def start(self, num_processes=1):
"""Starts this server in the `.IOLoop`.
By default, we run the server in this process and do not fork any
additional child process.
If num_processes is ``None`` or <= 0, we detect the number of cores
available on this machine and fork that number of child
processes. If num_processes is given and > 1, we fork that
specific number of sub-processes.
Since we use processes and not threads, there is no shared memory
between any server code.
Note that multiple processes are not compatible with the autoreload
module (or the ``autoreload=True`` option to `webalchemy.tornado.web.Application`
which defaults to True when ``debug=True``).
When using multiple processes, no IOLoops can be created or
referenced until after the call to ``TCPServer.start(n)``.
"""
assert not self._started
self._started = True
if num_processes != 1:
process.fork_processes(num_processes)
sockets = self._pending_sockets
self._pending_sockets = []
self.add_sockets(sockets)
def test_multi_process(self):
# This test can't work on twisted because we use the global reactor
# and have no way to get it back into a sane state after the fork.
skip_if_twisted()
with ExpectLog(gen_log, "(Starting .* processes|child .* exited|uncaught exception)"):
self.assertFalse(IOLoop.initialized())
sock, port = bind_unused_port()
def get_url(path):
return "http://127.0.0.1:%d%s" % (port, path)
# ensure that none of these processes live too long
signal.alarm(5) # master process
try:
id = fork_processes(3, max_restarts=3)
self.assertTrue(id is not None)
signal.alarm(5) # child processes
except SystemExit as e:
# if we exit cleanly from fork_processes, all the child processes
# finished with status 0
self.assertEqual(e.code, 0)
self.assertTrue(task_id() is None)
sock.close()
return
try:
if id in (0, 1):
self.assertEqual(id, task_id())
server = HTTPServer(self.get_app())
server.add_sockets([sock])
IOLoop.instance().start()
elif id == 2:
self.assertEqual(id, task_id())
sock.close()
# Always use SimpleAsyncHTTPClient here; the curl
# version appears to get confused sometimes if the
# connection gets closed before it's had a chance to
# switch from writing mode to reading mode.
client = HTTPClient(SimpleAsyncHTTPClient)
def fetch(url, fail_ok=False):
try:
return client.fetch(get_url(url))
except HTTPError as e:
if not (fail_ok and e.code == 599):
raise
# Make two processes exit abnormally
fetch("/?exit=2", fail_ok=True)
fetch("/?exit=3", fail_ok=True)
# They've been restarted, so a new fetch will work
int(fetch("/").body)
# Now the same with signals
# Disabled because on the mac a process dying with a signal
# can trigger an "Application exited abnormally; send error
# report to Apple?" prompt.
# fetch("/?signal=%d" % signal.SIGTERM, fail_ok=True)
# fetch("/?signal=%d" % signal.SIGABRT, fail_ok=True)
# int(fetch("/").body)
# Now kill them normally so they won't be restarted
fetch("/?exit=0", fail_ok=True)
# One process left; watch it's pid change
pid = int(fetch("/").body)
fetch("/?exit=4", fail_ok=True)
pid2 = int(fetch("/").body)
self.assertNotEqual(pid, pid2)
# Kill the last one so we shut down cleanly
fetch("/?exit=0", fail_ok=True)
os._exit(0)
except Exception:
logging.error("exception in child process %d", id, exc_info=True)
raise