feat: Support ActiveSupport::BroadcastLogger

Rails 7.1+ uses ActiveSupport::BroadcastLogger. This needs to protect
against emitting duplicate logs in a different way than
ActiveSupport::Logger.broadcast.

Emits the log record for the first logger in the broadcast,
skip the others. Reset everything at the end of the method call.

instrumentation/logger/Gemfile

@@ -22,4 +22,4 @@ group :test do
 end
 
 # Temporary for testing, Appraisal does not work with gems installed from git source
-gem 'rails', '~> 7.0.0'
+gem 'rails', '~> 7.1.0'

instrumentation/logger/lib/opentelemetry/instrumentation/logger/instrumentation.rb

@@ -29,6 +29,7 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
 
         def patch
           ::Logger.prepend(Patches::Logger)
+          active_support_broadcast_logger_patch
           active_support_patch
         end
 
@@ -37,11 +38,18 @@ def require_dependencies
         end
 
         def active_support_patch
-          return unless defined?(::ActiveSupport::Logger)
+          return unless defined?(::ActiveSupport::Logger) && !defined?(::ActiveSupport::BroadcastLogger)
 
           require_relative 'patches/active_support_logger'
           ::ActiveSupport::Logger.singleton_class.prepend(Patches::ActiveSupportLogger)
         end
+
+        def active_support_broadcast_logger_patch
+          return unless defined?(::ActiveSupport::BroadcastLogger)
+
+          require_relative 'patches/active_support_broadcast_logger'
+          ::ActiveSupport::BroadcastLogger.prepend(Patches::ActiveSupportBroadcastLogger)
+        end
       end
     end
   end

instrumentation/logger/lib/opentelemetry/instrumentation/logger/patches/active_support_broadcast_logger.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Instrumentation
+    module Logger
+      module Patches
+        # Patches for the ActiveSupport::BroadcastLogger class included in Rails 7.1+
+        module ActiveSupportBroadcastLogger
+          def add(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          def debug(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          def info(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          def warn(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          def error(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          def fatal(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          def unknown(*args)
+            emit_one_broadcast(*args) { super }
+          end
+
+          private
+
+          # Emit logs from only one of the loggers in the broadcast.
+          # Set @skip_instrumenting to `true` to the rest of the loggers before emitting the logs.
+          # Set @skip_instrumenting to `false` after the log is emitted.
+          def emit_one_broadcast(*args)
+            broadcasts[1..-1].each { |broadcasted_logger| broadcasted_logger.instance_variable_set(:@skip_instrumenting, true) }
+            yield
+            broadcasts.each { |broadcasted_logger| broadcasted_logger.instance_variable_set(:@skip_instrumenting, false) }
+          end
+        end
+      end
+    end
+  end
+end

instrumentation/logger/test/opentelemetry/instrumentation/logger/patches/active_support_broadcast_logger_test.rb

@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+require 'test_helper'
+
+require_relative '../../../../../lib/opentelemetry/instrumentation/logger/patches/active_support_broadcast_logger'
+
+describe OpenTelemetry::Instrumentation::Logger::Patches::ActiveSupportBroadcastLogger do
+  let(:instrumentation) { OpenTelemetry::Instrumentation::Logger::Instrumentation.instance }
+  let(:logger) { Logger.new(LOG_STREAM) }
+  let(:logger2) { Logger.new(BROADCASTED_STREAM) }
+  let(:broadcast) { ActiveSupport::BroadcastLogger.new(logger, logger2) }
+
+  before do
+    skip unless defined?(::ActiveSupport::BroadcastLogger)
+    EXPORTER.reset
+    instrumentation.install
+  end
+
+  after { instrumentation.instance_variable_set(:@installed, false) }
+
+  describe '#add' do
+    it 'emits the log to the broadcasted loggers' do
+      body = "Ground control to Major Tom"
+      broadcast.add(Logger::DEBUG, body)
+
+      assert_includes(LOG_STREAM.string, body)
+      assert_includes(BROADCASTED_STREAM.string, body)
+    end
+
+    it 'emits only one OpenTelemetry log record' do
+      body = "Wake up, you sleepyhead"
+      broadcast.add(Logger::DEBUG, body)
+      log_records = EXPORTER.emitted_log_records
+
+      assert_equal 1, log_records.size
+      assert_equal 'DEBUG', log_records.first.severity_text
+      assert_equal body, log_records.first.body
+    end
+  end
+
+  describe '#unknown' do
+    it 'emits the log to the broadcasted loggers' do
+      body = "I know when to go out"
+      broadcast.unknown(body)
+
+      assert_includes(LOG_STREAM.string, body)
+      assert_includes(BROADCASTED_STREAM.string, body)
+    end
+
+    it 'emits only one OpenTelemetry log record' do
+      body = "You've got your mother in a whirl"
+      broadcast.unknown(body)
+
+      log_records = EXPORTER.emitted_log_records
+
+      assert_equal 1, log_records.size
+      assert_equal 'ANY', log_records.first.severity_text
+      assert_equal body, log_records.first.body
+    end
+  end
+
+  %w[debug info warn error fatal].each do |severity|
+    describe "##{severity}" do
+      it 'emits the log to the broadcasted loggers' do
+        body = "Still don't know what I was waiting for...#{rand(7)}"
+        broadcast.send(severity.to_sym, body)
+
+        assert_includes(LOG_STREAM.string, body)
+        assert_includes(BROADCASTED_STREAM.string, body)
+      end
+
+      it 'emits only one OpenTelemetry log record' do
+        body = "They pulled in just behind the bridge...#{rand(7)}"
+        broadcast.send(severity.to_sym, body)
+
+        log_records = EXPORTER.emitted_log_records
+
+        assert_equal 1, log_records.size
+        assert_equal severity.upcase, log_records.first.severity_text
+        assert_equal body, log_records.first.body
+      end
+    end
+  end
+end

instrumentation/logger/test/opentelemetry/instrumentation/logger/patches/active_support_logger_test.rb

@@ -14,6 +14,7 @@
   let(:broadcasted_logger) { ActiveSupport::Logger.new(BROADCASTED_STREAM) }
 
   before do
+    skip unless defined?(::ActiveSupport::Logger) && !defined?(::ActiveSupport::BroadcastLogger)
     EXPORTER.reset
     Rails.logger = main_logger.extend(ActiveSupport::Logger.broadcast(broadcasted_logger))
     instrumentation.install