sequence
This article mainly studies how reactor-netty's TcpClient submits tasks to eventLoop
example
TcpClient client = TcpClient.create("localhost", 8888);
LOGGER.info("client:{}",client.getClass());
Mono<? extends NettyContext> handler = client.newHandler((inbound,outbound) -> {
return outbound.sendString(Mono.just("Hello World!")).then(inbound.receive()
.asString().next().log().then());
});
LOGGER.info("handler:{}",handler.getClass()); //NOTE reactor.core.publisher.MonoCreate
handler.subscribe();
TcpClient.newHandler
reactor-netty-0.7.3.RELEASE-sources.jar!/reactor/ipc/netty/tcp/TcpClient.java
protected Mono<NettyContext> newHandler(BiFunction<? super NettyInbound, ? super NettyOutbound, ? extends Publisher<Void>> handler,
InetSocketAddress address,
boolean secure,
Consumer<? super Channel> onSetup) {
final BiFunction<? super NettyInbound, ? super NettyOutbound, ? extends Publisher<Void>>
targetHandler =
null == handler ? ChannelOperations.noopHandler() : handler;
return Mono.create(sink -> {
SocketAddress remote = address != null ? address : options.getAddress();
ChannelPool pool = null;
PoolResources poolResources = options.getPoolResources();
if (poolResources != null) {
pool = poolResources.selectOrCreate(remote, options,
doHandler(null, sink, secure, remote, null, null),
options.getLoopResources().onClient(options.preferNative()));
}
ContextHandler<SocketChannel> contextHandler =
doHandler(targetHandler, sink, secure, remote, pool, onSetup);
sink.onCancel(contextHandler);
if (pool == null) {
Bootstrap b = options.get();
b.remoteAddress(remote);
b.handler(contextHandler);
contextHandler.setFuture(b.connect());
}
else {
contextHandler.setFuture(pool.acquire());
}
});
}
Note the pool.acquire() or b.connect() here
SimpleChannelPool.acquireHealthyFromPoolOrNew
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/pool/SimpleChannelPool.java
/**
* Tries to retrieve healthy channel from the pool if any or creates a new channel otherwise.
* @param promise the promise to provide acquire result.
* @return future for acquiring a channel.
*/
private Future<Channel> acquireHealthyFromPoolOrNew(final Promise<Channel> promise) {
try {
final Channel ch = pollChannel();
if (ch == null) {
// No Channel left in the pool bootstrap a new Channel
Bootstrap bs = bootstrap.clone();
bs.attr(POOL_KEY, this);
ChannelFuture f = connectChannel(bs);
if (f.isDone()) {
notifyConnect(f, promise);
} else {
f.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
notifyConnect(future, promise);
}
});
}
return promise;
}
EventLoop loop = ch.eventLoop();
if (loop.inEventLoop()) {
doHealthCheck(ch, promise);
} else {
loop.execute(new Runnable() {
@Override
public void run() {
doHealthCheck(ch, promise);
}
});
}
} catch (Throwable cause) {
promise.tryFailure(cause);
}
return promise;
}
/**
* Bootstrap a new {@link Channel}. The default implementation uses {@link Bootstrap#connect()}, sub-classes may
* override this.
* <p>
* The {@link Bootstrap} that is passed in here is cloned via {@link Bootstrap#clone()}, so it is safe to modify.
*/
protected ChannelFuture connectChannel(Bootstrap bs) {
return bs.connect();
}
The last call of pool.acquire() is SimpleChannelPool.acquireHealthyFromPoolOrNew, which finally calls connectChannel and also calls Bootstrap.connect
Bootstrap.connect
netty-transport-4.1.20.Final-sources.jar!/io/netty/bootstrap/Bootstrap.java
/**
* Connect a {@link Channel} to the remote peer.
*/
public ChannelFuture connect() {
validate();
SocketAddress remoteAddress = this.remoteAddress;
if (remoteAddress == null) {
throw new IllegalStateException("remoteAddress not set");
}
return doResolveAndConnect(remoteAddress, config.localAddress());
}
/**
* @see #connect()
*/
private ChannelFuture doResolveAndConnect(final SocketAddress remoteAddress, final SocketAddress localAddress) {
final ChannelFuture regFuture = initAndRegister();
final Channel channel = regFuture.channel();
if (regFuture.isDone()) {
if (!regFuture.isSuccess()) {
return regFuture;
}
return doResolveAndConnect0(channel, remoteAddress, localAddress, channel.newPromise());
} else {
// Registration future is almost always fulfilled already, but just in case it's not.
final PendingRegistrationPromise promise = new PendingRegistrationPromise(channel);
regFuture.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
// Directly obtain the cause and do a null check so we only need one volatile read in case of a
// failure.
