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Add channel pool for remote execution to overcome gRPC connections li…
…mitation. This PR add a `ReferenceCountedChannelPool` which will create `poolSize` number of channels and round-robin across them for gRPC requests. The `poolSize` is calculated as `jobs / 100`. Fixes #11801. Closes #11937. PiperOrigin-RevId: 326619592
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,124 @@ | ||
| // Copyright 2020 The Bazel Authors. All rights reserved. | ||
| // | ||
| // Licensed 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 com.google.devtools.build.lib.remote; | ||
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| import com.google.common.collect.ImmutableList; | ||
| import io.grpc.CallOptions; | ||
| import io.grpc.ClientCall; | ||
| import io.grpc.ManagedChannel; | ||
| import io.grpc.MethodDescriptor; | ||
| import io.netty.util.AbstractReferenceCounted; | ||
| import io.netty.util.ReferenceCounted; | ||
| import java.util.concurrent.TimeUnit; | ||
| import java.util.concurrent.atomic.AtomicInteger; | ||
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| /** | ||
| * A wrapper around a {@link io.grpc.ManagedChannel} exposing a reference count and performing a | ||
| * round-robin load balance across a list of channels. When instantiated the reference count is 1. | ||
| * {@link ManagedChannel#shutdown()} will be called on the wrapped channel when the reference count | ||
| * reaches 0. | ||
| * | ||
| * <p>See {@link ReferenceCounted} for more information about reference counting. | ||
| */ | ||
| public class ReferenceCountedChannelPool extends ReferenceCountedChannel { | ||
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| private final AtomicInteger indexTicker = new AtomicInteger(); | ||
| private final ImmutableList<ManagedChannel> channels; | ||
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| public ReferenceCountedChannelPool(ImmutableList<ManagedChannel> channels) { | ||
| super( | ||
| channels.get(0), | ||
| new AbstractReferenceCounted() { | ||
| @Override | ||
| protected void deallocate() { | ||
| for (ManagedChannel channel : channels) { | ||
| channel.shutdown(); | ||
| } | ||
| } | ||
|
|
||
| @Override | ||
| public ReferenceCounted touch(Object o) { | ||
| return null; | ||
| } | ||
| }); | ||
| this.channels = channels; | ||
| } | ||
|
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||
| @Override | ||
| public boolean isShutdown() { | ||
| for (ManagedChannel channel : channels) { | ||
| if (!channel.isShutdown()) { | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
|
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||
| @Override | ||
| public boolean isTerminated() { | ||
| for (ManagedChannel channel : channels) { | ||
| if (!channel.isTerminated()) { | ||
| return false; | ||
| } | ||
| } | ||
| return true; | ||
| } | ||
|
|
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| @Override | ||
| public boolean awaitTermination(long timeout, TimeUnit timeUnit) throws InterruptedException { | ||
| long endTimeNanos = System.nanoTime() + timeUnit.toNanos(timeout); | ||
| for (ManagedChannel channel : channels) { | ||
| long awaitTimeNanos = endTimeNanos - System.nanoTime(); | ||
| if (awaitTimeNanos <= 0) { | ||
| break; | ||
| } | ||
| channel.awaitTermination(awaitTimeNanos, TimeUnit.NANOSECONDS); | ||
| } | ||
| return isTerminated(); | ||
| } | ||
|
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| @Override | ||
| public <RequestT, ResponseT> ClientCall<RequestT, ResponseT> newCall( | ||
| MethodDescriptor<RequestT, ResponseT> methodDescriptor, CallOptions callOptions) { | ||
| return getNextChannel().newCall(methodDescriptor, callOptions); | ||
| } | ||
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| @Override | ||
| public String authority() { | ||
| // Assume all channels have the same authority. | ||
| return channels.get(0).authority(); | ||
| } | ||
|
|
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| /** | ||
| * Performs a simple round robin on the list of {@link ManagedChannel}s in the {@code channels} | ||
| * list. | ||
| * | ||
| * @see <a href="https://github.com/grpc/grpc/issues/21386#issuecomment-564742173">Suggestion from | ||
| * gRPC team.</a> | ||
| * @return A {@link ManagedChannel} that can be used for a single RPC call. | ||
| */ | ||
| private ManagedChannel getNextChannel() { | ||
| return getChannel(indexTicker.getAndIncrement()); | ||
| } | ||
|
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| private ManagedChannel getChannel(int affinity) { | ||
| int index = affinity % channels.size(); | ||
| index = Math.abs(index); | ||
| // If index is the most negative int, abs(index) is still negative. | ||
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| if (index < 0) { | ||
| index = 0; | ||
| } | ||
| return channels.get(index); | ||
| } | ||
| } | ||
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Nitpick: while it's true that Math.abs can return a negative result, index cannot be the most negative int here because you first perform a modulo operation two lines above. (Or can it? Maybe consider extracting this to a static method and adding some unit tests?)