Add support for Vernier profiler

- Introduce `Sentry::Vernier::Profiler`
- Introduce `Sentry.config.profiler` that can be set to a class that
  should be used for profiling. By default it's set to `Sentry::Profiler`

sentry-ruby/Gemfile

@@ -5,7 +5,8 @@ gem "sentry-ruby", path: "./"
 
 rack_version = ENV["RACK_VERSION"]
 rack_version = "3.0.0" if rack_version.nil?
-gem "rack", "~> #{Gem::Version.new(rack_version)}" unless rack_version == "0"
+# gem "rack", "~> #{Gem::Version.new(rack_version)}" unless rack_version == "0"
+gem "rack", "~> 3.1"
 
 redis_rb_version = ENV.fetch("REDIS_RB_VERSION", "5.0")
 gem "redis", "~> #{redis_rb_version}"
@@ -14,6 +15,7 @@ gem "puma"
 
 gem "timecop"
 gem "stackprof" unless RUBY_PLATFORM == "java"
+gem "vernier", platforms: :ruby if RUBY_VERSION >= "3.2.1"
 
 gem "graphql", ">= 2.2.6" if RUBY_VERSION.to_f >= 2.7
 

sentry-ruby/lib/sentry/configuration.rb

@@ -284,6 +284,10 @@ def capture_exception_frame_locals=(value)
     # @return [Symbol]
     attr_reader :instrumenter
 
+    # The profiler class
+    # @return [Class]
+    attr_accessor :profiler
+
     # Take a float between 0.0 and 1.0 as the sample rate for capturing profiles.
     # Note that this rate is relative to traces_sample_rate / traces_sampler,
     # i.e. the profile is sampled by this rate after the transaction is sampled.
@@ -393,6 +397,8 @@ def initialize
       self.traces_sampler = nil
       self.enable_tracing = nil
 
+      self.profiler = Sentry::Profiler
+
       @transport = Transport::Configuration.new
       @cron = Cron::Configuration.new
       @metrics = Metrics::Configuration.new

sentry-ruby/lib/sentry/profiler.rb

@@ -1,9 +1,12 @@
 # frozen_string_literal: true
 
 require "securerandom"
+require_relative "profiler/helpers"
 
 module Sentry
   class Profiler
+    include Profiler::Helpers
+
     VERSION = "1"
     PLATFORM = "ruby"
     # 101 Hz in microseconds
@@ -189,43 +192,6 @@ def log(message)
       Sentry.logger.debug(LOGGER_PROGNAME) { "[Profiler] #{message}" }
     end
 
-    def in_app?(abs_path)
-      abs_path.match?(@in_app_pattern)
-    end
-
-    # copied from stacktrace.rb since I don't want to touch existing code
-    # TODO-neel-profiler try to fetch this from stackprof once we patch
-    # the native extension
-    def compute_filename(abs_path, in_app)
-      return nil if abs_path.nil?
-
-      under_project_root = @project_root && abs_path.start_with?(@project_root)
-
-      prefix =
-        if under_project_root && in_app
-          @project_root
-        else
-          longest_load_path = $LOAD_PATH.select { |path| abs_path.start_with?(path.to_s) }.max_by(&:size)
-
-          if under_project_root
-            longest_load_path || @project_root
-          else
-            longest_load_path
-          end
-        end
-
-      prefix ? abs_path[prefix.to_s.chomp(File::SEPARATOR).length + 1..-1] : abs_path
-    end
-
-    def split_module(name)
-      # last module plus class/instance method
-      i = name.rindex("::")
-      function = i ? name[(i + 2)..-1] : name
-      mod = i ? name[0...i] : nil
-
-      [function, mod]
-    end
-
     def record_lost_event(reason)
       Sentry.get_current_client&.transport&.record_lost_event(reason, "profile")
     end

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

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require "securerandom"
+
+module Sentry
+  class Profiler
+    module Helpers
+      def in_app?(abs_path)
+        abs_path.match?(@in_app_pattern)
+      end
+
+      # copied from stacktrace.rb since I don't want to touch existing code
+      # TODO-neel-profiler try to fetch this from stackprof once we patch
+      # the native extension
+      def compute_filename(abs_path, in_app)
+        return nil if abs_path.nil?
+
+        under_project_root = @project_root && abs_path.start_with?(@project_root)
+
+        prefix =
+          if under_project_root && in_app
+            @project_root
+          else
+            longest_load_path = $LOAD_PATH.select { |path| abs_path.start_with?(path.to_s) }.max_by(&:size)
+
+            if under_project_root
+              longest_load_path || @project_root
+            else
+              longest_load_path
+            end
+          end
+
+        prefix ? abs_path[prefix.to_s.chomp(File::SEPARATOR).length + 1..-1] : abs_path
+      end
+
+      def split_module(name)
+        # last module plus class/instance method
+        i = name.rindex("::")
+        function = i ? name[(i + 2)..-1] : name
+        mod = i ? name[0...i] : nil
+
+        [function, mod]
+      end
+    end
+  end
+end

sentry-ruby/lib/sentry/transaction.rb

@@ -85,7 +85,7 @@ def initialize(
       @effective_sample_rate = nil
       @contexts = {}
       @measurements = {}
-      @profiler = Profiler.new(@configuration)
+      @profiler = @configuration.profiler.new(@configuration)
       init_span_recorder
     end
 

sentry-ruby/lib/sentry/transaction_event.rb

@@ -74,8 +74,7 @@ def populate_profile(transaction)
           id: event_id,
           name: transaction.name,
           trace_id: transaction.trace_id,
-          # TODO-neel-profiler stubbed for now, see thread_id note in profiler.rb
-          active_thead_id: "0"
+          active_thread_id: Thread.current.object_id.to_s
         }
       )
 

