Add config.metrics.before_emit callback

CHANGELOG.md

@@ -9,6 +9,7 @@
   - Add main APIs and `Aggregator` thread [#2247](https://github.com/getsentry/sentry-ruby/pull/2247)
   - Add `Sentry::Metrics.timing` API for measuring block duration [#2254](https://github.com/getsentry/sentry-ruby/pull/2254)
   - Add metric summaries on spans [#2255](https://github.com/getsentry/sentry-ruby/pull/2255)
+  - Add `config.metrics.before_emit` callback [#2258](https://github.com/getsentry/sentry-ruby/pull/2258)
 
     The SDK now supports recording and aggregating metrics. A new thread will be started
     for aggregation and will flush the pending data to Sentry every 5 seconds.
@@ -44,6 +45,18 @@
     Sentry::Metrics.timing('how_long') { sleep(1) }
     # timing - measure duration of code block in other duraton units
     Sentry::Metrics.timing('how_long_ms', unit: 'millisecond') { sleep(0.5) }
+
+    # add a before_emit callback to filter keys or update tags
+    Sentry.init do |config|
+      # ...
+      config.metrics.enabled = true
+      config.metrics.before_emit = lambda do |key, tags|
+        return nil if key == 'foo'
+        tags[:bar] = 42
+        tags.delete(:baz)
+        true
+      end
+    end
     ```
 
 ### Bug Fixes

sentry-ruby/lib/sentry/configuration.rb

@@ -576,12 +576,6 @@ def error_messages
 
     private
 
-    def check_callable!(name, value)
-      unless value == nil || value.respond_to?(:call)
-        raise ArgumentError, "#{name} must be callable (or nil to disable)"
-      end
-    end
-
     def init_dsn(dsn_string)
       return if dsn_string.nil? || dsn_string.empty?
 

sentry-ruby/lib/sentry/metrics/aggregator.rb

@@ -24,6 +24,7 @@ class Aggregator
       def initialize(configuration, client)
         @client = client
         @logger = configuration.logger
+        @before_emit = configuration.metrics.before_emit
 
         @default_tags = {}
         @default_tags['release'] = configuration.release if configuration.release
@@ -55,8 +56,11 @@ def add(type,
         # this is integer division and thus takes the floor of the division
         # and buckets into 10 second intervals
         bucket_timestamp = (timestamp / ROLLUP_IN_SECONDS) * ROLLUP_IN_SECONDS
+        updated_tags = get_updated_tags(tags)
 
-        serialized_tags = serialize_tags(get_updated_tags(tags))
+        return if @before_emit && !@before_emit.call(key, updated_tags)
+
+        serialized_tags = serialize_tags(updated_tags)
         bucket_key = [type, key, unit, serialized_tags]
 
         added = @mutex.synchronize do

sentry-ruby/lib/sentry/metrics/configuration.rb

@@ -3,15 +3,38 @@
 module Sentry
   module Metrics
     class Configuration
+      include ArgumentCheckingHelper
+
       # Enable metrics usage
       # Starts a new {Sentry::Metrics::Aggregator} instance to aggregate metrics
       # and a thread to aggregate flush every 5 seconds.
       # @return [Boolean]
       attr_accessor :enabled
 
+      # Optional Proc, called before emitting a metric to the aggregator.
+      # Use it to filter keys (return false/nil) or update tags.
+      # Make sure to return true at the end.
+      #
+      # @example
+      #   config.metrics.before_emit = lambda do |key, tags|
+      #     return nil if key == 'foo'
+      #     tags[:bar] = 42
+      #     tags.delete(:baz)
+      #     true
+      #   end
+      #
+      # @return [Proc, nil]
+      attr_reader :before_emit
+
       def initialize
         @enabled = false
       end
+
+      def before_emit=(value)
+        check_callable!("metrics.before_emit", value)
+
+        @before_emit = value
+      end
     end
   end
 end

sentry-ruby/lib/sentry/utils/argument_checking_helper.rb

@@ -15,5 +15,11 @@ def check_argument_includes!(argument, values)
         raise ArgumentError, "expect the argument to be one of #{values.map(&:inspect).join(' or ')}, got #{argument.inspect}"
       end
     end
+
+    def check_callable!(name, value)
+      unless value == nil || value.respond_to?(:call)
+        raise ArgumentError, "#{name} must be callable (or nil to disable)"
+      end
+    end
   end
 end

sentry-ruby/spec/sentry/metrics/aggregator_spec.rb

@@ -188,6 +188,38 @@
       expect(metric.value).to eq(Set[1])
     end
 
+    describe 'with before_emit callback' do
+      before do
+        perform_basic_setup do |config|
+          config.metrics.enabled = true
+          config.enable_tracing = true
+          config.release = 'test-release'
+          config.environment = 'test'
+          config.logger = Logger.new(string_io)
+
+          config.metrics.before_emit = lambda do |key, tags|
+            return nil if key == 'foo'
+            tags[:add_tag] = 42
+            tags.delete(:remove_tag)
+            true
+          end
+        end
+      end
+
+      it 'does not emit metric with filtered key' do
+        expect(Sentry::Metrics::CounterMetric).not_to receive(:new)
+        subject.add(:c, 'foo', 1)
+        expect(subject.buckets).to eq({})
+      end
+
+      it 'updates the tags according to the callback' do
+        subject.add(:c, 'bar', 1, tags: { remove_tag: 99 })
+        _, _, _, tags = subject.buckets.values.first.keys.first
+        expect(tags).not_to include(['remove_tag', '99'])
+        expect(tags).to include(['add_tag', '42'])
+      end
+    end
+
     describe 'local aggregation for span metric summaries' do
       it 'does nothing without an active scope span' do
         expect_any_instance_of(Sentry::Metrics::LocalAggregator).not_to receive(:add)

sentry-ruby/spec/sentry/metrics/configuration_spec.rb

@@ -0,0 +1,11 @@
+require 'spec_helper'
+
+RSpec.describe Sentry::Metrics::Configuration do
+  describe '#before_emit=' do
+    it 'raises error when setting before_emit to anything other than callable or nil' do
+      subject.before_emit = -> { }
+      subject.before_emit = nil
+      expect { subject.before_emit = true }.to raise_error(ArgumentError, 'metrics.before_emit must be callable (or nil to disable)')
+    end
+  end
+end