[Sampler] rename 'paths' to 'targets', making it generic

README.md

@@ -356,7 +356,7 @@ These can be overridden like:
 ```ruby
 AppProfiler.profile_sampler_config = AppProfiler::Sampler::Config.new(
   sample_rate: 0.5,
-  paths: ["/foo"],
+  targets: ["/foo"],
   backends_probability: { stackprof: 0.5, vernier: 0.5 },
   backend_configs: {
     stackprof: AppProfiler::Sampler::StackprofConfig.new,
@@ -367,7 +367,7 @@ AppProfiler.profile_sampler_config = AppProfiler::Sampler::Config.new(
 
 Rails.application.config.app_profiler = AppProfiler::Sampler::Config.new(
   sample_rate: 0.5,
-  paths: ["/foo"],
+  targets: ["/foo"],
   backends_probability: { stackprof: 0.5, vernier: 0.5 },
   backend_configs: {
     stackprof: AppProfiler::Sampler::StackprofConfig.new,
@@ -380,12 +380,12 @@ All the configuration parameters are optional and have default values. The defau
 
 ```ruby
 
-| Sampler Config                      | Default         |
-| --------                            | -------         |
-| sample_rate (0.0 - 1.0)             | 0.001 (0.1 %)   |
-| paths                               | ['/']           |
-| stackprof_probability               | 1.0             |
-| vernier_probability                 | 0.0             |
+| Sampler Config                                         | Default         |
+| --------                                               | -------         |
+| sample_rate (0.0 - 1.0)                                | 0.001 (0.1 %)   |
+| targets (request paths, job_names etc )                | ['/']           |
+| stackprof_probability                                  | 1.0             |
+| vernier_probability                                    | 0.0             |
 
 | StackprofConfig                     | Default |
 | --------                            | ------- |

lib/app_profiler.rb

@@ -64,6 +64,7 @@ module Viewer
   mattr_reader :after_process_queue, default: nil
   mattr_accessor :forward_metadata_on_upload, default: false
   mattr_accessor :profile_sampler_enabled, default: false
+  mattr_accessor :profile_sampler_killswitch_on, default: nil
   mattr_accessor :profile_sampler_config
 
   class << self

lib/app_profiler/middleware.rb

@@ -52,6 +52,7 @@ def profile_params(params)
       return params if params.valid?
 
       return unless AppProfiler.profile_sampler_enabled
+      return if AppProfiler.profile_sampler_killswitch_on&.call
 
       AppProfiler::Sampler.profile_params(params, AppProfiler.profile_sampler_config)
     end

lib/app_profiler/railtie.rb

@@ -43,6 +43,7 @@ class Railtie < Rails::Railtie
       AppProfiler.backend = app.config.app_profiler.profiler_backend || :stackprof
       AppProfiler.forward_metadata_on_upload = app.config.app_profiler.forward_metadata_on_upload || false
       AppProfiler.profile_sampler_enabled = app.config.app_profiler.profile_sampler_enabled || false
+      AppProfiler.profile_sampler_killswitch_on = app.config.app_profiler.profile_sampler_killswitch_on || nil
       AppProfiler.profile_sampler_config = app.config.app_profiler.profile_sampler_config ||
         AppProfiler::Sampler::Config.new
     end

lib/app_profiler/sampler.rb

@@ -5,18 +5,21 @@ module AppProfiler
   module Sampler
     class << self
       def profile_params(request, config)
-        return unless sample?(config, request)
+        profile_params_for(request.path, config)
+      end
+
+      def profile_params_for(target, config)
+        return unless sample?(config, target)
 
         get_profile_params(config)
       end
 
       private
 
-      def sample?(config, request)
+      def sample?(config, target)
         return false if Kernel.rand > config.sample_rate
 
-        path = request.path
-        return false unless config.paths.any? { |p| path.match?(p) }
+        return false unless config.targets.any? { |t| target.match?(t) }
 
         true
       end

lib/app_profiler/sampler/config.rb

@@ -5,28 +5,31 @@
 module AppProfiler
   module Sampler
     class Config
-      attr_reader :sample_rate, :paths, :cpu_interval, :backends_probability
+      attr_reader :sample_rate, :targets, :cpu_interval, :backends_probability
 
       SAMPLE_RATE = 0.001 # 0.1%
-      PATHS = ["/"]
+      TARGETS = ["/"]
       BACKEND_PROBABILITES = { stackprof: 1.0, vernier: 0.0 }
       @backends = {}
 
       def initialize(sample_rate: SAMPLE_RATE,
-        paths: PATHS,
+        targets: TARGETS,
         backends_probability: BACKEND_PROBABILITES,
         backends_config: {
           stackprof: StackprofConfig.new,
-        })
+        },
+        paths: nil)
 
         if sample_rate < 0.0 || sample_rate > 1.0
           raise ArgumentError, "sample_rate must be between 0 and 1"
         end
 
         raise ArgumentError, "mode probabilities must sum to 1" unless backends_probability.values.sum == 1.0
 
+        warn("paths is deprecated, use targets instead") if paths
+
         @sample_rate = sample_rate
-        @paths = paths
+        @targets = paths || targets
         @backends_config = backends_config
         @backends_probability = backends_probability
       end

test/app_profiler/middleware_test.rb

@@ -376,7 +376,7 @@ def call(env)
         with_google_cloud_storage do
           AppProfiler.profile_sampler_config = AppProfiler::Sampler::Config.new(
             sample_rate: 1.0,
-            paths: ["/"],
+            targets: ["/"],
           )
 
           assert_profiles_dumped(0) do
@@ -399,6 +399,21 @@ def call(env)
       end
     end
 
+    test "request is not sampled when killswitch is on" do
+      old_killswitch = AppProfiler.profile_sampler_killswitch_on
+      with_google_cloud_storage do
+        AppProfiler.profile_sampler_config = AppProfiler::Sampler::Config.new(sample_rate: 1.0)
+        AppProfiler.profile_sampler_killswitch_on = -> { true }
+        assert_profiles_dumped(0) do
+          middleware = AppProfiler::Middleware.new(app_env)
+          response = middleware.call(mock_request_env(path: "/"))
+          assert_nil(response[1]["X-Profile-Async"])
+        end
+      end
+    ensure
+      AppProfiler.profile_sampler_killswitch_on = old_killswitch
+    end
+
     private
 
     def with_profile_sampler_enabled

test/app_profiler/sampler/config_test.rb

@@ -21,7 +21,7 @@ class ConfigTest < TestCase
       test "default config" do
         config = Config.new
         assert_equal(Config::SAMPLE_RATE, config.sample_rate)
-        assert_equal(Config::PATHS, config.paths)
+        assert_equal(Config::TARGETS, config.targets)
         assert_equal(Config::BACKEND_PROBABILITES, config.backends_probability)
         assert_not_nil(config.get_backend_config(:stackprof))
         assert_nil(config.get_backend_config(:vernier))

test/app_profiler/sampler/sampler_test.rb

@@ -48,7 +48,7 @@ class SamplerTest < TestCase
         Kernel.stubs(:rand).returns(0.1)
         config = Config.new(
           sample_rate: 1.0,
-          paths: ["/foo"],
+          targets: ["/foo"],
         )
 
         request = RequestParameters.new(Rack::Request.new({ "PATH_INFO" => "/foo" }))