Merge pull request #279 from Eagllus/django_2_compat

Django 2 compatiblity

django_q/cluster.py

@@ -10,7 +10,7 @@ import signal
 import socket
 import ast
 from time import sleep
-from multiprocessing import Queue, Event, Process, Value, current_process
+from multiprocessing import Event, Process, Value, current_process
 
 # external
 import arrow
@@ -30,7 +30,7 @@ from django_q.models import Task, Success, Schedule
 from django_q.status import Stat, Status
 from django_q.brokers import get_broker
 from django_q.signals import pre_execute
-
+from django_q.queues import Queue
 
 
 class Cluster(object):

django_q/conf.py

@@ -1,7 +1,7 @@
 import logging
 from copy import deepcopy
 from signal import signal
-from multiprocessing import cpu_count, Queue
+from multiprocessing import cpu_count
 
 # django
 from django.utils.translation import ugettext_lazy as _
@@ -11,6 +11,9 @@ from django.conf import settings
 import os
 import pkg_resources
 
+# local
+from django_q.queues import Queue
+
 # optional
 try:
     import psutil

django_q/core_signing.py

@@ -0,0 +1,76 @@
+from __future__ import unicode_literals
+
+import datetime
+import time
+import zlib
+
+from django.utils import baseconv
+from django.utils.crypto import constant_time_compare
+from django.utils.encoding import force_bytes, force_str, force_text
+from django.core.signing import BadSignature, SignatureExpired, b64_decode, JSONSerializer, \
+    Signer as Sgnr, TimestampSigner as TsS, dumps
+
+dumps = dumps
+
+
+"""
+The loads function is the same as the `django.core.signing.loads` function
+The difference is that `this` loads function calls `TimestampSigner` and `Signer`
+"""
+def loads(s, key=None, salt='django.core.signing', serializer=JSONSerializer, max_age=None):
+    """
+    Reverse of dumps(), raise BadSignature if signature fails.
+
+    The serializer is expected to accept a bytestring.
+    """
+    # TimestampSigner.unsign() returns str but base64 and zlib compression
+    # operate on bytes.
+    base64d = force_bytes(TimestampSigner(key, salt=salt).unsign(s, max_age=max_age))
+    decompress = False
+    if base64d[:1] == b'.':
+        # It's compressed; uncompress it first
+        base64d = base64d[1:]
+        decompress = True
+    data = b64_decode(base64d)
+    if decompress:
+        data = zlib.decompress(data)
+    return serializer().loads(data)
+
+
+class Signer(Sgnr):
+
+    def unsign(self, signed_value):
+        # force_str is removed in Django 2.0
+        signed_value = force_str(signed_value)
+        if self.sep not in signed_value:
+            raise BadSignature('No "%s" found in value' % self.sep)
+        value, sig = signed_value.rsplit(self.sep, 1)
+        if constant_time_compare(sig, self.signature(value)):
+            # force_text is removed in Django 2.0
+            return force_text(value)
+        raise BadSignature('Signature "%s" does not match' % sig)
+
+
+"""
+TimestampSigner is also the same as `django.core.signing.TimestampSigner` but is
+calling `this` Signer.
+"""
+class TimestampSigner(Signer, TsS):
+
+    def unsign(self, value, max_age=None):
+        """
+        Retrieve original value and check it wasn't signed more
+        than max_age seconds ago.
+        """
+        result = super().unsign(value)
+        value, timestamp = result.rsplit(self.sep, 1)
+        timestamp = baseconv.base62.decode(timestamp)
+        if max_age is not None:
+            if isinstance(max_age, datetime.timedelta):
+                max_age = max_age.total_seconds()
+            # Check timestamp is not older than max_age
+            age = time.time() - timestamp
+            if age > max_age:
+                raise SignatureExpired(
+                    'Signature age %s > %s seconds' % (age, max_age))
+        return value

