mirror of
https://github.com/discourse/discourse.git
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23c38cbf11
This commit introduces the following changes: 1. Introduce the `SignalTrapLogger` singleton which starts a single thread that polls a queue to log messages with the specified logger. This thread is necessary becasue most loggers cannot be used inside the `Signal.trap` context as they rely on mutexes which are not allowed within the context. 2. Moves the monkey patch in `freedom_patches/unicorn_http_server_patch.rb` to `config/unicorn.config.rb` which is already monkey patching `Unicorn::HttpServer`. 3. `Unicorn::HttpServer` will now automatically send a `USR2` signal to a unicorn worker 2 seconds before the worker is timed out by the Unicorn master. 4. When a Unicorn worker receives a `USR2` signal, it will now log only the main thread's backtraces to `Rails.logger`. Previously, it was `put`ing the backtraces to `STDOUT` which most people wouldn't read. Logging it via `Rails.logger` will make the backtraces easily accessible via `/logs`.
244 lines
4.5 KiB
Ruby
244 lines
4.5 KiB
Ruby
# frozen_string_literal: true
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module Demon
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end
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# intelligent fork based demonizer
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class Demon::Base
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def self.demons
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@demons
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end
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def self.start(count = 1, verbose: false, logger: nil)
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@demons ||= {}
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count.times { |i| (@demons["#{prefix}_#{i}"] ||= new(i, verbose:, logger:)).start }
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end
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def self.stop
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return unless @demons
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@demons.values.each { |demon| demon.stop }
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end
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def self.restart
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return unless @demons
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@demons.values.each do |demon|
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demon.stop
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demon.start
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end
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end
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def self.ensure_running
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@demons.values.each { |demon| demon.ensure_running }
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end
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def self.kill(signal)
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return unless @demons
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@demons.values.each { |demon| demon.kill(signal) }
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end
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attr_reader :pid, :parent_pid, :started, :index
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attr_accessor :stop_timeout
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def initialize(index, rails_root: nil, parent_pid: nil, verbose: false, logger: nil)
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@index = index
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@pid = nil
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@parent_pid = parent_pid || Process.pid
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@started = false
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@stop_timeout = 10
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@rails_root = rails_root || Rails.root
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@verbose = verbose
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@logger = logger || Logger.new(STDERR)
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end
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def log(message, level: :info)
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@logger.public_send(level, message)
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end
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def pid_file
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"#{@rails_root}/tmp/pids/#{self.class.prefix}_#{@index}.pid"
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end
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def alive?(pid = nil)
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pid ||= @pid
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if pid
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Demon::Base.alive?(pid)
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else
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false
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end
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end
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def kill(signal)
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Process.kill(signal, @pid)
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end
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def stop_signal
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"HUP"
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end
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def stop
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@started = false
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if @pid
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Process.kill(stop_signal, @pid)
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wait_for_stop =
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lambda do
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timeout = @stop_timeout
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while alive? && timeout > 0
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timeout -= (@stop_timeout / 10.0)
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sleep(@stop_timeout / 10.0)
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begin
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Process.waitpid(@pid, Process::WNOHANG)
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rescue StandardError
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-1
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end
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end
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begin
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Process.waitpid(@pid, Process::WNOHANG)
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rescue StandardError
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-1
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end
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end
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wait_for_stop.call
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if alive?
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log("Process would not terminate cleanly, force quitting. pid: #{@pid} #{self.class}")
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Process.kill("KILL", @pid)
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end
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wait_for_stop.call
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@pid = nil
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@started = false
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end
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end
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def ensure_running
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return unless @started
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if !@pid
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@started = false
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start
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return
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end
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dead =
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begin
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Process.waitpid(@pid, Process::WNOHANG)
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rescue StandardError
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-1
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end
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if dead
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log("Detected dead worker #{@pid}, restarting...")
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@pid = nil
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@started = false
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start
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end
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end
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def start
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return if @pid || @started
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if existing = already_running?
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# should not happen ... so kill violently
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log("Attempting to kill pid #{existing}")
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Process.kill("TERM", existing)
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end
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@started = true
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run
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end
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def run
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@pid =
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fork do
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Process.setproctitle("discourse #{self.class.prefix}")
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monitor_parent
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establish_app
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after_fork
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end
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write_pid_file
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end
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def already_running?
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if File.exist? pid_file
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pid = File.read(pid_file).to_i
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return pid if Demon::Base.alive?(pid)
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end
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nil
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end
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def self.alive?(pid)
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Process.kill(0, pid)
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true
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rescue StandardError
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false
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end
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private
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def verbose(msg)
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puts msg if @verbose
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end
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def write_pid_file
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verbose("writing pid file #{pid_file} for #{@pid}")
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FileUtils.mkdir_p(@rails_root + "tmp/pids")
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File.open(pid_file, "w") { |f| f.write(@pid) }
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end
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def delete_pid_file
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File.delete(pid_file)
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end
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def monitor_parent
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Thread.new do
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while true
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begin
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unless alive?(@parent_pid)
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Process.kill "TERM", Process.pid
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sleep 10
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Process.kill "KILL", Process.pid
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end
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rescue => e
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log("URGENT monitoring thread had an exception #{e}")
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end
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sleep 1
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end
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end
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end
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def suppress_stdout
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true
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end
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def suppress_stderr
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true
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end
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def establish_app
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Discourse.after_fork if defined?(Discourse)
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Signal.trap("HUP") do
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begin
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delete_pid_file
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ensure
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# TERM is way cleaner than exit
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Process.kill("TERM", Process.pid)
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end
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end
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# keep stuff simple for now
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$stdout.reopen("/dev/null", "w") if suppress_stdout
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$stderr.reopen("/dev/null", "w") if suppress_stderr
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end
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def after_fork
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end
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end
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