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changeset 1:32222d11961f

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Initial commit with two tested backends: memcached protocol and Amazon SQS. Because of the non-guaranteed nature of SQS queues, some tests may fail even though the library is working properly.
author mcroydon
date Thu, 08 Jan 2009 07:49:35 +0000
parents 17e60d0dfb44
children 4a8876e38944
files LICENSE build/lib/queues/__init__.py build/lib/queues/backends/__init__.py build/lib/queues/backends/base.py build/lib/queues/backends/memcached.py build/lib/queues/backends/sqs.py queues/__init__.py queues/backends/__init__.py queues/backends/base.py queues/backends/memcached.py queues/backends/sqs.py setup.py test.py test/memcached.py
diffstat 14 files changed, 706 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/LICENSE	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,19 @@
+Copyright (c) 2008-2009 Matt Croydon
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
\ No newline at end of file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/lib/queues/__init__.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,58 @@
+"""
+A pluggable abstract queueing API designed to be used within a Django project
+but useful within a general Python application too.  The design is modeled
+after a pluggable backend system ala django.core.cache.
+
+Backends that merit investigation
+
+x http://aws.amazon.com/ (SQS)
+* http://code.google.com/p/django-queue-service/
+x https://rubyforge.org/projects/starling/ (memcache)
+x http://code.google.com/p/sparrow/ (memcache)
+* http://xph.us/software/beanstalkd/ (not persistent)
+* http://code.google.com/p/peafowl/ (python/memcache)
+* http://memcachedb.org/memcacheq/ (memcache)
+
+Other backends that might be worth checking out
+
+* http://stompserver.rubyforge.org/
+* http://www.spread.org/
+* http://code.google.com/p/stomperl/
+* RabbitMQ
+"""
+import os
+
+__version__ = "0.2"
+
+class InvalidBackend(Exception):
+    pass
+
+class QueueException(Exception):
+    pass
+
+# TODO: raise exceptions when stuff doesn't get stored/returned properly?
+# i.e. unified API and handle what each backend returns.
+
+# Handle QUEUE_BACKEND set from either DJANGO_SETTINGS_MODULE or an environment variable.
+# If set both places, django takes precedence.
+try:
+    from django.conf import settings
+    BACKEND = settings.get('QUEUE_BACKEND', None)
+except:
+    BACKEND = os.environ.get('QUEUE_BACKEND')
+
+if not BACKEND:
+    raise InvalidBackend("QUEUE_BACKEND not set.")
+
+# Set up queues.queues to point to the proper backend.
+try:
+    # Most of the time we'll be importing a bundled backend,
+    # so look here first.  You might recall this pattern from
+    # such web frameworks as Django.
+    queues = __import__('queues.backends.%s' % BACKEND, {}, {}, [''])
+except ImportError, e:
+    # If that didn't work, try an external import.
+    try:
+        queues = __import__(BACKEND, {}, {}, [''])
+    except ImportError:
+        raise InvalidBackend("Unable to import QUEUE BACKEND '%s'" % BACKEND)
\ No newline at end of file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/lib/queues/backends/__init__.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,27 @@
+import os
+from queues import InvalidBackend
+
+__all__ = ['backend']
+
+# Handle QUEUE_BACKEND set from either DJANGO_SETTINGS_MODULE or an environment variable.
+# If set both places, django takes precedence.
+try:
+    from django.conf import settings
+    BACKEND = settings.get('QUEUE_BACKEND', None)
+except:
+    BACKEND = os.environ.get('QUEUE_BACKEND', None)
+
+if not BACKEND:
+    raise InvalidBackend("QUEUE_BACKEND not set.")
+
+try:
+    # Most of the time we'll be importing a bundled backend,
+    # so look here first.  You might recall this pattern from
+    # such web frameworks as Django.
+    backend = __import__('queues.backends.%s' % BACKEND, {}, {}, [''])
+except ImportError, e:
+    # If that didn't work, try an external import.
+    try:
+        backend = __import__(BACKEND, {}, {}, [''])
+    except ImportError:
+        raise InvalidBackend("Unable to import QUEUE BACKEND '%s'" % BACKEND)
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/lib/queues/backends/base.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,27 @@
+"Base queue class"
+
+# Things to think about:
+# - timeout/visibility timeout (boto)
+
+class BaseQueue(object):
+    """
+    Abstract base class for queue backends.
