parveensania commented on code in PR #37840: URL: https://github.com/apache/beam/pull/37840#discussion_r2992479411
########## runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/windmill/client/grpc/stubs/FailoverChannel.java: ########## @@ -0,0 +1,345 @@ +/* + * 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.beam.runners.dataflow.worker.windmill.client.grpc.stubs; + +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.function.LongSupplier; +import javax.annotation.Nullable; +import javax.annotation.concurrent.GuardedBy; +import org.apache.beam.sdk.annotations.Internal; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.CallCredentials; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.CallOptions; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.ClientCall; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.ConnectivityState; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.ForwardingClientCall.SimpleForwardingClientCall; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.ForwardingClientCallListener.SimpleForwardingClientCallListener; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.ManagedChannel; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.Metadata; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.MethodDescriptor; +import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.Status; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A {@link ManagedChannel} that wraps a primary and a fallback channel. + * + * <p>Routes requests to either primary or fallback channel based on two independent failover modes: + * + * <ul> + * <li><b>Connection Status Failover:</b> If the primary channel is not ready for 10+ seconds + * (e.g., during network issues), routes to fallback channel. Switches back as soon as the + * primary channel becomes READY again. + * <li><b>RPC Failover:</b> If primary channel RPC fails with transient errors ({@link + * Status.Code#UNAVAILABLE} or {@link Status.Code#UNKNOWN}), or with {@link + * Status.Code#DEADLINE_EXCEEDED} before receiving any response (indicating the connection was + * never established) and connection status is not READY, switches to fallback channel and + * waits for a 1-hour cooling period before retrying primary. + * </ul> + */ +@Internal +public final class FailoverChannel extends ManagedChannel { + private static final Logger LOG = LoggerFactory.getLogger(FailoverChannel.class); + // Time to wait before retrying the primary channel after an RPC-based fallback. + private static final long FALLBACK_COOLING_PERIOD_NANOS = TimeUnit.HOURS.toNanos(1); + private static final long PRIMARY_NOT_READY_WAIT_NANOS = TimeUnit.SECONDS.toNanos(10); + + private final ManagedChannel primary; + private final ManagedChannel fallback; + @Nullable private final CallCredentials fallbackCallCredentials; + private final LongSupplier nanoClock; + // Held only during registration to prevent duplicate listener registration. + private final AtomicBoolean stateChangeListenerRegistered = new AtomicBoolean(false); + // All mutable routing state is consolidated here to ensure related fields are updated atomically. + private final FailoverState state = new FailoverState(); + + private static final class FailoverState { + // Set when primary's connection state has been unavailable for too long. + @GuardedBy("this") + boolean useFallbackDueToState; + // Set when an RPC on primary fails with an error. + @GuardedBy("this") + boolean useFallbackDueToRPC; + // Timestamp when RPC-based fallback was triggered. Only meaningful when useFallbackDueToRPC + // is true. + @GuardedBy("this") + long lastRPCFallbackTimeNanos; + // Time when primary first became not-ready. -1 when primary is currently READY. + @GuardedBy("this") + long primaryNotReadySinceNanos = -1; + } + + private FailoverChannel( + ManagedChannel primary, + ManagedChannel fallback, + @Nullable CallCredentials fallbackCallCredentials, + LongSupplier nanoClock) { + this.primary = primary; + this.fallback = fallback; + this.fallbackCallCredentials = fallbackCallCredentials; + this.nanoClock = nanoClock; + // Register callback to monitor primary channel state changes + registerPrimaryStateChangeListener(); + } + + public static FailoverChannel create( + ManagedChannel primary, ManagedChannel fallback, CallCredentials fallbackCallCredentials) { + return new FailoverChannel(primary, fallback, fallbackCallCredentials, System::nanoTime); + } + + static FailoverChannel forTest( + ManagedChannel primary, + ManagedChannel fallback, + CallCredentials fallbackCallCredentials, + LongSupplier nanoClock) { + return new FailoverChannel(primary, fallback, fallbackCallCredentials, nanoClock); + } + + @Override + public String authority() { + return primary.authority(); + } + + @Override + public <ReqT, RespT> ClientCall<ReqT, RespT> newCall( + MethodDescriptor<ReqT, RespT> methodDescriptor, CallOptions callOptions) { + // Read connectivity state before acquiring the lock to avoid calling an external API while + // holding our lock. + ConnectivityState primaryState = primary.getState(false); + final boolean useFallback; + synchronized (state) { + // Step 1: If we switched to fallback due to a failed RPC, check whether enough time has + // elapsed to retry primary. If so, clear the flag — the next step will then re-evaluate + // whether primary is actually healthy before committing to routing there. + if (state.useFallbackDueToRPC) { + long timeSinceLastFallback = nanoClock.getAsLong() - state.lastRPCFallbackTimeNanos; Review Comment: Done -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
