Send Datadog tags to statsd [exometer_report_statsd]

[nicolasgarnil]

Problem

The reporter exometer_report_statsd doesn't support including Datadog tags in the datagram which is sent to statsd.

Solution

Be able to pass the tags to :exometer.update as well as the metric value.

E.g:

:exometer.update[:app_name, :webapp, :resp_time], %{value: 25, tags: [algorithm: "one"]}

[uwiger]

Passing tags in the update operation would be difficult. However, it would be possible to add tags as part of Extra for a given subscription entry, and extend the exometer_report_statsd module to look for a tags option and append those tags to the output line. One could also add a tags option when initializing a statsd reporter. Actually, both these could be implemented, and the exometer_report callback could check both for tags in Extra and in the reporter state.