAsync(connection, endpoint, redisURI,
() -> new CommandHandler(clientOptions, clientResources, endpoint));
//注册监听器，在结束时触发
future.whenComplete((channelHandler, throwable) -> {
//如果异常不为null则表示连接创建异常，则需要关闭连接
if (throwable != null) {
connection.close();
}
});
//返回
return future;
}
在newStatefulRedisConnection中只是创建了连接对象,此时还不是一个可用连接
protected <K, V> StatefulRedisConnectionImpl<K, V> newStatefulRedisConnection(RedisChannelWriter channelWriter,
RedisCodec<K, V> codec, Duration timeout) {
return new StatefulRedisConnectionImpl<>(channelWriter, codec, timeout);
}
可以看到在创建 StatefulRedisConnectionImpl实例的时候实际上是创建了多种方式连接,异步连接,同步连接响应式连接
/**
* 初始化一个新的连接
*/
public StatefulRedisConnectionImpl(RedisChannelWriter writer, RedisCodec<K, V> codec, Duration timeout) {
super(writer, timeout);
this.codec = codec;
//创建异步步连接
this.async = newRedisAsyncCommandsImpl();
//创建同步连接
this.sync = newRedisSyncCommandsImpl();
//创建响应式连接
this.reactive = newRedisReactiveCommandsImpl();
}
其中异步连接的方法如下:
protected RedisAsyncCommandsImpl<K, V> newRedisAsyncCommandsImpl() {
//使用装饰器模式对当前实例进行增强
return new RedisAsyncCommandsImpl<>(this, codec);
}
此时创建的连接对象还不是一个可用连接,关键逻辑还是在connectionStatefulAsync中实现
private <K, V, S> ConnectionFuture<S> connectStatefulAsync(StatefulRedisConnectionImpl<K, V> connection,
DefaultEndpoint endpoint, RedisURI redisURI, Supplier<CommandHandler> commandHandlerSupplier) {
//connetion构造器，在Lettuce中对于构造器模式运用很多
ConnectionBuilder connectionBuilder;
//根据是否是SSL选择不同构造器
if (redisURI.isSsl()) {
SslConnectionBuilder sslConnectionBuilder = SslConnectionBuilder.sslConnectionBuilder();
sslConnectionBuilder.ssl(redisURI);
connectionBuilder = sslConnectionBuilder;
} else {
connectionBuilder = ConnectionBuilder.connectionBuilder();
}
//设置connection
connectionBuilder.connection(connection);
//设置客户端选项
connectionBuilder.clientOptions(clientOptions);
//设置客户端资源
connectionBuilder.clientResources(clientResources);
//设置命令处理器以及endpoint
connectionBuilder.commandHandler(commandHandlerSupplier).endpoint(endpoint);
//填充连接构造器，
connectionBuilder(getSocketAddressSupplier(redisURI), connectionBuilder, redisURI);
//设置频道类型，同时根据频道类型设置客户端NIO线程组
channelType(connectionBuilder, redisURI);
//在连接生效前是否需要ping
if (clientOptions.isPingBeforeActivateConnection()) {
if (hasPassword(redisURI)) {
connectionBuilder.enableAuthPingBeforeConnect();
} else {
connectionBuilder.enablePingBeforeConnect();
}
}
//创建异步通道
ConnectionFuture<RedisChannelHandler<K, V>> future = initializeChannelAsync(connectionBuilder);
//如果客户端选项配置了pingBeforeActivateConnection同时有密码
if (!clientOptions.isPingBeforeActivateConnection() && hasPassword(redisURI)) {
future = future.thenApplyAsync(channelHandler -> {
connection.async().auth(new String(redisURI.getPassword()));
return channelHandler;
}, clientResources.eventExecutorGroup());
}
if (LettuceStrings.isNotEmpty(redisURI.getClientName())) {
future.thenApply(channelHandler -> {
connection.setClientName(redisURI.getClientName());
return channelHandler;
});
}
if (redisURI.getDatabase() != 0) {
future = future.thenApplyAsync(channelHandler -> {
connection.async().select(redisURI.getDatabase());
return channelHandler;
}, clientResources.eventExecutorGroup());
}
return future.thenApply(channelHandler -> (S) connection);
}
在connectionBuilder方法中创建了Netty的客户端Bootstrap
protected void connectionBuilder(Supplier<SocketAddress> socketAddressSupplier, ConnectionBuilder connectionBuilder,
RedisURI redisURI) {
//创建Bootstrap netty启动器
Bootstrap redisBootstrap = new Bootstrap();
//设置channel选项
redisBootstrap.option(ChannelOption.WRITE_BUFFER_HIGH_WATER_MARK, 32 * 1024);
redisBootstrap.option(ChannelOption.WRITE_BUFFER_LOW_WATER_MARK, 8 * 1024);
redisBootstrap.option(ChannelOption.ALLOCATOR, BUF_ALLOCATOR);
