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.ecm.platform.importer.mqueues.mqueues; 020 021import java.io.Externalizable; 022import java.time.Duration; 023import java.util.Collection; 024 025/** 026 * Sequential reader for a partition or multiple partitions. 027 * 028 * A tailer is not thread safe and should not be shared by multiple threads. 029 * 030 */ 031public interface MQTailer<M extends Externalizable> extends AutoCloseable { 032 033 /** 034 * Returns the consumer group. 035 * 036 */ 037 String group(); 038 039 /** 040 * Returns the list of MQueue name/partition tuples currently assigned to this tailer. 041 * Assignments can change only if the tailer has been created using {@link MQManager#subscribe}. 042 */ 043 Collection<MQPartition> assignments(); 044 045 /** 046 * Read a message from assigned partitions within the timeout. 047 * 048 * @return null if there is no message in the queue after the timeout. 049 * @throws MQRebalanceException if a partition rebalancing happen during the read, 050 * this is possible only when using {@link MQManager#subscribe}. 051 */ 052 MQRecord<M> read(Duration timeout) throws InterruptedException; 053 054 /** 055 * Commit current positions for all partitions (last message offset returned by read). 056 */ 057 void commit(); 058 059 /** 060 * Commit current position for the partition. 061 * 062 * @return the committed offset, can return null if there was no previous read done on this partition. 063 */ 064 MQOffset commit(MQPartition partition); 065 066 /** 067 * Set the current positions to the end of all partitions. 068 */ 069 void toEnd(); 070 071 /** 072 * Set the current position to the fist message of all partitions. 073 */ 074 void toStart(); 075 076 /** 077 * Set the current positions to previously committed positions. 078 */ 079 void toLastCommitted(); 080 081 /** 082 * Returns {@code true} if the tailer has been closed. 083 */ 084 boolean closed(); 085}