open-telemetry/opentelemetry-erlang

Tristan Sloughter

@tsloughter

yea

Peter Saxton

@CrowdHailer

I've also moved on to using the opentelemetry_exporter I can only find docs on jaeger about supporting protobuf.

From what it says here https://www.jaegertracing.io/docs/1.21/getting-started/ I "think" I need to point the opentelemetry_exporter to use localhost: 14250

What I'm not sure about is if model.proto means that it accepts the opentelemetry http_protobuf format. I'm guessing it does.

Tristan Sloughter

@tsloughter

hm, don't know. but you can use the zipkin exporter to write to jaeger

if you don't want to have to to the collector to get to jaeger

Peter Saxton

@CrowdHailer

The zipkin exporter doesn't work with {opentelemetry, 0.5.0}

What would you use to look at traces generated locally?

Or perhaps more relevant what services or local things can will accept what https://github.com/open-telemetry/opentelemetry-erlang/tree/master/apps/opentelemetry_exporter is sending

Tristan Sloughter

@tsloughter

not sure what else exists, opentelemetry collector might have a visualization option in its contrib repo

Tristan Sloughter

@tsloughter

and the update to the zipkin exporter to 0.5.0 shouldn't be much to change

Chulki Lee

@chulkilee

Hi - I'm working on improving docs - open-telemetry/opentelemetry-erlang#176 - and I have a few questions. 1) I see this gitter room is mentioned in one of README. Is this the place to join? Then I'll add it to all README

Chulki Lee

@chulkilee

Also.. do we have benchmark? seems like c25ac353602cf1ce8d655e2f5c7e850e147151ce removed code from samples.

Tristan Sloughter

@tsloughter

if I remember correctly the benchmarks were removed because the particular ones didn't make sense anymore and none have been added since

this gitter is like the official opentelemetry channel for the Erlang SIG. but discussion also happens through the Erlang Ecosystem Foundation observability working group channel in the Erlang slack

Chulki Lee

@chulkilee

When instrumenting a project your application should only depend on the OpenTelemetry API application, found in directory apps/opentelemetry_api of this repo which is published as the hex package opentelemetry_api.

This is confusing - since to instrumnet my project, isn’t it supposed to use SDK, not API? e.g. SDK actually holds the implementation, and sdk depends on api, not vice versa

Tristan Sloughter

@tsloughter

instrumentation is done with just the API -- meaning just adding calls to create spans and instruments and record metrics

you then include an SDK that makes the instrumentation actually do something

phrasing can be better for sure, that or start with definitions of stuff like "instrumenting", so it is clear that just refers to adding those calls like with_span to the code

Tristan Sloughter

@tsloughter

I gotta go but if you leave more questions tomorrow my morning. thanks for the work on docs!

Chulki Lee

@chulkilee

Instrumentation is hooked with just the API - but it’s no-op so end users MUST include an implementation - and opentelemetry provides it. So saying “you should only depned on opentelemetry-api” is definitely incorrect. I’ll make some changes in the PR - open-telemetry/opentelemetry-erlang#176

Chulki Lee

@chulkilee

Aha probably the confusion is whether “application” is of the end-user project (e.g. project to run a web service), or my library package (e.g. HTTP library “application”). Is there any good terminology in Erlang?

https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/library-guidelines.md uses “final application” vs “third party libraries/frameworks” btw.

Chulki Lee

@chulkilee

Oh… and another source of confusion - we use apps/opentelemetry_api is for API, apps/opentelemetry for SDK.. but opentelemetry module is defined at opentelemetry_api. Hm..

3 replies

Tristan Sloughter

@tsloughter

yea, we shouldn't use "application" the same way opentelemetry spec does because it has special meaning in OTP.

Chulki Lee

@chulkilee

For traces to actually be tracked, propagated and exported, the opentelemetry Application must be included as a dependency of your project, likely as part of a Release and not as a dependency of an individual Application within the Release.

What’s the reason? I guess it is to start and supervise opentelemetry application (SDK) at the top level, not a child of a specific application. Is it correct?

Tristan Sloughter

@tsloughter

no, either way it is started at the top level. it is simply to try driving home the fact that you should be depending on only the API unless you are writing something like an exporter

Tristan Sloughter

@tsloughter

meeting tomorrow morning will discuss: open-telemetry/opentelemetry-erlang#188 so the more attendance the better :)

Tristan Sloughter

@tsloughter

yo, I'm on vaca and won't be around for a meeting today.

Bogdan Drutu

@bogdandrutu

@tsloughter can I delete this repo https://github.com/open-telemetry/opentelemetry-erlang-api ?

Tristan Sloughter

@tsloughter

eh... I'd say yes except there is the possibility someone somewhere still points to it in the dependencies and then their build will break

Bogdan Drutu

@bogdandrutu

:))

so the final answer is?

Tristan Sloughter

@tsloughter

preferably wait. when 1.0 is cut I'd say its fine to delete

Bogdan Drutu

@bogdandrutu

If I change the default branch to main do I cause the same issue ?

Tristan Sloughter

@tsloughter

nope, thats fine

dmy-gh

@dmy-gh

Hey there :)
Playing around with Elixir I can't figure out how to set the parent span for a new span declared in an anonymous function in a Task.async.
I tried something like this:

    OpenTelemetry.Tracer.with_span "span_1" do
      span_ctx = OpenTelemetry.Tracer.current_span_ctx()

      task =
        Task.async(fn ->
          OpenTelemetry.Tracer.with_span "span_2", %{parent: span_ctx} do
            nil
          end
        end)

      ... 
    end

But the parent option does not seem to do anything.
Can you please help me on what I am probably doing wrong here?

dmy-gh

@dmy-gh

Digging into the code I couldn't find the parent key involved in the span creation.

Tristan Sloughter

@tsloughter

actually working on an example for this for the docs page right now :)

parent as an optoin is gone

what is suggested for a spawned process is to create a new span before spawning and setting it to active in the spawned function

in erlang this would look like

SpanCtx = ?start_span(<<"child">>),
Ctx = otel_ctx:get_current(),

proc_lib:start_link(fun() ->
                        otel_ctx:attach(Ctx),
                        ?set_current_span(SpanCtx)
                        %% do work here
                    end),

spawn not start...

I don't do much Elixir so haven't got the Task version done yet

linking is also an option when spawning a new process, since it doesn't necessarily have a parent/child relationship:

SpanCtx = ?current_span_ctx,
proc_lib:spawn_link(fun() ->
                        Link = opentelemetry:link(SpanCtx),
                        ?with_span(<<"other-process">>, #{links => [Link]},
                                   fun() -> ok end)
                    end),

Tristan Sloughter

@tsloughter

ok, made a test that shows how to do this. should really have a way to automatically end a Task's span.. for now I'm just ending it manually

https://gist.github.com/tsloughter/ddd8653dc245b88c9d612fc5d85fe4e2

there are a couple ways of doing the context part which may make it confusing

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