Throwable cause = future.cause();
if (cause != null) {
// Registration on the EventLoop failed so fail the ChannelPromise directly to not cause an
// IllegalStateException once we try to access the EventLoop of the Channel.
promise.setFailure(cause);
} else {
// Registration was successful, so set the correct executor to use.
// See https://github.com/netty/netty/issues/2586
promise.registered();
doResolveAndConnect0(channel, remoteAddress, localAddress, promise);
}
}
});
return promise;
}
}
Note that initAndRegister is called here and then doResolveAndConnect0 is called
initAndRegister
netty-transport-4.1.20.Final-sources.jar!/io/netty/bootstrap/AbstractBootstrap.java
final ChannelFuture initAndRegister() {
Channel channel = null;
try {
channel = channelFactory.newChannel();
init(channel);
} catch (Throwable t) {
if (channel != null) {
// channel can be null if newChannel crashed (eg SocketException("too many open files"))
channel.unsafe().closeForcibly();
// as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
return new DefaultChannelPromise(channel, GlobalEventExecutor.INSTANCE).setFailure(t);
}
// as the Channel is not registered yet we need to force the usage of the GlobalEventExecutor
return new DefaultChannelPromise(new FailedChannel(), GlobalEventExecutor.INSTANCE).setFailure(t);
}
ChannelFuture regFuture = config().group().register(channel);
if (regFuture.cause() != null) {
if (channel.isRegistered()) {
channel.close();
} else {
channel.unsafe().closeForcibly();
}
}
// If we are here and the promise is not failed, it's one of the following cases:
// 1) If we attempted registration from the event loop, the registration has been completed at this point.
// i.e. It's safe to attempt bind() or connect() now because the channel has been registered.
// 2) If we attempted registration from the other thread, the registration request has been successfully
// added to the event loop's task queue for later execution.
// i.e. It's safe to attempt bind() or connect() now:
// because bind() or connect() will be executed *after* the scheduled registration task is executed
// because register(), bind(), and connect() are all bound to the same thread.
return regFuture;
}
Here, first call channelFactory.newChannel() to create a channel, and then initialize it. SocketException("too many open files") may be thrown here. If there is an exception, directly set fail and return DefaultChannelPromise. Note that config().group() is called here. .register(channel), in reactor-netty this group is MultithreadEventLoopGroup.java
io.netty.channel.ReflectiveChannelFactory.newChannel()
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/ReflectiveChannelFactory.java
public T newChannel() {
try {
return clazz.getConstructor().newInstance();
} catch (Throwable t) {
throw new ChannelException("Unable to create Channel from class " + clazz, t);
}
}
这里new的是NioSocketChannel.class netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/socket/nio/NioSocketChannel.java
private static final SelectorProvider DEFAULT_SELECTOR_PROVIDER = SelectorProvider.provider();
private static SocketChannel newSocket(SelectorProvider provider) {
try {
/**
* Use the {@link SelectorProvider} to open {@link SocketChannel} and so remove condition in
* {@link SelectorProvider#provider()} which is called by each SocketChannel.open() otherwise.
*
* See <a href="https://github.com/netty/netty/issues/2308">#2308</a>.
*/
return provider.openSocketChannel();
} catch (IOException e) {
throw new ChannelException("Failed to open a socket.", e);
}
}
/**
* Create a new instance using the given {@link SelectorProvider}.