+    """
+    
+    def read(self):
+        raise NotImplementedError
+
+    def write(self, message):
+        raise NotImplementedError
+
+    def __len__(self):
+        raise NotImplementedError
+
+def create_queue():
+    raise NotImplementedError
+
+def delete_queue(name):
+    raise NotImplementedError
+
+def get_list():
+    raise NotImplementedError
\ No newline at end of file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/lib/queues/backends/memcached.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,82 @@
+"""
+Backend for queues that implement the memcache protocol, including starling.
+
+This backend requires either the memcache or cmemcache libraries to be installed.
+"""
+
+from queues.backends.base import BaseQueue
+from queues import InvalidBackend, QueueException
+import os, re
+
+try:
+    from cmemcache import Client
+    
+except ImportError:
+    try:
+        from memcache import Client
+    except:
+        raise InvalidBackend("Unable to import a memcache library.")
+
+try:
+    from django.conf import settings
+    CONN = settings.get('QUEUE_MEMCACHE_CONNECTION', None)
+except:
+    CONN = os.environ.get('QUEUE_MEMCACHE_CONNECTION', None)
+
+if not CONN:
+    raise InvalidBackend("QUEUE_MEMCACHE_CONNECTION not set.")
+
+class Queue(BaseQueue):
+    
+    def __init__(self, name):
+        self._connection = Client(CONN.split(';'))
+        self.backend = 'memcached'
+        self.name = name
+
+    def read(self):
+        try:
+            return self._connection.get(self.name)
+        except (memcache.MemcachedKeyError, MemcachedStringEncodingError), e:
+            raise QueueException, e
+
+    def write(self, message):
+        try:
+            return self._connection.set(self.name, message, 0)
+        except (memcache.MemcachedKeyError, MemcachedStringEncodingError), e:
+            raise QueueException, e
+
+    def __len__(self):
+        try:
+            try:
+                return int(self._connection.get_stats()[0][1]['queue_%s_items' % self.name])
+            except (memcache.MemcachedKeyError, MemcachedStringEncodingError), e:
+                raise QueueException, e
+        except AttributeError:
+            # If this memcached backend doesn't support starling-style stats
+            # or if this queue doesn't exist
+            return 0
+
+    def __repr__(self):
+        return "<Queue %s>" % self.name
+
+def create_queue():
+    """This isn't required, so we noop.  Kept here for swapability."""
+    return True
+
+def delete_queue(name):
+    """Memcached backends don't provide a way to do this."""
+    raise NotImplementedError
+
+def get_list():
+    """Supports starling/peafowl-style queue_<name>_items introspection via stats."""
+    conn = Client(CONN.split(';'))
+    queue_list = []
+    queue_re = re.compile(r'queue\_(.*?)\_total_items')
+    try:
+        for server in conn.get_stats():
+            for key in server[1].keys():
+                if queue_re.findall(key):
+                    queue_list.append(queue_re.findall(key)[0])
+    except (KeyError, AttributeError, memcache.MemcachedKeyError, MemcachedStringEncodingError):
+        pass
+    return queue_list
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/build/lib/queues/backends/sqs.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,99 @@
+"""
+Backend for Amazon's Simple Queue Service.
+
+This backend requires that the boto library is installed.
+"""
+
+from queues.backends.base import BaseQueue
+from queues import InvalidBackend, QueueException
+import os
+
+try:
+    from boto.sqs.connection import SQSConnection
+    from boto.sqs.message import Message
+    from boto.exception import SQSError
+except ImportError:
+    raise InvalidBackend("Unable to import boto.")
+
+try:
+    from django.conf import settings
+    KEY = settings.get('AWS_ACCESS_KEY_ID', None)
+    SECRET = settings.get('AWS_SECRET_ACCESS_KEY', None)
+except:
+    KEY = os.environ.get('AWS_ACCESS_KEY_ID', None)
+    SECRET = os.environ.get('AWS_SECRET_ACCESS_KEY', None)
+
+if not KEY:
+    raise InvalidBackend("AWS_ACCESS_KEY_ID not set.")
+if not SECRET:
+    raise InvalidBackend("AWS_SECRET_ACCESS_KEY not set.")
+
+# ... and one connection to bind them.
