Fred.Telemetry (Fred v0.4.0)

Telemetry integration for the Fred library.

Fred emits telemetry events using :telemetry.span/3 for every API request. Each span produces three possible events:

Events

[:fred, :request, :start]

Emitted when a request begins.

Measurements:

• :system_time - System time at the start of the request (in native units)

Metadata:

• :url - The requested URL
• :params - The query parameters map (with :api_key redacted)

[:fred, :request, :stop]

Emitted when a request completes successfully (the HTTP round-trip finished, regardless of API-level errors like 404s).

Measurements:

• :duration - Total wall-clock duration in native time units. Convert with System.convert_time_unit(duration, :native, :millisecond).

Metadata:

• :url - The requested URL
• :params - The query parameters map (with :api_key redacted)
• :status - HTTP status code (integer) or nil if the request never completed
• :result - :ok or :error
• :error - The %Fred.Error{} struct (only present when :result is :error)

[:fred, :request, :exception]

Emitted when the request raises an unexpected exception.

Measurements:

• :duration - Wall-clock duration until the exception

Metadata:

• :url - The requested URL
• :params - The query parameters map (with :api_key redacted)
• :kind - The exception kind (:throw, :error, :exit)
• :reason - The exception or thrown value
• :stacktrace - The stacktrace

Attaching Handlers

You can attach your own handlers to any of these events:

:telemetry.attach(
  "my-fred-handler",
  [:fred, :request, :stop],
  &MyApp.handle_fred_event/4,
  nil
)

Or use the built-in logger for quick request observability:

# In your Application.start/2:
Fred.Telemetry.Logger.attach()