ivandika3 commented on code in PR #9641: URL: https://github.com/apache/ozone/pull/9641#discussion_r2715974403
########## hadoop-ozone/common/src/main/java/org/apache/hadoop/ozone/om/ha/HadoopRpcOMFollowerReadFailoverProxyProvider.java: ########## @@ -0,0 +1,414 @@ +/* + * 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.ozone.om.ha; + +import static org.apache.hadoop.ozone.om.ha.OMFailoverProxyProviderBase.getLeaderNotReadyException; +import static org.apache.hadoop.ozone.om.ha.OMFailoverProxyProviderBase.getNotLeaderException; + +import com.google.common.annotations.VisibleForTesting; +import com.google.protobuf.Message; +import com.google.protobuf.RpcController; +import com.google.protobuf.ServiceException; +import java.io.IOException; +import java.io.InterruptedIOException; +import java.lang.reflect.InvocationTargetException; +import java.lang.reflect.Method; +import java.lang.reflect.Proxy; +import java.util.List; +import org.apache.hadoop.hdds.conf.ConfigurationSource; +import org.apache.hadoop.io.retry.FailoverProxyProvider; +import org.apache.hadoop.io.retry.RetryPolicy; +import org.apache.hadoop.ipc_.Client.ConnectionId; +import org.apache.hadoop.ipc_.RPC; +import org.apache.hadoop.ipc_.RpcInvocationHandler; +import org.apache.hadoop.ipc_.RpcNoSuchProtocolException; +import org.apache.hadoop.ozone.OmUtils; +import org.apache.hadoop.ozone.om.exceptions.OMLeaderNotReadyException; +import org.apache.hadoop.ozone.om.exceptions.OMNotLeaderException; +import org.apache.hadoop.ozone.om.protocolPB.OzoneManagerProtocolPB; +import org.apache.hadoop.ozone.protocol.proto.OzoneManagerProtocolProtos.OMRequest; +import org.apache.hadoop.security.UserGroupInformation; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A {@link org.apache.hadoop.io.retry.FailoverProxyProvider} implementation + * that supports reading from follower OM(s) (i.e. non-leader OMs also includes + * OM listeners). + * <p> + * This constructs a wrapper proxy might send the read request to follower + * OM(s), if follower read is enabled. It will try to send read requests + * to the first OM node. If RPC failed, it will try to failover to the next OM node. + * It will fail back to the leader OM after it has exhausted all the OMs. + * TODO: Currently the logic does not prioritize forwarding to followers since + * it requires an extra RPC latency to check the OM role info. + * In the future, we can try to try to pick the followers before forwarding + * the request to the leader (similar to ObserverReadProxyProvider). + * <p> + * Read and write requests will still be sent to leader OM if reading from + * follower is disabled. + */ +public class HadoopRpcOMFollowerReadFailoverProxyProvider<T> implements FailoverProxyProvider<T> { + @VisibleForTesting + public static final Logger LOG = LoggerFactory.getLogger(HadoopRpcOMFollowerReadFailoverProxyProvider.class); + + private final Class<T> protocolClass; + + /** The inner proxy provider used for leader-based failover. */ + private final HadoopRpcOMFailoverProxyProvider<T> failoverProxy; + + /** The combined proxy which redirects to other proxies as necessary. */ + private final ProxyInfo<T> combinedProxy; + + /** + * Whether reading from follower is enabled. If this is false, all read + * requests will still go to OM leader. + */ + private volatile boolean followerReadEnabled; + + /** + * The current index of the underlying leader-based proxy provider's omNodesInOrder currently being used. + * Should only be accessed in synchronized methods. + */ + private int currentIndex = -1; + + /** + * The proxy currently being used to send the read request. + * Should only be accessed in synchronized methods. + */ + private OMProxyInfo<T> currentProxy; + + /** The last proxy that has been used. Only used for testing. */ + private volatile OMProxyInfo<T> lastProxy = null; + + public HadoopRpcOMFollowerReadFailoverProxyProvider( + ConfigurationSource configuration, UserGroupInformation ugi, String omServiceId, Class<T> protocol) + throws IOException { + this(omServiceId, protocol, + new HadoopRpcOMFailoverProxyProvider<>(configuration, ugi, omServiceId, protocol)); + } + + @SuppressWarnings("unchecked") + public HadoopRpcOMFollowerReadFailoverProxyProvider(String omServiceId, Class<T> protocol, + HadoopRpcOMFailoverProxyProvider<T> failoverProxy) throws IOException { + this.protocolClass = protocol; + this.failoverProxy = failoverProxy; + + // Create a wrapped proxy containing all the proxies. Since this combined + // proxy is just redirecting to other proxies, all invocations can share it. + StringBuilder combinedInfo = new StringBuilder("["); + for (int i = 0; i < failoverProxy.getOMProxies().size(); i++) { + if (i > 0) { + combinedInfo.append(','); + } + combinedInfo.append(failoverProxy.getOMProxies().get(i).proxyInfo); + } + combinedInfo.append(']'); + T wrappedProxy = (T) Proxy.newProxyInstance( + FollowerReadInvocationHandler.class.getClassLoader(), + new Class<?