1184851 - Add mock publisher and stats drain to taskcluster-base

Status: RESOLVED WONTFIX

(Taskcluster :: Services, defect)

Description

[Morgan Phillips [:mrrrgn]]

It's difficult to write pure unit tests for taskcluster right now, since using the publisher requires a pulse account, and the stats drain requires an influxdb instance. Simply stubbing out these objects is possible, but that, in turn, makes it impossible to access features/data which would be desirable (e.g. schema validation). 

As per discussion on: https://github.com/taskcluster/taskcluster-github/pull/1

"I'm not oppose to these things. But stubbing out the publisher means that you skip validation etc... and it very quickly becomes rather boring... So if we really want to do something like this, perhaps we should add an option to base.Exchanges such that a boolean config option can be used to get a dummy publisher that just validates messages and emits them as events on the process object.

We should probably do the same for stats.Influx, such that it looks like:

statsDrain = new base.stats.Influx({
  connectionString:   cfg.get('influx:connectionString'),
  // then in config/test.js, set influx:connectionString = "null"
  // and modify base.stats.Influx such that connectionString means it will print stats as debug messages
  // and emit them as events on the process object.
  maxDelay:           cfg.get('influx:maxDelay'),
  maxPendingPoints:   cfg.get('influx:maxPendingPoints')
});"

We should either 1.) add an offline mode to the publisher/influx objects or 2.) creates official mock versions of these objects.

Comment 1

[Jonas Finnemann Jensen (:jonasfj)]

I think this is a good idea. Note, we already have a mock version for influx called NullDrain.
But it adds extra code to everywhere when we add
  if (useMock) {drain = NullDrain()} else { drain = Influx(...)}
(and this is boring duplicated code, the worst kind of code!)

So having it as a configuration option, or special connectionString, would reduce complications and we
would be able to set the mode from a configuration profile. IMO, integration tests are valuable, but
since Influx and Exchange bindings are so heavily tested in taskcluster-base, giving them an "offline"
mode, seems pretty reasonable. In both cases we still want type/schema validation, etc.

Comment 2

[Jonas Finnemann Jensen (:jonasfj)]

I think dustin did some of this already... regardless the code have been refactored since, let's close.