+connection = SQSConnection()
+
+class Queue(BaseQueue):
+    def __init__(self, name):
+        self.name = name
+        self.backend = 'sqs'
+        self._connection = connection
+        self._queue = self._connection.get_queue(self.name)
+        if not self._queue:
+            self._queue = self._connection.create_queue(name)
+
+    def read(self):
+        try:
+            m = self._queue.read()
+            if not m:
+                return None
+            else:
+                self._queue.delete()
+                return m.get_body()
+        except SQSError, e:
+            raise QueueException, "%s" % e.code
+
+    def write(self, message):
+        try:
+            m = Message()
+            m.set_body(message)
+            return self._queue.write(m)
+        except SQSError, e:
+            raise QueueException, "%s" % e.code
+
+    def __len__(self):
+        try:
+            length = self._queue.count()
+            if not length:
+                length = 0
+            return int(length)
+        except SQSError, e:
+            raise QueueException, "%s" % e.code
+
+    def __repr__(self):
+        return "<Queue %s>" % self.name
+
+def create_queue(name):
+    """Create a queue for the given name."""
+    try:
+        return connection.create_queue(name)
+    except SQSError, e:
+        raise QueueException, "%s" % e.code
+
+def delete_queue(name):
+    """
+    Deletes a queue and any messages in it.
+    """
+    # TODO: too fragile.
+    try:
+        return connection.get_status('DeleteQueue', None, '/' + name)
+    except SQSError, e:
+        raise QueueException, "%s" % e.code
+
+def get_list():
+    """
+    Get a list of names for all queues.  Returns a list of ``queues.backends.sqs.Queue`` objects.
+    """
+    # TODO: too fragile.
+    try:
+        return [q.id[1:] for q in connection.get_all_queues()]
+    except SQSError, e:
+        raise QueueException, "%s" % e.code
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/queues/__init__.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,58 @@
+"""
+A pluggable abstract queueing API designed to be used within a Django project
+but useful within a general Python application too.  The design is modeled
+after a pluggable backend system ala django.core.cache.
+
+Backends that merit investigation
+
+x http://aws.amazon.com/ (SQS)
+* http://code.google.com/p/django-queue-service/
+x https://rubyforge.org/projects/starling/ (memcache)
+x http://code.google.com/p/sparrow/ (memcache)
+* http://xph.us/software/beanstalkd/ (not persistent)
+* http://code.google.com/p/peafowl/ (python/memcache)
+* http://memcachedb.org/memcacheq/ (memcache)
+
+Other backends that might be worth checking out
+
+* http://stompserver.rubyforge.org/
+* http://www.spread.org/
+* http://code.google.com/p/stomperl/
+* RabbitMQ
+"""
+import os
+
+__version__ = "0.2"
+
+class InvalidBackend(Exception):
+    pass
+
+class QueueException(Exception):
+    pass
+
+# TODO: raise exceptions when stuff doesn't get stored/returned properly?
+# i.e. unified API and handle what each backend returns.
+
+# Handle QUEUE_BACKEND set from either DJANGO_SETTINGS_MODULE or an environment variable.
+# If set both places, django takes precedence.
+try:
+    from django.conf import settings
+    BACKEND = settings.get('QUEUE_BACKEND', None)
+except:
+    BACKEND = os.environ.get('QUEUE_BACKEND')
+
+if not BACKEND:
+    raise InvalidBackend("QUEUE_BACKEND not set.")
+
+# Set up queues.queues to point to the proper backend.
+try:
+    # Most of the time we'll be importing a bundled backend,
+    # so look here first.  You might recall this pattern from
+    # such web frameworks as Django.
+    queues = __import__('queues.backends.%s' % BACKEND, {}, {}, [''])
+except ImportError, e:
+    # If that didn't work, try an external import.
+    try:
+        queues = __import__(BACKEND, {}, {}, [''])
+    except ImportError:
+        raise InvalidBackend("Unable to import QUEUE BACKEND '%s'" % BACKEND)
\ No newline at end of file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/queues/backends/__init__.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,27 @@
+import os
+from queues import InvalidBackend
+
+__all__ = ['backend']
+
+# Handle QUEUE_BACKEND set from either DJANGO_SETTINGS_MODULE or an environment variable.
+# If set both places, django takes precedence.
+try:
+    from django.conf import settings
+    BACKEND = settings.get('QUEUE_BACKEND', None)
+except:
+    BACKEND = os.environ.get('QUEUE_BACKEND', None)
+
+if not BACKEND:
+    raise InvalidBackend("QUEUE_BACKEND not set.")
+
+try:
+    # Most of the time we'll be importing a bundled backend,
+    # so look here first.  You might recall this pattern from
+    # such web frameworks as Django.
