rocketmq采用netty作为底层通信框架，其中具体技术细节如下：

1、通信协议

rocketmq通信协议采用netty作为底层通信框架，协议格式采用自定义方式实现。具体协议如下：

rocketmq协议格式

（4个字节的数据包长度与4个字节的头长度，这个包长与头长怎么会一样？感觉可以再优化下）

2、通信加密

rocketmq采用netty链接时可以使用netty 的sslContext方式加密传输，不过需要加相关启动参数上（-Dkey=value），启动参数如下(省略-D）：

tls.server.mode=disabled (不加密传输) / permissive (默认) / enforcing   （当然了，如果没有检测到证书路径也不会选择加密传输）

tls.server.certPath=xxx

tls.server.keyPath=xxx

tls.server.trustCertPath=xxx

以上三个均是证书路径，不过是服务端的，客户端也有，客户端如下：

tls.client.certPath=xxx

tls.client.keyPath=xxx

tls.client.trustCertPath=xxx

3、rocketmq-netty默认线程数量

rocketmq采用主从线程模型

thread-acceptor : 1

thread-boss : 3

thread-worker : 8

4、rocketmq可配参数

rocketmq组件配置架构图

1）netty-server-config参数

listenPort=8888

serverWorkerThreads=8 （这是worker线程）

serverCallbackExecutorThreads=0

serverSelectorThreads=3 （这是boss线程）

serverOnewaySemaphoreValue=256

serverAsyncSemaphoreValue=64

serverChannelMaxIdleTimeSeconds=120（默认空闲2分钟断掉）

serverSocketSndBufSize=65535

serverSocketRcvBufSize=65535

serverPooledByteBufAllocatorEnable=true（是否使用内存池，默认使用）

useEpollNativeSelector=false（是否采用netty自己实现的EpollLoopGroup）

2)  netty-client-config参数

clientWorkerThreads =4

clientCallbackExecutorThreads=核心数量

clientOnewaySemaphoreValue = 65535

clientAsyncSemaphoreValue = 65535

connectTimeoutMillis =3000

channelNotActiveInterval=1000 *60

clientChannelMaxIdleTimeSeconds=120

clientSocketSndBufSize = 65535

clientSocketRcvBufSize = 65535

clientPooledByteBufAllocatorEnable=false

clientCloseSocketIfTimeout=false

useTLS=false

3）nameserver-config参数

rocketmq.home.dir=xxx（这是启动参数，not properties）

user.home=xxx（启动参数，存放kvConfig.json、namesrv.properties）

productEnvName=center（默认生产环境名称）

orderMessageEnable=false（有序消息可用性）

4)  broker-config参数

aclEnable=false

adminBrokerThreadPoolNums=16

autoCreateSubscriptionGroup=true

autoCreateTopicEnable=true

brokerClusterName=DefaultCluster

brokerFastFailureEnable=true

brokerId=0

brokerIP1=localhost

brokerIP2=localhost

brokerName=localhost

brokerPermission=4 | 2 (read | write)

brokerTopicEnable=true

clientManagerThreadPoolQueueCapacity=1000000

clientManageThreadPoolNums=32

clusterTopicEnable=true

commercialBaseCount=1

commercialBigCount=1

commercialEnable=true

commercialTimerCount=1

commercialTransCount=1

compressedRegister=false

consumerFallbehindThreshold=1024L *1024 *1024 *16

consumerManagerThreadPoolQueueCapacity=1000000

consumerManageThreadPoolNums=32

defaultTopicQueueNums=8

disableConsumeIfConsumerReadSlowly=false

enableCalcFilterBitMap=false

enablePropertyFilter=false

endTransactionPoolQueueCapacity=100000

endTransactionThreadPoolNums=8 + 核心数量 *2

expectConsumerNumUseFilter=32

fetchNamesrvAddrByAddressServer=false

filterDataCleanTimeSpan=24 *3600 *1000

filterServerNums=0

filterSupportRetry=false

flushConsumerOffsetHistoryInterval=1000 *60

flushConsumerOffsetInterval=1000 *5

forceRegister=true

heartbeatThreadPoolNums=Math.min(32, 核心数量)

heartbeatThreadPoolQueueCapacity=50000

highSpeedMode=false

longPollingEnable=true

maxDelayTime=40

maxErrorRateOfBloomFilter=20

messageStorePlugIn=""

