Launch the second EC2 instance as a Slave

Procedure

Go into the directory /opt/talend/activemq/current/bin/.
```
cd /opt/talend/activemq/current/bin/
```
Stop the ActiveMQ broker since it has been configured to start with the EC2 instance.
```
./activemq stop
```
Enter the /opt directory.
```
cd /opt 
```
To mount the shared file system using the same mount command, you have two options:
- Option 1: If you have copied the Amazon EC2 Mount instructions in your favorite editor.
- Option 2: If you did not copy/paste the Amazon EC2 Mount instructions.

Restart the ActiveMQ broker.

cd /opt/talend/activemq/current/bin/
./activemq start

Open the file ActiveMQ log file at /opt/talend/activemq/current/data/activemq.log using cat or tail command.

You should see the following lines at the end of the file:

ec2-user@ip-10-0-0-28 bin]$ tailf /opt/talend/activemq/current/data/activemq.log
2017-03-15 21:25:45,713 | WARN  | Temporary Store limit is 51200 mb (current store usage is 0 mb). The data directory: /opt/talend/activemq/apache-activemq-5.14.0/data only has 6664 mb of usable space. - resetting to maximum available disk space: 6664 mb | org.apache.activemq.broker.BrokerService | main
2017-03-15 21:25:46,372 | INFO  | No Spring WebApplicationInitializer types detected on classpath | /admin | main
2017-03-15 21:25:46,507 | INFO  | ActiveMQ WebConsole available at http://0.0.0.0:8161/ | org.apache.activemq.web.WebConsoleStarter | main
2017-03-15 21:25:46,507 | INFO  | ActiveMQ Jolokia REST API available at http://0.0.0.0:8161/api/jolokia/ | org.apache.activemq.web.WebConsoleStarter | main
2017-03-15 21:25:46,547 | INFO  | Initializing Spring FrameworkServlet 'dispatcher' | /admin | main
2017-03-15 21:25:46,848 | INFO  | No Spring WebApplicationInitializer types detected on classpath | /api | main
2017-03-15 21:25:46,882 | INFO  | jolokia-agent: Using policy access restrictor classpath:/jolokia-access.xml | /api | main
2017-03-15 21:39:14,900 | INFO  | Refreshing org.apache.activemq.xbean.XBeanBrokerFactory$1@1e0c1853: startup date [Wed Mar 15 21:39:14 UTC 2017]; root of context hierarchy | org.apache.activemq.xbean.XBeanBrokerFactory$1 | main
2017-03-15 21:39:16,178 | INFO  | Using Persistence Adapter: KahaDBPersistenceAdapter[/opt/efs/kahadb] | org.apache.activemq.broker.BrokerService | main
2017-03-15 21:39:16,199 | INFO  | Database /opt/efs/kahadb/lock is locked by another server. This broker is now in slave mode waiting a lock to be acquired | org.apache.activemq.store.SharedFileLocker | main

The line telling that This broker is now in slave mode waiting a lock to be acquired is proof that the second instance has launched as a Slave in our Master/Slave configuration.

Note:

The new broker shares the same EFS filesystem as the first broker
Because the first broker is still running and has already acquired the file lock, the new broker goes into slave mode, waiting for the master to die and release the file lock to then become the master.
The Master/Slave broker nodes will rotate depending on which one has acquired the file lock first
Consumers and Producers of messages for the broker should be configured with the endpoint of both the master and slave broker instances so that they are agnostic to which broker is the master or slave.

Results

Congratulations, you have successfully installed and configured ActiveMQ in Master/Slave mode with KahaDB on AWS Elastic File System!

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