I found a minimal change to Ash.ProcessHelpers that makes carrying the ecto dynamic repo info around possible:
That enables this preparation to work:
prepare fn query, _context ->
if %{arguments: %{tenant: tenant}} = query do
pid = Dyndb.Repo.get_connection!(tenant)
Dyndb.Repo.put_dynamic_repo(pid)
Ash.set_context(%{dynamic_repo_module: Dyndb.Repo})
end
query
end
So, I added a comment to your PR that you linked to, but I believe that the preparation you added plus a custom tracer ought to do what you need. The custom tracer example is here: Using an Ash Resource with a Dynamic Repository - #10 by zachdaniel
I’ve tried that again and I’m running into the same problem as before - in the preparation I set the span context (which does a Process.put) and set the tracer in the query context, but then get_span_context (which would do a Process.get and then call put_dynamic_repo) is never called.
prepare fn query, context ->
if %{arguments: %{tenant: tenant}} = query do
pid = Dyndb.Repo.get_connection!(tenant)
Ash.Tracer.set_span_context(Dyndb.DynamicRepoTracer, {Dyndb.Repo, pid})
Ash.Query.set_context(query, %{tracer: Dyndb.DynamicRepoTracer})
else
query
end
end
…and the tracer…
defmodule Dyndb.DynamicRepoTracer do
use Ash.Tracer
@impl Ash.Tracer
def get_span_context() do
{repo_module, repo_pid} = Process.get(:dynamic_repo_tracer)
repo_module.put_dynamic_repo(repo_pid)
end
@impl Ash.Tracer
def set_span_context({_repo_module, _repo_pid} = dynamic_repo) do
Process.put(:dynamic_repo_tracer, dynamic_repo)
end
end
Did you configure your app to use the tracer?
config :ash, tracer: [Dyndb.DynamicRepoTracer]
Apologies if I forgot to mention that.
Hey I got it working with the tracer - having not used tracers before and couldn’t find examples of use was the problem. Now I’m worried that the tracer is being called everywhere - is there a way to only turn on the tracer for the duration/scope of a dynamic repo query?
Thanks for all your help!
The preparation:
prepare fn query, context ->
if %{arguments: %{tenant: tenant}} = query do
pid = Dyndb.Repo.get_connection!(tenant)
Dyndb.DynamicRepoTracer.set_span_context({Dyndb.Repo, pid})
end
query
end
…and the custom part of the tracer…
@impl Ash.Tracer
def get_span_context() do
Process.get(:dynamic_repo_tracer)
end
@impl Ash.Tracer
def set_span_context({repo_module, repo_pid} = dynamic_repo) do
Process.put(:dynamic_repo_tracer, dynamic_repo)
repo_module.put_dynamic_repo(repo_pid)
:ok
end
The github repo has been updated.
I don’t think that there is a way currently to conditionally enable the tracer, or at least not a way that I think would be seamless for you. However, Process.get/1 is very cheap, so I think that if your set_span_context just handles the case where that value is nil then it shouldn’t be a concern.