DropWizard metrics

[51-code]

Setup can be found in Metrics.java.

Includes new config parameter: prometheus.port with a default of 1234. This is the port for the Jetty server that provides the metrics.

Metrics include:

• records (how many messages have gone through)
• bytes (how many bytes have gone through)
• resends (how many times messages have been needed to resend to RELP)
• connects (how many times a connection has been made to RELP)
• retriedConnects (how many times a connection attempt has had to be retried)
• sendLatency (latency of processing the whole message as it comes in and sending it to RELP)
• connectLatency (latency of connecting to RELP)

I tried my best to not fill the existing objects with the metrics, so I made decorators where applicable. The metrics are somewhat scattered, as objects have different responsibilities:

• ManagedRelpConnection includes resends, retriedConnects, records and bytes. Would have liked to make this a decorator as well, but resends and retriedConnects are inner logic of the object when a message has been sent so this would need refactoring to do the metrics in a decorator.
• The new MetricRelpConnection includes connects and connectLatency. RelpConnection is the only object that actually deals with the connections so these metrics were placed in its decorator.
• The new MetricRelpConversion includes sendLatency because RelpConversion is the object that has a hold on the whole processing of the message.

[p000010u]

lgtm