Monitoring GraphQL fields with telemetry

Phoenix Forum Questions / Help
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1

Hey everybody, first post here :slight_smile:

I am trying to monitor our GraphQL (Absinthe) service’s entity resolution, to the granularity of a field.
That means, I want to be able to know which fields were being resolved in each entity - the purpose is to know when a field is not being used anymore, so I can remove it from the graph.

I am using Absinth’s telemetry abilities but it only report to the level of the resolver, and not the field. IE if I’m querying {user { friends { name }} it will report I have accessed User.friends but will leave the name part out.

Did you encounter this issue? Maybe you have a cool solution that I might’ve missed?
THANKS

2

Hi @nadavdav :wave: And welcome to the community!

If I understand correctly you want the “resolution path” on on each field that was resolved.
absinthe.resolved.field event might be the one you need.

:telemetry.attach_many(
  :resolved_paths,
  [
    [:absinthe, :resolve, :field, :stop]
  ],
  fn _event_name, _measurements, metadata, _config ->
    resolution_path = Absinthe.Resolution.path(metadata.resolution)
    
    IO.inspect(resolution_path, label: "RESOLVED PATH")
  end,
  []
)

This is supposed to print out resolved path on each resolved field. For example, for {user { friends { name }} it would emit and print 3 events:

["user"]
["user", "friends"]
["user", "friends", "name"]
3

Just small thing - you should not use anonymous functions as telemetry handlers outside debugging.

5 Likes
4

Hey @RudManusachi and @hauleth . thank you for the response!

I gave it a try and I still only get the path of the resolver, but not the field.
It kinda makes sense since the resolver is returning an object, and there isn’t any place to “hook” this reporting when reading the object.

Is it possible to translate 1 metric to multiple reports?

For example, If I am querying { user { info { color, age }} I have one resolution event for User.info (that returns an object) and I want to be able to maybe translate it to two events Info.color and Info.age.

does it make sense?

5

Huh, indeed! Fields are not included in path. However, looks like we can dig that info out from the resolution struct! (metadata.resolution.definition.selections is a list of fields requested to be resolved)

Don’t know if this is the most optimal way, but seems to be doing the trick:

:telemetry.attach(
  :resolved_paths,
  [:absinthe, :resolve, :field, :stop],
  fn _event_name, _measurements, metadata, _config ->
    Absinthe.Resolution.path(metadata.resolution)
    |> IO.inspect(label: "RESOLUTION PATH")
    
    # THIS
    # metadata.resolution.definition.selections 
    Absinthe.Resolution.project(metadata.resolution)
    |> Enum.map(fn field -> field.name end)
    |> IO.inspect(label: "SELECTED FIELDS")
  end,
  []
)

I guess it would print something like:

RESOLUTION PATH: ["user"]
SELECTED FIELDS: ["info"]
...
RESOLUTION PATH: ["user", "info"]
SELECTED FIELDS: ["age", "color"]

UPD looks like we could use Absinthe.Resolution.project/1

Get the child fields under the current field.

so we could replace metadata.resolution.definition.selections with
Absinthe.Resolution.project(metadata.resolution)

And probably that would be better approach, because that way we delegate “dealing with the internal structure of the resolution struct” to the function.

6

Thank you! I’ll try that soon and hopeful come back with positive results!