Add support for shared context and tagged log entries

lib/dry/logger/dispatcher.rb

@@ -17,6 +17,10 @@ class Dispatcher
       # @api private
       attr_reader :id
 
+      # @since 1.0.0
+      # @api public
+      attr_reader :context
+
       # @since 1.0.0
       # @api private
       attr_reader :backends
@@ -25,6 +29,10 @@ class Dispatcher
       # @api private
       attr_reader :options
 
+      # @since 1.0.0
+      # @api private
+      attr_reader :mutex
+
       # Set up a dispatcher
       #
       # @since 1.0.0
@@ -42,10 +50,18 @@ def self.setup(id, **options)
 
       # @since 1.0.0
       # @api private
-      def initialize(id, backends: [], **options)
+      def self.default_context
+        Thread.current[:__dry_logger__] ||= {}
+      end
+
+      # @since 1.0.0
+      # @api private
+      def initialize(id, backends: [], context: self.class.default_context, **options)
         @id = id
         @backends = backends
         @options = {**options, progname: id}
+        @mutex = Mutex.new
+        @context = context
       end
 
       # Log an entry with UNKNOWN severity
@@ -130,14 +146,28 @@ def log(severity, message = nil, **payload)
         case message
         when Hash then log(severity, nil, **message)
         else
-          entry = Entry.new(progname: id, severity: severity, message: message, payload: payload)
+          entry = Entry.new(
+            progname: id,
+            severity: severity,
+            message: message,
+            payload: {**context, **payload}
+          )
 
           each_backend { |backend| backend.__send__(severity, entry) if backend.log?(entry) }
         end
 
         true
       end
 
+      # @since 1.0.0
+      # @api public
+      def tagged(tag)
+        context[:tag] = tag
+        yield
+      ensure
+        context.delete(:tag)
+      end
+
       # Add a new backend to an existing dispatcher
       #
       # @since 1.0.0
@@ -153,7 +183,9 @@ def add_backend(instance = nil, **backend_options)
       # @since 1.0.0
       # @api private
       def each_backend(*_args, &block)
-        backends.each(&block)
+        mutex.synchronize do
+          backends.each(&block)
+        end
       end
 
       # Pass logging to all configured backends

spec/dry/logger/dispatcher_spec.rb

@@ -71,4 +71,32 @@
       expect(backend_two).to have_received(:close)
     end
   end
+
+  describe "#tagged" do
+    subject(:logger) { Dry.Logger(:test, stream: stream, template: "%<message>s", context: {}) }
+
+    it "sets tags in log entries" do
+      logger.tagged(:metrics) do
+        logger.info("test 1")
+        logger.info("test 2")
+      end
+
+      expect(stream).to include("test 1 tag=:metrics")
+      expect(stream).to include("test 2 tag=:metrics")
+    end
+  end
+
+  describe "#context" do
+    subject(:logger) { Dry.Logger(:test, stream: stream, template: "%<message>s", context: {}) }
+
+    it "allows set pre-defined payload data" do
+      logger.context[:component] = "test"
+
+      logger.info("test 1")
+      logger.info("test 2")
+
+      expect(stream).to include('test 1 component="test"')
+      expect(stream).to include('test 2 component="test"')
+    end
+  end
 end