io.netty.resolver.RoundRobinInetAddressResolver Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
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/*
* Copyright 2016 The Netty Project
*
* The Netty Project licenses this file to you 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:
*
* https://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.netty.resolver;
import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.FutureListener;
import io.netty.util.concurrent.Promise;
import io.netty.util.internal.PlatformDependent;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* A {@link NameResolver} that resolves {@link InetAddress} and force Round Robin by choosing a single address
* randomly in {@link #resolve(String)} and {@link #resolve(String, Promise)}
* if multiple are returned by the {@link NameResolver}.
* Use {@link #asAddressResolver()} to create a {@link InetSocketAddress} resolver
*/
public class RoundRobinInetAddressResolver extends InetNameResolver {
private final NameResolver nameResolver;
/**
* @param executor the {@link EventExecutor} which is used to notify the listeners of the {@link Future} returned by
* {@link #resolve(String)}
* @param nameResolver the {@link NameResolver} used for name resolution
*/
public RoundRobinInetAddressResolver(EventExecutor executor, NameResolver nameResolver) {
super(executor);
this.nameResolver = nameResolver;
}
@Override
protected void doResolve(final String inetHost, final Promise promise) throws Exception {
// hijack the doResolve request, but do a doResolveAll request under the hood.
// Note that InetSocketAddress.getHostName() will never incur a reverse lookup here,
// because an unresolved address always has a host name.
nameResolver.resolveAll(inetHost).addListener(new FutureListener>() {
@Override
public void operationComplete(Future> future) throws Exception {
if (future.isSuccess()) {
List inetAddresses = future.getNow();
int numAddresses = inetAddresses.size();
if (numAddresses > 0) {
// if there are multiple addresses: we shall pick one by one
// to support the round robin distribution
promise.setSuccess(inetAddresses.get(randomIndex(numAddresses)));
} else {
promise.setFailure(new UnknownHostException(inetHost));
}
} else {
promise.setFailure(future.cause());
}
}
});
}
@Override
protected void doResolveAll(String inetHost, final Promise> promise) throws Exception {
nameResolver.resolveAll(inetHost).addListener(new FutureListener>() {
@Override
public void operationComplete(Future> future) throws Exception {
if (future.isSuccess()) {
List inetAddresses = future.getNow();
if (!inetAddresses.isEmpty()) {
// create a copy to make sure that it's modifiable random access collection
List result = new ArrayList(inetAddresses);
// rotate by different distance each time to force round robin distribution
Collections.rotate(result, randomIndex(inetAddresses.size()));
promise.setSuccess(result);
} else {
promise.setSuccess(inetAddresses);
}
} else {
promise.setFailure(future.cause());
}
}
});
}
private static int randomIndex(int numAddresses) {
return numAddresses == 1 ? 0 : PlatformDependent.threadLocalRandom().nextInt(numAddresses);
}
@Override
public void close() {
nameResolver.close();
}
}