Absinthe request flow - flame graph

devmarco · May 20, 2024, 4:55pm

Hello,

I am trying to generate a flame graph for my Absinthe application and I am having a hard time understanding the whole Absinthe flow and how to make it work.

I am using the eflambe library and it contains a capture function where I have to specify the module and function that I want to trace.

Eg:
:eflambe.capture({Absinthe.Plug.GraphiQL, :call, 2}, 1, output_format: :brendan_gregg)

Can someone help me understand the entry point of an Absinthe request call and a module that I can use to trace the whole execution?

NOTE:

I don’t want to benchmark only the resolver call because Absinthe is doing a lot of more work after that and that’s what I want to see in a flame graph.

I realized that having nested fields might slow down things and this is what I am trying to see and improve.

Thanks in advance

benwilson512 · May 20, 2024, 5:18pm

Hey @devmarco Absinthe.run(document, schema, variables: variables, context: context) is probably what will work best for you.

Let me know what you find!

devmarco · May 20, 2024, 5:28pm

@benwilson512 It seems that eflamble does not work with external modules.

I think it only works with modules defined by my application. Or maybe because the code is not executing that after all.

I tried to run this, but after making a request I didn’t see any trigger to the capture function.

:eflambe.capture({Absinthe, :run, 3}, 1, output_format: :brendan_gregg)

When I use Absinthe.Plug.GraphiQL call function, it works. So I don’t think it’s an external module issue. Are we calling that even using the GraphiQL plug?

Do you know any other way where I can generate a flame graph for an Absinthe request?

benwilson512 · May 20, 2024, 5:44pm

I am not familiar with that library, sorry. Your theory about whether it works with external modules though is pretty easy to test, just call a simple function in another library and see what happens.

devmarco · May 20, 2024, 6:05pm

I did a couple of tests and it worked with Absinthe.Pipeline.run/2.

github.com

absinthe-graphql/absinthe_plug/blob/main/lib/absinthe/plug.ex#L540


      
          
          def run_request(%{batch: false, queries: [query]} = request, conn, conn_info, config) do
            Request.log(request, config.log_level)
            run_query(query, conn, conn_info, config)
          end
          
          defp run_query(query, conn, conn_info, config) do
            %{document: document, pipeline: pipeline} =
              Request.Query.add_pipeline(query, conn_info, config)
          
            case Absinthe.Pipeline.run(document, pipeline) do
              {:ok, %{result: result} = bp, _} ->
                conn = apply_before_send(conn, [bp], config)
                {conn, {:ok, result}}
          
              val ->
                {conn, val}
            end
          end
          
          #

Thank you @benwilson512