*/
public NioSocketChannel(SelectorProvider provider) {
this(newSocket(provider));
}
The provider here in the mac operating system is sun.nio.ch.KQueueSelectorProvider, and openSocketChannel calls the SelectorProviderImpl method
jre/lib/rt.jar!/sun/nio/ch/SelectorProviderImpl.class
public SocketChannel openSocketChannel() throws IOException {
return new SocketChannelImpl(this);
}
jre/lib/rt.jar!/sun/nio/ch/SocketChannelImpl.class
SocketChannelImpl(SelectorProvider var1) throws IOException {
super(var1);
this.fd = Net.socket(true);
this.fdVal = IOUtil.fdVal(this.fd);
this.state = 0;
}
Note that Net.socket(true) is called here to create a FileDescriptor, which may throw SocketException("too many open files")
Bootstrap.init(channel)
netty-transport-4.1.20.Final-sources.jar!/io/netty/bootstrap/Bootstrap.java
void init(Channel channel) throws Exception {
ChannelPipeline p = channel.pipeline();
p.addLast(config.handler());
final Map<ChannelOption<?>, Object> options = options0();
synchronized (options) {
setChannelOptions(channel, options, logger);
}
final Map<AttributeKey<?>, Object> attrs = attrs0();
synchronized (attrs) {
for (Entry<AttributeKey<?>, Object> e: attrs.entrySet()) {
channel.attr((AttributeKey<Object>) e.getKey()).set(e.getValue());
}
}
}
Here is mainly to set some options and properties
MultithreadEventLoopGroup.register(channel)
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/MultithreadEventLoopGroup.java
public ChannelFuture register(Channel channel) {
return next().register(channel);
}
The next return here is SingleThreadEventLoop
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/SingleThreadEventLoop.java
public ChannelFuture register(Channel channel) {
return register(new DefaultChannelPromise(channel, this));
}
public ChannelFuture register(final ChannelPromise promise) {
ObjectUtil.checkNotNull(promise, "promise");
promise.channel().unsafe().register(this, promise);
return promise;
}
The unsafe here is AbstractChannel$AbstractUnsafe
AbstractChannel$AbstractUnsafe
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/AbstractChannel.java
public final void register(EventLoop eventLoop, final ChannelPromise promise) {
if (eventLoop == null) {
throw new NullPointerException("eventLoop");
}
if (isRegistered()) {
promise.setFailure(new IllegalStateException("registered to an event loop already"));
return;
}
if (!isCompatible(eventLoop)) {
promise.setFailure(
new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
return;
}
AbstractChannel.this.eventLoop = eventLoop;
if (eventLoop.inEventLoop()) {
register0(promise);
} else {
try {
eventLoop.execute(new Runnable() {
@Override
public void run() {
register0(promise);
}
});
} catch (Throwable t) {
logger.warn(
"Force-closing a channel whose registration task was not accepted by an event loop: {}",
AbstractChannel.this, t);
closeForcibly();
closeFuture.setClosed();
safeSetFailure(promise, t);
}
}
}
Here you can see that eventLoop.execute is called, this eventLoop is NioEventLoop, and the parent class SingleThreadEventLoop.execute is called. Note that the ChannelPromise is repackaged here, and the register0 operation is called.
SingleThreadEventLoop.execute
public void execute(Runnable task) {
if (task == null) {
throw new NullPointerException("task");
}
boolean inEventLoop = inEventLoop();
if (inEventLoop) {
addTask(task);
} else {
startThread();
addTask(task);
if (isShutdown() && removeTask(task)) {
reject();
}
}
if (!addTaskWakesUp && wakesUpForTask(task)) {
wakeup(inEventLoop);
}
}
/**
* Add a task to the task queue, or throws a {@link RejectedExecutionException} if this instance was shutdown
* before.
*/
protected void addTask(Runnable task) {
if (task == null) {
throw new NullPointerException("task");
}
if (!offerTask(task)) {
reject(task);
}
}
final boolean offerTask(Runnable task) {
if (isShutdown()) {
reject();
}
return taskQueue.offer(task);
}
You can see that execute calls addTask, and addTask calls offerTask, and finally offers tasks to taskQueue
register0
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/AbstractChannel.java
private void register0(ChannelPromise promise) {
try {
// check if the channel is still open as it could be closed in the mean time when the register
// call was outside of the eventLoop
if (!promise.setUncancellable() || !ensureOpen(promise)) {
return;
}
boolean firstRegistration = neverRegistered;
doRegister();
neverRegistered = false;
registered = true;
// Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the
// user may already fire events through the pipeline in the ChannelFutureListener.
pipeline.invokeHandlerAddedIfNeeded();
safeSetSuccess(promise);
pipeline.fireChannelRegistered();
// Only fire a channelActive if the channel has never been registered. This prevents firing
// multiple channel actives if the channel is deregistered and re-registered.
if (isActive()) {
if (firstRegistration) {
pipeline.fireChannelActive();
} else if (config().isAutoRead()) {
// This channel was registered before and autoRead() is set. This means we need to begin read
// again so that we process inbound data.
