001/*
002 * (C) Copyright 2017 Nuxeo SA (http://nuxeo.com/) and others.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 *
016 * Contributors:
017 *     bdelbosc
018 */
019package org.nuxeo.lib.stream.log;
020
021import java.io.Externalizable;
022import java.time.Duration;
023import java.util.Objects;
024
025/**
026 * An appender is used to append message into a Log. Implementations must be thread safe.
027 *
028 * @since 9.3
029 */
030public interface LogAppender<M extends Externalizable> {
031
032    /**
033     * Returns the Log's name.
034     */
035    String name();
036
037    /**
038     * Returns the number of partitions in the Log.
039     */
040    int size();
041
042    /**
043     * Append a message into a partition, returns {@link LogOffset} position of the message. This method is thread safe,
044     * a queue can be shared by multiple producers.
045     *
046     * @param partition index lower than {@link #size()}
047     */
048    LogOffset append(int partition, M message);
049
050    /**
051     * Same as {@link #append(int, Externalizable)}, the queue is chosen using a hash of {@param key}.
052     */
053    default LogOffset append(String key, M message) {
054        Objects.requireNonNull(key);
055        // Provide a basic partitioning that works because:
056        // 1. String.hashCode is known to be constant even with different JVM (this is not the case for all objects)
057        // 2. the modulo operator is not optimal when rebalancing on partitions resizing but this should not happen.
058        // and yes hashCode can be negative.
059        int queue = (key.hashCode() & 0x7fffffff) % size();
060        return append(queue, message);
061    }
062
063    /**
064     * Wait for consumer to process a message up to the offset. The message is processed if a consumer of the group
065     * commits a greater or equals offset. Return {@code true} if the message has been consumed, {@code false} in case
066     * of timeout.
067     */
068    boolean waitFor(LogOffset offset, String group, Duration timeout) throws InterruptedException;
069
070    /**
071     * Returns {@code true} if the appender has been closed by the manager.
072     */
073    boolean closed();
074}