RouterObserverReadProxyProvider.java
/**
* 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
* <p>
* http://www.apache.org/licenses/LICENSE-2.0
* <p>
* 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.hdfs.server.namenode.ha;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.URI;
import java.util.concurrent.TimeUnit;
import org.apache.hadoop.classification.VisibleForTesting;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hdfs.ClientGSIContext;
import org.apache.hadoop.hdfs.protocol.ClientProtocol;
import org.apache.hadoop.ipc.AlignmentContext;
import org.apache.hadoop.ipc.Client;
import org.apache.hadoop.ipc.RPC;
import org.apache.hadoop.ipc.RpcInvocationHandler;
import org.apache.hadoop.util.Time;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import static org.apache.hadoop.hdfs.server.namenode.ha.ObserverReadProxyProvider.AUTO_MSYNC_PERIOD_KEY_PREFIX;
import static org.apache.hadoop.hdfs.server.namenode.ha.ObserverReadProxyProvider.AUTO_MSYNC_PERIOD_DEFAULT;
/**
* A {@link org.apache.hadoop.io.retry.FailoverProxyProvider} implementation
* to support automatic msync-ing when using routers.
*
* This constructs a wrapper proxy around an internal one, and
* injects msync calls when necessary via the InvocationHandler.
*/
public class RouterObserverReadProxyProvider<T> extends AbstractNNFailoverProxyProvider<T> {
@VisibleForTesting
static final Logger LOG = LoggerFactory.getLogger(RouterObserverReadProxyProvider.class);
/** Client-side context for syncing with the NameNode server side. */
private final AlignmentContext alignmentContext;
/** The inner proxy provider used for active/standby failover. */
private final AbstractNNFailoverProxyProvider<T> innerProxy;
/** The proxy which redirects the internal one. */
private final ProxyInfo<T> wrapperProxy;
/**
* Whether reading from observer is enabled. If this is false, this proxy
* will not call msync.
*/
private final boolean observerReadEnabled;
/**
* This adjusts how frequently this proxy provider should auto-msync to the
* Active NameNode, automatically performing an msync() call to the active
* to fetch the current transaction ID before submitting read requests to
* observer nodes. See HDFS-14211 for more description of this feature.
* If this is below 0, never auto-msync. If this is 0, perform an msync on
* every read operation. If this is above 0, perform an msync after this many
* ms have elapsed since the last msync.
*/
private final long autoMsyncPeriodMs;
/**
* The time, in millisecond epoch, that the last msync operation was
* performed. This includes any implicit msync (any operation which is
* serviced by the Active NameNode).
*/
private volatile long lastMsyncTimeMs = -1;
public RouterObserverReadProxyProvider(Configuration conf, URI uri, Class<T> xface,
HAProxyFactory<T> factory) {
this(conf, uri, xface, factory, new IPFailoverProxyProvider<>(conf, uri, xface, factory));
}
@SuppressWarnings("unchecked")
public RouterObserverReadProxyProvider(Configuration conf, URI uri, Class<T> xface,
HAProxyFactory<T> factory, AbstractNNFailoverProxyProvider<T> failoverProxy) {
super(conf, uri, xface, factory);
this.alignmentContext = new ClientGSIContext();
factory.setAlignmentContext(alignmentContext);
this.innerProxy = failoverProxy;
String proxyInfoString = "RouterObserverReadProxyProvider for " + innerProxy.getProxy();
T wrappedProxy = (T) Proxy.newProxyInstance(
RouterObserverReadInvocationHandler.class.getClassLoader(),
new Class<?>[]{xface}, new RouterObserverReadInvocationHandler());
this.wrapperProxy = new ProxyInfo<>(wrappedProxy, proxyInfoString);
autoMsyncPeriodMs = conf.getTimeDuration(
// The host of the URI is the name service ID
AUTO_MSYNC_PERIOD_KEY_PREFIX + "." + uri.getHost(),
AUTO_MSYNC_PERIOD_DEFAULT, TimeUnit.MILLISECONDS);
if (wrappedProxy instanceof ClientProtocol) {
this.observerReadEnabled = true;
} else {
LOG.info("Disabling observer reads for {} because the requested proxy "
+ "class does not implement {}", uri, ClientProtocol.class.getName());
this.observerReadEnabled = false;
}
}
public AlignmentContext getAlignmentContext() {
return alignmentContext;
}
@Override
public ProxyInfo<T> getProxy() {
return wrapperProxy;
}
@Override
public void performFailover(T currentProxy) {
innerProxy.performFailover(currentProxy);
}
@Override
public boolean useLogicalURI() {
return innerProxy.useLogicalURI();
}
@Override
public void close() throws IOException {
innerProxy.close();
}
/**
* Return the input proxy, cast as a {@link ClientProtocol}. This catches any
* {@link ClassCastException} and wraps it in a more helpful message. This
* should ONLY be called if the caller is certain that the proxy is, in fact,
* a {@link ClientProtocol}.
*/
private ClientProtocol getProxyAsClientProtocol(T proxy) {
assert proxy instanceof ClientProtocol : "BUG: Attempted to use proxy of class "
+ proxy.getClass()
+ " as if it was a ClientProtocol.";
return (ClientProtocol) proxy;
}
/**
* This will call {@link ClientProtocol#msync()} on the active NameNode
* (via the {@link #innerProxy}) to update the state of this client, only
* if at least {@link #autoMsyncPeriodMs} ms has elapsed since the last time
* an msync was performed.
*
* @see #autoMsyncPeriodMs
*/
private void autoMsyncIfNecessary() throws IOException {
if (autoMsyncPeriodMs == 0) {
// Always msync
getProxyAsClientProtocol(innerProxy.getProxy().proxy).msync();
} else if (autoMsyncPeriodMs > 0) {
if (Time.monotonicNow() - lastMsyncTimeMs > autoMsyncPeriodMs) {
synchronized (this) {
// Use a synchronized block so that only one thread will msync
// if many operations are submitted around the same time.
// Re-check the entry criterion since the status may have changed
// while waiting for the lock.
if (Time.monotonicNow() - lastMsyncTimeMs > autoMsyncPeriodMs) {
getProxyAsClientProtocol(innerProxy.getProxy().proxy).msync();
lastMsyncTimeMs = Time.monotonicNow();
}
}
}
}
}
/**
* Check if a method is read-only.
*
* @return whether the 'method' is a read-only operation.
*/
private static boolean isRead(Method method) {
if (!method.isAnnotationPresent(ReadOnly.class)) {
return false;
}
return !method.getAnnotationsByType(ReadOnly.class)[0].activeOnly();
}
private class RouterObserverReadInvocationHandler implements RpcInvocationHandler {
@Override
public Client.ConnectionId getConnectionId() {
return RPC.getConnectionIdForProxy(innerProxy.getProxy().proxy);
}
@Override
public void close() throws IOException {
innerProxy.close();
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (observerReadEnabled && isRead(method)) {
autoMsyncIfNecessary();
}
try {
return method.invoke(innerProxy.getProxy().proxy, args);
} catch (InvocationTargetException e) {
// This exception will be handled by higher layers
throw e.getCause();
}
}
}
}