//
// See https://github.com/netty/netty/issues/4805
beginRead();
}
}
} catch (Throwable t) {
// Close the channel directly to avoid FD leak.
closeForcibly();
closeFuture.setClosed();
safeSetFailure(promise, t);
}
}
TaskQueue takes out the register0 operation, mainly fireChannelRegistered and fireChannelActive, this method sets the registered field to true
netty-transport-4.1.20.Final-sources.jar!/io/netty/channel/socket/nio/NioSocketChannel.java
public boolean isActive() {
SocketChannel ch = javaChannel();
return ch.isOpen() && ch.isConnected();
}
Whether active mainly judges whether it is open, and connected
Bootstrap.doResolveAndConnect0
netty-transport-4.1.20.Final-sources.jar!/io/netty/bootstrap/Bootstrap.java
private ChannelFuture doResolveAndConnect0(final Channel channel, SocketAddress remoteAddress,
final SocketAddress localAddress, final ChannelPromise promise) {
try {
final EventLoop eventLoop = channel.eventLoop();
final AddressResolver<SocketAddress> resolver = this.resolver.getResolver(eventLoop);
if (!resolver.isSupported(remoteAddress) || resolver.isResolved(remoteAddress)) {
// Resolver has no idea about what to do with the specified remote address or it's resolved already.
doConnect(remoteAddress, localAddress, promise);
return promise;
}
final Future<SocketAddress> resolveFuture = resolver.resolve(remoteAddress);
if (resolveFuture.isDone()) {
final Throwable resolveFailureCause = resolveFuture.cause();
if (resolveFailureCause != null) {
// Failed to resolve immediately
channel.close();
promise.setFailure(resolveFailureCause);
} else {
// Succeeded to resolve immediately; cached? (or did a blocking lookup)
doConnect(resolveFuture.getNow(), localAddress, promise);
}
return promise;
}
// Wait until the name resolution is finished.
resolveFuture.addListener(new FutureListener<SocketAddress>() {
@Override
public void operationComplete(Future<SocketAddress> future) throws Exception {
if (future.cause() != null) {
channel.close();
promise.setFailure(future.cause());
} else {
doConnect(future.getNow(), localAddress, promise);
}
}
});
} catch (Throwable cause) {
promise.tryFailure(cause);
}
return promise;
}
private static void doConnect(
final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise connectPromise) {
// This method is invoked before channelRegistered() is triggered. Give user handlers a chance to set up
// the pipeline in its channelRegistered() implementation.
final Channel channel = connectPromise.channel();
channel.eventLoop().execute(new Runnable() {
@Override
public void run() {
if (localAddress == null) {
channel.connect(remoteAddress, connectPromise);
} else {
channel.connect(remoteAddress, localAddress, connectPromise);
}
connectPromise.addListener(ChannelFutureListener.CLOSE_ON_FAILURE);
}
});
}
Here, after the successful execution of initAndRegister, doResolveAndConnect0 will be triggered, and here is the real connection operation.
Main steps of Bootstrap.connect
How many connections can be performed, there are so many levels:
- Create and initialize channel: The ChannelFuture returned by newChannel and init() in the initAndRegister method of AbstractBootstrap is not failed, possibly because SocketException ("too many open files") cannot create a FileDescriptor
- Submit the task of registering the channel: register this register task with eventLoop. Here, the taskQueue queue is required to be able to accommodate, the default is Integer.MAX_VALUE, there is no problem; if it cannot accommodate, the task will be rejected, and RejectedExecutionException(
Force-closing a channel whose registration task was not accepted by an event loop) will be thrown, then the promise is set to failure, if initAndRegister is unsuccessful, the channel will be closed directly
The task register0 (promise) in taskQueue changes the state to REGISTERED, then triggers the following task to connect, and then judges whether it is open and connect, if so, the state changes to ACTIVE
- Register the operationComplete callback of this register ChannelFuture: call doResolveAndConnect0, doResolveAndConnect0 executes the connect of the channel
The state change of the channel is Created->REGISTERED->CONNECT->ACTIVE
21:53:50.934 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.resources.DefaultPoolResources - Created [id: 0x1ebe331c], now 1 active connections
21:53:50.941 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.ContextHandler - After pipeline DefaultChannelPipeline{(reactor.left.loggingHandler = io.netty.handler.logging.LoggingHandler), (SimpleChannelPool$1#0 = io.netty.channel.pool.SimpleChannelPool$1), (reactor.right.reactiveBridge = reactor.ipc.netty.channel.ChannelOperationsHandler)}
21:53:50.942 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c] REGISTERED
21:54:49.561 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c] CONNECT: localhost/127.0.0.1:8888
21:54:49.571 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] ACTIVE
Send and receive data and close the channel
