| /* |
| * 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.sdk.transforms.splittabledofn; |
| |
| import com.google.auto.value.AutoValue; |
| import java.math.BigDecimal; |
| import javax.annotation.Nullable; |
| |
| /** |
| * A representation for the amount of known work represented as a backlog. Note that backlog {@code |
| * byte[]} representations must be lexicographically comparable. Backlog {@code byte[]} |
| * representations should preferably represent a linear space and be comparable within the same |
| * partition. |
| * |
| * <p>It is up to each restriction tracker to convert between their natural representation of |
| * outstanding work and this representation. For example: |
| * |
| * <ul> |
| * <li>Block based file source (e.g. Avro): From the end of the current block, the remaining |
| * number of bytes to the end of the restriction represented as a big endian 64 bit unsigned |
| * integer. |
| * <li>Pull based queue based source (e.g. Pubsub): The local/global backlog available in number |
| * of messages or number of {@code messages / bytes} that have not been processed represented |
| * as a big endian 64 bit unsigned integer. |
| * <li>Key range based source (e.g. Shuffle, Bigtable, ...): Scale the start key to be one and end |
| * key to be zero and interpolate the position of the next splittable key as the backlog. If |
| * information about the probability density function or cumulative distribution function is |
| * available, backlog interpolation can be improved. Alternatively, if the number of encoded |
| * bytes for the keys and values is known for the key range, the backlog of remaining bytes |
| * can be used. |
| * </ul> |
| * |
| * <p>{@link RestrictionTracker}s should implement {@link Backlogs.HasBacklog} to report a backlog |
| * where the element and restriction pair uniquely identify the resource. Otherwise {@link |
| * RestrictionTracker}s should implement {@link Backlogs.HasPartitionedBacklog} to report a backlog |
| * for a shared resource such as a message queue. |
| * |
| * <p>See <a href="https://s.apache.org/beam-bundles-backlog-splitting">Bundles w/ SplittableDoFns: |
| * Backlog & Splitting</a> for further details. |
| */ |
| @AutoValue |
| public abstract class Backlog { |
| private static final Backlog UNKNOWN_BACKLOG = new AutoValue_Backlog(null); |
| |
| /** Returns a backlog represented by the specified bytes. */ |
| public static Backlog of(BigDecimal backlog) { |
| return new AutoValue_Backlog(backlog); |
| } |
| |
| /** Returns an unknown backlog. */ |
| public static Backlog unknown() { |
| return UNKNOWN_BACKLOG; |
| } |
| |
| /** Returns whether this backlog is known or unknown. */ |
| public boolean isUnknown() { |
| return backlogInternal() == null; |
| } |
| |
| /** |
| * Returns the {@code byte[]} representation of the backlog if it is known. |
| * |
| * @throws IllegalStateException if the backlog is unknown. |
| */ |
| public BigDecimal backlog() { |
| if (isUnknown()) { |
| throw new IllegalStateException("Backlog is unknown, there is no byte[] representation."); |
| } |
| return backlogInternal(); |
| } |
| |
| @SuppressWarnings("mutable") |
| @Nullable |
| protected abstract BigDecimal backlogInternal(); |
| } |