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module Raemon
class Master
include Instrumentation
WORKERS = {}
SELF_PIPE = []
SIG_QUEUE = []
CHUNK_SIZE = (16 * 1024)
# list of signals we care about and trap in master.
QUEUE_SIGS = [:WINCH, :QUIT, :INT, :TERM, :USR1, :USR2, :HUP, :TTIN, :TTOU]
attr_accessor :name, :num_workers, :worker_class,
:master_pid, :pid_file,
:logger, :timeout, :memory_limit
def self.start(num_workers, worker_class, options={})
master = new(options)
master.start(num_workers, worker_class)
end
def self.stop(options={})
pid_file = options[:pid_file]
pid = options[:pid] || (File.read(pid_file).to_i rescue 0)
Process.kill('QUIT', pid) if pid > 0
rescue Errno::ESRCH
end
def initialize(options={})
@detach = options[:detach] || false
@name = options[:name] || 'Raemon'
@pid_file = options[:pid_file]
@logger = options[:logger] || Logger.new(STDOUT)
@timeout = options[:timeout] || 180 # 3 minutes
@memory_limit = options[:memory_limit] # in MB
@master_pid = Process.pid
daemonize if @detach
end
def start(num_workers, worker_class)
logger.info "=> Starting #{name} with #{num_workers} worker(s)"
instrument 'master.start', :pid => master_pid
@num_workers = num_workers
@worker_class = worker_class
ensure_worker_class_is_valid
master_loop!
end
# Terminates all workers, but does not exit master process
def stop(graceful=true)
kill_each_worker(graceful ? :QUIT : :TERM)
timeleft = timeout
step = 0.2
reap_all_workers
until WORKERS.empty?
sleep(step)
reap_all_workers
(timeleft -= step) > 0 and next
kill_each_worker(:KILL)
end
Configuration.on_stop.call
instrument 'master.stop', :pid => master_pid
end
def worker_heartbeat!(worker)
return if timeout <= 0
@last_pulse ||= 0
begin
if Time.now.to_i > @last_pulse + (timeout/2)
# Pulse (our lifeline to the master process)
@last_pulse = Time.now.to_i
@p = 0 == @p ? 1 : 0
worker.pulse.chmod(@p)
# Make sure master is still around otherwise exit
master_pid == Process.ppid or return
end
rescue => ex
if worker.pulse
logger.error "Unhandled listen loop exception #{ex.inspect}"
logger.error ex.backtrace.join("\n")
instrument 'error', :error => ex
end
end
end
private
# monitors children and receives signals forever, or until a termination
# signal is sent. This handles signals one-at-a-time time and we'll
# happily drop signals in case somebody is signalling us too often.
def master_loop!
# this pipe is used to wake us up from select(2) in #join when signals
# are trapped. See trap_deferred
init_self_pipe!
respawn = true
QUEUE_SIGS.each { |sig| trap_deferred(sig) }
trap(:CHLD) { |sig_nr| awaken_master }
process_name 'master'
logger.info 'master process ready'
# Spawn workers for the first time
maintain_worker_count
begin
loop do
monitor_memory_usage
reap_all_workers
case SIG_QUEUE.shift
when nil
murder_lazy_workers
maintain_worker_count if respawn
master_sleep
when :QUIT # graceful shutdown
stop
break
when :TERM, :INT # immediate shutdown
stop(false)
break
when :USR1
kill_each_worker(:USR1)
when :USR2
kill_each_worker(:USR2)
when :WINCH
if Process.ppid == 1 || Process.getpgrp != $$
respawn = false
logger.info "gracefully stopping all workers"
kill_each_worker(:QUIT)
else
logger.info "SIGWINCH ignored because we're not daemonized"
end
when :TTIN
@num_workers += 1
when :TTOU
@num_workers -= 1 if @num_workers > 0
when :HUP
# TODO: should restart the workers, but a :QUIT could stall
# respawn = true
# kill_each_worker(:QUIT)
end
end
rescue Errno::EINTR
retry
rescue => ex
logger.error "Unhandled master loop exception #{ex.inspect}."
logger.error ex.backtrace.join("\n")
instrument 'error', :error => ex
retry
end
logger.info "master complete"
# Close resources
unlink_pid_safe(pid_file) if pid_file
logger.close
end
# defer a signal for later processing in #master_loop! (master process)
def trap_deferred(signal)
trap(signal) do |sig_nr|
if SIG_QUEUE.size < 5
SIG_QUEUE << signal
awaken_master
else
logger.error "ignoring SIG#{signal}, queue=#{SIG_QUEUE.inspect}"
end
end
end
# wait for a signal handler to wake us up and then consume the pipe
# Wake up every second anyways to run murder_lazy_workers
def master_sleep
begin
ready = IO.select([SELF_PIPE.first], nil, nil, 1) or return
ready.first && ready.first.first or return
loop { SELF_PIPE.first.read_nonblock(CHUNK_SIZE) }
rescue Errno::EAGAIN, Errno::EINTR
end
end
def awaken_master
begin
SELF_PIPE.last.write_nonblock('.') # wakeup master process from select
rescue Errno::EAGAIN, Errno::EINTR
# pipe is full, master should wake up anyways
retry
end
end
# reaps all unreaped workers
def reap_all_workers
begin
loop do
wpid, status = Process.waitpid2(-1, Process::WNOHANG)
wpid or break
worker = WORKERS.delete(wpid) and worker.pulse.close rescue nil
worker_id = worker.id rescue 'unknown'
instrument 'worker.stop', :pid => worker.pid
logger.info "reaped #{status.inspect} worker=#{worker_id}"
