聊聊AsyncHttpClient的exception

本文主要是介绍聊聊AsyncHttpClient的exception，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

序

本文主要研究一下AsyncHttpClient的exception

ChannelClosedException

org/asynchttpclient/exception/ChannelClosedException.java

public final class ChannelClosedException extends IOException {public static final ChannelClosedException INSTANCE = unknownStackTrace(new ChannelClosedException(), ChannelClosedException.class, "INSTANCE");private ChannelClosedException() {super("Channel closed");}
}

ChannelClosedException用于表示Channel closed的异常

handleUnexpectedClosedChannel

org/asynchttpclient/netty/request/NettyRequestSender.java

  public void handleUnexpectedClosedChannel(Channel channel, NettyResponseFuture<?> future) {if (Channels.isActiveTokenSet(channel)) {if (future.isDone()) {channelManager.closeChannel(channel);} else if (future.incrementRetryAndCheck() && retry(future)) {future.pendingException = null;} else {abort(channel, future,future.pendingException != null ? future.pendingException : RemotelyClosedException.INSTANCE);}}}

NettyRequestSender定义了handleUnexpectedClosedChannel方法，它会关闭或abort当前的channel

PoolAlreadyClosedException

org/asynchttpclient/exception/PoolAlreadyClosedException.java

public class PoolAlreadyClosedException extends IOException {public static final PoolAlreadyClosedException INSTANCE = unknownStackTrace(new PoolAlreadyClosedException(), PoolAlreadyClosedException.class, "INSTANCE");private PoolAlreadyClosedException() {super("Pool is already closed");}
}

PoolAlreadyClosedException用于表示连接池已经关闭的异常

sendRequestWithNewChannel

org/asynchttpclient/netty/request/NettyRequestSender.java

  private <T> ListenableFuture<T> sendRequestWithNewChannel(Request request,ProxyServer proxy,NettyResponseFuture<T> future,AsyncHandler<T> asyncHandler) {// some headers are only set when performing the first requestHttpHeaders headers = future.getNettyRequest().getHttpRequest().headers();Realm realm = future.getRealm();Realm proxyRealm = future.getProxyRealm();requestFactory.addAuthorizationHeader(headers, perConnectionAuthorizationHeader(request, proxy, realm));requestFactory.setProxyAuthorizationHeader(headers, perConnectionProxyAuthorizationHeader(request, proxyRealm));future.setInAuth(realm != null && realm.isUsePreemptiveAuth() && realm.getScheme() != AuthScheme.NTLM);future.setInProxyAuth(proxyRealm != null && proxyRealm.isUsePreemptiveAuth() && proxyRealm.getScheme() != AuthScheme.NTLM);try {if (!channelManager.isOpen()) {throw PoolAlreadyClosedException.INSTANCE;}// Do not throw an exception when we need an extra connection for a// redirect.future.acquirePartitionLockLazily();} catch (Throwable t) {abort(null, future, getCause(t));// exit and don't try to resolve addressreturn future;}//......
}    

sendRequestWithNewChannel在channelManager非open的时候会抛出PoolAlreadyClosedException

RemotelyClosedException

org/asynchttpclient/exception/RemotelyClosedException.java

public final class RemotelyClosedException extends IOException {public static final RemotelyClosedException INSTANCE = unknownStackTrace(new RemotelyClosedException(), RemotelyClosedException.class, "INSTANCE");RemotelyClosedException() {super("Remotely closed");}
}

RemotelyClosedException用于表示Remotely closed的异常

handleUnexpectedClosedChannel

org/asynchttpclient/netty/request/NettyRequestSender.java

  public void handleUnexpectedClosedChannel(Channel channel, NettyResponseFuture<?> future) {if (Channels.isActiveTokenSet(channel)) {if (future.isDone()) {channelManager.closeChannel(channel);} else if (future.incrementRetryAndCheck() && retry(future)) {future.pendingException = null;} else {abort(channel, future,future.pendingException != null ? future.pendingException : RemotelyClosedException.INSTANCE);}}}

NettyRequestSender的handleUnexpectedClosedChannel的时候，对于future未完成也没有重试的时候会执行abort，并抛出RemotelyClosedException

TooManyConnectionsException

org/asynchttpclient/exception/TooManyConnectionsException.java

public class TooManyConnectionsException extends IOException {public TooManyConnectionsException(int max) {super("Too many connections: " + max);}
}

TooManyConnectionsException用于表示全局连接超过限制的异常

TooManyConnectionsPerHostException

org/asynchttpclient/exception/TooManyConnectionsPerHostException.java

public class TooManyConnectionsPerHostException extends IOException {public TooManyConnectionsPerHostException(int max) {super("Too many connections: " + max);}
}

TooManyConnectionsPerHostException用于表示连接超出单host限制的异常

acquireChannelLock

org/asynchttpclient/netty/channel/ConnectionSemaphore.java

  public void acquireChannelLock(Object partitionKey) throws IOException {if (!tryAcquireGlobal())throw tooManyConnections;if (!tryAcquirePerHost(partitionKey)) {freeChannels.release();throw tooManyConnectionsPerHost;}}

acquireChannelLock方法在全局连接超出限制时抛出tooManyConnections，在单host连接超出限制时抛出tooManyConnectionsPerHost

小结

AsyncHttpClient一共定义了五个异常，它们都继承了IOException，分别是ChannelClosedException、PoolAlreadyClosedException、RemotelyClosedException、TooManyConnectionsException、TooManyConnectionsPerHostException。

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