/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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
*
* 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 org.apache.hadoop.io.retry;
import com.google.common.annotations.VisibleForTesting;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.io.retry.FailoverProxyProvider.ProxyInfo;
import org.apache.hadoop.io.retry.RetryPolicy.RetryAction;
import org.apache.hadoop.ipc.*;
import org.apache.hadoop.ipc.Client.ConnectionId;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Collections;
import java.util.Map;
/**
* A {@link RpcInvocationHandler} which supports client side retry .
*/
@InterfaceAudience.Private
public class RetryInvocationHandler<T> implements RpcInvocationHandler {
public static final Log LOG = LogFactory.getLog(RetryInvocationHandler.class);
private static class Counters {
/** Counter for retries. */
private int retries;
/** Counter for method invocation has been failed over. */
private int failovers;
}
private static class ProxyDescriptor<T> {
private final FailoverProxyProvider<T> fpp;
/** Count the associated proxy provider has ever been failed over. */
private long failoverCount = 0;
private ProxyInfo<T> proxyInfo;
ProxyDescriptor(FailoverProxyProvider<T> fpp) {
this.fpp = fpp;
this.proxyInfo = fpp.getProxy();
}
synchronized ProxyInfo<T> getProxyInfo() {
return proxyInfo;
}
synchronized T getProxy() {
return proxyInfo.proxy;
}
synchronized long getFailoverCount() {
return failoverCount;
}
synchronized void failover(long expectedFailoverCount, Method method) {
// Make sure that concurrent failed invocations only cause a single
// actual failover.
if (failoverCount == expectedFailoverCount) {
fpp.performFailover(proxyInfo.proxy);
failoverCount++;
} else {
LOG.warn("A failover has occurred since the start of "
+ proxyInfo.getString(method.getName()));
}
proxyInfo = fpp.getProxy();
}
boolean idempotentOrAtMostOnce(Method method) throws NoSuchMethodException {
final Method m = fpp.getInterface()
.getMethod(method.getName(), method.getParameterTypes());
return m.isAnnotationPresent(Idempotent.class)
|| m.isAnnotationPresent(AtMostOnce.class);
}
void close() throws IOException {
fpp.close();
}
}
private static class RetryInfo {
private final long delay;
private final RetryAction failover;
private final RetryAction fail;
private final Exception failException;
RetryInfo(long delay, RetryAction failover, RetryAction fail,
Exception failException) {
this.delay = delay;
this.failover = failover;
this.fail = fail;
this.failException = failException;
}
Exception getFailException() {
return failException;
}
static RetryInfo newRetryInfo(RetryPolicy policy, Exception e,
Counters counters, boolean idempotentOrAtMostOnce) throws Exception {
long maxRetryDelay = 0;
RetryAction failover = null;
RetryAction retry = null;
RetryAction fail = null;
Exception ex = null;
final Iterable<Exception> exceptions = e instanceof MultiException ?
((MultiException) e).getExceptions().values()
: Collections.singletonList(e);
for (Exception exception : exceptions) {
final RetryAction a = policy.shouldRetry(exception,
counters.retries, counters.failovers, idempotentOrAtMostOnce);
if (a.action == RetryAction.RetryDecision.FAIL) {
fail = a;
ex = exception;
} else {
// must be a retry or failover
if (a.action == RetryAction.RetryDecision.FAILOVER_AND_RETRY) {
failover = a;
} else {
retry = a;
}
if (a.delayMillis > maxRetryDelay) {
maxRetryDelay = a.delayMillis;
}
}
}
return new RetryInfo(maxRetryDelay, failover,
failover == null && retry == null? fail: null, ex);
}
}
private final ProxyDescriptor<T> proxyDescriptor;
private volatile boolean hasMadeASuccessfulCall = false;
private final RetryPolicy defaultPolicy;
private final Map<String,RetryPolicy> methodNameToPolicyMap;
protected RetryInvocationHandler(FailoverProxyProvider<T> proxyProvider,
RetryPolicy retryPolicy) {
this(proxyProvider, retryPolicy, Collections.<String, RetryPolicy>emptyMap());
}
protected RetryInvocationHandler(FailoverProxyProvider<T> proxyProvider,
RetryPolicy defaultPolicy,
Map<String, RetryPolicy> methodNameToPolicyMap) {
this.proxyDescriptor = new ProxyDescriptor<>(proxyProvider);
this.defaultPolicy = defaultPolicy;
this.methodNameToPolicyMap = methodNameToPolicyMap;
}
private RetryPolicy getRetryPolicy(Method method) {
final RetryPolicy policy = methodNameToPolicyMap.get(method.getName());
return policy != null? policy: defaultPolicy;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
final boolean isRpc = isRpcInvocation(proxyDescriptor.getProxy());
final int callId = isRpc? Client.nextCallId(): RpcConstants.INVALID_CALL_ID;
return invoke(method, args, isRpc, callId, new Counters());
}
private Object invoke(final Method method, final Object[] args,
final boolean isRpc, final int callId, final Counters counters)
throws Throwable {
final RetryPolicy policy = getRetryPolicy(method);
while (true) {
// The number of times this invocation handler has ever been failed over,
// before this method invocation attempt. Used to prevent concurrent
// failed method invocations from triggering multiple failover attempts.
