聊聊rocketmq的HAClient

序

本文主要研究一下rocketmq的HAClient

HAClient

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

    class HAClient extends ServiceThread {
        private static final int READ_MAX_BUFFER_SIZE = 1024 * 1024 * 4;
        private final AtomicReference<String> masterAddress = new AtomicReference<>();
        private final ByteBuffer reportOffset = ByteBuffer.allocate(8);
        private SocketChannel socketChannel;
        private Selector selector;
        private long lastWriteTimestamp = System.currentTimeMillis();

        private long currentReportedOffset = 0;
        private int dispatchPosition = 0;
        private ByteBuffer byteBufferRead = ByteBuffer.allocate(READ_MAX_BUFFER_SIZE);
        private ByteBuffer byteBufferBackup = ByteBuffer.allocate(READ_MAX_BUFFER_SIZE);

        public HAClient() throws IOException {
            this.selector = RemotingUtil.openSelector();
        }

        //......

        @Override
        public void run() {
            log.info(this.getServiceName() + " service started");

            while (!this.isStopped()) {
                try {
                    if (this.connectMaster()) {

                        if (this.isTimeToReportOffset()) {
                            boolean result = this.reportSlaveMaxOffset(this.currentReportedOffset);
                            if (!result) {
                                this.closeMaster();
                            }
                        }

                        this.selector.select(1000);

                        boolean ok = this.processReadEvent();
                        if (!ok) {
                            this.closeMaster();
                        }

                        if (!reportSlaveMaxOffsetPlus()) {
                            continue;
                        }

                        long interval =
                            HAService.this.getDefaultMessageStore().getSystemClock().now()
                                - this.lastWriteTimestamp;
                        if (interval > HAService.this.getDefaultMessageStore().getMessageStoreConfig()
                            .getHaHousekeepingInterval()) {
                            log.warn("HAClient, housekeeping, found this connection[" + this.masterAddress
                                + "] expired, " + interval);
                            this.closeMaster();
                            log.warn("HAClient, master not response some time, so close connection");
                        }
                    } else {
                        this.waitForRunning(1000 * 5);
                    }
                } catch (Exception e) {
                    log.warn(this.getServiceName() + " service has exception. ", e);
                    this.waitForRunning(1000 * 5);
                }
            }

            log.info(this.getServiceName() + " service end");
        }

        @Override
        public String getServiceName() {
            return HAClient.class.getSimpleName();
        }

        //......

        private boolean processReadEvent() {
            int readSizeZeroTimes = 0;
            while (this.byteBufferRead.hasRemaining()) {
                try {
                    int readSize = this.socketChannel.read(this.byteBufferRead);
                    if (readSize > 0) {
                        readSizeZeroTimes = 0;
                        boolean result = this.dispatchReadRequest();
                        if (!result) {
                            log.error("HAClient, dispatchReadRequest error");
                            return false;
                        }
                    } else if (readSize == 0) {
                        if (++readSizeZeroTimes >= 3) {
                            break;
                        }
                    } else {
                        log.info("HAClient, processReadEvent read socket < 0");
                        return false;
                    }
                } catch (IOException e) {
                    log.info("HAClient, processReadEvent read socket exception", e);
                    return false;
                }
            }

            return true;
        }

        //......        
    }

• HAClient继承了ServiceThread，其run方法以isStopped为false进行while循环，之后通过connectMaster方法判断是否连上masterAddress，连不上则执行waitForRunning(1000 * 5)；连上了master之后再判断isTimeToReportOffset，即判断当前时间与lastWriteTimestamp的差值，若该值大于defaultMessageStore.getMessageStoreConfig().getHaSendHeartbeatInterval()，则返回true；最后执行processReadEvent；processReadEvent在byteBufferRead.hasRemaining()前提下会执行dispatchReadRequest

dispatchReadRequest

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

    class HAClient extends ServiceThread {

        //......

        private boolean dispatchReadRequest() {
            final int msgHeaderSize = 8 + 4; // phyoffset + size
            int readSocketPos = this.byteBufferRead.position();

            while (true) {
                int diff = this.byteBufferRead.position() - this.dispatchPosition;
                if (diff >= msgHeaderSize) {
                    long masterPhyOffset = this.byteBufferRead.getLong(this.dispatchPosition);
                    int bodySize = this.byteBufferRead.getInt(this.dispatchPosition + 8);

                    long slavePhyOffset = HAService.this.defaultMessageStore.getMaxPhyOffset();

                    if (slavePhyOffset != 0) {
                        if (slavePhyOffset != masterPhyOffset) {
                            log.error("master pushed offset not equal the max phy offset in slave, SLAVE: "
                                + slavePhyOffset + " MASTER: " + masterPhyOffset);
                            return false;
                        }
                    }

                    if (diff >= (msgHeaderSize + bodySize)) {
                        byte[] bodyData = new byte[bodySize];
                        this.byteBufferRead.position(this.dispatchPosition + msgHeaderSize);
                        this.byteBufferRead.get(bodyData);

                        HAService.this.defaultMessageStore.appendToCommitLog(masterPhyOffset, bodyData);

                        this.byteBufferRead.position(readSocketPos);
                        this.dispatchPosition += msgHeaderSize + bodySize;

                        if (!reportSlaveMaxOffsetPlus()) {
                            return false;
                        }

                        continue;
                    }
                }

                if (!this.byteBufferRead.hasRemaining()) {
                    this.reallocateByteBuffer();
                }

                break;
            }

            return true;
        }

        //......
    }

• dispatchReadRequest会判断diff >= (msgHeaderSize + bodySize)，若成立则执行defaultMessageStore.appendToCommitLog(masterPhyOffset, bodyData)

小结

• HAClient继承了ServiceThread，其run方法以isStopped为false进行while循环，之后通过connectMaster方法判断是否连上masterAddress，连不上则执行waitForRunning(1000 * 5)；连上了master之后再判断isTimeToReportOffset，即判断当前时间与lastWriteTimestamp的差值，若该值大于defaultMessageStore.getMessageStoreConfig().getHaSendHeartbeatInterval()，则返回true；最后执行processReadEvent；processReadEvent在byteBufferRead.hasRemaining()前提下会执行dispatchReadRequest

doc

• HAService