OpenTracing instrumentation library for the Erlang/OTP standard modules.
This uses passage as OpenTracing API library.
This example uses following simple echo server.
-module(echo_server).
-compile({parse_transform, passage_transform}). % Enables `passage_trace` attribute
-behaviour(gen_server).
-export([start_link/0, echo/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
%% Exported Functions
start_link() ->
%% Uses `gen_server_passage` instead of `gen_server`
gen_server_passage:start_link({local, ?MODULE}, ?MODULE, [], []).
echo(Message) ->
%% Uses `gen_server_passage` instead of `gen_server`
gen_server_passage:call(?MODULE, {echo, Message}).
%% `gen_server` Callbacks
init(_) -> {ok, []}.
handle_call({echo, Message}, _, State) ->
log(Message),
{reply, Message, State}.
handle_cast(_, State) -> {noreply, State}.
handle_info(_, State) -> {noreply, State}.
terminate(_, _) -> ok.
code_change(_, State, _) -> {ok, State}.
%% Internal Functions
-passage_trace([]). % Annotation for tracing.
log(Message) ->
io:format("Received: ~p\n", [Message]),
ok.By using jaeger and jaeger_passage, you can easily trace and visualize the behaviour of the above server.
As the first step, you need to start jaeger daemons.
$ docker run -d -p6831:6831/udp -p6832:6832/udp -p16686:16686 jaegertracing/all-in-one:latestNext, start Erlang shell and execute following commands.
% Starts `example_tracer`
> Sampler = passage_sampler_all:new().
> ok = jaeger_passage:start_tracer(example_tracer, Sampler).
% Starts `echo_server`
> {ok, _} = echo_server:start_link().
% Traces an echo request
> passage_pd:with_span(echo, [{tracer, example_tracer}],
fun () -> echo_server:echo(hello) end).You can see the tracing result by your favorite browser (in this example, firefox).
$ firefox http://localhost:16686/
https://github.com/sile/otp_passage
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