| /* |
| * 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; |
| |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.ConcurrentSkipListMap; |
| import org.apache.beam.sdk.metrics.MetricsContainer; |
| import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.FluentIterable; |
| |
| /** |
| * Manages the instances of {@link MetricsContainer} that have been created for a specific context. |
| * |
| * <p>This class is thread-safe. In Batch mode it there is a single thread creating containers and a |
| * separate thread calling {@link #getContainers()} to report tentative results. In Streaming all |
| * execution threads use the same registry. Thus it supports concurrent retrieval and creation of |
| * containers, as well as the ability to iterate over the containers. |
| */ |
| public abstract class MetricsContainerRegistry<T extends MetricsContainer> { |
| |
| private final ConcurrentMap<String, T> containers = new ConcurrentSkipListMap<>(); |
| |
| /** Retrieve (creating if necessary) the {@link MetricsContainer} to use with the given step. */ |
| public T getContainer(String stepName) { |
| return containers.computeIfAbsent(stepName, unused -> createContainer(stepName)); |
| } |
| |
| /** |
| * Returns all of the containers that have been created with this registry. It returns a weakly |
| * consistent view of the containers that have been created in this registry. That is: |
| * |
| * <ul> |
| * <li>iteration may proceed concurrently with other operations |
| * <li>iteration will never throw ConcurrentModificationException |
| * <li>iteration is guaranteed to traverse elements as they existed upon construction exactly |
| * once, and may (but are not guaranteed to) reflect any modifications subsequent to |
| * construction. |
| * </ul> |
| */ |
| public FluentIterable<T> getContainers() { |
| return FluentIterable.from(containers.values()); |
| } |
| |
| /** Create the container for a given step. */ |
| protected abstract T createContainer(String stepName); |
| } |