当目前没有新消息产生时，判断是否暂停等待，有暂停的标志和broker允许等待，判断长轮训是否可用
private boolean longPollingEnable = true;
private long shortPollingTimeMills = 1000;
case ResponseCode.PULL_NOT_FOUND:
if (brokerAllowSuspend && hasSuspendFlag) {
long pollingTimeMills = suspendTimeoutMillisLong;
if (!this.brokerController.getBrokerConfig().isLongPollingEnable()) {
pollingTimeMills = this.brokerController.getBrokerConfig().getShortPollingTimeMills();
}
String topic = requestHeader.getTopic();
long offset = requestHeader.getQueueOffset();
int queueId = requestHeader.getQueueId();
PullRequest pullRequest = new PullRequest(request, channel, pollingTimeMills,
this.brokerController.getMessageStore().now(), offset, subscriptionData, messageFilter);
this.brokerController.getPullRequestHoldService().suspendPullRequest(topic, queueId, pullRequest);
response = null;
break;
}构造拉取请求，放入请求持有线程中等待重新拉取，把response设为空，这样就不会回应请求者
public void suspendPullRequest(final String topic, final int queueId, final PullRequest pullRequest) {
String key = this.buildKey(topic, queueId);
ManyPullRequest mpr = this.pullRequestTable.get(key);
if (null == mpr) {
mpr = new ManyPullRequest();
ManyPullRequest prev = this.pullRequestTable.putIfAbsent(key, mpr);
if (prev != null) {
mpr = prev;
}
}
mpr.addPullRequest(pullRequest);
}拉取请求线程在broker启动后就开始执行，长轮训等待5s
public void run() {
log.info("{} service started", this.getServiceName());
while (!this.isStopped()) {
try {
if (this.brokerController.getBrokerConfig().isLongPollingEnable()) {
this.waitForRunning(5 * 1000);
} else {
this.waitForRunning(this.brokerController.getBrokerConfig().getShortPollingTimeMills());
}
long beginLockTimestamp = this.systemClock.now();
this.checkHoldRequest();
long costTime = this.systemClock.now() - beginLockTimestamp;
if (costTime > 5 * 1000) {
log.info("[NOTIFYME] check hold request cost {} ms.", costTime);
}
} catch (Throwable e) {
log.warn(this.getServiceName() + " service has exception. ", e);
}
}
log.info("{} service end", this.getServiceName());
}查找topic和队列的最大下标
private void checkHoldRequest() {
for (String key : this.pullRequestTable.keySet()) {
String[] kArray = key.split(TOPIC_QUEUEID_SEPARATOR);
if (2 == kArray.length) {
String topic = kArray[0];
int queueId = Integer.parseInt(kArray[1]);
final long offset = this.brokerController.getMessageStore().getMaxOffsetInQueue(topic, queueId);
try {
this.notifyMessageArriving(topic, queueId, offset);
} catch (Throwable e) {
log.error("check hold request failed. topic={}, queueId={}", topic, queueId, e);
}
}
}
}通知消息到达，到下标大于请求的下标时，先进行消息tag过滤
public void notifyMessageArriving(final String topic, final int queueId, final long maxOffset) {
notifyMessageArriving(topic, queueId, maxOffset, null, 0, null, null);
}
public void notifyMessageArriving(final String topic, final int queueId, final long maxOffset, final Long tagsCode,
long msgStoreTime, byte[] filterBitMap, Map<String, String> properties) {
String key = this.buildKey(topic, queueId);
ManyPullRequest mpr = this.pullRequestTable.get(key);
if (mpr != null) {
List<PullRequest> requestList = mpr.cloneListAndClear();
if (requestList != null) {
List<PullRequest> replayList = new ArrayList<PullRequest>();
for (PullRequest request : requestList) {
long newestOffset = maxOffset;
if (newestOffset <= request.getPullFromThisOffset()) {
newestOffset = this.brokerController.getMessageStore().getMaxOffsetInQueue(topic, queueId);
}
if (newestOffset > request.getPullFromThisOffset()) {
boolean match = request.getMessageFilter().isMatchedByConsumeQueue(tagsCode,
new ConsumeQueueExt.CqExtUnit(tagsCode, msgStoreTime, filterBitMap));
// match by bit map, need eval again when properties is not null.
