Merge pull request #1334 from appsignal/addDefaultAttributesToLogger

Add default attributes to Logger

.changesets/add-default-attributes-to-logger.md

@@ -0,0 +1,12 @@
+---
+bump: patch
+type: add
+---
+
+Allow for default attributes to be given when initialising a `Logger` instance:
+
+```ruby
+order_logger = Appsignal::Logger.new("app", attributes: { order_id: 123 })
+```
+
+All log lines reported by this logger will contain the given attribute. Attributes given when reporting the log line will be merged with the default attributes for the logger, with those in the log line taking priority.

lib/appsignal/extension/jruby.rb

@@ -80,7 +80,7 @@ def self.lib_extension
 
         # Logging methods
         attach_function :appsignal_log,
-          [:appsignal_string, :int32, :appsignal_string, :pointer],
+          [:appsignal_string, :int32, :int32, :appsignal_string, :pointer],
           :void
 
         # Transaction methods
@@ -273,10 +273,11 @@ def get_server_state(key)
         make_ruby_string state if state[:len] > 0
       end
 
-      def log(group, level, message, attributes)
+      def log(group, level, format, message, attributes)
         appsignal_log(
           make_appsignal_string(group),
           level,
+          format,
           make_appsignal_string(message),
           attributes.pointer
         )

lib/appsignal/logger.rb

@@ -25,15 +25,18 @@ class Logger < ::Logger
     # Create a new logger instance
     #
     # @param group Name of the group for this logger.
-    # @param level Log level to filter with
+    # @param level Minimum log level to report. Log lines below this level will be ignored.
+    # @param format Format to use to parse log line attributes.
+    # @param attributes Default attributes for all log lines.
     # @return [void]
-    def initialize(group, level: INFO, format: PLAINTEXT)
+    def initialize(group, level: INFO, format: PLAINTEXT, attributes: {})
       raise TypeError, "group must be a string" unless group.is_a? String
 
       @group = group
       @level = level
       @format = format
       @mutex = Mutex.new
+      @default_attributes = attributes
     end
 
     # We support the various methods in the Ruby
@@ -156,8 +159,10 @@ def silence(_severity = ERROR, &block)
 
     private
 
+    attr_reader :default_attributes
+
     def add_with_attributes(severity, message, group, attributes)
-      Thread.current[:appsignal_logger_attributes] = attributes
+      Thread.current[:appsignal_logger_attributes] = default_attributes.merge(attributes)
       add(severity, message, group)
     ensure
       Thread.current[:appsignal_logger_attributes] = nil

spec/lib/appsignal/logger_spec.rb

@@ -182,6 +182,36 @@
     end
   end
 
+  describe "a logger with default attributes" do
+    it "adds the attributes when a message is logged" do
+      logger = Appsignal::Logger.new("group", :attributes => { :some_key => "some_value" })
+
+      expect(Appsignal::Extension).to receive(:log).with("group", 6, 0, "Some message",
+        Appsignal::Utils::Data.generate({ :other_key => "other_value", :some_key => "some_value" }))
+      logger.error("Some message", { :other_key => "other_value" })
+    end
+
+    it "does not modify the original attribute hashes passed" do
+      default_attributes = { :some_key => "some_value" }
+      logger = Appsignal::Logger.new("group", :attributes => default_attributes)
+
+      line_attributes = { :other_key => "other_value" }
+      logger.error("Some message", line_attributes)
+
+      expect(default_attributes).to eq({ :some_key => "some_value" })
+      expect(line_attributes).to eq({ :other_key => "other_value" })
+    end
+
+    it "prioritises line attributes over default attributes" do
+      logger = Appsignal::Logger.new("group", :attributes => { :some_key => "some_value" })
+
+      expect(Appsignal::Extension).to receive(:log).with("group", 6, 0, "Some message",
+        Appsignal::Utils::Data.generate({ :some_key => "other_value" }))
+
+      logger.error("Some message", { :some_key => "other_value" })
+    end
+  end
+
   describe "#error with exception object" do
     it "logs the exception class and its message" do
       error =