"""A thread-based worker pool."""
from __future__ import absolute_import, division, print_function
__metaclass__ = type
import threading
import time
import socket
from six.moves import queue
__all__ = ('WorkerThread', 'ThreadPool')
class TrueyZero:
"""Object which equals and does math like the integer 0 but evals True."""
def __add__(self, other):
return other
def __radd__(self, other):
return other
trueyzero = TrueyZero()
_SHUTDOWNREQUEST = None
class WorkerThread(threading.Thread):
"""Thread which continuously polls a Queue for Connection objects.
Due to the timing issues of polling a Queue, a WorkerThread does not
check its own 'ready' flag after it has started. To stop the thread,
it is necessary to stick a _SHUTDOWNREQUEST object onto the Queue
(one for each running WorkerThread).
"""
conn = None
"""The current connection pulled off the Queue, or None."""
server = None
"""The HTTP Server which spawned this thread, and which owns the
Queue and is placing active connections into it."""
ready = False
"""A simple flag for the calling server to know when this thread
has begun polling the Queue."""
def __init__(self, server):
"""Initialize WorkerThread instance.
Args:
server (cheroot.server.HTTPServer): web server object
receiving this request
"""
self.ready = False
self.server = server
self.requests_seen = 0
self.bytes_read = 0
self.bytes_written = 0
self.start_time = None
self.work_time = 0
self.stats = {
'Requests': lambda s: self.requests_seen + (
(self.start_time is None) and
trueyzero or
self.conn.requests_seen
),
'Bytes Read': lambda s: self.bytes_read + (
(self.start_time is None) and
trueyzero or
self.conn.rfile.bytes_read
),
'Bytes Written': lambda s: self.bytes_written + (
(self.start_time is None) and
trueyzero or
self.conn.wfile.bytes_written
),
'Work Time': lambda s: self.work_time + (
(self.start_time is None) and
trueyzero or
time.time() - self.start_time
),
'Read Throughput': lambda s: s['Bytes Read'](s) / (
s['Work Time'](s) or 1e-6),
'Write Throughput': lambda s: s['Bytes Written'](s) / (
s['Work Time'](s) or 1e-6),
}
threading.Thread.__init__(self)
def run(self):
"""Process incoming HTTP connections.
Retrieves incoming connections from thread pool.
"""
self.server.stats['Worker Threads'][self.getName()] = self.stats
try:
self.ready = True
while True:
conn = self.server.requests.get()
if conn is _SHUTDOWNREQUEST:
return
self.conn = conn
if self.server.stats['Enabled']:
self.start_time = time.time()
try:
conn.communicate()
finally:
conn.close()
if self.server.stats['Enabled']:
self.requests_seen += self.conn.requests_seen
self.bytes_read += self.conn.rfile.bytes_read
self.bytes_written += self.conn.wfile.bytes_written
self.work_time += time.time() - self.start_time
self.start_time = None
self.conn = None
except (KeyboardInterrupt, SystemExit) as ex:
self.server.interrupt = ex
class ThreadPool:
"""A Request Queue for an HTTPServer which pools threads.
ThreadPool objects must provide min, get(), put(obj), start()
and stop(timeout) attributes.
"""
def __init__(
self, server, min=10, max=-1, accepted_queue_size=-1,
accepted_queue_timeout=10):
"""Initialize HTTP requests queue instance.
Args:
server (cheroot.server.HTTPServer): web server object
receiving this request
min (int): minimum number of worker threads
max (int): maximum number of worker threads
accepted_queue_size (int): maximum number of active
requests in queue
accepted_queue_timeout (int): timeout for putting request
into queue
"""
self.server = server
self.min = min
self.max = max
self._threads = []
self._queue = queue.Queue(maxsize=accepted_queue_size)
self._queue_put_timeout = accepted_queue_timeout
self.get = self._queue.get
def start(self):
"""Start the pool of threads."""
for i in range(self.min):
self._threads.append(WorkerThread(self.server))
for worker in self._threads:
worker.setName('CP Server ' + worker.getName())
worker.start()
for worker in self._threads:
while not worker.ready:
time.sleep(.1)
@property
def idle(self): # noqa: D401; irrelevant for properties
"""Number of worker threads which are idle. Read-only."""
return len([t for t in self._threads if t.conn is None])
def put(self, obj):
"""Put request into queue.
Args:
obj (cheroot.server.HTTPConnection): HTTP connection
waiting to be processed
"""
self._queue.put(obj, block=True, timeout=self._queue_put_timeout)
if obj is _SHUTDOWNREQUEST:
return
def grow(self, amount):
"""Spawn new worker threads (not above self.max)."""
if self.max > 0:
budget = max(self.max - len(self._threads), 0)
else:
# self.max <= 0 indicates no maximum
budget = float('inf')
n_new = min(amount, budget)
workers = [self._spawn_worker() for i in range(n_new)]
while not all(worker.ready for worker in workers):
time.sleep(.1)
self._threads.extend(workers)
def _spawn_worker(self):
worker = WorkerThread(self.server)
worker.setName('CP Server ' + worker.getName())
worker.start()
return worker
def shrink(self, amount):
"""Kill off worker threads (not below self.min)."""
# Grow/shrink the pool if necessary.
# Remove any dead threads from our list
for t in self._threads:
if not t.isAlive():
self._threads.remove(t)
amount -= 1
# calculate the number of threads above the minimum
n_extra = max(len(self._threads) - self.min, 0)
# don't remove more than amount
n_to_remove = min(amount, n_extra)
# put shutdown requests on the queue equal to the number of threads
# to remove. As each request is processed by a worker, that worker
# will terminate and be culled from the list.
for n in range(n_to_remove):
self._queue.put(_SHUTDOWNREQUEST)
def stop(self, timeout=5):
"""Terminate all worker threads.
Args:
timeout (int): time to wait for threads to stop gracefully
"""
# Must shut down threads here so the code that calls
# this method can know when all threads are stopped.
for worker in self._threads:
self._queue.put(_SHUTDOWNREQUEST)
# Don't join currentThread (when stop is called inside a request).
current = threading.currentThread()
if timeout is not None and timeout >= 0:
endtime = time.time() + timeout
while self._threads:
worker = self._threads.pop()
if worker is not current and worker.isAlive():
try:
if timeout is None or timeout < 0:
worker.join()
else:
remaining_time = endtime - time.time()
if remaining_time > 0:
worker.join(remaining_time)
if worker.isAlive():
# We exhausted the timeout.
# Forcibly shut down the socket.
c = worker.conn
if c and not c.rfile.closed:
try:
c.socket.shutdown(socket.SHUT_RD)
except TypeError:
# pyOpenSSL sockets don't take an arg
c.socket.shutdown()
worker.join()
except (AssertionError,
# Ignore repeated Ctrl-C.
# See
# https://github.com/cherrypy/cherrypy/issues/691.
KeyboardInterrupt):
pass
@property
def qsize(self):
"""Return the queue size."""
return self._queue.qsize()