# Sending your deploy markers to Appsignal from a Phoenix app.

AppSignal deploy markers are a way to keep track of what git commit the bug happened, or when the slowdown started appearing in your app.

![image](https://elixirforum.com/uploads/default/original/3X/9/1/918e41d27e398b3bd55b2144cd59573dc905608e.png align="left")

[https://docs.appsignal.com/application/markers/deploy-markers.html](https://docs.appsignal.com/application/markers/deploy-markers.html)

As long as you have an `APP_REVISION` environment variable set, you will send it to Appsignal through the integration library.

In the case of [Railway](https://railway.com) you can quite easily add the variable to your Dockerfile and have everything work out nicely in 2 lines.

Railway even provides the variable automatically for you.

```dockerfile
# At the very end of your Dockerfile:

# This is a variable Railway automatically exposes.
# Add the variable.
ARG RAILWAY_GIT_COMMIT_SHA 

# Use the variable
ENV APP_REVISION=$RAILWAY_GIT_COMMIT_SHA

CMD ["/app/bin/server"]
```

And that's it. Deploy markers will now work for you.