Settings View Source Tesla.Middleware.Telemetry (tesla v1.7.0)

Emits events using the :telemetry library to expose instrumentation.

examples

Examples

defmodule MyClient do
  use Tesla

  plug Tesla.Middleware.Telemetry
end

:telemetry.attach(
  "my-tesla-telemetry",
  [:tesla, :request, :stop],
  fn event, measurements, meta, config ->
    # Do something with the event
  end,
  nil
)

options

Options

• :metadata - additional metadata passed to telemetry events

telemetry-events

Telemetry Events

• [:tesla, :request, :start] - emitted at the beginning of the request.

  • Measurement: %{system_time: System.system_time()}
  • Metadata: %{env: Tesla.Env.t()}

• [:tesla, :request, :stop] - emitted at the end of the request.

  • Measurement: %{duration: native_time}

  • Metadata: %{env: Tesla.Env.t()} | %{env: Tesla.Env.t(), error: term()}

• [:tesla, :request, :exception] - emitted when an exception has been raised.

  • Measurement: %{duration: native_time}
  • Metadata: %{env: Tesla.Env.t(), kind: Exception.kind(), reason: term(), stacktrace: Exception.stacktrace()}

legacy-telemetry-events

Legacy Telemetry Events

• [:tesla, :request] - This event is emitted for backwards compatibility only and should be considered deprecated. This event can be disabled by setting config :tesla, Tesla.Middleware.Telemetry, disable_legacy_event: true in your config. Be sure to run mix deps.compile --force tesla after changing this setting to ensure the change is picked up.

Please check the telemetry for the further usage.

url-event-scoping-with-tesla-middleware-pathparams-and-tesla-middleware-keeprequest

URL event scoping with Tesla.Middleware.PathParams and Tesla.Middleware.KeepRequest

Sometimes, it is useful to have access to a template url (i.e. "/users/:user_id") for grouping Telemetry events. For such cases, a combination of the Tesla.Middleware.PathParams, Tesla.Middleware.Telemetry and Tesla.Middleware.KeepRequest may be used.

defmodule MyClient do
  use Tesla

  # The KeepRequest middleware sets the template url as a Tesla.Env.opts entry
  # Said entry must be used because on happy-path scenarios,
  # the Telemetry middleware will receive the Tesla.Env.url resolved by PathParams.
  plug Tesla.Middleware.KeepRequest
  plug Tesla.Middleware.Telemetry
  plug Tesla.Middleware.PathParams
end

:telemetry.attach(
  "my-tesla-telemetry",
  [:tesla, :request, :stop],
  fn event, measurements, meta, config ->
    path_params_template_url = meta.env.opts[:req_url]
    # The meta.env.url key will only present the resolved URL on happy-path scenarios.
    # Error cases will still return the original template url.
    path_params_resolved_url = meta.env.url
  end,
  nil
)