Add latest changes from gitlab-org/gitlab@master

1 files changed, 136 insertions, 0 deletions

diff --git a/lib/gitlab/stack_prof.rb b/lib/gitlab/stack_prof.rb
new file mode 100644
index 00000000000..4b7d93c91ce
--- /dev/null
+++ b/lib/gitlab/stack_prof.rb
@@ -0,0 +1,136 @@
+# frozen_string_literal: true
+
+# trigger stackprof by sending a SIGUSR2 signal
+#
+# Docs: https://docs.gitlab.com/ee/development/performance.html#production
+
+module Gitlab
+  class StackProf
+    DEFAULT_FILE_PREFIX = Dir.tmpdir
+    DEFAULT_TIMEOUT_SEC = 30
+    DEFAULT_MODE = :cpu
+    # Sample interval as a frequency in microseconds (~99hz); appropriate for CPU profiles
+    DEFAULT_INTERVAL_US = 10_100
+    # Sample interval in event occurrences (n = every nth event); appropriate for allocation profiles
+    DEFAULT_INTERVAL_EVENTS = 100
+
+    # this is a workaround for sidekiq, which defines its own SIGUSR2 handler.
+    # by defering to the sidekiq startup event, we get to set up our own
+    # handler late enough.
+    # see also: https://github.com/mperham/sidekiq/pull/4653
+    def self.install
+      require 'stackprof'
+      require 'tmpdir'
+
+      if Gitlab::Runtime.sidekiq?
+        Sidekiq.configure_server do |config|
+          config.on :startup do
+            on_worker_start
+          end
+        end
+      else
+        Gitlab::Cluster::LifecycleEvents.on_worker_start do
+          on_worker_start
+        end
+      end
+    end
+
+    def self.on_worker_start
+      log_event('listening for SIGUSR2 signal')
+
+      # create a pipe in order to propagate signal out of the signal handler
+      # see also: https://cr.yp.to/docs/selfpipe.html
+      read, write = IO.pipe
+
+      # create a separate thread that polls for signals on the pipe.
+      #
+      # this way we do not execute in signal handler context, which
+      # lifts restrictions and also serializes the calls in a thread-safe
+      # manner.
+      #
+      # it's very similar to a goroutine and channel design.
+      #
+      # another nice benefit of this method is that we can timeout the
+      # IO.select call, allowing the profile to automatically stop after
+      # a given interval (by default 30 seconds), avoiding unbounded memory
+      # growth from a profile that was started and never stopped.
+      t = Thread.new do
+        timeout_s = ENV['STACKPROF_TIMEOUT_S']&.to_i || DEFAULT_TIMEOUT_SEC
+        current_timeout_s = nil
+        loop do
+          read.getbyte if IO.select([read], nil, nil, current_timeout_s)
+
+          if ::StackProf.running?
+            stackprof_file_prefix = ENV['STACKPROF_FILE_PREFIX'] || DEFAULT_FILE_PREFIX
+            stackprof_out_file = "#{stackprof_file_prefix}/stackprof.#{Process.pid}.#{SecureRandom.hex(6)}.profile"
+
+            log_event(
+              'stopping profile',
+              profile_filename: stackprof_out_file,
+              profile_timeout_s: timeout_s
+            )
+
+            ::StackProf.stop
+            ::StackProf.results(stackprof_out_file)
+            current_timeout_s = nil
+          else
+            mode = ENV['STACKPROF_MODE']&.to_sym || DEFAULT_MODE
+            interval = ENV['STACKPROF_INTERVAL']&.to_i
+            interval ||= (mode == :object ? DEFAULT_INTERVAL_EVENTS : DEFAULT_INTERVAL_US)
+
+            log_event(
+              'starting profile',
+              profile_mode: mode,
+              profile_interval: interval,
+              profile_timeout: timeout_s
+            )
+
+            ::StackProf.start(
+              mode: mode,
+              raw: Gitlab::Utils.to_boolean(ENV['STACKPROF_RAW'] || 'true'),
+              interval: interval
+            )
+            current_timeout_s = timeout_s
+          end
+        end
+      rescue StandardError => e
+        log_event("stackprof failed: #{e}")
+      end
+      t.abort_on_exception = true
+
+      # in the case of puma, this will override the existing SIGUSR2 signal handler
+      # that can be used to trigger a restart.
+      #
+      # puma cluster has two types of restarts:
+      # * SIGUSR1: phased restart
+      # * SIGUSR2: restart
+      #
+      # phased restart is not supported in our configuration, because we use
+      # preload_app. this means we will always perform a normal restart.
+      # additionally, phased restart is not supported when sending a SIGUSR2
+      # directly to a puma worker (as opposed to the master process).
+      #
+      # the result is that the behaviour of SIGUSR1 and SIGUSR2 is identical in
+      # our configuration, and we can always use a SIGUSR1 to perform a restart.
+      #
+      # thus, it is acceptable for us to re-appropriate the SIGUSR2 signal, and
+      # override the puma behaviour.
+      #
+      # see also:
+      # * https://github.com/puma/puma/blob/master/docs/signals.md#puma-signals
+      # * https://github.com/phusion/unicorn/blob/master/SIGNALS
+      # * https://github.com/mperham/sidekiq/wiki/Signals
+      Signal.trap('SIGUSR2') do
+        write.write('.')
+      end
+    end
+
+    def self.log_event(event, labels = {})
+      Gitlab::AppJsonLogger.info({
+        event: 'stackprof',
+        message: event,
+        pid: Process.pid
+      }.merge(labels.compact))
+    end
+  end
+end