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/*******************************************************************************
* ============LICENSE_START=======================================================
* org.onap.dmaap
* ================================================================================
* Copyright © 2017 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* Licensed 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.
* ============LICENSE_END=========================================================
*
* ECOMP is a trademark and service mark of AT&T Intellectual Property.
*
*******************************************************************************/
package com.att.dmf.mr.backends.memory;
import java.util.ArrayList;
import java.util.HashMap;
import com.att.dmf.mr.backends.Consumer;
import com.att.dmf.mr.backends.Publisher.message;
/**
* When broker type is memory, then this class is doing all the topic related
* operations
*
* @author anowarul.islam
*
*/
public class MemoryQueue {
// map from topic to list of msgs
private HashMap<String, LogBuffer> fQueue;
private HashMap<String, HashMap<String, Integer>> fOffsets;
/**
* constructor storing hashMap objects in Queue and Offsets object
*/
public MemoryQueue() {
fQueue = new HashMap<>();
fOffsets = new HashMap<>();
}
/**
* method used to create topic
*
* @param topic
*/
public synchronized void createTopic(String topic) {
LogBuffer q = fQueue.get(topic);
if (q == null) {
q = new LogBuffer(1024 * 1024);
fQueue.put(topic, q);
}
}
/**
* method used to remove topic
*
* @param topic
*/
public synchronized void removeTopic(String topic) {
LogBuffer q = fQueue.get(topic);
if (q != null) {
fQueue.remove(topic);
}
}
/**
* method to write message on topic
*
* @param topic
* @param m
*/
public synchronized void put(String topic, message m) {
LogBuffer q = fQueue.get(topic);
if (q == null) {
createTopic(topic);
q = fQueue.get(topic);
}
q.push(m.getMessage());
}
/**
* method to read consumer messages
*
* @param topic
* @param consumerName
* @return
*/
public synchronized Consumer.Message get(String topic, String consumerName) {
final LogBuffer q = fQueue.get(topic);
if (q == null) {
return null;
}
HashMap<String, Integer> offsetMap = fOffsets.get(consumerName);
if (offsetMap == null) {
offsetMap = new HashMap<>();
fOffsets.put(consumerName, offsetMap);
}
Integer offset = offsetMap.get(topic);
if (offset == null) {
offset = 0;
}
final msgInfo result = q.read(offset);
if (result != null && result.msg != null) {
offsetMap.put(topic, result.offset + 1);
}
return result;
}
/**
* static inner class used to details about consumed messages
*
* @author anowarul.islam
*
*/
private static class msgInfo implements Consumer.Message {
/**
* published message which is consumed
*/
public String msg;
/**
* offset associated with message
*/
public int offset;
/**
* get offset of messages
*/
@Override
public long getOffset() {
return offset;
}
/**
* get consumed message
*/
@Override
public String getMessage() {
return msg;
}
}
/**
*
* @author sneha.d.desai
*
* private LogBuffer class has synchronized push and read method
*/
private class LogBuffer {
private int fBaseOffset;
private final int fMaxSize;
private final ArrayList<String> fList;
/**
* constructor initializing the offset, maxsize and list
*
* @param maxSize
*/
public LogBuffer(int maxSize) {
fBaseOffset = 0;
fMaxSize = maxSize;
fList = new ArrayList<>();
}
/**
* pushing message
*
* @param msg
*/
public synchronized void push(String msg) {
fList.add(msg);
while (fList.size() > fMaxSize) {
fList.remove(0);
fBaseOffset++;
}
}
/**
* reading messages
*
* @param offset
* @return
*/
public synchronized msgInfo read(int offset) {
final int actual = Math.max(0, offset - fBaseOffset);
final msgInfo mi = new msgInfo();
mi.msg = (actual >= fList.size()) ? null : fList.get(actual);
if (mi.msg == null)
return null;
mi.offset = actual + fBaseOffset;
return mi;
}
}
}
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