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Add :telemetry_prefix option to Tesla.Middleware.Telemetry #390

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Add :telemetry_prefix option to Tesla.Middleware.Telemetry #390

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bc7659b
adds telemetry_prefix config w/ tests
keatz55 Jun 12, 2020
ac2e14e
adds better configuration options and docs
keatz55 Jun 12, 2020
619f19c
makes requested changes
keatz55 Jun 15, 2020
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76 changes: 44 additions & 32 deletions lib/tesla/middleware/telemetry.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,28 @@ if Code.ensure_loaded?(:telemetry) do
end)
```

## Options
- `:prefix` - replaces default `[:tesla]` with desired Telemetry event prefix (see below)

## Custom Prefix

All events will use a `:prefix` which defaults to `[:tesla]`.

You can customize events by providing your own `:prefix` locally:

```
defmodule MyClient do
use Tesla

plug Tesla.Middleware.Telemetry, prefix: [:custom, :prefix]

end

:telemetry.attach("my-tesla-telemetry", [:custom, :prefix, :request, :stop], fn event, measurements, meta, config ->
# Do something with the event
end)
```

## Telemetry Events

* `[:tesla, :request, :start]` - emitted at the beginning of the request.
Expand Down Expand Up @@ -46,11 +68,14 @@ if Code.ensure_loaded?(:telemetry) do

@behaviour Tesla.Middleware

@default_prefix [:tesla]

@impl Tesla.Middleware
def call(env, next, _opts) do
def call(env, next, opts) do
start_time = System.monotonic_time()
prefix = Keyword.get(opts, :prefix, @default_prefix)

emit_start(%{env: env})
emit_start(%{env: env}, prefix)

try do
Tesla.run(env, next)
Expand All @@ -59,62 +84,49 @@ if Code.ensure_loaded?(:telemetry) do
stacktrace = System.stacktrace()
duration = System.monotonic_time() - start_time

emit_exception(duration, %{kind: kind, reason: reason, stacktrace: stacktrace})
emit_exception(duration, %{kind: kind, reason: reason, stacktrace: stacktrace}, prefix)

:erlang.raise(kind, reason, stacktrace)
else
{:ok, env} = result ->
duration = System.monotonic_time() - start_time

emit_stop(duration, %{env: env})
emit_legacy_event(duration, result)
emit_stop(duration, %{env: env}, prefix)
emit_legacy_event(duration, result, prefix)

result

{:error, reason} = result ->
duration = System.monotonic_time() - start_time

emit_stop(duration, %{env: env, error: reason})
emit_legacy_event(duration, result)
emit_stop(duration, %{env: env, error: reason}, prefix)
emit_legacy_event(duration, result, prefix)

result
end
end

defp emit_start(metadata) do
:telemetry.execute(
[:tesla, :request, :start],
%{system_time: System.system_time()},
metadata
)
defp emit_start(metadata, prefix) do
event = prefix ++ [:request, :start]
:telemetry.execute(event, %{system_time: System.system_time()}, metadata)
end

defp emit_stop(duration, metadata) do
:telemetry.execute(
[:tesla, :request, :stop],
%{duration: duration},
metadata
)
defp emit_stop(duration, metadata, prefix) do
event = prefix ++ [:request, :stop]
:telemetry.execute(event, %{duration: duration}, metadata)
end

defp emit_legacy_event(duration, result) do
defp emit_legacy_event(duration, result, prefix) do
if !@disable_legacy_event do
event = prefix ++ [:request]
duration_µs = System.convert_time_unit(duration, :native, :microsecond)

:telemetry.execute(
[:tesla, :request],
%{request_time: duration_µs},
%{result: result}
)
:telemetry.execute(event, %{request_time: duration_µs}, %{result: result})
end
end

defp emit_exception(duration, metadata) do
:telemetry.execute(
[:tesla, :request, :exception],
%{duration: duration},
metadata
)
defp emit_exception(duration, metadata, prefix) do
event = prefix ++ [:request, :exception]
:telemetry.execute(event, %{duration: duration}, metadata)
end
end
end
115 changes: 86 additions & 29 deletions test/tesla/middleware/telemetry_test.exs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