+    backend = __import__('queues.backends.%s' % BACKEND, {}, {}, [''])
+except ImportError, e:
+    # If that didn't work, try an external import.
+    try:
+        backend = __import__(BACKEND, {}, {}, [''])
+    except ImportError:
+        raise InvalidBackend("Unable to import QUEUE BACKEND '%s'" % BACKEND)
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/queues/backends/base.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,27 @@
+"Base queue class"
+
+# Things to think about:
+# - timeout/visibility timeout (boto)
+
+class BaseQueue(object):
+    """
+    Abstract base class for queue backends.
+    """
+    
+    def read(self):
+        raise NotImplementedError
+
+    def write(self, message):
+        raise NotImplementedError
+
+    def __len__(self):
+        raise NotImplementedError
+
+def create_queue():
+    raise NotImplementedError
+
+def delete_queue(name):
+    raise NotImplementedError
+
+def get_list():
+    raise NotImplementedError
\ No newline at end of file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/queues/backends/memcached.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,82 @@
+"""
+Backend for queues that implement the memcache protocol, including starling.
+
+This backend requires either the memcache or cmemcache libraries to be installed.
+"""
+
+from queues.backends.base import BaseQueue
+from queues import InvalidBackend, QueueException
+import os, re
+
+try:
+    from cmemcache import Client
+    
+except ImportError:
+    try:
+        from memcache import Client
+    except:
+        raise InvalidBackend("Unable to import a memcache library.")
+
+try:
+    from django.conf import settings
+    CONN = settings.get('QUEUE_MEMCACHE_CONNECTION', None)
+except:
+    CONN = os.environ.get('QUEUE_MEMCACHE_CONNECTION', None)
+
+if not CONN:
+    raise InvalidBackend("QUEUE_MEMCACHE_CONNECTION not set.")
+
+class Queue(BaseQueue):
+    
+    def __init__(self, name):
+        self._connection = Client(CONN.split(';'))
+        self.backend = 'memcached'
+        self.name = name
+
+    def read(self):
+        try:
+            return self._connection.get(self.name)
+        except (memcache.MemcachedKeyError, MemcachedStringEncodingError), e:
+            raise QueueException, e
+
+    def write(self, message):
+        try:
+            return self._connection.set(self.name, message, 0)
+        except (memcache.MemcachedKeyError, MemcachedStringEncodingError), e:
+            raise QueueException, e
+
+    def __len__(self):
+        try:
+            try:
+                return int(self._connection.get_stats()[0][1]['queue_%s_items' % self.name])
+            except (memcache.MemcachedKeyError, MemcachedStringEncodingError), e:
+                raise QueueException, e
+        except AttributeError:
+            # If this memcached backend doesn't support starling-style stats
+            # or if this queue doesn't exist
+            return 0
+
+    def __repr__(self):
+        return "<Queue %s>" % self.name
+
+def create_queue():
+    """This isn't required, so we noop.  Kept here for swapability."""
+    return True
+
+def delete_queue(name):
+    """Memcached backends don't provide a way to do this."""
+    raise NotImplementedError
+
+def get_list():
+    """Supports starling/peafowl-style queue_<name>_items introspection via stats."""
+    conn = Client(CONN.split(';'))
+    queue_list = []
+    queue_re = re.compile(r'queue\_(.*?)\_total_items')
+    try:
+        for server in conn.get_stats():
+            for key in server[1].keys():
+                if queue_re.findall(key):
+                    queue_list.append(queue_re.findall(key)[0])
+    except (KeyError, AttributeError, memcache.MemcachedKeyError, MemcachedStringEncodingError):
+        pass
+    return queue_list
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/queues/backends/sqs.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,99 @@
+"""
+Backend for Amazon's Simple Queue Service.
+
+This backend requires that the boto library is installed.
+"""
+
+from queues.backends.base import BaseQueue
+from queues import InvalidBackend, QueueException
+import os
+
+try:
+    from boto.sqs.connection import SQSConnection
+    from boto.sqs.message import Message
+    from boto.exception import SQSError
+except ImportError:
+    raise InvalidBackend("Unable to import boto.")
+
+try:
+    from django.conf import settings
+    KEY = settings.get('AWS_ACCESS_KEY_ID', None)
+    SECRET = settings.get('AWS_SECRET_ACCESS_KEY', None)
+except:
+    KEY = os.environ.get('AWS_ACCESS_KEY_ID', None)
+    SECRET = os.environ.get('AWS_SECRET_ACCESS_KEY', None)
+
+if not KEY:
+    raise InvalidBackend("AWS_ACCESS_KEY_ID not set.")
