| // Copyright 2021 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.grpc; |
| |
| import com.google.devtools.build.lib.remote.grpc.SharedConnectionFactory.SharedConnection; |
| import io.reactivex.rxjava3.core.Single; |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.concurrent.atomic.AtomicBoolean; |
| import javax.annotation.concurrent.GuardedBy; |
| |
| /** |
| * A {@link ConnectionPool} that creates new connection with given {@link ConnectionFactory} on |
| * demand and applies rate limiting w.r.t {@code maxConcurrencyPerConnection} for one underlying |
| * connection. It also uses Round-Robin algorithm to load balancing between underlying connections. |
| * |
| * <p>Connections must be closed with {@link Connection#close()} in order to be reused later. |
| */ |
| public class DynamicConnectionPool implements ConnectionPool { |
| private final ConnectionFactory connectionFactory; |
| private final int maxConcurrencyPerConnection; |
| private final int maxConnections; |
| private final AtomicBoolean closed = new AtomicBoolean(false); |
| |
| @GuardedBy("this") |
| private final ArrayList<SharedConnectionFactory> factories; |
| |
| @GuardedBy("this") |
| private int indexTicker = 0; |
| |
| public DynamicConnectionPool( |
| ConnectionFactory connectionFactory, int maxConcurrencyPerConnection) { |
| this(connectionFactory, maxConcurrencyPerConnection, /*maxConnections=*/ 0); |
| } |
| |
| public DynamicConnectionPool( |
| ConnectionFactory connectionFactory, int maxConcurrencyPerConnection, int maxConnections) { |
| this.connectionFactory = connectionFactory; |
| this.maxConcurrencyPerConnection = maxConcurrencyPerConnection; |
| this.maxConnections = maxConnections; |
| this.factories = new ArrayList<>(); |
| } |
| |
| public boolean isClosed() { |
| return closed.get(); |
| } |
| |
| @Override |
| public void close() throws IOException { |
| if (closed.compareAndSet(false, true)) { |
| synchronized (this) { |
| for (SharedConnectionFactory factory : factories) { |
| factory.close(); |
| } |
| factories.clear(); |
| } |
| } |
| } |
| |
| @GuardedBy("this") |
| private SharedConnectionFactory nextFactory() { |
| int index = Math.abs(indexTicker % factories.size()); |
| indexTicker += 1; |
| return factories.get(index); |
| } |
| |
| /** |
| * Performs a simple round robin on the list of {@link SharedConnectionFactory}. |
| * |
| * <p>This will try to find a factory that has available connections at this moment. If no factory |
| * has available connections, and the number of factories is less than {@link #maxConnections}, it |
| * will create a new {@link SharedConnectionFactory}. |
| */ |
| private SharedConnectionFactory nextAvailableFactory() { |
| if (closed.get()) { |
| throw new IllegalStateException("closed"); |
| } |
| |
| synchronized (this) { |
| for (int times = 0; times < factories.size(); ++times) { |
| SharedConnectionFactory factory = nextFactory(); |
| if (factory.numAvailableConnections() > 0) { |
| return factory; |
| } |
| } |
| |
| if (maxConnections <= 0 || factories.size() < maxConnections) { |
| SharedConnectionFactory factory = |
| new SharedConnectionFactory(connectionFactory, maxConcurrencyPerConnection); |
| factories.add(factory); |
| return factory; |
| } else { |
| return nextFactory(); |
| } |
| } |
| } |
| |
| @Override |
| public Single<SharedConnection> create() { |
| return Single.defer( |
| () -> { |
| SharedConnectionFactory factory = nextAvailableFactory(); |
| return factory.create(); |
| }); |
| } |
| } |