defmodule Tesla.Middleware.TelemetryTest do
use ExUnit.Case, async: true

@moduletag capture_log: true

defmodule Client do
use Tesla

Expand All @@ -26,47 +28,102 @@ defmodule Tesla.Middleware.TelemetryTest do
:ok
end

test "events are all emitted properly" do
Enum.each(["/telemetry", "/telemetry_error"], fn path ->
:telemetry.attach("start event", [:tesla, :request, :start], &echo_event/4, %{
caller: self()
})
describe "Telemetry" do
test "events are all emitted properly" do
Enum.each(["/telemetry", "/telemetry_error"], fn path ->
:telemetry.attach("start event", [:tesla, :request, :start], &echo_event/4, %{
caller: self()
})

:telemetry.attach("stop event", [:tesla, :request, :stop], &echo_event/4, %{
caller: self()
})
:telemetry.attach("stop event", [:tesla, :request, :stop], &echo_event/4, %{
caller: self()
})

:telemetry.attach("legacy event", [:tesla, :request], &echo_event/4, %{caller: self()})

Client.get(path)

:telemetry.attach("legacy event", [:tesla, :request], &echo_event/4, %{
assert_receive {:event, [:tesla, :request, :start], %{system_time: time},
%{env: %Tesla.Env{url: path, method: :get}}}

assert_receive {:event, [:tesla, :request, :stop], %{duration: time},
%{env: %Tesla.Env{url: path, method: :get}}}

assert_receive {:event, [:tesla, :request], %{request_time: time}, %{result: result}}
end)
end

test "with an exception raised" do
:telemetry.attach("with_exception", [:tesla, :request, :exception], &echo_event/4, %{
caller: self()
})

Client.get(path)
assert_raise RuntimeError, fn ->
Client.get("/telemetry_exception")
end

assert_receive {:event, [:tesla, :request, :exception], %{duration: time},
%{kind: kind, reason: reason, stacktrace: stacktrace}}
end
end

describe "with :prefix" do
defmodule ClientWithPrefix do
use Tesla

assert_receive {:event, [:tesla, :request, :start], %{system_time: time},
%{env: %Tesla.Env{url: path, method: :get}}}
plug Tesla.Middleware.Telemetry, prefix: [:custom, :prefix]

assert_receive {:event, [:tesla, :request, :stop], %{duration: time},
%{env: %Tesla.Env{url: path, method: :get}}}
adapter fn env ->
case env.url do
"/telemetry" -> {:ok, env}
"/telemetry_error" -> {:error, :econnrefused}
"/telemetry_exception" -> raise "some exception"
end
end
end

assert_receive {:event, [:tesla, :request], %{request_time: time}, %{result: result}}
end)
end
test "events are all emitted properly" do
Enum.each(["/telemetry", "/telemetry_error"], fn path ->
:telemetry.attach("start event", [:custom, :prefix, :request, :start], &echo_event/4, %{
caller: self()
})

:telemetry.attach("stop event", [:custom, :prefix, :request, :stop], &echo_event/4, %{
caller: self()
})

test "with an exception raised" do
:telemetry.attach("with_exception", [:tesla, :request, :exception], &echo_event/4, %{
caller: self()
})
:telemetry.attach("legacy event", [:custom, :prefix, :request], &echo_event/4, %{
caller: self()
})

assert_raise RuntimeError, fn ->
Client.get("/telemetry_exception")
ClientWithPrefix.get(path)

assert_receive {:event, [:custom, :prefix, :request, :start], %{system_time: time},
%{env: %Tesla.Env{url: path, method: :get}}}

assert_receive {:event, [:custom, :prefix, :request, :stop], %{duration: time},
%{env: %Tesla.Env{url: path, method: :get}}}

assert_receive {:event, [:custom, :prefix, :request], %{request_time: time},
%{result: result}}
end)
end

assert_receive {:event, [:tesla, :request, :exception], %{duration: time},
%{
kind: kind,
reason: reason,
stacktrace: stacktrace
}}
test "with an exception raised" do
:telemetry.attach(
"with_exception",
[:custom, :prefix, :request, :exception],
&echo_event/4,
%{caller: self()}
)

assert_raise RuntimeError, fn ->
ClientWithPrefix.get("/telemetry_exception")
end

assert_receive {:event, [:custom, :prefix, :request, :exception], %{duration: time},
%{kind: kind, reason: reason, stacktrace: stacktrace}}
end
end

def echo_event(event, measurements, metadata, config) do
Expand Down