if (match && properties != null) {
match = request.getMessageFilter().isMatchedByCommitLog(null, properties);
}
if (match) {
try {
this.brokerController.getPullMessageProcessor().executeRequestWhenWakeup(request.getClientChannel(),
request.getRequestCommand());
} catch (Throwable e) {
log.error("execute request when wakeup failed.", e);
}
continue;
}
}
if (System.currentTimeMillis() >= (request.getSuspendTimestamp() + request.getTimeoutMillis())) {
try {
this.brokerController.getPullMessageProcessor().executeRequestWhenWakeup(request.getClientChannel(),
request.getRequestCommand());
} catch (Throwable e) {
log.error("execute request when wakeup failed.", e);
}
continue;
}
replayList.add(request);
}
if (!replayList.isEmpty()) {
mpr.addPullRequest(replayList);
}
}
}
}如果校验通过的话，说明消息真的达到，重新处理一次拉取请求，这次不允许暂停，还有就是当前时间超过暂停时间所需要暂停的时间后也强制唤醒请求。
public void executeRequestWhenWakeup(final Channel channel,
final RemotingCommand request) throws RemotingCommandException {
Runnable run = new Runnable() {
@Override
public void run() {
try {
final RemotingCommand response = PullMessageProcessor.this.processRequest(channel, request, false);
if (response != null) {
response.setOpaque(request.getOpaque());
response.markResponseType();
try {
channel.writeAndFlush(response).addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
if (!future.isSuccess()) {
log.error("processRequestWrapper response to {} failed",
future.channel().remoteAddress(), future.cause());
log.error(request.toString());
log.error(response.toString());
}
}
});
} catch (Throwable e) {
log.error("processRequestWrapper process request over, but response failed", e);
log.error(request.toString());
log.error(response.toString());
}
}
} catch (RemotingCommandException e1) {
log.error("excuteRequestWhenWakeup run", e1);
}
}
};
this.brokerController.getPullMessageExecutor().submit(new RequestTask(run, channel, request));
}除了达到持有线程的定时时间可以唤醒拉取请求外，当有符合条件的消息生成时，会直接唤醒，下面是ReputMessageService线程的代码，主要是构造消息的消费队列以及索引等功能。
if (BrokerRole.SLAVE != DefaultMessageStore.this.getMessageStoreConfig().getBrokerRole()
&& DefaultMessageStore.this.brokerConfig.isLongPollingEnable()) {
DefaultMessageStore.this.messageArrivingListener.arriving(dispatchRequest.getTopic(),
dispatchRequest.getQueueId(), dispatchRequest.getConsumeQueueOffset() + 1,
dispatchRequest.getTagsCode(), dispatchRequest.getStoreTimestamp(),
dispatchRequest.getBitMap(), dispatchRequest.getPropertiesMap());
}
public void arriving(String topic, int queueId, long logicOffset, long tagsCode,
long msgStoreTime, byte[] filterBitMap, Map<String, String> properties) {
this.pullRequestHoldService.notifyMessageArriving(topic, queueId, logicOffset, tagsCode,
msgStoreTime, filterBitMap, properties);
}只有消费端直接的请求，有提交下标标志的，并且是主broker可以存储消费偏移量
boolean storeOffsetEnable = brokerAllowSuspend;
storeOffsetEnable = storeOffsetEnable && hasCommitOffsetFlag;
storeOffsetEnable = storeOffsetEnable
&& this.brokerController.getMessageStoreConfig().getBrokerRole() != BrokerRole.SLAVE;
if (storeOffsetEnable) {
this.brokerController.getConsumerOffsetManager().commitOffset(RemotingHelper.parseChannelRemoteAddr(channel),
requestHeader.getConsumerGroup(), requestHeader.getTopic(), requestHeader.getQueueId(), requestHeader.getCommitOffset());
}
public void commitOffset(final String clientHost, final String group, final String topic, final int queueId,
final long offset) {
// topic@group
String key = topic + TOPIC_GROUP_SEPARATOR + group;
this.commitOffset(clientHost, key, queueId, offset);
}
private void commitOffset(final String clientHost, final String key, final int queueId, final long offset) {
ConcurrentMap<Integer, Long> map = this.offsetTable.get(key);
if (null == map) {
map = new ConcurrentHashMap<Integer, Long>(32);
map.put(queueId, offset);
this.offsetTable.put(key, map);
} else {
Long storeOffset = map.put(queueId, offset);
if (storeOffset != null && offset < storeOffset) {
log.warn("[NOTIFYME]update consumer offset less than store. clientHost={}, key={}, queueId={}, requestOffset={}, storeOffset={}", clientHost, key, queueId, offset, storeOffset);
}
}
}
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