Run before_fork only once on bootpuma-init-restart

This aligns behavior of before_fork with Puma where before_fork
is called only on master boot, also none of our code needs to be run
before each worker fork, instead we have a use-case for deleting
Prometheus files only on boot time.

6 files changed, 30 insertions, 26 deletions

diff --git a/config/initializers/7_prometheus_metrics.rb b/config/initializers/7_prometheus_metrics.rb
index 68f8487d377..54cdefc2a10 100644
--- a/config/initializers/7_prometheus_metrics.rb
+++ b/config/initializers/7_prometheus_metrics.rb
@@ -43,14 +43,21 @@ if !Rails.env.test? && Gitlab::Metrics.prometheus_metrics_enabled?
   end
 end
 
-Gitlab::Cluster::LifecycleEvents.on_master_restart do
+def cleanup_prometheus_multiproc_dir
   # The following is necessary to ensure stale Prometheus metrics don't
   # accumulate over time. It needs to be done in this hook as opposed to
   # inside an init script to ensure metrics files aren't deleted after new
   # unicorn workers start after a SIGUSR2 is received.
-  prometheus_multiproc_dir = ENV['prometheus_multiproc_dir']
-  if prometheus_multiproc_dir
-    old_metrics = Dir[File.join(prometheus_multiproc_dir, '*.db')]
+  if dir = ::Prometheus::Client.configuration.multiprocess_files_dir
+    old_metrics = Dir[File.join(dir, '*.db')]
     FileUtils.rm_rf(old_metrics)
   end
 end
+
+Gitlab::Cluster::LifecycleEvents.on_master_start do
+  cleanup_prometheus_multiproc_dir
+end
+
+Gitlab::Cluster::LifecycleEvents.on_master_restart do
+  cleanup_prometheus_multiproc_dir
+end
diff --git a/config/puma.example.development.rb b/config/puma.example.development.rb
index 7cb9fb01b25..9df24bf74e3 100644
--- a/config/puma.example.development.rb
+++ b/config/puma.example.development.rb
@@ -49,10 +49,6 @@ on_restart do
 end
 
 before_fork do
-  # We want to clean things up (e.g. metric files) at first boot. So make sure
-  # Puma calls the same callback at boot as Unicorn.
-  Gitlab::Cluster::LifecycleEvents.do_master_restart
-
   # Signal to the puma killer
   Gitlab::Cluster::PumaWorkerKillerInitializer.start @config.options unless ENV['DISABLE_PUMA_WORKER_KILLER']
 
diff --git a/config/puma.rb.example b/config/puma.rb.example
index 731c2563150..6558dbc6cfe 100644
--- a/config/puma.rb.example
+++ b/config/puma.rb.example
@@ -44,10 +44,6 @@ on_restart do
 end
 
 before_fork do
-  # We want to clean things up (e.g. metric files) at first boot. So make sure
-  # Puma calls the same callback at boot as Unicorn.
-  Gitlab::Cluster::LifecycleEvents.do_master_restart
-
   # Signal to the puma killer
   Gitlab::Cluster::PumaWorkerKillerInitializer.start @config.options unless ENV['DISABLE_PUMA_WORKER_KILLER']
 
diff --git a/config/unicorn.rb.example b/config/unicorn.rb.example
index b4da1568511..581fde84c95 100644
--- a/config/unicorn.rb.example
+++ b/config/unicorn.rb.example
@@ -92,17 +92,18 @@ run_once = true
 
 before_fork do |server, worker|
   if run_once
+    # There is a difference between Puma and Unicorn:
+    # - Puma calls before_fork once when booting up master process
+    # - Unicorn runs before_fork whenever new work is spawned
+    # To unify this behavior we call before_fork only once (we use
+    # this callback for deleting Prometheus files so for our purposes
+    # it makes sense to align behavior with Puma)
     run_once = false
 
-    # The Unicorn before_exec hook only gets called on a Unicorn
-    # restart, but we want to clean things up (e.g. metric files) at
-    # first boot.
-    Gitlab::Cluster::LifecycleEvents.do_master_restart
+    # Signal application hooks that we're about to fork
+    Gitlab::Cluster::LifecycleEvents.do_before_fork
   end
 
-  # Signal application hooks that we're about to fork
-  Gitlab::Cluster::LifecycleEvents.do_before_fork
-
   # The following is only recommended for memory/DB-constrained
   # installations.  It is not needed if your system can house
   # twice as many worker_processes as you have configured.
diff --git a/config/unicorn.rb.example.development b/config/unicorn.rb.example.development
index 1ff55701c14..9a02d5f1007 100644
--- a/config/unicorn.rb.example.development
+++ b/config/unicorn.rb.example.development
@@ -25,17 +25,18 @@ run_once = true
 
 before_fork do |server, worker|
   if run_once
+    # There is a difference between Puma and Unicorn:
+    # - Puma calls before_fork once when booting up master process
+    # - Unicorn runs before_fork whenever new work is spawned
+    # To unify this behavior we call before_fork only once (we use
+    # this callback for deleting Prometheus files so for our purposes
+    # it makes sense to align behavior with Puma)
     run_once = false
 
-    # The Unicorn before_exec hook only gets called on a Unicorn
-    # restart, but we want to clean things up (e.g. metric files) at
-    # first boot.
-    Gitlab::Cluster::LifecycleEvents.do_master_restart
+    # Signal application hooks that we're about to fork
+    Gitlab::Cluster::LifecycleEvents.do_before_fork
   end
 
-  # Signal application hooks that we're about to fork
-  Gitlab::Cluster::LifecycleEvents.do_before_fork
-
   # The following is only recommended for memory/DB-constrained
   # installations.  It is not needed if your system can house
   # twice as many worker_processes as you have configured.
diff --git a/lib/gitlab/cluster/lifecycle_events.rb b/lib/gitlab/cluster/lifecycle_events.rb
index e0f9eb59924..8f796748199 100644
--- a/lib/gitlab/cluster/lifecycle_events.rb
+++ b/lib/gitlab/cluster/lifecycle_events.rb
@@ -11,6 +11,9 @@ module Gitlab
     # We have three lifecycle events.
     #
     # - before_fork (only in forking processes)
+    #     In forking processes (Unicorn and Puma in multiprocess mode) this
+    #     will be called exactly once, on startup, before the workers are
+    #     forked. This will be called in the parent process.
     # - worker_start
     # - before_master_restart (only in forking processes)
     #