final long failoverCount = proxyDescriptor.getFailoverCount();
if (isRpc) {
Client.setCallIdAndRetryCount(callId, counters.retries);
}
try {
final Object ret = invokeMethod(method, args);
hasMadeASuccessfulCall = true;
return ret;
} catch (Exception ex) {
if (Thread.currentThread().isInterrupted()) {
// If interrupted, do not retry.
throw ex;
}
handleException(method, policy, failoverCount, counters, ex);
}
}
}
private void handleException(final Method method, final RetryPolicy policy,
final long expectedFailoverCount, final Counters counters,
final Exception ex) throws Exception {
final RetryInfo retryInfo = RetryInfo.newRetryInfo(policy, ex, counters,
proxyDescriptor.idempotentOrAtMostOnce(method));
counters.retries++;
if (retryInfo.fail != null) {
// fail.
if (retryInfo.fail.reason != null) {
if (LOG.isDebugEnabled()) {
LOG.debug("Exception while invoking "
+ proxyDescriptor.getProxyInfo().getString(method.getName())
+ ". Not retrying because " + retryInfo.fail.reason, ex);
}
}
throw retryInfo.getFailException();
}
// retry
final boolean isFailover = retryInfo.failover != null;
log(method, isFailover, counters.failovers, retryInfo.delay, ex);
if (retryInfo.delay > 0) {
try {
Thread.sleep(retryInfo.delay);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
if (LOG.isDebugEnabled()) {
LOG.debug("Interrupted while waiting to retry", e);
}
InterruptedIOException intIOE = new InterruptedIOException(
"Retry interrupted");
intIOE.initCause(e);
throw intIOE;
}
}
if (isFailover) {
proxyDescriptor.failover(expectedFailoverCount, method);
counters.failovers++;
}
}
private void log(final Method method, final boolean isFailover,
final int failovers, final long delay, final Exception ex) {
// log info if this has made some successful calls or
// this is not the first failover
final boolean info = hasMadeASuccessfulCall || failovers != 0;
if (!info && !LOG.isDebugEnabled()) {
return;
}
final StringBuilder b = new StringBuilder()
.append(ex + ", while invoking ")
.append(proxyDescriptor.getProxyInfo().getString(method.getName()));
if (failovers > 0) {
b.append(" after ").append(failovers).append(" failover attempts");
}
b.append(isFailover? ". Trying to failover ": ". Retrying ");
b.append(delay > 0? "after sleeping for " + delay + "ms.": "immediately.");
if (info) {
LOG.info(b.toString());
} else {
LOG.debug(b.toString(), ex);
}
}
protected Object invokeMethod(Method method, Object[] args) throws Throwable {
try {
if (!method.isAccessible()) {
method.setAccessible(true);
}
return method.invoke(proxyDescriptor.getProxy(), args);
} catch (InvocationTargetException e) {
throw e.getCause();
}
}
@VisibleForTesting
static boolean isRpcInvocation(Object proxy) {
if (proxy instanceof ProtocolTranslator) {
proxy = ((ProtocolTranslator) proxy).getUnderlyingProxyObject();
}
if (!Proxy.isProxyClass(proxy.getClass())) {
return false;
}
final InvocationHandler ih = Proxy.getInvocationHandler(proxy);
return ih instanceof RpcInvocationHandler;
}
@Override
public void close() throws IOException {
proxyDescriptor.close();
}
@Override //RpcInvocationHandler
public ConnectionId getConnectionId() {
return RPC.getConnectionIdForProxy(proxyDescriptor.getProxy());
}
}