>[] {protocol}, new FollowerReadInvocationHandler()); + combinedProxy = new ProxyInfo<>(wrappedProxy, combinedInfo.toString()); + + if (wrappedProxy instanceof OzoneManagerProtocolPB) { + this.followerReadEnabled = true; + } else { + LOG.debug("Disabling follower reads for {} because the requested proxy " + + "class does not implement {}", omServiceId, OzoneManagerProtocolPB.class.getName()); + this.followerReadEnabled = false; + } + } + + @Override + public Class<T> getInterface() { + return protocolClass; + } + + @Override + public ProxyInfo<T> getProxy() { + return combinedProxy; + } + + @Override + public void performFailover(T currProxy) { + // Since FollowerReadInvocationHandler might user or fallback to leader-based failover logic, + // we should delegate the failover logic to the leader's failover. + failoverProxy.performFailover(currProxy); + } + + public RetryPolicy getRetryPolicy(int maxFailovers) { + // We use the OMFailoverProxyProviderBase's RetryPolicy instead of using our own retry policy + // for a few reasons + // 1. We want to ensure that the retry policy behavior remains the same when we use the leader proxy + // (when follower read is disabled or using write request) + // 2. The FollowerInvocationHandler is also written so that the thrown exception is handled by the + // OMFailoverProxyProviderbase's RetryPolicy + return failoverProxy.getRetryPolicy(maxFailovers); + } + + /** + * Parse the OM request from the request args. + * + * @return parsed OM request. + */ + private static OMRequest parseOMRequest(Object[] args) throws Throwable { + if (args == null || args.length < 2 || !(args[1] instanceof Message)) { + LOG.error("Request failed since OM request is null and cannot be parsed"); + // Throws a non-retriable exception to prevent retry and failover + // See the HddsUtils#shouldNotFailoverOnRpcException used in + // OMFailoverProxyProviderBase#shouldFailover + throw wrapInServiceException( + new RpcNoSuchProtocolException("OM request is null and cannot be parsed")); + } + final Message theRequest = (Message) args[1]; + return (OMRequest) theRequest; + } + + @VisibleForTesting + void setFollowerReadEnabled(boolean flag) { + this.followerReadEnabled = flag; + } + + @VisibleForTesting + public ProxyInfo<T> getLastProxy() { + return lastProxy; + } + + /** + * Return the currently used proxy. If there is none, first calls + * {@link #changeProxy(OMProxyInfo)} to initialize one. + */ + @VisibleForTesting + public OMProxyInfo<T> getCurrentProxy() { + return changeProxy(null); + } + + /** + * Move to the next proxy in the proxy list. If the OMProxyInfo supplied by + * the caller does not match the current proxy, the call is ignored; this is + * to handle concurrent calls (to avoid changing the proxy multiple times). + * The service state of the newly selected proxy will be updated before + * returning. + * + * @param initial The expected current proxy + * @return The new proxy that should be used. + */ + private synchronized OMProxyInfo<T> changeProxy(OMProxyInfo<T> initial) { + if (currentProxy != initial) { + // Must have been a concurrent modification; ignore the move request + return currentProxy; + } + currentIndex = (currentIndex + 1) % failoverProxy.getOmNodesInOrder().size(); + String currentOmNodeId = failoverProxy.getOmNodesInOrder().get(currentIndex); + currentProxy = (OMProxyInfo<T>) failoverProxy.createOMProxyIfNeeded(currentOmNodeId); + LOG.debug("Changed current proxy from {} to {}", + initial == null ? "none" : initial.proxyInfo, + currentProxy.proxyInfo); + return currentProxy; + } + + /** + * An InvocationHandler to handle incoming requests. This class's invoke + * method contains the primary logic for redirecting to followers. + * <p> + * If follower reads are enabled, attempt to send read operations to the + * current proxy which can be either a leader or follower. If the current + * proxy's OM node fails, adjust the current proxy and return on the next one. + * <p> + * Write requests are always forwarded to the leader. + */ + private class FollowerReadInvocationHandler implements RpcInvocationHandler { + + @Override + public Object invoke(Object proxy, final Method method, final Object[] args) + throws Throwable { + lastProxy = null; + if (method.getDeclaringClass() == Object.class) { Review Comment: Additionally, I tried to change the proxy to be pass through From ```java return method.invoke(this, args); ``` to ```java return method.invoke(proxy, args); ``` However, it seems because `org.apache.hadoop.ozone.protocol.proto.OzoneManagerProtocolProtos$OzoneManagerService$BlockingInterface` is not concrete class, it throws exception. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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