Avamar: MCS fails to start, reporting "Unable to connect to node rabbit@localhost: nodedown"

During a Management Console Service (MCS) restart, an exception message is logged: (/usr/local/avamar/var/mc/server_log/mcserver.log.0)

Caused by: org.springframework.amqp.AmqpConnectException: java.net.ConnectException: Connection refused
        at org.springframework.amqp.rabbit.support.RabbitExceptionTranslator.convertRabbitAccessException(RabbitExceptionTranslator.java:51)
        at org.springframework.amqp.rabbit.connection.AbstractConnectionFactory.createBareConnection(AbstractConnectionFactory.java:185)
        at org.springframework.amqp.rabbit.connection.CachingConnectionFactory.createConnection(CachingConnectionFactory.java:228)
        at org.springframework.amqp.rabbit.connection.ConnectionFactoryUtils$1.createConnection(ConnectionFactoryUtils.java:77)
        at org.springframework.amqp.rabbit.connection.ConnectionFactoryUtils.doGetTransactionalResourceHolder(ConnectionFactoryUtils.java:125)
        at org.springframework.amqp.rabbit.connection.ConnectionFactoryUtils.getTransactionalResourceHolder(ConnectionFactoryUtils.java:67)
        at org.springframework.amqp.rabbit.connection.RabbitAccessor.getTransactionalResourceHolder(RabbitAccessor.java:102)
        at org.springframework.amqp.rabbit.core.RabbitTemplate.execute(RabbitTemplate.java:618)
        at org.springframework.amqp.rabbit.core.RabbitAdmin.declareQueue(RabbitAdmin.java:133)
        at com.avamar.mc.jms.push.JmsPushService.enable(JmsPushService.java:418)
        at com.avamar.mc.jms.push.JmsPushService.start(JmsPushService.java:191)
        at com.avamar.asn.service.ServiceContainerImpl.installService(ServiceContainerImpl.java:472)
        ... 6 more

The Rabbimq status reports an error: Unable to connect to node rabbit@localhost: nodedown

service rabbitmq-server status

Status of node rabbit@localhost ...
Error: unable to connect to node rabbit@localhost: nodedown 

The Backup and Recovery Manager (BRM) is enabled:

grep Brm /usr/local/avamar/var/mc/server_data/prefs/mcserver.xml

<entry key="enableBrmService" value="true" /> 

The cause is unknown, however a potential workaround has been provided below.

1. Log in to the Avamar Utility Node as admin.

2. Elevate to root privilege.

3. Rename the /usr/local/avamar/var/rabbitmq/mnesia directory:

mv /usr/local/avamar/var/rabbitmq/mnesia /usr/local/avamar/var/rabbitmq/mnesia.`date +%y%m%d` 

4. Restart rabbitmq:

service rabbitmq-server start 

5. Verify that the /usr/local/avamar/var/rabbitmq/mnesia directory exists:

ls -ld /usr/local/avamar/var/rabbitmq/mnesia* 

Example output:

drwxr-x--- 4 rabbitmq rabbitmq 97 Jul 21 19:46 /usr/local/avamar/var/rabbitmq/mnesia
drwxr-xr-x 4 rabbitmq rabbitmq 97 Jan 22 16:30 /usr/local/avamar/var/rabbitmq/mnesia.250721

6. Restart MCS per Avamar: How to Restart Management Console Server.