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

@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+require "json"
+require "rbconfig"
+
+module Sentry
+  module Vernier
+    class Output
+      include Profiler::Helpers
+
+      attr_reader :profile
+
+      def initialize(profile, project_root:, in_app_pattern:, app_dirs_pattern:)
+        @profile = profile
+        @project_root = project_root
+        @in_app_pattern = in_app_pattern
+        @app_dirs_pattern = app_dirs_pattern
+      end
+
+      def to_h
+        @to_h ||= {
+          frames: frames,
+          stacks: stacks,
+          samples: samples,
+          thread_metadata: thread_metadata
+        }
+      end
+
+      private
+
+      def thread_metadata
+        profile.threads.map { |thread_id, thread_info|
+          [thread_id, { name: thread_info[:name] }]
+        }.to_h
+      end
+
+      def samples
+        profile.threads.flat_map { |thread_id, thread_info|
+          started_at = thread_info[:started_at]
+          samples, timestamps = thread_info.values_at(:samples, :timestamps)
+
+          samples.zip(timestamps).map { |stack_id, timestamp|
+            elapsed_since_start_ns = timestamp - started_at
+
+            next if elapsed_since_start_ns < 0
+
+            {
+              thread_id: thread_id.to_s,
+              stack_id: stack_id,
+              elapsed_since_start_ns: elapsed_since_start_ns.to_s
+            }
+          }.compact
+        }
+      end
+
+      def frames
+        funcs = stack_table_hash[:frame_table].fetch(:func)
+        lines = stack_table_hash[:func_table].fetch(:first_line)
+
+        funcs.map { |idx|
+          function, mod = split_module(stack_table_hash[:func_table][:name][idx])
+
+          abs_path = stack_table_hash[:func_table][:filename][idx]
+          in_app = in_app?(abs_path)
+          filename = compute_filename(abs_path, in_app)
+
+          {
+            function: function,
+            module: mod,
+            filename: filename,
+            abs_path: abs_path,
+            lineno: (lineno = lines[idx]) > 0 ? lineno : nil,
+            in_app: in_app
+          }.compact
+        }
+      end
+
+      def stacks
+        sample_stacks = profile.threads.flat_map { |_, thread_info|
+          samples = thread_info[:samples].map { |stack_id| profile.stack(stack_id) }
+
+          samples.map { |stack| [stack.idx, stack.frames.map(&:idx)] }
+        }.to_h
+
+        stacks = profile._stack_table.stack_count.times.map do |stack_id|
+          (sample_stacks[stack_id] || profile.stack(stack_id).frames.map(&:idx))
+        end
+
+        stacks
+      end
+
+      def stack_table_hash
+        @stack_table_hash ||= profile._stack_table.to_h
+      end
+    end
+  end
+end

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

@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+require "securerandom"
+require_relative "../profiler/helpers"
+require_relative "output"
+
+begin
+  require "vernier"
+rescue LoadError
+end
+
+module Sentry
+  module Vernier
+    class Profiler
+      EMPTY_RESULT = {}.freeze
+
+      attr_reader :started, :event_id, :result
+
+      def initialize(configuration)
+        @event_id = SecureRandom.uuid.delete("-")
+
+        @started = false
+        @sampled = nil
+
+        @profiling_enabled = defined?(Vernier) && configuration.profiling_enabled?
+        @profiles_sample_rate = configuration.profiles_sample_rate
+        @project_root = configuration.project_root
+        @app_dirs_pattern = configuration.app_dirs_pattern || Backtrace::APP_DIRS_PATTERN
+        @in_app_pattern = Regexp.new("^(#{@project_root}/)?#{@app_dirs_pattern}")
+      end
+
+      def set_initial_sample_decision(transaction_sampled)
+        unless @profiling_enabled
+          @sampled = false
+          return
+        end
+
+        unless transaction_sampled
+          @sampled = false
+          log("Discarding profile because transaction not sampled")
+          return
+        end
+
+        case @profiles_sample_rate
+        when 0.0
+          @sampled = false
+          log("Discarding profile because sample_rate is 0")
+          return
+        when 1.0
+          @sampled = true
+          return
+        else
+          @sampled = Random.rand < @profiles_sample_rate
+        end
+
+        log("Discarding profile due to sampling decision") unless @sampled
+      end
+
+      def start
+        return unless @sampled && !@started
+
+        ::Vernier.start_profile
+        @started = true
+
+        log("Started")
+
+        @started
+      rescue RuntimeError => e
+        # TODO: once Vernier raises something more dedicated, we should catch that instead
+        if e.message.include?("Profile already started")
+          log("Not started since running elsewhere")
+        else
+          log("Failed to start: #{e.message}")
+          raise e
+        end
+      end
+
+      def stop
+        return unless @sampled
+        return unless @started
+
+        @result = ::Vernier.stop_profile
+
+        log("Stopped")
+      end
+
+      def to_hash
+        return EMPTY_RESULT unless @started
+
+        unless @sampled
+          record_lost_event(:sample_rate)
+          return EMPTY_RESULT
+        end
+
+        { **profile_meta, profile: output.to_h }
+      end
+
+      private
+
+      def log(message)
+        Sentry.logger.debug(LOGGER_PROGNAME) { "[Profiler::Vernier] #{message}" }
+      end
+
+      def record_lost_event(reason)
+        Sentry.get_current_client&.transport&.record_lost_event(reason, "profile")
+      end
+
+      def profile_meta
+        {
+          event_id: @event_id,
+          version: "1",
+          platform: "ruby"
+        }
+      end
+
+      def output
+        @output ||= Output.new(
+          result,
+          project_root: @project_root,
+          app_dirs_pattern: @app_dirs_pattern,
+          in_app_pattern: @in_app_pattern
+        )
+      end
+    end
+  end
+end