//获取套接字选项
SocketOptions socketOptions = getOptions().getSocketOptions();
//设置连接超时时间
redisBootstrap.option(ChannelOption.CONNECT_TIMEOUT_MILLIS,
Math.toIntExact(socketOptions.getConnectTimeout().toMillis()));
//如果redisURI中没有socket选择参数则根据clientresouce设置
if (LettuceStrings.isEmpty(redisURI.getSocket())) {
//是否保持长连接
redisBootstrap.option(ChannelOption.SO_KEEPALIVE, socketOptions.isKeepAlive());
//是否要求TCP低延迟
redisBootstrap.option(ChannelOption.TCP_NODELAY, socketOptions.isTcpNoDelay());
}
//设置超时时间
connectionBuilder.timeout(redisURI.getTimeout());
//设置密码
connectionBuilder.password(redisURI.getPassword());
//设置bootstrap
connectionBuilder.bootstrap(redisBootstrap);
connectionBuilder.channelGroup(channels).connectionEvents(connectionEvents).timer(timer);
connectionBuilder.socketAddressSupplier(socketAddressSupplier);
}
在channelType方法中设置了EeventLoopGroup
protected void channelType(ConnectionBuilder connectionBuilder, ConnectionPoint connectionPoint) {
LettuceAssert.notNull(connectionPoint, "ConnectionPoint must not be null");
//设置客户端线程组，EventLoopGroup用来处理所有频道事件
connectionBuilder.bootstrap().group(getEventLoopGroup(connectionPoint));
if (connectionPoint.getSocket() != null) {
NativeTransports.assertAvailable();
connectionBuilder.bootstrap().channel(NativeTransports.domainSocketChannelClass());
} else {
connectionBuilder.bootstrap().channel(Transports.socketChannelClass());
}
}
/**
* 异步处理连接同时通过connectionBuilder初始化一个通道
*/
@SuppressWarnings("unchecked")
protected <K, V, T extends RedisChannelHandler<K, V>> ConnectionFuture<T> initializeChannelAsync(
ConnectionBuilder connectionBuilder) {
//获取socketAddress
SocketAddress redisAddress = connectionBuilder.socketAddress();
//如果线程池关闭则抛出异常
if (clientResources.eventExecutorGroup().isShuttingDown()) {
throw new IllegalStateException("Cannot connect, Event executor group is terminated.");
}
logger.debug("Connecting to Redis at {}", redisAddress);
//频道准备就绪future
CompletableFuture<Channel> channelReadyFuture = new CompletableFuture<>();
//获取bootstrap
Bootstrap redisBootstrap = connectionBuilder.bootstrap();
//创建redis通道初始化器
RedisChannelInitializer initializer = connectionBuilder.build();
//设置netty的处理器
redisBootstrap.handler(initializer);
//netty自定设置处理
clientResources.nettyCustomizer().afterBootstrapInitialized(redisBootstrap);
CompletableFuture<Boolean> initFuture = initializer.channelInitialized();
//连接Redis服务器，在该处才是真正和服务器创建连接
ChannelFuture connectFuture = redisBootstrap.connect(redisAddress);
//增加监听器
connectFuture.addListener(future -> {
//没有成功
if (!future.isSuccess()) {
logger.debug("Connecting to Redis at {}: {}", redisAddress, future.cause());
connectionBuilder.endpoint().initialState();
//通过准备就绪异步结果异常结束
channelReadyFuture.completeExceptionally(future.cause());
return;
}
//completableFuture特性，在future结束的时候执行
initFuture.whenComplete((success, throwable) -> {
//如果throwable不为null表示存在异常
if (throwable == null) {
logger.debug("Connecting to Redis at {}: Success", redisAddress);
//获取RedisChannelHandler
RedisChannelHandler<?, ?> connection = connectionBuilder.connection();
//注册可关闭资源，在connection关闭的时候关闭可关闭资源
connection.registerCloseables(closeableResources, connection);
//频道准备就绪
channelReadyFuture.complete(connectFuture.channel());
return;
}
logger.debug("Connecting to Redis at {}, initialization: {}", redisAddress, throwable);
connectionBuilder.endpoint().initialState();
Throwable failure;
if (throwable instanceof RedisConnectionException) {
failure = throwable;
} else if (throwable instanceof TimeoutException) {
failure = new RedisConnectionException("Could not initialize channel within "
+ connectionBuilder.getTimeout(), throwable);
} else {
failure = throwable;
}
