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[bryannaegele]

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[himadrica]

Hi, I am Himadri. I am a software developer. Currently learning Erlang and I have a project about instrumenting Erlang app with opentelemtry. So my design is a java application and an Erlang app taking each other with http call. I am making a http request to the java rest endpoint but I am getting two separate traces instead of 1 trace between Erlang and Java. Here is my Erlang oepntelemetry configurations

sys.config
[ {opentelemetry, [{processors, [{otel_batch_processor, #{exporter => {opentelemetry_exporter, #{protocol => grpc, endpoints => [{http, "localhost", 4317, []}]}}}}]}]} , {text_map_propagators, [baggage, trace_context]} ].

rebar.config

`{erl_opts, [debug_info]}.
{deps, [
{opentelemetry_api, "> 1.0"},
{opentelemetry, "> 1.0"},
{amqp_client, "3.9.11"},
{opentelemetry_exporter, {git_subdir, "http://github.com/open-telemetry/opentelemetry-erlang", {branch, "main"}, "apps/opentelemetry_exporter"}}
]}.

{relx, [
{release, {otel_multi_node, "0.1.0"},
[
opentelemetry_exporter,
{opentelemetry, temporary},
otel_multi_node,
sasl
]
},

    {mode, dev},

    %% automatically picked up if the files
    %% exist but can be set manually, which
    %% is required if the names aren't exactly
    %% sys.config and vm.args
    {sys_config, "./config/sys.config"},
    {vm_args, "./config/vm.args"}

    %% the .src form of the configuration files do
    %% not require setting RELX_REPLACE_OS_VARS
    %% {sys_config_src, "./config/sys.config.src"},
    %% {vm_args_src, "./config/vm.args.src"}

]}.`

*.app.src
`{application, otel_multi_node,
[{description, "An OTP application"},
{vsn, "0.1.0"},
{registered, []},
{mod, {otel_multi_node_app, []}},
{applications,
[kernel,
stdlib,
opentelemetry_api,
opentelemetry
]},
{env,[]},
{modules, []},

{licenses, ["Apache 2.0"]},
{links, []}
]}.
`

erlang function:
httpCall() -> Attributes = #{ 'http.client_ip' => 'localhost', 'http.flavor' => 'http', 'http.host' => 'localhost:8080', 'http.host.port' => '8080', 'http.method' => 'GET', 'http.scheme' => '', 'http.target' => 'producer', 'net.host.ip' => '127.0.0.1', 'net.transport' => 'IP.TCP' }, ?with_span(<<"http call to producer">>, Attributes, fun(_whatever) -> Method = get, URL = <<"http://localhost:8080/send?msg=hello">>, Headers = [], Payload = <<>>, Options = [], httpc:request(URL) end), ok.

I am not sure why the context is not propagating. Am I missing any configuration or do I need some other instrumentation?

[tsloughter]

Hi @himadrica please make a separate discussion topic to discuss specific questions like this. But I can also note that for httpc you need to include the propagation headers yourself (httpc has no middleware/hook support). There is actually an example of just this in the interop tests: https://github.com/open-telemetry/opentelemetry-erlang/blob/main/interop/w3c_trace_context_interop.erl#L52-L59

[himadrica]

Thank you @tsloughter for your reply. I will create a separate topic.