6 files changed, 67 insertions, 6 deletions
diff --git a/config/initializers/7_prometheus_metrics.rb b/config/initializers/7_prometheus_metrics.rb
index 146c4b1e024..8052880cc3d 100644
--- a/config/initializers/7_prometheus_metrics.rb
+++ b/config/initializers/7_prometheus_metrics.rb
@@ -26,9 +26,25 @@ Sidekiq.configure_server do |config|
 end
 
 if !Rails.env.test? && Gitlab::Metrics.prometheus_metrics_enabled?
-  unless Sidekiq.server?
-    Gitlab::Metrics::Samplers::UnicornSampler.initialize_instance(Settings.monitoring.unicorn_sampler_interval).start
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    defined?(::Prometheus::Client.reinitialize_on_pid_change) && Prometheus::Client.reinitialize_on_pid_change
+
+    unless Sidekiq.server?
+      Gitlab::Metrics::Samplers::UnicornSampler.initialize_instance(Settings.monitoring.unicorn_sampler_interval).start
+    end
+
+    Gitlab::Metrics::Samplers::RubySampler.initialize_instance(Settings.monitoring.ruby_sampler_interval).start
   end
+end
 
-  Gitlab::Metrics::Samplers::RubySampler.initialize_instance(Settings.monitoring.ruby_sampler_interval).start
+Gitlab::Cluster::LifecycleEvents.on_master_restart do
+  # 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')]
+    FileUtils.rm_rf(old_metrics)
+  end
 end
diff --git a/config/initializers/8_metrics.rb b/config/initializers/8_metrics.rb
index eccf82ab8dc..c8d261d415e 100644
--- a/config/initializers/8_metrics.rb
+++ b/config/initializers/8_metrics.rb
@@ -158,7 +158,9 @@ if Gitlab::Metrics.enabled? && !Rails.env.test?
 
   GC::Profiler.enable
 
-  Gitlab::Metrics::Samplers::InfluxSampler.initialize_instance.start
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    Gitlab::Metrics::Samplers::InfluxSampler.initialize_instance.start
+  end
 
   module TrackNewRedisConnections
     def connect(*args)
diff --git a/config/initializers/active_record_lifecycle.rb b/config/initializers/active_record_lifecycle.rb
new file mode 100644
index 00000000000..7fa37121efc
--- /dev/null
+++ b/config/initializers/active_record_lifecycle.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# Don't handle sidekiq configuration as it
+# has its own special active record configuration here
+if defined?(ActiveRecord::Base) && !Sidekiq.server?
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    ActiveSupport.on_load(:active_record) do
+      ActiveRecord::Base.establish_connection
+
+      Rails.logger.debug("ActiveRecord connection established")
+    end
+  end
+end
+
+if defined?(ActiveRecord::Base)
+  Gitlab::Cluster::LifecycleEvents.on_before_fork do
+    # the following is highly recommended for Rails + "preload_app true"
+    # as there's no need for the master process to hold a connection
+    ActiveRecord::Base.connection.disconnect!
+
+    Rails.logger.debug("ActiveRecord connection disconnected")
+  end
+end
diff --git a/config/initializers/macos.rb b/config/initializers/macos.rb
new file mode 100644
index 00000000000..f410af6ed47
--- /dev/null
+++ b/config/initializers/macos.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+if /darwin/ =~ RUBY_PLATFORM
+  Gitlab::Cluster::LifecycleEvents.on_before_fork do
+    require 'fiddle'
+
+    # Dynamically load Foundation.framework, ~implicitly~ initialising
+    # the Objective-C runtime before any forking happens in Unicorn
+    #
+    # From https://bugs.ruby-lang.org/issues/14009
+    Fiddle.dlopen '/System/Library/Frameworks/Foundation.framework/Foundation'
+  end
+end
diff --git a/config/initializers/rbtrace.rb b/config/initializers/rbtrace.rb
new file mode 100644
index 00000000000..6a1b71bf4bd
--- /dev/null
+++ b/config/initializers/rbtrace.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+if ENV['ENABLE_RBTRACE']
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    # Unicorn clears out signals before it forks, so rbtrace won't work
+    # unless it is enabled after the fork.
+    require 'rbtrace'
+  end
+end
diff --git a/config/initializers/sidekiq.rb b/config/initializers/sidekiq.rb
index bc6b7aed6aa..565efc858d1 100644
--- a/config/initializers/sidekiq.rb
+++ b/config/initializers/sidekiq.rb
@@ -14,8 +14,6 @@ Sidekiq.default_worker_options = { retry: 3 }
 enable_json_logs = Gitlab.config.sidekiq.log_format == 'json'
 
 Sidekiq.configure_server do |config|
-  require 'rbtrace' if ENV['ENABLE_RBTRACE']
-
   config.redis = queues_config_hash
 
   config.server_middleware do |chain|