channelReadyFuture.completeExceptionally(failure);
CompletableFuture<Boolean> response = new CompletableFuture<>();
response.completeExceptionally(failure);
});
});
//针对connectionBuilder.connection()的结果进行装饰，增加获取remoteAddress功能
return new DefaultConnectionFuture<T>(redisAddress, channelReadyFuture.thenApply(channel -> (T) connectionBuilder
.connection()));
}
public RedisChannelInitializer build() {
return new PlainChannelInitializer(pingCommandSupplier, this::buildHandlers, clientResources, timeout);
}
在buildHandlers中创建了一些处理器,这些处理器都是有序的
- 命令编码器,用户将命令编码为Redis通信协议规定的格式
- CammandHanler lettuce核心功能
- ConnectionWatchDog 用于自动重连
- ConnectionEventTriger 用于发布connection事件
protected List<ChannelHandler> buildHandlers() {
LettuceAssert.assertState(channelGroup != null, "ChannelGroup must be set");
LettuceAssert.assertState(connectionEvents != null, "ConnectionEvents must be set");
LettuceAssert.assertState(connection != null, "Connection must be set");
LettuceAssert.assertState(clientResources != null, "ClientResources must be set");
LettuceAssert.assertState(endpoint != null, "Endpoint must be set");
List<ChannelHandler> handlers = new ArrayList<>();
//设置clientOptions
connection.setOptions(clientOptions);
//添加频道监控，如果频道有效则将频道添加到频道组中，如果频道无效则从频道组中删除
handlers.add(new ChannelGroupListener(channelGroup));
//添加命令编码器
handlers.add(new CommandEncoder());
//添加commandHander
handlers.add(commandHandlerSupplier.get());
//如果设置自动重连，则设置看门狗处理器
if (clientOptions.isAutoReconnect()) {
handlers.add(createConnectionWatchdog());
}
//设置connectionEvenTrigger
handlers.add(new ConnectionEventTrigger(connectionEvents, connection, clientResources.eventBus()));
if (clientOptions.isAutoReconnect()) {
handlers.add(createConnectionWatchdog());
}
return handlers;
}
@Override
protected void initChannel(Channel channel) throws Exception {
//如果pipeline中没有配置channelActivator则需要添加channelActivator处理器
if (channel.pipeline().get("channelActivator") == null) {
channel.pipeline().addLast("channelActivator", new RedisChannelInitializerImpl() {
private AsyncCommand<?, ?, ?> pingCommand;
@Override
public CompletableFuture<Boolean> channelInitialized() {
return initializedFuture;
}
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
//如果通道断开连接
clientResources.eventBus().publish(new DisconnectedEvent(local(ctx), remote(ctx)));
//如果初始化没有完成则抛出异常
if (!initializedFuture.isDone()) {
initializedFuture.completeExceptionally(new RedisConnectionException("Connection closed prematurely"));
}
initializedFuture = new CompletableFuture<>();
pingCommand = null;
super.channelInactive(ctx);
}
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
if (evt instanceof ConnectionEvents.Activated) {
if (!initializedFuture.isDone()) {
initializedFuture.complete(true);
clientResources.eventBus().publish(new ConnectionActivatedEvent(local(ctx), remote(ctx)));
}
}
super.userEventTriggered(ctx, evt);
}
@Override
public void channelActive(final ChannelHandlerContext ctx) throws Exception {
//通过事件总线发送连接事件
clientResources.eventBus().publish(new ConnectedEvent(local(ctx), remote(ctx)));
//如果ping命令提供器不是NO_PING则发送执行ping
if (pingCommandSupplier != NO_PING) {
pingCommand = pingCommandSupplier.get();
pingBeforeActivate(pingCommand, initializedFuture, ctx, clientResources, timeout);
} else {
super.channelActive(ctx);
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
if (!initializedFuture.isDone()) {
initializedFuture.completeExceptionally(cause);
}
super.exceptionCaught(ctx, cause);
}
});
}
//将hanler提供器提供的的处理器添加到该频道的管道中
for (ChannelHandler handler : handlers.get()) {
channel.pipeline().addLast(handler);
}
//扩展点，用户可以对向pipline中添加自定义的channel
clientResources.nettyCustomizer().afterChannelInitialized(channel);
}