msgTraceTopicName=RMQ_SYS_TRACE_TOPIC

namesrvAddr=localhost:8080;localhost:8080

notifyConsumerIdsChangedEnable=true

pullMessageThreadPoolNums=16 + 核心数量 *2

pullThreadPoolQueueCapacity=100000

queryMessageThreadPoolNums=8 + 核心数量

queryThreadPoolQueueCapacity=20000

regionId=DefaultRegion

registerBrokerTimeoutMills=6000

registerNameServerPeriod=1000 *30

rejectTransactionMessage=false

rocketmqHome=你的环境变量-ROCKETMQ_HOME

sendMessageThreadPoolNums=1

sendThreadPoolQueueCapacity=10000

shortPollingTimeMills=1000

slaveReadEnable=false

startAcceptSendRequestTimeStamp=0

traceOn=true

traceTopicEnable=false

transactionCheckInterval=60 *1000

transactionCheckMax=15

transactionTimeOut=6 *1000

transferMsgByHeap=true

waitTimeMillsInHeartbeatQueue=31 *1000

waitTimeMillsInPullQueue=5 *1000

waitTimeMillsInSendQueue=200

waitTimeMillsInTransactionQueue=3 *1000

5) message-store-config

accessMessageInMemoryMaxRatio=40

bitMapLengthConsumeQueueExt=64

brokerRole=ASYNC_MASTER

checkCRCOnRecover=true

cleanFileForciblyEnable=true

cleanResourceInterval=10000

commitCommitLogLeastPages=4

commitCommitLogThoroughInterval=200

commitIntervalCommitLog=200

debugLockEnable=false

defaultQueryMaxNum=32

deleteCommitLogFilesInterval=100

deleteConsumeQueueFilesInterval=100

deleteWhen="04" // When to delete,default is at 4 am

destroyMapedFileIntervalForcibly=1000 *120

diskFallRecorded=true

diskMaxUsedSpaceRatio=75

duplicationEnable=false

enableConsumeQueueExt=false

fastFailIfNoBufferInStorePool=false

fileReservedTime=72

flushCommitLogLeastPages=4

flushCommitLogThoroughInterval=1000 *10

flushCommitLogTimed=false

flushConsumeQueueLeastPages=2

flushConsumeQueueThoroughInterval=1000 *60

flushDelayOffsetInterval=1000 *10

flushDiskType=ASYNC_FLUSH

flushIntervalCommitLog=500

flushIntervalConsumeQueue=1000

flushLeastPagesWhenWarmMapedFile=1024 /4 *16

haHousekeepingInterval=1000 *20

haListenPort=10912

haSendHeartbeatInterval=1000 *5

haSlaveFallbehindMax=1024 *1024 *256

haTransferBatchSize=1024 *32

mapedFileSizeCommitLog=1024 *1024 *1024

mappedFileSizeConsumeQueueExt=48 *1024 *1024

maxHashSlotNum=5000000

maxIndexNum=5000000 *4

maxMessageSize=1024 *1024 *4

maxMsgsNumBatch=64

maxTransferBytesOnMessageInDisk=1024 *64

maxTransferBytesOnMessageInMemory=1024 *256

maxTransferCountOnMessageInDisk=8

maxTransferCountOnMessageInMemory=32

messageDelayLevel=1s 5s 10s 30s 1m 2m 3m 4m 5m 6m 7m 8m 9m 10m 20m 30m 1h 2h

messageIndexEnable=true

messageIndexSafe=false

offsetCheckInSlave=false

osPageCacheBusyTimeOutMills=1000

putMsgIndexHightWater=600000

redeleteHangedFileInterval=1000 *120

storePathCommitLog=...

storePathRootDir=...

syncFlushTimeout=1000 *5

transientStorePoolEnable=false

transientStorePoolSize=5

useReentrantLockWhenPutMessage=false

warmMapedFileEnable=false

5 特殊参数

broker可以动态调整nameserver地址，频率是每2分钟以http的请求方式获取nameserver地址然后更新，这样可以增加系统高可用。热备broker链接nameserver需要启动参数，非配置文件，启动参数如下：

-Drocketmq.namesrv.domain=jmenv.tbsite.net

-Drocketmq.namesrv.domain.subgroup=nsaddr

默认 jmenv.tbsite.net:8080/rocketmq/nsaddr