聊聊rocketmq的suggestPullingFromSlave

序

本文主要研究一下rocketmq的suggestPullingFromSlave

suggestPullingFromSlave

rocketmq-all-4.6.0-source-release/store/src/main/java/org/apache/rocketmq/store/GetMessageResult.java

public class GetMessageResult {

    private final List<SelectMappedBufferResult> messageMapedList =
        new ArrayList<SelectMappedBufferResult>(100);

    private final List<ByteBuffer> messageBufferList = new ArrayList<ByteBuffer>(100);

    private GetMessageStatus status;
    private long nextBeginOffset;
    private long minOffset;
    private long maxOffset;

    private int bufferTotalSize = 0;

    private boolean suggestPullingFromSlave = false;

    private int msgCount4Commercial = 0;

    //......

    public boolean isSuggestPullingFromSlave() {
        return suggestPullingFromSlave;
    }

    public void setSuggestPullingFromSlave(boolean suggestPullingFromSlave) {
        this.suggestPullingFromSlave = suggestPullingFromSlave;
    }

    //......    
}

• GetMessageResult定義了suggestPullingFromSlave屬性，默認爲false

getMessage

rocketmq-all-4.6.0-source-release/store/src/main/java/org/apache/rocketmq/store/DefaultMessageStore.java

public class DefaultMessageStore implements MessageStore {

    //......

    public GetMessageResult getMessage(final String group, final String topic, final int queueId, final long offset,
        final int maxMsgNums,
        final MessageFilter messageFilter) {
        if (this.shutdown) {
            log.warn("message store has shutdown, so getMessage is forbidden");
            return null;
        }

        if (!this.runningFlags.isReadable()) {
            log.warn("message store is not readable, so getMessage is forbidden " + this.runningFlags.getFlagBits());
            return null;
        }

        long beginTime = this.getSystemClock().now();

        GetMessageStatus status = GetMessageStatus.NO_MESSAGE_IN_QUEUE;
        long nextBeginOffset = offset;
        long minOffset = 0;
        long maxOffset = 0;

        GetMessageResult getResult = new GetMessageResult();

        final long maxOffsetPy = this.commitLog.getMaxOffset();

        ConsumeQueue consumeQueue = findConsumeQueue(topic, queueId);
        if (consumeQueue != null) {
            minOffset = consumeQueue.getMinOffsetInQueue();
            maxOffset = consumeQueue.getMaxOffsetInQueue();

            if (maxOffset == 0) {
                status = GetMessageStatus.NO_MESSAGE_IN_QUEUE;
                nextBeginOffset = nextOffsetCorrection(offset, 0);
            } else if (offset < minOffset) {
                status = GetMessageStatus.OFFSET_TOO_SMALL;
                nextBeginOffset = nextOffsetCorrection(offset, minOffset);
            } else if (offset == maxOffset) {
                status = GetMessageStatus.OFFSET_OVERFLOW_ONE;
                nextBeginOffset = nextOffsetCorrection(offset, offset);
            } else if (offset > maxOffset) {
                status = GetMessageStatus.OFFSET_OVERFLOW_BADLY;
                if (0 == minOffset) {
                    nextBeginOffset = nextOffsetCorrection(offset, minOffset);
                } else {
                    nextBeginOffset = nextOffsetCorrection(offset, maxOffset);
                }
            } else {
                SelectMappedBufferResult bufferConsumeQueue = consumeQueue.getIndexBuffer(offset);
                if (bufferConsumeQueue != null) {
                    try {
                        status = GetMessageStatus.NO_MATCHED_MESSAGE;

                        long nextPhyFileStartOffset = Long.MIN_VALUE;
                        long maxPhyOffsetPulling = 0;

                        int i = 0;
                        final int maxFilterMessageCount = Math.max(16000, maxMsgNums * ConsumeQueue.CQ_STORE_UNIT_SIZE);
                        final boolean diskFallRecorded = this.messageStoreConfig.isDiskFallRecorded();
                        ConsumeQueueExt.CqExtUnit cqExtUnit = new ConsumeQueueExt.CqExtUnit();
                        for (; i < bufferConsumeQueue.getSize() && i < maxFilterMessageCount; i += ConsumeQueue.CQ_STORE_UNIT_SIZE) {
                            long offsetPy = bufferConsumeQueue.getByteBuffer().getLong();
                            int sizePy = bufferConsumeQueue.getByteBuffer().getInt();
                            long tagsCode = bufferConsumeQueue.getByteBuffer().getLong();

                            maxPhyOffsetPulling = offsetPy;

                            //......

                            this.storeStatsService.getGetMessageTransferedMsgCount().incrementAndGet();
                            getResult.addMessage(selectResult);
                            status = GetMessageStatus.FOUND;
                            nextPhyFileStartOffset = Long.MIN_VALUE;
                        }

                        //......

