def start(self):
"""
Start fork loop.
"""
# Load configuration here to make sure that everything for it is loaded
self.cfg = getConfiguration()
# Must import here because we don't have DB on bootup yet
from Globals import DB
# TODO: Fetch adapter with interface
self.storage_index = FileStorageIndex(DB.storage)
# SIGCHLD tells us that child process has really died and we can spawn
# new child
registerHandler(signal.SIGCHLD, self._waitChildToDieAndScheduleNew)
# With SIGUSR1 child can tell that it dies by request, not by exception
# etc.
registerHandler(signal.SIGUSR1, self._childIsGoingToDie)
self.loop()
class ForkLoop(object):
def __init__(self):
self.fork = True # Create child on start
self.active = False
self.pause = False
self.killed_child = True
self.forking = False
self.exit = False
self.parent_pid = os.getpid()
self.child_pid = None
# Timers
self.boot_started = None
self.child_started = None
self.cfg = None
self.storage_index = None
def isChild(self):
return self.child_pid == 0
def startBootTimer(self):
if not self.boot_started:
self.boot_started = time.time()
def startChildBooTimer(self):
self.child_started = time.time()
def isChildAlive(self):
if self.isChild():
return True
return (self.child_pid is not None
and os.path.exists("/proc/%i" % self.child_pid))
def _scheduleFork(self, signum=None, frame=None):
self.fork = True
def _childIsGoingToDie(self, signum=None, frame=None):
self.killed_child = True
def start(self):
"""
Start fork loop.
"""
# Load configuration here to make sure that everything for it is loaded
self.cfg = getConfiguration()
# Must import here because we don't have DB on bootup yet
from Globals import DB
# TODO: Fetch adapter with interface
self.storage_index = FileStorageIndex(DB.storage)
# SIGCHLD tells us that child process has really died and we can spawn
# new child
registerHandler(signal.SIGCHLD, self._waitChildToDieAndScheduleNew)
# With SIGUSR1 child can tell that it dies by request, not by exception
# etc.
registerHandler(signal.SIGUSR1, self._childIsGoingToDie)
self.loop()
def loop(self):
"""
Magic happens here
"""
registerHandler(signal.SIGINT, self._parentExitHandler)
registerHandler(signal.SIGTERM, self._parentExitHandler)
self.active = True
logger.info("Fork loop starting on parent. PID %i" % os.getpid())
while True:
self.forking = False
if self.exit:
return
if self.fork:
self.fork = False
if self.pause:
# Pause mode. No forks now.
continue
if not self.killed_child:
errline()
errline("Child died on bootup. Pausing fork loop for now. ")
errline("Fix possible errors and save edits and we'll try booting again.")
errline("Waiting...")
# Child died because of unknown reason. Mark it as killed
# and go into pause mode.
self.killed_child = True
self.pause = True
continue
if self.isChildAlive():
# Child is still alive for some reason. Lets wait few
# rounds for it to die.
continue
self.forking = True
self.startChildBooTimer()
self.child_pid = os.fork()
if self.child_pid == 0:
break
self.killed_child = False
time.sleep(1)
logger.setChildLogger()
logger.info("Forked new child. Installing reloadable products...")
self._prepareNewChild()
self.forking = False
logger.info("Booted up new new child in %s seconds. PID %i" % (
time.time() - self.child_started, os.getpid()))
notify(NewChildIsReady(self))
def _prepareNewChild(self):
"""
Prepare newly forked child. Make sure that it can properly read DB
and install deferred products.
"""
# Register exit listener. We cannot immediately spawn new child when we
# get a modified event. Must wait that child has closed database etc.
atexit.register(self._childExitHandler)
# Make sure that PID files and locks stay here, because dying child
# will clear them.
self.makeLockFile()
self.makePidFile()
self.storage_index.restore()
notify(NewChildForked(self))
autoinclude.include_deferred()
fiveconfigure.install_deferred()
def spawnNewChild(self):
"""
STEP 1 (parent): New child spawning starts by killing the current
child.
"""
if not self.active:
raise CannotSpawnNewChild("Loop not started yet")
if self.forking:
raise CannotSpawnNewChild("Serious forking action is already going on. Cannot fork now.")
if self.child_pid is None:
raise CannotSpawnNewChild("No killing yet. Not started child yet")
self.pause = False
if not self.killed_child or self.isChild():
self._killChild()
else:
# Ok, we already have sent the SIGINT the child, but asking for new child
logger.info("Not sending SIGINT because we already killed the child. Just scheduling new fork.")
self._scheduleFork()
self.killed_child = True
def _killChild(self):
if self.isChild():
# Signal parent that this is requested kill, not an error situation
os.kill(self.parent_pid, signal.SIGUSR1)
# Kill itself
os.kill(os.getpid(), signal.SIGINT)
else:
os.kill(self.child_pid, signal.SIGINT)
def _parentExitHandler(self, signum=None, frame=None):
if self.isChild():
return
self.exit = True
if self.isChildAlive():
logger.info("Parent dying. Killing child first.")
self._killChild()
def _childExitHandler(self):
"""
STEP 2 (child): Child is about to die. Fix DB.
"""
self.storage_index.save()
def _waitChildToDieAndScheduleNew(self, signal=None, frame=None):
"""
STEP 3 (parent): Child told us via SIGCHLD that we can spawn new child
"""
# Acknowledge dead child
os.wait()
# Schedule new
self._scheduleFork()
# Modified from Zope2/Startup/__init__.py
def makePidFile(self):
if not self.cfg.zserver_read_only_mode:
# write the pid into the pidfile if possible
try:
if os.path.exists(self.cfg.pid_filename):
os.unlink(self.cfg.pid_filename)
f = open(self.cfg.pid_filename, 'w')
f.write(str(self.parent_pid))
f.close()
except IOError:
pass
# Modified from Zope2/Startup/__init__.py
def makeLockFile(self):
if not self.cfg.zserver_read_only_mode:
from Zope2.Startup.misc.lock_file import lock_file
lock_filename = self.cfg.lock_filename
try:
if os.path.exists(lock_filename):
os.unlink(lock_filename)
lockfile = open(lock_filename, 'w')
lock_file(lockfile)
lockfile.write(str(self.parent_pid))
lockfile.flush()
except IOError:
pass