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|
# frozen_string_literal: true
module Gitlab
module Cluster
#
# LifecycleEvents lets Rails initializers register application startup hooks
# that are sensitive to forking. For example, to defer the creation of
# watchdog threads. This lets us abstract away the Unix process
# lifecycles of Unicorn, Sidekiq, Puma, Puma Cluster, etc.
#
# We have the following lifecycle events.
#
# - on_master_start:
#
# Unicorn/Puma Cluster: This will be called exactly once,
# on startup, before the workers are forked. This is
# called in the PARENT/MASTER process.
#
# Sidekiq/Puma Single: This is called immediately.
#
# - on_before_fork:
#
# Unicorn/Puma Cluster: This will be called exactly once,
# on startup, before the workers are forked. This is
# called in the PARENT/MASTER process.
#
# Sidekiq/Puma Single: This is not called.
#
# - on_worker_start:
#
# Unicorn/Puma Cluster: This is called in the worker process
# exactly once before processing requests.
#
# Sidekiq/Puma Single: This is called immediately.
#
# - on_before_graceful_shutdown:
#
# Unicorn/Puma Cluster: This will be called before a graceful
# shutdown of workers starts happening.
# This is called on `master` process.
#
# Sidekiq/Puma Single: This is not called.
#
# - on_before_master_restart:
#
# Unicorn: This will be called before a new master is spun up.
# This is called on forked master before `execve` to become
# a new masterfor Unicorn. This means that this does not really
# affect old master process.
#
# Puma Cluster: This will be called before a new master is spun up.
# This is called on `master` process.
#
# Sidekiq/Puma Single: This is not called.
#
# Blocks will be executed in the order in which they are registered.
#
class LifecycleEvents
class << self
#
# Hook registration methods (called from initializers)
#
def on_worker_start(&block)
if in_clustered_environment?
# Defer block execution
(@worker_start_hooks ||= []) << block
else
yield
end
end
def on_before_fork(&block)
# Defer block execution
(@before_fork_hooks ||= []) << block
end
# Read the config/initializers/cluster_events_before_phased_restart.rb
def on_before_graceful_shutdown(&block)
# Defer block execution
(@master_graceful_shutdown ||= []) << block
end
def on_before_master_restart(&block)
# Defer block execution
(@master_restart_hooks ||= []) << block
end
def on_master_start(&block)
if in_clustered_environment?
on_before_fork(&block)
else
on_worker_start(&block)
end
end
#
# Lifecycle integration methods (called from unicorn.rb, puma.rb, etc.)
#
def do_worker_start
@worker_start_hooks&.each do |block|
block.call
end
end
def do_before_fork
@before_fork_hooks&.each do |block|
block.call
end
end
def do_before_graceful_shutdown
@master_graceful_shutdown&.each do |block|
block.call
end
end
def do_before_master_restart
@master_restart_hooks&.each do |block|
block.call
end
end
# DEPRECATED
alias_method :do_master_restart, :do_before_master_restart
# Puma doesn't use singletons (which is good) but
# this means we need to pass through whether the
# puma server is running in single mode or cluster mode
def set_puma_options(options)
@puma_options = options
end
private
def in_clustered_environment?
# Sidekiq doesn't fork
return false if Sidekiq.server?
# Unicorn always forks
return true if defined?(::Unicorn)
# Puma sometimes forks
return true if in_clustered_puma?
# Default assumption is that we don't fork
false
end
def in_clustered_puma?
return false unless defined?(::Puma)
@puma_options && @puma_options[:workers] && @puma_options[:workers] > 0
end
end
end
end
end
|
