Add new config.profiles_sample_interval

Author: sl0thentr0py

CHANGELOG.md

@@ -42,6 +42,8 @@
       config.trace_ignore_status_codes = [404, (501..503)]
   end
   ```
+- Add `config.profiles_sample_interval` to control sampling frequency ([#2745](https://github.com/getsentry/sentry-ruby/pull/2745))
+  - Both `stackprof` and `vernier` now get sampled at a default frequency of 101 Hz.
 
 ### Internal
 

sentry-ruby/lib/sentry/configuration.rb

@@ -319,6 +319,15 @@ class Configuration
     # @return [Float, nil]
     attr_reader :profiles_sample_rate
 
+    # Interval in microseconds at which to take samples.
+    # The default is 1e6 / 101, or 101Hz.
+    # Note that the 101 is intentional to avoid lockstep sampling.
+    #
+    # @example
+    #   config.profiles_sample_interval = 1e5 / 101
+    # @return [Float]
+    attr_accessor :profiles_sample_interval
+
     # Array of patches to apply.
     # Default is {DEFAULT_PATCHES}
     # @return [Array<Symbol>]
@@ -373,6 +382,9 @@ class Configuration
 
     APP_DIRS_PATTERN = /(bin|exe|app|config|lib|test|spec)/
 
+    # 101 Hz in microseconds
+    DEFAULT_PROFILES_SAMPLE_INTERVAL = 1e6 / 101
+
     class << self
       # Post initialization callbacks are called at the end of initialization process
       # allowing extending the configuration of sentry-ruby by multiple extensions
@@ -492,6 +504,7 @@ def initialize
       self.enable_logs = false
 
       self.profiler_class = Sentry::Profiler
+      self.profiles_sample_interval = DEFAULT_PROFILES_SAMPLE_INTERVAL
 
       @transport = Transport::Configuration.new
       @cron = Cron::Configuration.new

sentry-ruby/lib/sentry/profiler.rb

@@ -10,8 +10,6 @@ class Profiler
 
     VERSION = "1"
     PLATFORM = "ruby"
-    # 101 Hz in microseconds
-    DEFAULT_INTERVAL = 1e6 / 101
     MICRO_TO_NANO_SECONDS = 1e3
     MIN_SAMPLES_REQUIRED = 2
 
@@ -24,6 +22,7 @@ def initialize(configuration)
 
       @profiling_enabled = defined?(StackProf) && configuration.profiling_enabled?
       @profiles_sample_rate = configuration.profiles_sample_rate
+      @profiles_sample_interval = configuration.profiles_sample_interval
       @project_root = configuration.project_root
       @app_dirs_pattern = configuration.app_dirs_pattern
       @in_app_pattern = Regexp.new("^(#{@project_root}/)?#{@app_dirs_pattern}")
@@ -32,7 +31,7 @@ def initialize(configuration)
     def start
       return unless @sampled
 
-      @started = StackProf.start(interval: DEFAULT_INTERVAL,
+      @started = StackProf.start(interval: @profiles_sample_interval,
                                  mode: :wall,
                                  raw: true,
                                  aggregate: false)

sentry-ruby/lib/sentry/vernier/profiler.rb

@@ -20,6 +20,7 @@ def initialize(configuration)
 
         @profiling_enabled = defined?(Vernier) && configuration.profiling_enabled?
         @profiles_sample_rate = configuration.profiles_sample_rate
+        @profiles_sample_interval = configuration.profiles_sample_interval
         @project_root = configuration.project_root
         @app_dirs_pattern = configuration.app_dirs_pattern
         @in_app_pattern = Regexp.new("^(#{@project_root}/)?#{@app_dirs_pattern}")
@@ -56,7 +57,7 @@ def start
         return unless @sampled
         return if @started
 
-        @started = ::Vernier.start_profile
+        @started = ::Vernier.start_profile(interval: @profiles_sample_interval)
 
         log("Started")
 

sentry-ruby/spec/sentry/configuration_spec.rb

@@ -194,6 +194,12 @@
     end
   end
 
+  describe "#profiles_sample_interval" do
+    it "defaults to 101 Hz" do
+      expect(subject.profiles_sample_interval).to eq(1e6 / 101)
+    end
+  end
+
   describe "#transport" do
     it "returns an initialized Transport::Configuration object" do
       transport_config = subject.transport

sentry-ruby/spec/sentry/profiler_spec.rb

@@ -74,6 +74,30 @@
         expect(subject.started).to eq(false)
       end
     end
+
+    context 'with custom profiles_sample_interval' do
+      before do
+        perform_basic_setup do |config|
+          config.traces_sample_rate = 1.0
+          config.profiles_sample_rate = 1.0
+          config.profiles_sample_interval = 1e5 / 101
+        end
+      end
+
+      it 'starts StackProf with custom interval' do
+        subject.set_initial_sample_decision(true)
+
+        expect(StackProf).to receive(:start).with(
+          interval: 1e5 / 101,
+          mode: :wall,
+          raw: true,
+          aggregate: false
+        ).and_call_original
+
+        subject.start
+        expect(subject.started).to eq(true)
+      end
+    end
   end
 
   describe '#stop' do

sentry-ruby/spec/sentry/vernier/profiler_spec.rb

@@ -74,15 +74,15 @@
       end
 
       it 'starts Vernier if sampled' do
-        expect(Vernier).to receive(:start_profile).and_return(true)
+        expect(Vernier).to receive(:start_profile).with(interval: 1e6 / 101).and_return(true)
 
         profiler.start
 
         expect(profiler.started).to eq(true)
       end
 
       it 'does not start Vernier again if already started' do
-        expect(Vernier).to receive(:start_profile).and_return(true).once
+        expect(Vernier).to receive(:start_profile).with(interval: 1e6 / 101).and_return(true).once
 
         profiler.start
         profiler.start
@@ -110,6 +110,25 @@
         expect(profiler.started).to eq(false)
       end
     end
+
+    context 'with custom profiles_sample_interval' do
+      before do
+        perform_basic_setup do |config|
+          config.traces_sample_rate = 1.0
+          config.profiles_sample_rate = 1.0
+          config.profiles_sample_interval = 1e5 / 101
+        end
+      end
+
+      it 'starts Vernier with custom interval' do
+        expect(Vernier).to receive(:start_profile).with(interval: 1e5 / 101).and_return(true)
+
+        profiler.set_initial_sample_decision(true)
+        profiler.start
+
+        expect(profiler.started).to eq(true)
+      end
+    end
   end
 
   describe '#stop' do