monitoring: report configured queue.mem.*, output.elasticsearch.workers, output.elasticsearch.bulk_max_size

[axw]

Describe the enhancement:

Report additional metrics for telemetry/stack monitoring:

• queue.mem.events
• output.elasticsearch.workers
• output.elasticsearch.bulk_max_size

Describe a specific use case for the enhancement or feature:

Part of the tuning exercise for APM Server is to tweak output parameters (https://www.elastic.co/guide/en/apm/server/current/tune-apm-server.html): queue.mem.events, output.elasticsearch.workers, and output.elasticsearch.bulk_max_size. At the moment there is no way to see, through Kibana, what the currently configured values are.

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[axw]

@elastic/apm-server will take a look at implementing this.