django_q/queues.py

@@ -0,0 +1,69 @@
+"""
+The code is derived from https://github.com/althonos/pronto/commit/3384010dfb4fc7c66a219f59276adef3288a886b
+"""
+
+import multiprocessing
+import multiprocessing.queues
+
+
+class SharedCounter(object):
+    """ A synchronized shared counter.
+
+    The locking done by multiprocessing.Value ensures that only a single
+    process or thread may read or write the in-memory ctypes object. However,
+    in order to do n += 1, Python performs a read followed by a write, so a
+    second process may read the old value before the new one is written by
+    the first process. The solution is to use a multiprocessing.Lock to
+    guarantee the atomicity of the modifications to Value.
+
+    This class comes almost entirely from Eli Bendersky's blog:
+    http://eli.thegreenplace.net/2012/01/04/shared-counter-with-pythons-multiprocessing/
+    """
+
+    def __init__(self, n=0):
+        self.count = multiprocessing.Value('i', n)
+
+    def increment(self, n=1):
+        """ Increment the counter by n (default = 1) """
+        with self.count.get_lock():
+            self.count.value += n
+
+    @property
+    def value(self):
+        """ Return the value of the counter """
+        return self.count.value
+
+
+class Queue(multiprocessing.queues.Queue):
+    """ A portable implementation of multiprocessing.Queue.
+
+    Because of multithreading / multiprocessing semantics, Queue.qsize() may
+    raise the NotImplementedError exception on Unix platforms like Mac OS X
+    where sem_getvalue() is not implemented. This subclass addresses this
+    problem by using a synchronized shared counter (initialized to zero) and
+    increasing / decreasing its value every time the put() and get() methods
+    are called, respectively. This not only prevents NotImplementedError from
+    being raised, but also allows us to implement a reliable version of both
+    qsize() and empty().
+    """
+
+    def __init__(self, *args, **kwargs):
+        super(Queue, self).__init__(*args, ctx=multiprocessing.get_context(), **kwargs)
+        self.size = SharedCounter(0)
+
+    def put(self, *args, **kwargs):
+        super(Queue, self).put(*args, **kwargs)
+        self.size.increment(1)
+
+    def get(self, *args, **kwargs):
+        x = super(Queue, self).get(*args, **kwargs)
+        self.size.increment(-1)
+        return x
+
+    def qsize(self):
+        """ Reliable implementation of multiprocessing.Queue.qsize() """
+        return self.size.value
+
+    def empty(self):
+        """ Reliable implementation of multiprocessing.Queue.empty() """
+        return not self.qsize() > 0

django_q/signing.py

@@ -4,7 +4,7 @@ try:
 except ImportError:
     import pickle
 
-from django.core import signing
+from django_q import core_signing as signing
 
 from django_q.conf import Conf
 

django_q/tasks.py

@@ -1,5 +1,5 @@
 """Provides task functionality."""
-from multiprocessing import Queue, Value
+from multiprocessing import Value
 
 # django
 from django.db import IntegrityError
@@ -14,6 +14,7 @@ from django_q.models import Schedule, Task
 from django_q.humanhash import uuid
 from django_q.brokers import get_broker
 from django_q.signals import pre_enqueue
+from django_q.queues import Queue
 
 
 def async(func, *args, **kwargs):

django_q/tests/settings.py

@@ -1,4 +1,5 @@
 import os
+import django
 
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
@@ -28,6 +29,7 @@ INSTALLED_APPS = (
     'django_redis'
 )
 
+
 MIDDLEWARE_CLASSES = (
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.common.CommonMiddleware',

django_q/tests/test_cached.py

@@ -1,4 +1,4 @@
-from multiprocessing import Event, Queue, Value
+from multiprocessing import Event, Value
 
 import pytest
 
@@ -8,6 +8,7 @@ from django_q.conf import Conf
 from django_q.tasks import async, result, fetch, count_group, result_group, fetch_group, delete_group, delete_cached, \
     async_iter, Chain, async_chain, Iter, Async
 from django_q.brokers import get_broker
+from django_q.queues import Queue
 
 
 @pytest.fixture

django_q/tests/test_cluster.py

@@ -1,6 +1,6 @@
 import sys
 import threading
-from multiprocessing import Queue, Event, Value
+from multiprocessing import Event, Value
 from time import sleep
 from django.utils import timezone
 
@@ -19,6 +19,7 @@ from django_q.conf import Conf
 from django_q.status import Stat
 from django_q.brokers import get_broker
 from django_q.tests.tasks import multiply
+from django_q.queues import Queue
 
 
 class WordClass(object):

django_q/tests/test_scheduler.py

@@ -1,5 +1,5 @@
 from datetime import timedelta
-from multiprocessing import Queue, Event, Value
+from multiprocessing import Event, Value
 
 import arrow
 import pytest
@@ -10,6 +10,7 @@ from django_q.brokers import get_broker
 from django_q.cluster import pusher, worker, monitor, scheduler
 from django_q.conf import Conf
 from django_q.tasks import Schedule, fetch, schedule as create_schedule
+from django_q.queues import Queue
 
 
 @pytest.fixture