                        long diff = maxOffsetPy - maxPhyOffsetPulling;
                        long memory = (long) (StoreUtil.TOTAL_PHYSICAL_MEMORY_SIZE
                            * (this.messageStoreConfig.getAccessMessageInMemoryMaxRatio() / 100.0));
                        getResult.setSuggestPullingFromSlave(diff > memory);
                    } finally {

                        bufferConsumeQueue.release();
                    }
                } else {
                    status = GetMessageStatus.OFFSET_FOUND_NULL;
                    nextBeginOffset = nextOffsetCorrection(offset, consumeQueue.rollNextFile(offset));
                    log.warn("consumer request topic: " + topic + "offset: " + offset + " minOffset: " + minOffset + " maxOffset: "
                        + maxOffset + ", but access logic queue failed.");
                }
            }
        } else {
            status = GetMessageStatus.NO_MATCHED_LOGIC_QUEUE;
            nextBeginOffset = nextOffsetCorrection(offset, 0);
        }

        if (GetMessageStatus.FOUND == status) {
            this.storeStatsService.getGetMessageTimesTotalFound().incrementAndGet();
        } else {
            this.storeStatsService.getGetMessageTimesTotalMiss().incrementAndGet();
        }
        long elapsedTime = this.getSystemClock().now() - beginTime;
        this.storeStatsService.setGetMessageEntireTimeMax(elapsedTime);

        getResult.setStatus(status);
        getResult.setNextBeginOffset(nextBeginOffset);
        getResult.setMaxOffset(maxOffset);
        getResult.setMinOffset(minOffset);
        return getResult;
    }

    //......
}

• DefaultMessageStore的getMessage會計算diff(maxOffsetPy - maxPhyOffsetPulling)，而後同memory(StoreUtil.TOTAL_PHYSICAL_MEMORY_SIZE * (this.messageStoreConfig.getAccessMessageInMemoryMaxRatio() / 100.0))對比，大於則設置getResult的suggestPullingFromSlave爲true

processRequest

rocketmq-all-4.6.0-source-release/broker/src/main/java/org/apache/rocketmq/broker/processor/PullMessageProcessor.java

public class PullMessageProcessor implements NettyRequestProcessor {

    //......

    private RemotingCommand processRequest(final Channel channel, RemotingCommand request, boolean brokerAllowSuspend)
        throws RemotingCommandException {
        RemotingCommand response = RemotingCommand.createResponseCommand(PullMessageResponseHeader.class);
        final PullMessageResponseHeader responseHeader = (PullMessageResponseHeader) response.readCustomHeader();
        final PullMessageRequestHeader requestHeader =
            (PullMessageRequestHeader) request.decodeCommandCustomHeader(PullMessageRequestHeader.class);

        response.setOpaque(request.getOpaque());

        //......

        final GetMessageResult getMessageResult =
            this.brokerController.getMessageStore().getMessage(requestHeader.getConsumerGroup(), requestHeader.getTopic(),
                requestHeader.getQueueId(), requestHeader.getQueueOffset(), requestHeader.getMaxMsgNums(), messageFilter);
        if (getMessageResult != null) {
            response.setRemark(getMessageResult.getStatus().name());
            responseHeader.setNextBeginOffset(getMessageResult.getNextBeginOffset());
            responseHeader.setMinOffset(getMessageResult.getMinOffset());
            responseHeader.setMaxOffset(getMessageResult.getMaxOffset());

            if (getMessageResult.isSuggestPullingFromSlave()) {
                responseHeader.setSuggestWhichBrokerId(subscriptionGroupConfig.getWhichBrokerWhenConsumeSlowly());
            } else {
                responseHeader.setSuggestWhichBrokerId(MixAll.MASTER_ID);
            }

            switch (this.brokerController.getMessageStoreConfig().getBrokerRole()) {
                case ASYNC_MASTER:
                case SYNC_MASTER:
                    break;
                case SLAVE:
                    if (!this.brokerController.getBrokerConfig().isSlaveReadEnable()) {
                        response.setCode(ResponseCode.PULL_RETRY_IMMEDIATELY);
                        responseHeader.setSuggestWhichBrokerId(MixAll.MASTER_ID);
                    }
                    break;
            }

            if (this.brokerController.getBrokerConfig().isSlaveReadEnable()) {
                // consume too slow ,redirect to another machine
                if (getMessageResult.isSuggestPullingFromSlave()) {
                    responseHeader.setSuggestWhichBrokerId(subscriptionGroupConfig.getWhichBrokerWhenConsumeSlowly());
                }
                // consume ok
                else {
                    responseHeader.setSuggestWhichBrokerId(subscriptionGroupConfig.getBrokerId());
                }
            } else {
                responseHeader.setSuggestWhichBrokerId(MixAll.MASTER_ID);
            }

            //......

        } else {
            response.setCode(ResponseCode.SYSTEM_ERROR);
            response.setRemark("store getMessage return null");
        }

        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());
        }
        return response;
    }

    //......
}

• processRequest方法會經過brokerController.getMessageStore().getMessage方法獲取getMessageResult，以後判斷getMessageResult.isSuggestPullingFromSlave()是否爲true，是的話則執行responseHeader.setSuggestWhichBrokerId(subscriptionGroupConfig.getWhichBrokerWhenConsumeSlowly())，不然執行responseHeader.setSuggestWhichBrokerId(MixAll.MASTER_ID)

小結

DefaultMessageStore的getMessage會計算diff(maxOffsetPy - maxPhyOffsetPulling)，而後同memory(StoreUtil.TOTAL_PHYSICAL_MEMORY_SIZE * (this.messageStoreConfig.getAccessMessageInMemoryMaxRatio() / 100.0))對比，大於則設置getResult的suggestPullingFromSlave爲true

doc

• GetMessageResult