1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 package org.apache.giraph.comm.flow_control; 20 21 import org.apache.giraph.comm.netty.handler.AckSignalFlag; 22 import org.apache.giraph.comm.requests.WritableRequest; 23 24 /** 25 * Interface representing flow control policy in sending requests 26 */ 27 public interface FlowControl { 28 /** 29 * This method is called by a network client for all requests that should be 30 * handled by a *remote* task. All these requests should be controlled and/or 31 * monitored by the flow control policy. The flow control policy may choose to 32 * temporarily hold off from sending to a particular remote task and keep the 33 * request in some cache for later transfer. A flow control mechanism is free 34 * to implement this method as blocking or non-blocking. Note that, a 35 * flow-control policy should adhere to exactly-once semantic, meaning it 36 * should always send one and only one copy of each request that should be 37 * handled by a remote task. 38 * 39 * @param destTaskId id of the worker to send the request to 40 * @param request request to send 41 */ 42 void sendRequest(int destTaskId, WritableRequest request); 43 44 /** 45 * Notify the flow control policy that an open request is completed. 46 * 47 * @param taskId id of the task to which the open request is completed 48 * @param requestId id of the open request which is completed 49 * @param response the response heard from the client 50 */ 51 void messageAckReceived(int taskId, long requestId, int response); 52 53 /** 54 * Decode the acknowledgement signal from the response after an open request 55 * is completed 56 * 57 * @param response the response heard after completion of a request 58 * @return the Acknowledgement signal decoded from the response 59 */ 60 AckSignalFlag getAckSignalFlag(int response); 61 62 /** 63 * There may be requests in possession of the flow control mechanism, as the 64 * mechanism controls whether a task should send a request or not. 65 * Calling this method causes the caller to wait until all requests in 66 * possession of the flow control mechanism are sent out. 67 */ 68 void waitAllRequests(); 69 70 /** 71 * @return number of unsent requests in possession of the flow control policy 72 */ 73 int getNumberOfUnsentRequests(); 74 75 /** 76 * Calculate/Build the response to piggyback with acknowledgement 77 * 78 * @param flag indicating the status of processing of the request (whether it 79 * was a new request or it was a duplicate) 80 * @param taskId id of the task the acknowledgement is for 81 * @return the response to piggyback along with the acknowledgement message 82 */ 83 int calculateResponse(AckSignalFlag flag, int taskId); 84 85 /** 86 * Log the status of the flow control 87 */ 88 void logInfo(); 89 }