Investigate AmazonMQ warning logs on application start

[rieckpil]

During the bootstrap phase of our Spring Boot backend, we currently see the following two warnings:

2021-04-30 07:20:37.380 WARN 1 --- [nio-8080-exec-2] o.apache.activemq.broker.BrokerService : Memory Usage for the Broker (1024mb) is more than the maximum available for the JVM: 123 mb - resetting to 70% of maximum available: 86 mb 
2021-04-30 07:20:38.481 WARN 1 --- [nio-8080-exec-2] o.apache.activemq.broker.BrokerService : Temporary Store limit is 51200 mb (current store usage is 0 mb). The data directory: / only has 18559 mb of usable space. - resetting to maximum available disk space: 18559 mb 

[BjoernKW]

This seems to be a misconfiguration for the instance type mq.t2.micro on the AWS side because that one should have 1 gb of memory available according to https://docs.aws.amazon.com/amazon-mq/latest/developer-guide/broker-instance-types.html

As for Active MQ performance in general see https://docs.aws.amazon.com/amazon-mq/latest/developer-guide/ensuring-effective-amazon-mq-performance.html:

When you use ActiveMQ in persistent mode, writing to storage normally occurs when there are either few consumers or when the consumers are slow. In non-persistent mode, writing to storage also occurs with slow consumers if the heap memory of the broker instance is full.

Maybe, that could be another use case for monitoring, too (see: https://github.com/awsdocs/amazon-mq-developer-guide/blob/master/doc_source/security-logging-monitoring-cloudwatch.md)

[rieckpil]

We can close this issue, the warning is indeed non-critical and due to the small instance.