+if not SECRET:
+    raise InvalidBackend("AWS_SECRET_ACCESS_KEY not set.")
+
+# ... and one connection to bind them.
+connection = SQSConnection()
+
+class Queue(BaseQueue):
+    def __init__(self, name):
+        self.name = name
+        self.backend = 'sqs'
+        self._connection = connection
+        self._queue = self._connection.get_queue(self.name)
+        if not self._queue:
+            self._queue = self._connection.create_queue(name)
+
+    def read(self):
+        try:
+            m = self._queue.read()
+            if not m:
+                return None
+            else:
+                self._queue.delete()
+                return m.get_body()
+        except SQSError, e:
+            raise QueueException, "%s" % e.code
+
+    def write(self, message):
+        try:
+            m = Message()
+            m.set_body(message)
+            return self._queue.write(m)
+        except SQSError, e:
+            raise QueueException, "%s" % e.code
+
+    def __len__(self):
+        try:
+            length = self._queue.count()
+            if not length:
+                length = 0
+            return int(length)
+        except SQSError, e:
+            raise QueueException, "%s" % e.code
+
+    def __repr__(self):
+        return "<Queue %s>" % self.name
+
+def create_queue(name):
+    """Create a queue for the given name."""
+    try:
+        return connection.create_queue(name)
+    except SQSError, e:
+        raise QueueException, "%s" % e.code
+
+def delete_queue(name):
+    """
+    Deletes a queue and any messages in it.
+    """
+    # TODO: too fragile.
+    try:
+        return connection.get_status('DeleteQueue', None, '/' + name)
+    except SQSError, e:
+        raise QueueException, "%s" % e.code
+
+def get_list():
+    """
+    Get a list of names for all queues.  Returns a list of ``queues.backends.sqs.Queue`` objects.
+    """
+    # TODO: too fragile.
+    try:
+        return [q.id[1:] for q in connection.get_all_queues()]
+    except SQSError, e:
+        raise QueueException, "%s" % e.code
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/setup.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,13 @@
+#!/usr/bin/env python
+
+from distutils.core import setup
+import queues
+setup(name='queues',
+      version='0.2',
+      description='A lowest-common-denominator API for interacting with lightweight queue services.',
+      author='Matt Croydon',
+      author_email='mcroydon@gmail.com',
+      url='http://postneo.com', # TODO: Fixme
+      packages=['queues', 'queues.backends'],
+      package_dir={'queues': 'queues'},
+     )
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,48 @@
+"""
+Test basic queue functionality
+
+>>> from queues import queues
+>>> import time
+>>> queue_name = 'test_queues_%.f' % time.time()
+
+Verify that the queue does not exist
+>>> queue_name in queues.get_list()
+False
+
+Create the queue
+>>> q = queues.Queue(queue_name)
+
+Write to the queue
+>>> q.write('test')
+True
+
+Verify that it is indeed in the list
+>>> queue_name in queues.get_list()
+True
+
+Get the length of the queue
+
+Note that SQS doesn't guarantee that the message
+we just wrote will be immediately available
+>>> len(q)
+1
+
+Read from the queue
+>>> q.read()
+'test'
+
+The queue should now be empty
+Note that SQS doesn't guarantee an accurate count
+>>> len(q)
+0
+
+>>> try:
+...     queues.delete_queue(queue_name)
+... except NotImplementedError:
+...     print True
+True
+"""
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
\ No newline at end of file
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/memcached.py	Thu Jan 08 07:49:35 2009 +0000
@@ -0,0 +1,40 @@
+"""
+Test basic queue functionality
+
+>>> from queues import queues
+>>> import datetime
+>>> queue_name = 'test_queues_%s' % datetime.datetime.now().isoformat()
+
+Verify that the queue does not exist
+>>> queue_name in queues.get_list()
+False
+
+Create the queue
+>>> q = queues.Queue(queue_name)
+
+Write to the queue
+>>> q.write('test')
+True
+
+Verify that it is indeed in the list
+>>> queue_name in queues.get_list()
+True
+
+Get the length of the queue
+>>> len(q)
+1
+
+Read from the queue
+>>> q.read()
+'test'
+
+The queue should now be empty
+>>> len(q)
+0
+
+TODO: get rid of the queue?
+"""
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()
\ No newline at end of file