Observability

A simple repo to demonstrated how to wired up basic observability in a Phoenix app.

We'll start with a basic Phoenix app and show how the basic metrics can be visualized with Grafana by having Prometheus scrape the /metrics endpoint.

Then we'll add a custom metric and show how to add a custom span to the metrics.

Finally, we'll show how to use Telemetry to trace a request through the system.

Install Elixir, Phoenix, and generate a basic phoenix app.

Install Elixir and phoenix https://hexdocs.pm/phoenix/installation.html

Generate a basic phoenix app. Called observability https://hexdocs.pm/phoenix/up_and_running.html

https://cri.dev/posts/2020-05-10-Elixir-trick:-start-an-Observer-window-with-mix/

To give us something to work with, extend it with basic Accounts and Users https://hexdocs.pm/phoenix/Mix.Tasks.Phx.Gen.Json.html

mix phx.gen.json Accounts User users name:string age:integer mix ecto.migrate

Get basic /metrics working

https://hexdocs.pm/prom_ex/readme.html

• Addprom_ex.ex Ecto metrics. https://hexdocs.pm/prom_ex/readme.html#setting-up-promex
• Install Prometheus and Grafana.
• Add Phoenix metrics.

Add a custom metric

• One basic custom metric.

Add Telemetry tracing

Add custom span with raw Telemetry

Context propagation to custom span from controller call

Replace custom span with @decorate

Use Ctor and Protocol to @decorate implementation

Create new app to show cross-app context propagation

Notes

https://cri.dev/posts/2020-05-10-Elixir-trick:-start-an-Observer-window-with-mix/ https://hexdocs.pm/elixir/debugging.html http://localhost:4000/dev/dashboard/applications?limit=50&search=&sort_by=name&sort_dir=asc