Otel.Metrics.Aggregation behaviour (otel v0.4.1)

Aggregation behaviour and default instrument-to-aggregation mapping (metrics/sdk.md §Aggregation L612-L860).

Public API

Callback	Role
`aggregate/4`	SDK (OTel API MUST) — record a measurement into an ETS-backed cell
`collect/3`	SDK (OTel API MUST) — emit datapoints for the configured temporality

References

OTel Metrics SDK §Aggregation: opentelemetry-specification/specification/metrics/sdk.md L612-L860
Built-in implementations: Otel.Metrics.Aggregation.{Sum,LastValue,ExplicitBucketHistogram}

Summary

Types

agg_key()

Per-stream-per-attribute-set aggregation key.

datapoint()

primitive()

primitive_any()

stream_key()

Stream-level identity used by collect/3 callbacks — the instrument's name (the prefix of agg_key/0 minus attributes).

Callbacks

aggregate(metrics_tab, key, value, opts)

collect(metrics_tab, stream_key, opts)

Types

agg_key()

@type agg_key() ::
  {name :: String.t(), attributes :: %{required(String.t()) => primitive_any()}}

Per-stream-per-attribute-set aggregation key.

Used as the ETS key in the metrics table to identify a single aggregation cell — combining the stream name and the attribute set the cell aggregates over. Constructed at every aggregate/4 call site (e.g. Otel.Metrics.Meter) and at exemplar reservoir lookups.

InstrumentationScope is not part of the key: minikube hardcodes a single scope (project memory project_minikube_hardcode_decisions § Follow-on #457), so threading it through every cell key would be redundant. Apps that share an instrument name across logical components namespace via the name itself (e.g. phoenix.requests / ecto.requests).

datapoint()

@type datapoint() :: %{
  attributes: %{required(String.t()) => primitive_any()},
  value: term(),
  start_time: non_neg_integer(),
  time: non_neg_integer()
}

primitive()

@type primitive() ::
  String.t() | {:bytes, binary()} | boolean() | integer() | float() | nil

primitive_any()

@type primitive_any() ::
  primitive() | [primitive_any()] | %{required(String.t()) => primitive_any()}

stream_key()

@type stream_key() :: String.t()

Stream-level identity used by collect/3 callbacks — the instrument's name (the prefix of agg_key/0 minus attributes).

Callbacks

aggregate(metrics_tab, key, value, opts)

@callback aggregate(
  metrics_tab :: :ets.table(),
  key :: agg_key(),
  value :: number(),
  opts :: map()
) :: :ok

collect(metrics_tab, stream_key, opts)

@callback collect(
  metrics_tab :: :ets.table(),
  stream_key :: stream_key(),
  opts :: map()
) :: [datapoint()]

Functions

default_for(atom)

@spec default_for(kind :: Otel.Metrics.Instrument.kind()) :: module()