Implement event filtering on measurements (#77)

lib/telemetry_metrics.ex

@@ -68,10 +68,12 @@ defmodule Telemetry.Metrics do
  * `:tag_values` - a function that receives the metadata and returns a map with
  the tags as keys and their respective values. Defaults to returning the
  metadata itself.
- * `:keep` - a predicate function that evaluates the metadata to conditionally
- record a given event. `:keep` and `:drop` cannot be combined. Defaults to `nil`.
- * `:drop` - a predicate function that evaluates the metadata to conditionally
- skip recording a given event. `:keep` and `:drop` cannot be combined. Defaults to `nil`.
+ * `:keep` - a predicate function that evaluates the metadata and measurement
+ to conditionally record a given event. `:keep` and `:drop` cannot be
+ combined. Defaults to `nil`.
+ * `:drop` - a predicate function that evaluates the metadata and measurement
+ to conditionally skip recording a given event. `:keep` and `:drop` cannot
+ be combined. Defaults to `nil`.
  * `:description` - human-readable description of the metric. Might be used by
  reporters for documentation purposes. Defaults to `nil`.
  * `:unit` - an atom describing the unit of selected measurement, typically in
@@ -408,7 +410,9 @@ defmodule Telemetry.Metrics do
  @type tag :: term()
  @type tags :: [tag()]
  @type tag_values :: (:telemetry.event_metadata() -> :telemetry.event_metadata())
- @type keep :: (:telemetry.event_metadata() -> boolean())
+ @type keep ::
+ (:telemetry.event_metadata() -> boolean())
+ | (:telemetry.event_metadata(), :telemetry.event_measurements() -> boolean())
  @type drop :: (:telemetry.event_metadata() -> boolean())
  @type description :: nil | String.t()
  @type unit :: atom()
@@ -614,11 +618,11 @@ defmodule Telemetry.Metrics do
  end
 
  defp validate_recording_rule_fun!(nil), do: nil
- defp validate_recording_rule_fun!(fun) when is_function(fun, 1), do: fun
+ defp validate_recording_rule_fun!(fun) when is_function(fun, 1) or is_function(fun, 2), do: fun
 
  defp validate_recording_rule_fun!(term) do
  raise ArgumentError,
- "expected recording rule to be a function accepting metadata, got #{inspect(term)}"
+ "expected recording rule to be a function accepting either metadata or metadata and measurements, got #{inspect(term)}"
  end
 
  defp validate_recording_rule_fun_options!(keep, drop) when is_nil(keep) or is_nil(drop), do: :ok
@@ -629,8 +633,9 @@ defmodule Telemetry.Metrics do
  end
 
  defp keep_fun(nil, nil), do: nil
- defp keep_fun(nil, drop), do: fn meta -> not drop.(meta) end
  defp keep_fun(keep, nil), do: keep
+ defp keep_fun(nil, drop) when is_function(drop, 1), do: &(not drop.(&1))
+ defp keep_fun(nil, drop) when is_function(drop, 2), do: &(not drop.(&1, &2))
 
  @spec fill_in_default_metric_options([metric_option()]) :: [metric_option()]
  defp fill_in_default_metric_options(options) do

lib/telemetry_metrics/console_reporter.ex

@@ -100,7 +100,7 @@ defmodule Telemetry.Metrics.ConsoleReporter do
  Measurement value missing (metric skipped)
  """
 
- not keep?(metric, metadata) ->
+ not keep?(metric, metadata, measurements) ->
  """
  Event dropped
  """
@@ -142,8 +142,13 @@ defmodule Telemetry.Metrics.ConsoleReporter do
  "#{inspect(measurement)} [via #{inspect(fun)}]"
  end
 
- defp keep?(%{keep: nil}, _metadata), do: true
- defp keep?(metric, metadata), do: metric.keep.(metadata)
+ defp keep?(metric, metadata, measurements) do
+ case metric do
+ %{keep: nil} -> true
+ %{keep: keep} when is_function(keep, 1) -> keep.(metadata)
+ %{keep: keep} when is_function(keep, 2) -> keep.(metadata, measurements)
+ end
+ end
 
  defp extract_measurement(metric, measurements, metadata) do
  case metric.measurement do

lib/telemetry_metrics/counter.ex

@@ -22,8 +22,8 @@ defmodule Telemetry.Metrics.Counter do
  event_name: :telemetry.event_name(),
  measurement: Metrics.measurement(),
  tags: Metrics.tags(),
- tag_values: (:telemetry.event_metadata() -> :telemetry.event_metadata()),
- keep: (:telemetry.event_metadata() -> boolean()),
+ tag_values: Metrics.tag_values(),
+ keep: Metrics.keep(),
  description: Metrics.description(),
  unit: Metrics.unit(),
  reporter_options: Metrics.reporter_options()

