def find_cron_daemon():
"""
Find the cron daemon process.
:returns: A :class:`~proc.tree.ProcessNode` object.
:raises: :exc:`CronDaemonNotRunning` when the cron daemon process cannot
be located.
"""
init = get_process_tree()
cron = init.find(exe_name='cron')
if not cron:
raise CronDaemonNotRunning(
"Failed to determine process id of cron daemon process! Is it running?"
)
return cron
def test_tree_construction(self, timeout=60):
"""Test the functionality of the :mod:`proc.tree` module."""
# Test argument validation.
self.assertRaises(TypeError, get_process_tree, obj_type=object)
# Spawn a child and grandchild (because of shell=True) that will live for a minute.
child = subprocess.Popen(['sleep 60'], shell=True)
# Use a try / finally block to make sure we kill our child before returning.
try:
# This test used to fail intermittently on Travis CI because the child
# and grandchild need a moment to initialize and the test wasn't giving
# the two processes the time they needed to initialize. However any
# given time.sleep(N) value is completely arbitrary (if a computer can
# be slow it can also be really slow :-) so instead I've decided to
# repeat the test until it succeeds, with a timeout in case it actually
# does fail and won't succeed despite waiting.
timer = Timer()
while True:
# Use a try / except block (in a while loop) to retry as long
# as the timeout hasn't been hit and bubble the exception when
# once we hit the timeout.
try:
# Construct a process tree.
init = get_process_tree()
# Locate our own process in the tree.
self = init.find(pid=os.getpid(), recursive=True)
# Verify that the child is visible in the process tree.
logger.debug("Children in process tree: %s",
list(self.children))
assert child.pid in [c.pid for c in self.children], \
"Child process not visible in process tree reported by get_process_tree()!"
# Verify that the grandchild is visible in the process tree.
logger.debug("Grandchildren in process tree: %s",
list(self.grandchildren))
assert any(gc.exe_name == 'sleep' for gc in self.grandchildren), \
"Grandchild process not visible in process tree reported by get_process_tree()!"
# Once both assertions have succeeded the test has also
# succeeded and we return (break out of the while loop).
return
except AssertionError:
if timer.elapsed_time >= timeout:
# Stop swallowing assertions once we hit the timeout.
raise
else:
# Don't burn CPU cycles too much.
time.sleep(0.1)
finally:
# Make sure we always kill our child.
child.terminate()
def find_apache_workers(exe_name='apache2'):
"""
Find Apache workers in the process tree reported by :func:`~proc.tree.get_process_tree()`.
:param exe_name: The base name of the Apache executable (a string).
:returns: A generator of :class:`MaybeApacheWorker` objects.
:raises: :exc:`ApacheDaemonNotRunning` when the Apache master process
cannot be found.
"""
init = get_process_tree(obj_type=MaybeApacheWorker)
candidates = list(init.find_all(exe_name=exe_name))
if len(candidates) > 1:
# If we find more than one process with the executable name `apache2'
# whose parent process is `init' (1) we will narrow down the list of
# candidates by disregarding any processes that are not running with
# superuser privileges.
candidates = [p for p in candidates if p.user_ids.real == 0]
if not candidates:
raise ApacheDaemonNotRunning("Could not find Apache master process! Is it running?")
master = candidates[0]
for process in master.children:
if process.comm == master.comm:
yield process