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/*-
* ============LICENSE_START=======================================================
* ONAP Policy Models
* ================================================================================
* Copyright (C) 2019, 2021 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=========================================================
*/
package org.onap.policy.models.sim.dmaap.provider;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import org.onap.policy.common.utils.coder.Coder;
import org.onap.policy.common.utils.coder.CoderException;
import org.onap.policy.common.utils.coder.StandardCoder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Data associated with a topic.
*
* <p/>
* Note: for ease of implementation, this adds a topic when a consumer polls it rather
* than when a publisher writes to it. This is the opposite of how the real DMaaP works.
* As a result, this will never return a topic-not-found message to the consumer.
*/
public class TopicData {
private static final Logger logger = LoggerFactory.getLogger(TopicData.class);
/**
* Name of the topic with which this data is associated.
*/
private final String topicName;
/**
* Maps a consumer group name to its associated data.
*/
private final Map<String, ConsumerGroupData> group2data = new ConcurrentHashMap<>();
/**
* Constructs the object.
*
* @param topicName name of the topic with which this object is associated
*/
public TopicData(String topicName) {
logger.info("Topic {}: added", topicName);
this.topicName = topicName;
}
/**
* Removes idle consumers from the topic. This is typically called once during each
* sweep cycle.
*/
public void removeIdleConsumers() {
Iterator<Entry<String, ConsumerGroupData>> iter = group2data.entrySet().iterator();
while (iter.hasNext()) {
Entry<String, ConsumerGroupData> ent = iter.next();
if (ent.getValue().shouldRemove()) {
/*
* We want the minimum amount of time to elapse between invoking
* shouldRemove() and iter.remove(), thus all other statements (e.g.,
* logging) should be done AFTER iter.remove().
*/
iter.remove();
logger.info("Topic {}: removed consumer group: {}", topicName, ent.getKey());
}
}
}
/**
* Reads from a particular consumer group's queue.
*
* @param consumerGroup name of the consumer group from which to read
* @param maxRead maximum number of messages to read
* @param waitMs time to wait, in milliseconds, if the queue is currently empty
* @return a list of messages read from the queue, empty if no messages became
* available before the wait time elapsed
* @throws InterruptedException if this thread was interrupted while waiting for the
* first message
*/
public List<String> read(String consumerGroup, int maxRead, long waitMs) throws InterruptedException {
/*
* It's possible that this thread may spin several times while waiting for
* removeIdleConsumers() to complete its call to iter.remove(), thus we create
* this closure once, rather than each time through the loop.
*/
Function<String, ConsumerGroupData> maker = this::makeData;
// loop until we get a readable list
List<String> result;
// @formatter:off
do {
result = group2data.computeIfAbsent(consumerGroup, maker).read(maxRead, waitMs);
} while (result == ConsumerGroupData.UNREADABLE_LIST);
// @formatter:on
return result;
}
/**
* Writes messages to the queues of every consumer group.
*
* @param messages messages to be written to the queues
* @return the number of messages enqueued
*/
public int write(List<Object> messages) {
List<String> list = convertMessagesToStrings(messages);
/*
* We don't care if a consumer group is deleted from the map while we're adding
* messages to it, as those messages will simply be ignored (and discarded by the
* garbage collector).
*/
for (ConsumerGroupData data : group2data.values()) {
data.write(list);
}
return list.size();
}
/**
* Converts a list of message objects to a list of message strings. If a message
* cannot be converted for some reason, then it is not added to the result list, thus
* the result list may be shorted than the original input list.
*
* @param messages objects to be converted
* @return a list of message strings
*/
protected List<String> convertMessagesToStrings(List<Object> messages) {
Coder coder = new StandardCoder();
List<String> list = new ArrayList<>(messages.size());
for (Object msg : messages) {
var str = convertMessageToString(msg, coder);
if (str != null) {
list.add(str);
}
}
return list;
}
/**
* Converts a message object to a message string.
*
* @param message message to be converted
* @param coder used to encode the message as a string
* @return the message string, or {@code null} if it cannot be converted
*/
protected String convertMessageToString(Object message, Coder coder) {
if (message == null) {
return null;
}
if (message instanceof String) {
return message.toString();
}
try {
return coder.encode(message);
} catch (CoderException e) {
logger.warn("cannot encode {}", message, e);
return null;
}
}
// this may be overridden by junit tests
/**
* Makes data for a consumer group.
*
* @param consumerGroup name of the consumer group to make
* @return new consumer group data
*/
protected ConsumerGroupData makeData(String consumerGroup) {
return new ConsumerGroupData(topicName, consumerGroup);
}
}
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