Allow dynamic service_name configuration (#5)

* Allow dynamic service_name configuration

Originally, service_name was limited to a simple string value. Modify
the middleware to allow a Callable that generates a service_name
dynamically from attributes as an alternative option.

* Version bump and changelog

Author: aalong-tr

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.1.0]
+- Support for dynamic service names by setting `DatadogQueueBus.service_name` to a Callable
+
 ## [2.0.0]
 - Replaces ddtrace with the updated `datadog` gem
 

README.md

@@ -32,6 +32,18 @@ To override the default service name (which will be `queue-bus` if not set):
 DatadogQueueBus.service_name = 'my-queue-bus-service'
 ```
 
+You can also set the service name to a Callable that accepts the attributes hash and returns a String, granting you flexibility to monitor larger installations as separate services:
+
+```ruby
+DatadogQueueBus.service_name = ->(attrs) do
+    if attrs['bus_rider_app_key'].nil? || attrs['bus_rider_app_key'].empty?
+      'default-queue-bus-service'
+    else
+        "#{attrs['bus_rider_app_key']}-queue-bus-service"
+    end
+ end
+```
+
 ## Development
 
 After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.

lib/datadog-queue-bus.rb

@@ -9,6 +9,7 @@
 module DatadogQueueBus
   class << self
     # Sets the service_name that will be used when reporting queue-bus spans.
+    # Set this to a String, or to a Callable that accepts an attributes hash and returns a String.
     attr_writer :service_name
 
     # Returns the service name that is used when reporting queue-bus spans.

lib/datadog_queue_bus/middleware.rb

@@ -13,9 +13,15 @@ def call(attrs)
       resource += " event=#{event_type}" if event_type
       resource += " sub=#{sub_key}" if sub_key
 
+      service_name = if DatadogQueueBus.service_name.respond_to?(:call)
+                      DatadogQueueBus.service_name.call(attrs)
+                    else
+                      DatadogQueueBus.service_name
+                    end
+
       # def trace(name, continue_from: nil, **span_options, &block)
       Datadog::Tracing.trace('queue-bus.worker',
-                             service: DatadogQueueBus.service_name,
+                             service: service_name,
                              resource: resource) do |span|
         attrs.keys.grep(/^bus_/).each do |key|
           span.set_tag("queue-bus.#{key}", attrs[key])

lib/datadog_queue_bus/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module DatadogQueueBus
-  VERSION = '2.0.0'
+  VERSION = '2.1.0'
 end

spec/datadog_queue_bus/middleware_spec.rb

@@ -20,7 +20,7 @@
     subject.call(attrs)
   end
 
-  context 'with a service name' do
+  context 'with a static service name' do
     let(:name) { rand.to_s }
 
     before do
@@ -35,6 +35,22 @@
     end
   end
 
+  context 'with a dynamic service name' do
+    let(:name) { rand.to_s }
+    let(:service_name) { ->(attrs) { name } }
+
+    before do
+      DatadogQueueBus.service_name = service_name
+    end
+
+    it 'sends the service name' do
+      expect(tracer)
+        .to receive(:trace)
+        .with('queue-bus.worker', hash_including(service: name))
+      subject.call(attrs)
+    end
+  end
+
   context 'with an event type' do
     let(:attrs) do
       super().merge('bus_event_type' => 'my_event')