lib/telemetry_metrics/distribution.ex

@@ -22,8 +22,8 @@ defmodule Telemetry.Metrics.Distribution do
  event_name: :telemetry.event_name(),
  measurement: Metrics.measurement(),
  tags: Metrics.tags(),
- tag_values: (:telemetry.event_metadata() -> :telemetry.event_metadata()),
- keep: (:telemetry.event_metadata() -> boolean()),
+ tag_values: Metrics.tag_values(),
+ keep: Metrics.keep(),
  description: Metrics.description(),
  unit: Metrics.unit(),
  reporter_options: Metrics.reporter_options()

lib/telemetry_metrics/last_value.ex

@@ -22,8 +22,8 @@ defmodule Telemetry.Metrics.LastValue do
  event_name: :telemetry.event_name(),
  measurement: Metrics.measurement(),
  tags: Metrics.tags(),
- tag_values: (:telemetry.event_metadata() -> :telemetry.event_metadata()),
- keep: (:telemetry.event_metadata() -> boolean()),
+ tag_values: Metrics.tag_values(),
+ keep: Metrics.keep(),
  description: Metrics.description(),
  unit: Metrics.unit(),
  reporter_options: Metrics.reporter_options()

lib/telemetry_metrics/sum.ex

@@ -22,8 +22,8 @@ defmodule Telemetry.Metrics.Sum do
  event_name: :telemetry.event_name(),
  measurement: Metrics.measurement(),
  tags: Metrics.tags(),
- tag_values: (:telemetry.event_metadata() -> :telemetry.event_metadata()),
- keep: (:telemetry.event_metadata() -> boolean()),
+ tag_values: Metrics.tag_values(),
+ keep: Metrics.keep(),
  description: Metrics.description(),
  unit: Metrics.unit(),
  reporter_options: Metrics.reporter_options()

lib/telemetry_metrics/summary.ex

@@ -22,8 +22,8 @@ defmodule Telemetry.Metrics.Summary do
  event_name: :telemetry.event_name(),
  measurement: Metrics.measurement(),
  tags: Metrics.tags(),
- tag_values: (:telemetry.event_metadata() -> :telemetry.event_metadata()),
- keep: (:telemetry.event_metadata() -> boolean()),
+ tag_values: Metrics.tag_values(),
+ keep: Metrics.keep(),
  description: Metrics.description(),
  unit: Metrics.unit(),
  reporter_options: Metrics.reporter_options()

test/telemetry_metrics_test.exs

@@ -146,28 +146,31 @@ defmodule Telemetry.MetricsTest do
  keep_metric =
  apply(Metrics, unquote(metric_type), [
  "my.repo.query",
- [
- keep: &match?(%{repo: :my_app_read_only_repo}, &1)
- ]
+ [keep: &match?(%{repo: :my_app_read_only_repo}, &1)]
  ])
 
  drop_metric =
  apply(Metrics, unquote(metric_type), [
  "my.repo.query",
- [
- drop: &match?(%{repo: :my_app_read_only_repo}, &1)
- ]
+ [drop: &match?(%{repo: :my_app_read_only_repo}, &1)]
  ])
 
- keep_filter_fun = keep_metric.keep
+ assert keep_metric.keep.(%{repo: :my_app_read_only_repo})
+ refute keep_metric.keep.(%{repo: :my_app_repo})
 
- assert keep_filter_fun.(%{repo: :my_app_read_only_repo})
- refute keep_filter_fun.(%{repo: :my_app_repo})
+ refute drop_metric.keep.(%{repo: :my_app_read_only_repo})
+ assert drop_metric.keep.(%{repo: :my_app_repo})
+ end
 
- drop_filter_fun = drop_metric.keep
+ test "using event filter that evaluates both metadata and measurement" do
+ metric =
+ apply(Metrics, unquote(metric_type), [
+ "my.repo.query",
+ [keep: &(match?(%{repo: :my_app_read_only_repo}, &1) and &2 > 100)]
+ ])
 
- refute drop_filter_fun.(%{repo: :my_app_read_only_repo})
- assert drop_filter_fun.(%{repo: :my_app_repo})
+ assert metric.keep.(%{repo: :my_app_read_only_repo}, 200)
+ refute metric.keep.(%{repo: :my_app_read_only_repo}, 50)
  end
 
  test "setting both keep and drop options raises" do
@@ -314,7 +317,7 @@ defmodule Telemetry.MetricsTest do
  end
  end
 
- test "raises when event filter is not a function with an arity of 2" do
+ test "raises when event filter is not a function with an arity of 1 or 2" do
  Enum.each([keep: fn -> true end, drop: fn -> true end], fn filter ->
  assert_raise ArgumentError, fn ->
  apply(Metrics, unquote(metric_type), [