end
rescue Errno::ECHILD
end
end
# forcibly terminate all workers that haven't checked-in in timeout
# seconds. The timeout is implemented using an unlinked File
# shared between the parent process and each worker. The worker
# runs File#chmod to modify the ctime of the File. If the ctime
# is stale for >timeout seconds, then we'll kill the corresponding
# worker.
def murder_lazy_workers
return if timeout <= 0
diff = stat = nil
WORKERS.dup.each_pair do |wpid, worker|
begin
stat = worker.pulse.stat
rescue => ex
logger.warn "worker=#{worker.id} PID:#{wpid} stat error: #{ex.inspect}"
kill_worker(:QUIT, wpid)
next
end
stat.mode == 0100000 and next
(diff = (Time.now - stat.ctime)) <= timeout and next
logger.error "worker=#{worker.id} PID:#{wpid} timeout (#{diff}s > #{timeout}s), killing"
kill_worker(:KILL, wpid) # take no prisoners for timeout violations
instrument 'worker.stop', :pid => wpid
end
end
# Fork the worker processes wrapped in the worker loop
def spawn_workers
(0...num_workers).each do |id|
WORKERS.values.include?(id) and next
worker = worker_class.new(self, id, Raemon::Util.tmpio)
worker_pid = fork { worker_loop!(worker) }
worker.pid = worker_pid
WORKERS[worker_pid] = worker
end
end
def maintain_worker_count
off = num_workers - WORKERS.size
if off.zero?
return
elsif off == num_workers
# None of the workers are running, lets be gentle
@spawn_attempts ||= 0
sleep 1 if @spawn_attempts > 1
if timeout > 0 && @spawn_attempts > timeout
# We couldn't get the workers going after timeout seconds, so let's
# assume this will never work
message = "Unable to spawn workers after #{@spawn_attempts} attempts"
logger.error(message)
instrument 'error', :error => message
master_quit
return
end
@spawn_attempts += 1
else
@spawn_attempts = nil
end
return spawn_workers if off > 0
WORKERS.dup.each_pair do |wpid, worker|
worker.id >= num_workers && kill_worker(:QUIT, wpid) rescue nil
end
end
# gets rid of stuff the worker has no business keeping track of
# to free some resources and drops all sig handlers.
def init_worker_process(worker)
worker.pid = Process.pid
QUEUE_SIGS.each { |sig| trap(sig, nil) }
trap(:CHLD, 'DEFAULT')
SIG_QUEUE.clear
process_name "worker[#{worker.id}]"
init_self_pipe!
WORKERS.values.each { |other_worker| other_worker.pulse.close rescue nil }
WORKERS.clear
worker.pulse.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
@timeout /= 2.0 # halve it for select
end
# runs inside each forked worker, this sits around and waits
# for connections and doesn't die until the parent dies (or is
# given a INT, QUIT, or TERM signal)
def worker_loop!(worker)
init_worker_process(worker)
# Graceful shutdown
trap(:QUIT) do
worker.stop
exit!(0)
end
# Immediate termination
[:TERM, :INT].each do |sig|
trap(sig) { exit!(0) }
end
worker.start
worker.run
end
# delivers a signal to a worker and fails gracefully if the worker
# is no longer running.
def kill_worker(signal, wpid)
begin
Process.kill(signal, wpid)
rescue Errno::ESRCH
worker = WORKERS.delete(wpid) and worker.pulse.close rescue nil
end
end
# delivers a signal to each worker
def kill_each_worker(signal)
WORKERS.keys.each { |wpid| kill_worker(signal, wpid) }
end
# Make the master quit
def master_quit
SIG_QUEUE << :QUIT
end
# unlinks a PID file at given +path+ if it contains the current PID
# still potentially racy without locking the directory (which is
# non-portable and may interact badly with other programs), but the
# window for hitting the race condition is small
def unlink_pid_safe(path)
(File.read(path).to_i == $$ and File.unlink(path)) rescue nil
end
# returns a PID if a given path contains a non-stale PID file,
# nil otherwise.
def valid_pid?(path)
wpid = File.read(path).to_i
wpid <= 0 and return
begin
Process.kill(0, wpid) # send null signal to check if its alive
return wpid
rescue Errno::ESRCH
# don't unlink stale pid files, racy without non-portable locking...
end
rescue Errno::ENOENT
end
def process_name(tag)
$0 = "#{name} #{tag}"
end
def init_self_pipe!
SELF_PIPE.each { |io| io.close rescue nil }
SELF_PIPE.replace(IO.pipe)
SELF_PIPE.each { |io| io.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC) }
end
def daemonize
exit if Process.fork
Process.setsid
Dir.chdir '/'
File.umask 0000
STDIN.reopen '/dev/null'
STDOUT.reopen '/dev/null', 'a'
STDERR.reopen '/dev/null', 'a'
File.open(pid_file, 'w') { |f| f.puts(Process.pid) } if pid_file
end
def memory_limit_in_bytes
memory_limit * 1024
end
# Check memory usage every 60 seconds if a memory limit is enforced
def monitor_memory_usage
return if memory_limit.nil?
@last_memory_chk ||= 0
if @last_memory_chk + 60 < Time.now.to_i
@last_memory_chk = Time.now.to_i
WORKERS.dup.each_pair do |wpid, worker|
memory_used = worker.memory_usage
instrument 'worker.memory_usage', :pid => wpid, :memory_used => memory_used
if memory_used > memory_limit_in_bytes
logger.warn "memory limit (#{memory_limit}MB) reached by worker=#{worker.id} (USED: #{memory_used})"
kill_worker :QUIT, wpid
end
end
end
end
# Check if the worker implements our interface
def ensure_worker_class_is_valid
unless worker_class.include?(Raemon::Worker)
error = 'Invalid Raemon worker'
logger.error(error)
logger.close
instrument 'error', :error => error
exit
end
end
end
end
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