ActiveMQ Configuring JDBC Master-Slave

Using JDBC to configure master-slave mode, persistent messages are stored in the database.

At the same time, only one master Broker,master accepts the client connection, and slave does not accept the connection.
When Master is offline due to shutdown, one of the slave is promoted to master, and then the client connection is accepted. But the original master's non-persistent message was lost, and the persistent message was saved in the database.

Broker XML configuration: Using MySQL data source

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Client configuration, producer and consumer are the same:

New Activemqconnectionfactory ("Failover: (tcp://localhost:61616,tcp://localhost:61618)");

As an example of MySQL database, 3 tables are created in MySQL after the broker is started:
ACTIVEMQ_MSGS Storing persistent messages
There is only one record in the Activemq_lock table, and the broker executes a SELECT * from the Activemq_lock for UPDATE acquires the lock, the broker that acquires the lock is the master
Activemq_acks

The call stack for the broker to get the lock is as follows:

//Org.apache.activemq.store.jdbc.DefaultDatabaseLocker Public voidDostart ()throwsException {log.info ("Attempting to acquire the exclusive lock to become the Master broker"); //SELECT * from Activemq_lock for UPDATEString sql =getstatements (). Getlockcreatestatement (); Log.debug ("Locking Query is" +SQL);  while(true) {        Try{Connection=datasource.getconnection (); Connection.setautocommit (false); Lockcreatestatement=connection.preparestatement (SQL); //Execute SELECT * from Activemq_lock for UPDATE//If successful, jump out of the loop. Throws an exception if it is timed outLockcreatestatement.execute ();  Break; } Catch(Exception e) {Try {                if(Isstopping ()) {Throw NewException ("Cannot start broker as being asked to shut." + "interrupted attempt to acquire Lock:" +e, E); }                if(Exceptionhandler! =NULL) {                    Try{exceptionhandler.handle (e); } Catch(Throwable handlerexception) {log.error ("The exception handler" +Exceptionhandler.getclass (). Getcanonicalname ()+ "Threw this exception:" +handlerexception+ "while trying-handle this exception:" +e, handlerexception); }                } Else{log.debug ("Lock failure:" +e, E); }            } finally {                //Let's make sure the database connection is properly//closed When a error occurs so the we ' re not leaking//Connections                if(NULL!=connection) {                    Try{connection.rollback (); } Catch(SQLException E1) {Log.debug ("Caught exception during rollback on connection:" +E1, E1); }                    Try{connection.close (); } Catch(SQLException E1) {Log.debug ("Caught exception while closing connection:" +E1, E1); } Connection=NULL; }            }        } finally {            if(NULL!=lockcreatestatement) {                Try{lockcreatestatement.close (); } Catch(SQLException E1) {Log.debug ("Caught while closing statement:" +E1, E1); } lockcreatestatement=NULL; }} log.info ("Failed to acquire lock. Sleeping for "+ Lockacquiresleepinterval +" milli (s) before trying again ... "); Try{thread.sleep (lockacquiresleepinterval); } Catch(Interruptedexception IE) {Log.warn ("Master Lock retry Sleep interrupted", IE); }} log.info ("Becoming the Master on DataSource:" +dataSource);}

The broker performs a SELECT * from Activemq_lock for UPDATE to get the lock, gets a success, then becomes master, and if it fails, continues to acquire the lock after a period of sleep.

The exception that is thrown when timed out:

ActiveMQ Configuring JDBC Master-Slave