How to Build a RocketMQ Cluster with Dual Master‑Slave Async Replication

1. Cluster Architecture

The tutorial creates a broker cluster with two masters and two slaves using asynchronous replication. Two physical hosts are used, each running a NameServer and a Broker. The role assignment is:

Host rocketmq1 (IP 192.168.1.8): NameServer + Broker (Master1 + Slave2)

Host rocketmq2 (IP 192.168.1.9): NameServer + Broker (Master1 + Slave2)

2. Prepare the RocketMQ Binary

Download the binary package from the Apache RocketMQ site, unzip it, and navigate to the configuration directory

/tools/rocketMq/rocketmq-all-4.9.4-bin-release/conf/2m-2s-async

.

3. Configure rocketmq1

Edit broker-a.properties with the following essential settings:

brokerClusterName=DefaultCluster
brokerName=broker-a
brokerId=0
deleteWhen=04
fileReservedTime=48
brokerRole=ASYNC_MASTER
flushDiskType=ASYNC_FLUSH
namesrvAddr=192.168.1.8:9876;192.168.1.9:9876

Then edit broker-b-s.properties (the slave configuration) similarly, but set brokerId=1 and brokerRole=SLAVE:

brokerClusterName=DefaultCluster
brokerName=broker-b
brokerId=1
deleteWhen=04
fileReservedTime=48
brokerRole=SLAVE
flushDiskType=ASYNC_FLUSH
namesrvAddr=192.168.1.8:9876;192.168.1.9:9876

4. Configure rocketmq2

Rename the host to rocketmq2 (or keep using the IP) and repeat the same edits for broker-b.properties (master) and broker-a-s.properties (slave) with the appropriate brokerId and brokerRole values.

5. Adjust Startup Scripts

Modify runserver.sh to reduce the NameServer JVM memory:

JAVA_OPT="${JAVA_OPT} -server -Xms2g -Xmx2g -Xmn1g -XX:MetaspaceSize=128m -XX:MaxMetaspaceSize=320m"

Modify runbroker.sh to reduce the broker JVM memory:

JAVA_OPT="${JAVA_OPT} -server -Xms2g -Xmx2g -Xmn1g"

6. Start the Services

On each host, start the NameServer:

nohup sh bin/mqnamesrv &
 tail -f nohup.out

Start the master brokers:

nohup sh bin/mqbroker -c conf/2m-2s-async/broker-a.properties > broker-a.log 2>&1 &
nohup sh bin/mqbroker -c conf/2m-2s-async/broker-b.properties > broker-b.log 2>&1 &

Start the slave brokers:

nohup sh bin/mqbroker -c conf/2m-2s-async/broker-b-s.properties > broker-b-s.log 2>&1 &
nohup sh bin/mqbroker -c conf/2m-2s-async/broker-a-s.properties > broker-a-s.log 2>&1 &

7. Verification

After all processes are running, the cluster provides asynchronous master‑slave replication across the two hosts. The tutorial recommends consulting the official RocketMQ documentation for deeper understanding.