001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.camel.spi; 018 019 import org.apache.camel.Consumer; 020 import org.apache.camel.Endpoint; 021 022 /** 023 * Strategy for a {@link org.apache.camel.PollingConsumer} when polling an {@link org.apache.camel.Endpoint}. 024 * <p/> 025 * This pluggable strategy allows to plugin different implementations what to do, most noticeable what to 026 * do in case the polling goes wrong. This can be handled in the 027 * {@link #rollback(org.apache.camel.Consumer , org.apache.camel.Endpoint , int, Exception) rollback} method. 028 * 029 * @version 030 */ 031 public interface PollingConsumerPollStrategy { 032 033 /** 034 * Called when poll is about to begin 035 * 036 * @param consumer the consumer 037 * @param endpoint the endpoint being consumed 038 * @return <tt>true</tt> to begin polling, or <tt>false</tt> to skip polling this time. 039 */ 040 boolean begin(Consumer consumer, Endpoint endpoint); 041 042 /** 043 * Called when poll is completed successfully 044 * 045 * @param consumer the consumer 046 * @param endpoint the endpoint being consumed 047 * @param polledMessages number of messages polled, will be <tt>0</tt> if no message was polled at all. 048 */ 049 void commit(Consumer consumer, Endpoint endpoint, int polledMessages); 050 051 /** 052 * Called when poll failed 053 * 054 * @param consumer the consumer 055 * @param endpoint the endpoint being consumed 056 * @param retryCounter current retry attempt, starting from 0. 057 * @param cause the caused exception 058 * @throws Exception can be used to rethrow the caused exception. Notice that thrown an exception will 059 * terminate the scheduler and thus Camel will not trigger again. So if you want to let the scheduler 060 * to continue to run then do <b>not</b> throw any exception from this method. 061 * @return whether to retry immediately or not. Return <tt>false</tt> to ignore the problem, 062 * <tt>true</tt> to try immediately again 063 */ 064 boolean rollback(Consumer consumer, Endpoint endpoint, int retryCounter, Exception cause) throws Exception; 065 066 }