聊聊rocketmq的pullThresholdForTopic

public class DefaultMQPushConsumer extends ClientConfig implements MQPushConsumer {
​
    //......
​
    /**
     * Flow control threshold on topic level, default value is -1(Unlimited)
     * <p>
     * The value of {@code pullThresholdForQueue} will be overwrote and calculated based on
     * {@code pullThresholdForTopic} if it is't unlimited
     * <p>
     * For example, if the value of pullThresholdForTopic is 1000 and 10 message queues are assigned to this consumer,
     * then pullThresholdForQueue will be set to 100
     */
    private int pullThresholdForTopic = -1;
​
    /**
     * Limit the cached message size on topic level, default value is -1 MiB(Unlimited)
     * <p>
     * The value of {@code pullThresholdSizeForQueue} will be overwrote and calculated based on
     * {@code pullThresholdSizeForTopic} if it is't unlimited
     * <p>
     * For example, if the value of pullThresholdSizeForTopic is 1000 MiB and 10 message queues are
     * assigned to this consumer, then pullThresholdSizeForQueue will be set to 100 MiB
     */
    private int pullThresholdSizeForTopic = -1;
​
    //......
​
    public int getPullThresholdForTopic() {
        return pullThresholdForTopic;
    }
​
    public void setPullThresholdForTopic(final int pullThresholdForTopic) {
        this.pullThresholdForTopic = pullThresholdForTopic;
    }
​
    public int getPullThresholdSizeForTopic() {
        return pullThresholdSizeForTopic;
    }
​
    public void setPullThresholdSizeForTopic(final int pullThresholdSizeForTopic) {
        this.pullThresholdSizeForTopic = pullThresholdSizeForTopic;
    }
​
    //......
}

public class DefaultMQPushConsumerImpl implements MQConsumerInner {
​
    //......
​
    private void checkConfig() throws MQClientException {
        Validators.checkGroup(this.defaultMQPushConsumer.getConsumerGroup());
​
        //......
​
        // pullThresholdForTopic
        if (this.defaultMQPushConsumer.getPullThresholdForTopic() != -1) {
            if (this.defaultMQPushConsumer.getPullThresholdForTopic() < 1 || this.defaultMQPushConsumer.getPullThresholdForTopic() > 6553500) {
                throw new MQClientException(
                    "pullThresholdForTopic Out of range [1, 6553500]"
                        + FAQUrl.suggestTodo(FAQUrl.CLIENT_PARAMETER_CHECK_URL),
                    null);
            }
        }
​
        if (this.defaultMQPushConsumer.getPullThresholdSizeForTopic() != -1) {
            // pullThresholdSizeForTopic
            if (this.defaultMQPushConsumer.getPullThresholdSizeForTopic() < 1 || this.defaultMQPushConsumer.getPullThresholdSizeForTopic() > 102400) {
                throw new MQClientException(
                    "pullThresholdSizeForTopic Out of range [1, 102400]"
                        + FAQUrl.suggestTodo(FAQUrl.CLIENT_PARAMETER_CHECK_URL),
                    null);
            }
        }
​
        //......    
    }
    
    //......   
}     

public class RebalancePushImpl extends RebalanceImpl {
    private final static long UNLOCK_DELAY_TIME_MILLS = Long.parseLong(System.getProperty("rocketmq.client.unlockDelayTimeMills", "20000"));
    private final DefaultMQPushConsumerImpl defaultMQPushConsumerImpl;
​
    public RebalancePushImpl(DefaultMQPushConsumerImpl defaultMQPushConsumerImpl) {
        this(null, null, null, null, defaultMQPushConsumerImpl);
    }
​
    public RebalancePushImpl(String consumerGroup, MessageModel messageModel,
        AllocateMessageQueueStrategy allocateMessageQueueStrategy,
        MQClientInstance mQClientFactory, DefaultMQPushConsumerImpl defaultMQPushConsumerImpl) {
        super(consumerGroup, messageModel, allocateMessageQueueStrategy, mQClientFactory);
        this.defaultMQPushConsumerImpl = defaultMQPushConsumerImpl;
    }
​
    @Override
    public void messageQueueChanged(String topic, Set<MessageQueue> mqAll, Set<MessageQueue> mqDivided) {
        /**
         * When rebalance result changed, should update subscription's version to notify broker.
         * Fix: inconsistency subscription may lead to consumer miss messages.
         */
        SubscriptionData subscriptionData = this.subscriptionInner.get(topic);
        long newVersion = System.currentTimeMillis();
        log.info("{} Rebalance changed, also update version: {}, {}", topic, subscriptionData.getSubVersion(), newVersion);
        subscriptionData.setSubVersion(newVersion);
​
        int currentQueueCount = this.processQueueTable.size();
        if (currentQueueCount != 0) {
            int pullThresholdForTopic = this.defaultMQPushConsumerImpl.getDefaultMQPushConsumer().getPullThresholdForTopic();
            if (pullThresholdForTopic != -1) {
                int newVal = Math.max(1, pullThresholdForTopic / currentQueueCount);
                log.info("The pullThresholdForQueue is changed from {} to {}",
                    this.defaultMQPushConsumerImpl.getDefaultMQPushConsumer().getPullThresholdForQueue(), newVal);
                this.defaultMQPushConsumerImpl.getDefaultMQPushConsumer().setPullThresholdForQueue(newVal);
            }
​
            int pullThresholdSizeForTopic = this.defaultMQPushConsumerImpl.getDefaultMQPushConsumer().getPullThresholdSizeForTopic();
            if (pullThresholdSizeForTopic != -1) {
                int newVal = Math.max(1, pullThresholdSizeForTopic / currentQueueCount);
                log.info("The pullThresholdSizeForQueue is changed from {} to {}",
                    this.defaultMQPushConsumerImpl.getDefaultMQPushConsumer().getPullThresholdSizeForQueue(), newVal);
                this.defaultMQPushConsumerImpl.getDefaultMQPushConsumer().setPullThresholdSizeForQueue(newVal);
            }
        }
​
        // notify broker
        this.getmQClientFactory().sendHeartbeatToAllBrokerWithLock();
    }
​
    //......
}