After becoming active, it will trigger the Lambda expression in the newHandler to write data to the channel and send it
22:13:12.174 [main] DEBUG reactor.ipc.netty.channel.PooledClientContextHandler - Acquiring existing channel from pool: DefaultPromise@97e93f1(success: [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888]) SimpleChannelPool{activeConnections=1}
22:13:19.773 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.PooledClientContextHandler - Acquired active channel: [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888]
22:13:25.291 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.ChannelOperations - [Channel] [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] handler is being applied: com.example.demo.TcpTest$$Lambda$7/1541049864@41d1fa89
22:15:17.748 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.ChannelOperationsHandler - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] Writing object FluxMapFuseable
22:15:21.719 [reactor-tcp-nio-4] DEBUG io.netty.util.Recycler - -Dio.netty.recycler.maxCapacityPerThread: 32768
22:15:21.719 [reactor-tcp-nio-4] DEBUG io.netty.util.Recycler - -Dio.netty.recycler.maxSharedCapacityFactor: 2
22:15:21.719 [reactor-tcp-nio-4] DEBUG io.netty.util.Recycler - -Dio.netty.recycler.linkCapacity: 16
22:15:21.719 [reactor-tcp-nio-4] DEBUG io.netty.util.Recycler - -Dio.netty.recycler.ratio: 8
22:15:21.742 [reactor-tcp-nio-4] DEBUG io.netty.buffer.AbstractByteBuf - -Dio.netty.buffer.bytebuf.checkAccessible: true
22:15:21.756 [reactor-tcp-nio-4] DEBUG io.netty.util.ResourceLeakDetectorFactory - Loaded default ResourceLeakDetector: io.netty.util.ResourceLeakDetector@5c2a00d6
22:15:23.010 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] WRITE: 12B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64 21 |Hello World! |
+--------+-------------------------------------------------+----------------+
22:15:25.042 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] FLUSH
22:15:27.861 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.FluxReceive - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] Subscribing inbound receiver [pending: 0, cancelled:false, inboundDone: false]
22:15:27.864 [reactor-tcp-nio-4] INFO reactor.Mono.Next.1 - onSubscribe(MonoNext.NextSubscriber)
22:15:27.869 [reactor-tcp-nio-4] INFO reactor.Mono.Next.1 - request(unbounded)
22:15:32.557 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] READ: 12B
+-------------------------------------------------+
| 0 1 2 3 4 5 6 7 8 9 a b c d e f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64 21 |Hello World! |
+--------+-------------------------------------------------+----------------+
22:15:34.292 [reactor-tcp-nio-4] INFO reactor.Mono.Next.1 - onNext(Hello World!)
22:15:34.292 [reactor-tcp-nio-4] INFO reactor.Mono.Next.1 - onComplete()
22:15:34.293 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.ChannelOperations - [Channel] [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] User Handler requesting close connection
22:15:34.296 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] USER_EVENT: [Handler Terminated]
22:15:34.296 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.ChannelOperationsHandler - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] Disposing context reactor.ipc.netty.channel.PooledClientContextHandler@28add41a
22:15:34.296 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.channel.PooledClientContextHandler - Releasing channel: [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888]
22:15:34.297 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 - R:localhost/127.0.0.1:8888] CLOSE
22:15:35.967 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.resources.DefaultPoolResources - Released [id: 0x1ebe331c, L:/127.0.0.1:55386 ! R:localhost/127.0.0.1:8888], now 0 active connections
22:15:35.968 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 ! R:localhost/127.0.0.1:8888] READ COMPLETE
22:15:35.969 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 ! R:localhost/127.0.0.1:8888] INACTIVE
22:15:35.969 [reactor-tcp-nio-4] DEBUG reactor.ipc.netty.tcp.TcpClient - [id: 0x1ebe331c, L:/127.0.0.1:55386 ! R:localhost/127.0.0.1:8888] UNREGISTERED
Note that the state/operation transition of the channel here is ACTIVE->WRITE->FLUSH->READ->CLOSE->Released->READ COMPLETE->INACTIVE->UNREGISTERED
summary
- You can see that TcpClient.newHandler triggers the Lambda expression to establish a connection when subscribe, and the last call is Bootstrap.connect
- Bootstrap.connect calls the MultithreadEventLoopGroup.register(channel) method, which is finally converted to DefaultChannelPromise to register through AbstractChannel$AbstractUnsafe
- AbstractChannel$AbstractUnsafe calls taskQueue.offer(task) to put this register0(promise) into the taskQueue of eventLoop
taskQueue is LinkedBlockingQueue, and its size is specified by the parameter DEFAULT_MAX_PENDING_TASKS: Math.max(16,SystemPropertyUtil.getInt("io.netty.eventLoop.maxPendingTasks", Integer.MAX_VALUE)), the default is Integer.MAX_VALUE, which is equivalent to Boundless.