RoketMq源码学习-六-Offset的存储

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Consumer维护OffSet的接口是：OffsetStore，有俩个实现类

  • RemoteBrokerOffsetStore：消息模式是Cluster会用到它
  • LocalFileOffsetStore：消息模式是BoardCast会用到它

我们以RemoteBrokerOffsetStore为例来看读取offset的顺序

RemoteBrokerOffsetStore读取offset的顺序

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public long readOffset(final MessageQueue mq, final ReadOffsetType type) {
    if (mq != null) {
        switch (type) {
            case MEMORY_FIRST_THEN_STORE:
            case READ_FROM_MEMORY: {
                AtomicLong offset = this.offsetTable.get(mq);
                if (offset != null) {
                    return offset.get();
                } else if (ReadOffsetType.READ_FROM_MEMORY == type) {
                    return -1;
                }
            }
            case READ_FROM_STORE: {
                try {
                    long brokerOffset = this.fetchConsumeOffsetFromBroker(mq);
                    AtomicLong offset = new AtomicLong(brokerOffset);
                    this.updateOffset(mq, offset.get(), false);
                    return brokerOffset;
                }
                // No offset in broker
                catch (MQBrokerException e) {
                    return -1;
                }
                //Other exceptions
                catch (Exception e) {
                    log.warn("fetchConsumeOffsetFromBroker exception, " + mq, e);
                    return -2;
                }
            }
            default:
                break;
        }
    }

    return -1;
}

当需要从broker读取的时候调用fetchConsumeOffsetFromBroker

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private long fetchConsumeOffsetFromBroker(MessageQueue mq) throws RemotingException, MQBrokerException,
        InterruptedException, MQClientException {
    //获取broker from memory
    FindBrokerResult findBrokerResult = this.mQClientFactory.findBrokerAddressInAdmin(mq.getBrokerName());
    if (null == findBrokerResult) {

        this.mQClientFactory.updateTopicRouteInfoFromNameServer(mq.getTopic());
        findBrokerResult = this.mQClientFactory.findBrokerAddressInAdmin(mq.getBrokerName());
    }

    //sendBroker get Offset
    if (findBrokerResult != null) {
        QueryConsumerOffsetRequestHeader requestHeader = new QueryConsumerOffsetRequestHeader();
        requestHeader.setTopic(mq.getTopic());
        requestHeader.setConsumerGroup(this.groupName);
        requestHeader.setQueueId(mq.getQueueId());

        //从broker取consumerOffSet
        return this.mQClientFactory.getMQClientAPIImpl().queryConsumerOffset(
                findBrokerResult.getBrokerAddr(), requestHeader, 1000 * 5);
    } else {
        throw new MQClientException("The broker[" + mq.getBrokerName() + "] not exist", null);
    }
}

    public long queryConsumerOffset(
        final String addr,
        final QueryConsumerOffsetRequestHeader requestHeader,
        final long timeoutMillis
) throws RemotingException, MQBrokerException, InterruptedException {
    RemotingCommand request = RemotingCommand.createRequestCommand(RequestCode.QUERY_CONSUMER_OFFSET, requestHeader);

    //发送同步请求,这时候当前线程会阻塞
    RemotingCommand response = this.remotingClient.invokeSync(MixAll.brokerVIPChannel(this.clientConfig.isVipChannelEnabled(), addr),
            request, timeoutMillis);
    assert response != null;
    switch (response.getCode()) {
        case ResponseCode.SUCCESS: {
            QueryConsumerOffsetResponseHeader responseHeader =
                    (QueryConsumerOffsetResponseHeader) response.decodeCommandCustomHeader(QueryConsumerOffsetResponseHeader.class);

            return responseHeader.getOffset();
        }
        default:
            break;
    }

    throw new MQBrokerException(response.getCode(), response.getRemark());
}

broker处理QUERY_CONSUMER_OFFSET请求的逻辑

从ConsumerQueue中获取offset

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private RemotingCommand queryConsumerOffset(ChannelHandlerContext ctx, RemotingCommand request)
    throws RemotingCommandException {
    //创建响应
    final RemotingCommand response =
        RemotingCommand.createResponseCommand(QueryConsumerOffsetResponseHeader.class);
    //响应头
    final QueryConsumerOffsetResponseHeader responseHeader =
        (QueryConsumerOffsetResponseHeader) response.readCustomHeader();
    //请求头
    final QueryConsumerOffsetRequestHeader requestHeader =
        (QueryConsumerOffsetRequestHeader) request
            .decodeCommandCustomHeader(QueryConsumerOffsetRequestHeader.class);

    long offset =
        this.brokerController.getConsumerOffsetManager().queryOffset(
            requestHeader.getConsumerGroup(), requestHeader.getTopic(), requestHeader.getQueueId());

    //如果>=0
    if (offset >= 0) {
        responseHeader.setOffset(offset);
        response.setCode(ResponseCode.SUCCESS);
        response.setRemark(null);
    } else {
        long minOffset =
            this.brokerController.getMessageStore().getMinOffsetInQueue(requestHeader.getTopic(),
                requestHeader.getQueueId());
        //如果小于等于0，并且创建ConsumerQueue成功
        if (minOffset <= 0
            && !this.brokerController.getMessageStore().checkInDiskByConsumeOffset(
            requestHeader.getTopic(), requestHeader.getQueueId(), 0)) {
            responseHeader.setOffset(0L);
            response.setCode(ResponseCode.SUCCESS);
            response.setRemark(null);
        } else {
            //错误
            response.setCode(ResponseCode.QUERY_NOT_FOUND);
            response.setRemark("Not found, V3_0_6_SNAPSHOT maybe this group consumer boot first");
        }
    }

    return response;
}


public long getMinOffsetInQueue(String topic, int queueId) {
    //getAndCreateQueue
    ConsumeQueue logic = this.findConsumeQueue(topic, queueId);
    if (logic != null) {
        //找到队列里最小的offsetminLogicOffset / CQ_STORE_UNIT_SIZE
        return logic.getMinOffsetInQueue();
    }

    return -1;
}

public ConsumeQueue findConsumeQueue(String topic, int queueId) {
    ConcurrentMap<Integer, ConsumeQueue> map = consumeQueueTable.get(topic);
    if (null == map) {
        //防止并发
        ConcurrentMap<Integer, ConsumeQueue> newMap = new ConcurrentHashMap<Integer, ConsumeQueue>(128);
        ConcurrentMap<Integer, ConsumeQueue> oldMap = consumeQueueTable.putIfAbsent(topic, newMap);
        if (oldMap != null) {
            map = oldMap;
        } else {
            map = newMap;
        }
    }

    ConsumeQueue logic = map.get(queueId);
    if (null == logic) {

        ConsumeQueue newLogic = new ConsumeQueue(
                topic,
                queueId,
                StorePathConfigHelper.getStorePathConsumeQueue(this.messageStoreConfig.getStorePathRootDir()),
                this.getMessageStoreConfig().getMapedFileSizeConsumeQueue(),
                this);

        //防止并发
        ConsumeQueue oldLogic = map.putIfAbsent(queueId, newLogic);
        if (oldLogic != null) {
            logic = oldLogic;
        } else {
            logic = newLogic;
        }
    }

    return logic;
}