Offer callback to set “current” span context?

[garthk]

I need a configurable callback I can use to set the seq_trace label per path at the beginning of its resolution. It'll be brittle, but I've little other hope of tying outbound spans to the fields rather than the whole blueprint.

[garthk]

From my poking around Absinthe so far, strikes me Absinthe.Phase.Document.Execution.Resolution will keep working on entries in res.middleware until it either finishes or gets %{state: :suspended} from one of the three async troublemakers. The good news is that we can set the “current” span context for the field/path at the beginning of res.middleware, and it'll be available whenever anything is kicked off during that first pass. The bad news is, I haven't yet found a way to put it back for any subsequent activity e.g. the post_batch_fun callback, nor to clear it at the end of the first pass.

[garthk]

Might be wrong about the end of the first pass: the after_resolution callback will fire. And, then, again as long as any of the plugins' pipeline/2 callbacks insert another Absinthe.Phase.Document.Execution.Resolution.

[garthk]

Would it be too intrusive to insert a phase to rewrite the blueprint to replace all the {Absinthe.Middleware.Batch, {batch_key, post_batch_fun}} tuples with something that'd call seq_trace first? I'd have to come last, somehow…

  def plugins do
    [Absinthe.Middleware.Dataloader] ++ AbsinthePlugin.defaults()
  end

… like putting myself at the end of that list, there.

[garthk]

Ugh. Absinthe.Phase.Document.Execution.Resolution.run_callbacks/4 always runs the plugins in order. We'll need two to measure the whole loop: one first, and one last.