From 3334b07b9ddaff9c2eadd829bdc2af8394988721 Mon Sep 17 00:00:00 2001
From: "Marco \"Efesto\" Polita" <polita.marco@gmail.com>
Date: Fri, 1 Oct 2021 18:30:49 +0200
Subject: [PATCH] Adds readme entry on Plug.Telemetry (#20)

* adds entry about Plug.Telemetry

* Adds reference to phoenix endpoint template
---
 instrumentation/opentelemetry_phoenix/README.md | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/instrumentation/opentelemetry_phoenix/README.md b/instrumentation/opentelemetry_phoenix/README.md
index 09d0d13..dd39f0f 100644
--- a/instrumentation/opentelemetry_phoenix/README.md
+++ b/instrumentation/opentelemetry_phoenix/README.md
@@ -27,3 +27,18 @@ def deps do
 end
 ```
 
+## Note on phoenix integration
+
+`OpentelemetryPhoenix` requires phoenix to use `Plug.Telemetry` in order to correctly trace endpoint calls.
+
+The `endpoint.ex` file should look like:
+```Elixir
+defmodule MyApp.Endpoint do
+  use Phoenix.Endpoint, otp_app: :my_app
+  ...
+  plug Plug.Telemetry, event_prefix: [:phoenix, :endpoint]
+  ...
+end
+```
+The [Phoenix endpoint.ex template](https://github.com/phoenixframework/phoenix/blob/v1.6.0/installer/templates/phx_web/endpoint.ex#L39) can be used as a reference
+