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ClientConnectionToChannelBridge.java
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ClientConnectionToChannelBridge.java
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/*
* Copyright 2016 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package io.reactivex.netty.client;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelPipeline;
import io.netty.util.AttributeKey;
import io.reactivex.netty.channel.AbstractConnectionToChannelBridge;
import io.reactivex.netty.channel.ChannelSubscriberEvent;
import io.reactivex.netty.channel.Connection;
import io.reactivex.netty.channel.ConnectionInputSubscriberResetEvent;
import io.reactivex.netty.channel.EmitConnectionEvent;
import io.reactivex.netty.client.events.ClientEventListener;
import io.reactivex.netty.client.pool.PooledConnection;
import io.reactivex.netty.events.EventAttributeKeys;
import io.reactivex.netty.events.EventPublisher;
import io.reactivex.netty.internal.ExecuteInEventloopAction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import rx.Subscriber;
import rx.functions.Action1;
import rx.functions.Actions;
import rx.observers.SafeSubscriber;
import rx.subscriptions.Subscriptions;
/**
* An implementation of {@link AbstractConnectionToChannelBridge} for clients.
*
* <h2>Reuse</h2>
*
* A channel can be reused for multiple operations, provided the reuses is signalled by {@link ConnectionReuseEvent}.
* Failure to do so, will result in errors on the {@link Subscriber} trying to reuse the channel.
* A typical reuse should have the following events:
*
<PRE>
ChannelSubscriberEvent => ConnectionInputSubscriberEvent => ConnectionReuseEvent =>
ConnectionInputSubscriberEvent => ConnectionReuseEvent => ConnectionInputSubscriberEvent
</PRE>
*
* @param <R> Type read from the connection held by this handler.
* @param <W> Type written to the connection held by this handler.
*/
public class ClientConnectionToChannelBridge<R, W> extends AbstractConnectionToChannelBridge<R, W> {
public static final AttributeKey<Boolean> DISCARD_CONNECTION = AttributeKey.valueOf("rxnetty_discard_connection");
private static final Logger logger = LoggerFactory.getLogger(ClientConnectionToChannelBridge.class);
private static final String HANDLER_NAME = "client-conn-channel-bridge";
private EventPublisher eventPublisher;
private ClientEventListener eventListener;
private final boolean isSecure;
private Channel channel;
private ClientConnectionToChannelBridge(boolean isSecure) {
super(HANDLER_NAME, EventAttributeKeys.CONNECTION_EVENT_LISTENER, EventAttributeKeys.EVENT_PUBLISHER);
this.isSecure = isSecure;
}
@Override
public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
channel = ctx.channel();
eventPublisher = channel.attr(EventAttributeKeys.EVENT_PUBLISHER).get();
eventListener = ctx.channel().attr(EventAttributeKeys.CLIENT_EVENT_LISTENER).get();
if (null == eventPublisher) {
logger.error("No Event publisher bound to the channel, closing channel.");
ctx.channel().close();
return;
}
if (eventPublisher.publishingEnabled() && null == eventListener) {
logger.error("No Event listener bound to the channel and event publishing is enabled., closing channel.");
ctx.channel().close();
return;
}
super.handlerAdded(ctx);
}
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
if (!isSecure) {/*When secure, the event is triggered post SSL handshake via the SslCodec*/
userEventTriggered(ctx, EmitConnectionEvent.INSTANCE);
}
super.channelActive(ctx);
}
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
super.userEventTriggered(ctx, evt); // Super handles ConnectionInputSubscriberResetEvent to reset the subscriber.
if (evt instanceof ConnectionReuseEvent) {
@SuppressWarnings("unchecked")
ConnectionReuseEvent<R, W> event = (ConnectionReuseEvent<R, W>) evt;
newConnectionReuseEvent(ctx.channel(), event);
}
}
@Override
protected void onNewReadSubscriber(Subscriber<? super R> subscriber) {
// Unsubscribe from the input closes the connection as there can only be one subscriber to the
// input and, if nothing is read, it means, nobody is using the connection.
// For fire-and-forget usecases, one should explicitly ignore content on the connection which
// adds a discard all subscriber that never unsubscribes. For this case, then, the close becomes
// explicit.
subscriber.add(Subscriptions.create(new ExecuteInEventloopAction(channel) {
@Override
public void run() {
if (!connectionInputSubscriberExists(channel)) {
Connection<?, ?> connection = channel.attr(Connection.CONNECTION_ATTRIBUTE_KEY).get();
if (null != connection) {
connection.closeNow();
}
}
}
}));
}
private void newConnectionReuseEvent(Channel channel, final ConnectionReuseEvent<R, W> event) {
Subscriber<? super PooledConnection<R, W>> subscriber = event.getSubscriber();
if (isValidToEmit(subscriber)) {
subscriber.onNext(event.getPooledConnection());
checkEagerSubscriptionIfConfigured(channel);
} else {
// If pooled connection not sent to the subscriber, release to the pool.
event.getPooledConnection().close(false).subscribe(Actions.empty(), new Action1<Throwable>() {
@Override
public void call(Throwable throwable) {
logger.error("Error closing connection.", throwable);
}
});
}
}
public static <R, W> ClientConnectionToChannelBridge<R, W> addToPipeline(ChannelPipeline pipeline,
boolean isSecure) {
ClientConnectionToChannelBridge<R, W> toAdd = new ClientConnectionToChannelBridge<>(isSecure);
pipeline.addLast(HANDLER_NAME, toAdd);
return toAdd;
}
/**
* An event to indicate channel/{@link Connection} reuse. This event should be used for clients that pool
* connections. For every reuse of a connection (connection creation still uses {@link ChannelSubscriberEvent})
* the corresponding subscriber must be sent via this event.
*
* Every instance of this event resets the older subscriber attached to the connection and connection input. This
* means sending an {@link Subscriber#onCompleted()} to both of those subscribers. It is assumed that the actual
* {@link Subscriber} is similar to {@link SafeSubscriber} which can handle duplicate terminal events.
*
* @param <I> Type read from the connection held by the event.
* @param <O> Type written to the connection held by the event.
*/
public static final class ConnectionReuseEvent<I, O> implements ConnectionInputSubscriberResetEvent {
private final Subscriber<? super PooledConnection<I, O>> subscriber;
private final PooledConnection<I, O> pooledConnection;
public ConnectionReuseEvent(Subscriber<? super PooledConnection<I, O>> subscriber,
PooledConnection<I, O> pooledConnection) {
this.subscriber = subscriber;
this.pooledConnection = pooledConnection;
}
public Subscriber<? super PooledConnection<I, O>> getSubscriber() {
return subscriber;
}
public PooledConnection<I, O> getPooledConnection() {
return pooledConnection;
}
}
/**
* An event to indicate release of a {@link PooledConnection}.
*/
public static final class PooledConnectionReleaseEvent {
public static final PooledConnectionReleaseEvent INSTANCE = new PooledConnectionReleaseEvent();
private PooledConnectionReleaseEvent() {
}
}
}