Initialize OpenTelemetry SDK and setup automatic instrumentations

- Setup Cowboy HTTP server instrumentation with correct Erlang module syntax
- Configure Phoenix instrumentation with cowboy2 adapter specification
- Initialize Ecto database query instrumentation
- Setup Absinthe GraphQL operation instrumentation
- Add startup logging for configuration verification
- Instrumentations initialized before application starts accepting requests

Author: caitlinhalla

manual-instrumentation/worms_in_space/lib/worms_in_space/application.ex

@@ -7,6 +7,9 @@ defmodule WormsInSpace.Application do
 
   @impl true
   def start(_type, _args) do
+    # Setup OpenTelemetry instrumentations
+    setup_opentelemetry()
+
     children = [
       # Start the Ecto repository
       WormsInSpace.Repo,
@@ -24,6 +27,23 @@ defmodule WormsInSpace.Application do
     Supervisor.start_link(children, opts)
   end
 
+  defp setup_opentelemetry do
+    # Setup OpenTelemetry SDK
+    :opentelemetry_cowboy.setup()
+    OpentelemetryPhoenix.setup(adapter: :cowboy2)
+    OpentelemetryEcto.setup([:worms_in_space, :repo])
+    OpentelemetryAbsinthe.setup()
+
+    # Log initialization status
+    if System.get_env("SPLUNK_ACCESS_TOKEN") do
+      service_name = System.get_env("OTEL_SERVICE_NAME", "worms-in-space-backend")
+      realm = System.get_env("SPLUNK_REALM", "us0")
+      IO.puts("OpenTelemetry initialized for #{service_name} sending to Splunk #{realm}")
+    else
+      IO.puts("OpenTelemetry: No Splunk access token configured. Traces will not be sent.")
+    end
+  end
+
   # Tell Phoenix to update the endpoint configuration
   # whenever the application is updated.
   @impl true