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kombu_appengine.py
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kombu_appengine.py
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#:coding=utf-8:
"""
A kombu transport for App Engine's
Pull Task Queue API.
"""
import logging
import socket
import base64
from Queue import Empty
from collections import deque, defaultdict
import httplib2
import anyjson as json
from kombu.transport import virtual
from kombu.utils import cached_property
from kombu.exceptions import (
StdConnectionError,
StdChannelError,
)
from apiclient.errors import HttpError
from apiclient.discovery import build
from oauth2client.file import Storage
logger = logging.getLogger(__name__)
def _debug_fun(func_name, args=None, kwargs=None):
arg_list = []
if args:
arg_list.extend(repr(arg) for arg in args)
if kwargs:
arg_list.extend('%s=%r' % (k,v) for k,v in kwargs.items())
logger.debug('%s(%s)' % (func_name, ", ".join(arg_list)))
class Channel(virtual.Channel):
"""
An implementation of a messaging channel using
Google App Engine's Pull Task Queue API.
"""
_service = None
_credentials = None
_queue_map = {} # Map of queue names to queue URIs
default_num_tasks = 1 # Number of tasks to buffer
default_lease_secs = 1800 # 30 minutes.
_noack_queues = set()
def __init__(self, *args, **kwargs):
super(Channel, self).__init__(*args, **kwargs)
self.buffers = defaultdict(lambda: deque())
def basic_consume(self, queue, no_ack, *args, **kwargs):
_debug_fun('basic_ack', (queue, no_ack) + args, kwargs)
if no_ack:
self._noack_queues.add(queue)
return super(Channel, self).basic_consume(queue, no_ack,
*args, **kwargs)
def basic_cancel(self, consumer_tag):
_debug_fun('basic_cancel', (consumer_tag,))
if consumer_tag in self._consumers:
queue = self._tag_to_queue[consumer_tag]
self._noack_queues.discard(queue)
return super(Channel, self).basic_cancel(consumer_tag)
def basic_ack(self, delivery_tag):
"""
Acknowledge the message.
For task queues this generally means that
task has been completed.
"""
_debug_fun('basic_ack', (delivery_tag,))
delivery_info = self.qos.get(delivery_tag).delivery_info
try:
queue = delivery_info['taskqueue_queue']
except KeyError:
pass
else:
self.service.tasks().delete(
project=self._get_project('delete'),
taskqueue=queue,
task=delivery_info['taskqueue_task_id'],
).execute()
super(Channel, self).basic_ack(delivery_tag)
def _buffer_tasks(self, queue):
"""
Buffer a number of tasks for consumers.
"""
lease = self.service.tasks().lease(
project=self._get_project('get'),
taskqueue=queue,
numTasks=self.num_tasks,
leaseSecs=self.lease_secs,
).execute()
if 'items' in lease and len(lease['items']) > 0:
for task in lease['items']:
self.buffers[queue].append(task)
def _get(self, queue, **kwargs):
_debug_fun('_get', (queue,), kwargs)
if not self.buffers[queue]:
self._buffer_tasks(queue)
if not self.buffers[queue]:
raise Empty()
task = self.buffers[queue].pop()
payload = json.loads(base64.b64decode(task['payloadBase64']))
if queue in self._noack_queues:
# For consumers which don't want to ack we
# optimistically delete from the queue.
self.service.tasks().delete(
project=self._get_project('delete'),
taskqueue=queue,
task=task['id'],
).execute()
else:
# For consumers that do ACK then we need to keep track
# of the queue name and task id so we can delete it later.
payload['properties']['delivery_info'].update({
'taskqueue_task_id': task['id'], 'taskqueue_queue': queue})
return payload
def _restore(self, message,
unwanted_delivery_info=('taskqueue_task_id', 'taskqueue_queue')):
"""
Remove unwanted delivery info. The task id and task queue name
should be JSON serializable but we go ahead and remove them
here for completeness' sake.
"""
_debug_fun('_restore', (message, unwanted_delivery_info))
for unwanted_key in unwanted_delivery_info:
# Remove objects that aren't JSON serializable.
message.delivery_info.pop(unwanted_key, None)
return super(Channel, self)._restore(message)
def _put(self, queue, message, **kwargs):
"""
Put a new task in the queue. The task is encoded as JSON
and converted to base64.
"""
_debug_fun('_put', (queue, message), kwargs)
task = self.service.tasks().insert(
project=self._get_project('insert'),
taskqueue=queue,
body={
# The kind of object returned, in this case set to task.
"kind": "taskqueues#task",
# Name of the queue that the task is in.
"queueName": queue,
# A bag of bytes which is the task payload. The payload on
# the JSON side is always Base64 encoded.
"payloadBase64": base64.b64encode(json.dumps(message)),
}
).execute()
logger.info('Inserted Task: %r', task)
def _purge(self, queue, **kwargs):
"""
Attempts to purge the queue by listing and
deleting all remaining tasks. Because each
task has to be deleted individually this
method could take a long time.
"""
_debug_fun('_purge', (queue,), kwargs)
while True:
# list returns a maximum of 100 tasks so
# continually list the remaining tasks until
# all tasks are deleted.
tasks = self.service.tasks().list(
project=self._get_project('get'),
taskqueue=queue,
).execute()
if ('items' not in tasks) or (len(tasks['items']) == 0):
# No more tasks in the queue.
break
else:
for task in tasks['items']:
self.service.tasks().delete(
project=self._get_project('delete'),
taskqueue=queue,
task=task['id'],
).execute()
def _size(self, queue, **kwargs):
_debug_fun('_size', (queue,), kwargs)
info = self.service.taskqueues().get(
project=self._get_project('get'),
taskqueue=queue,
getStats=True,
).execute()
logger.info('Got queue info: %r', info)
if 'stats' in info and 'totalTasks' in info['stats']:
return info['stats']['totalTasks']
else:
return 0
def _has_queue(self, queue, **kwargs):
_debug_fun('_has_queue', (queue,), kwargs)
try:
queue = self.service.taskqueues().get(
project=self._get_project('get'),
taskqueue=queue,
).execute()
return queue['id'] == queue
except HttpError:
return False
def _poll(self, *args, **kwargs):
_debug_fun('_poll', args, kwargs)
return super(Channel, self)._poll(*args, **kwargs)
def _get_project(self, op):
"""
A workaround to an issue where inserts and deletes
require that the project name have a s~ prefix.
See: https://code.google.com/p/googleappengine/issues/detail?id=10199
"""
project_name = self.transport_options.get('project_name')
hrd_project = self.transport_options.get('hrd_project', False)
if hrd_project and op in ('insert', 'delete'):
return 's~%s' % project_name
else:
return project_name
@property
def credentials(self):
if self._credentials is None:
# Load credentials
# TODO: options
cred_file = self.transport_options.get('credentials_file')
storage = Storage(cred_file)
self._credentials = storage.get()
return self._credentials
@property
def service(self):
if self._service is None:
http = httplib2.Http()
http = self.credentials.authorize(http)
self._service = build("taskqueue", "v1beta2", http=http)
return self._service
@property
def transport_options(self):
return self.connection.client.transport_options
@cached_property
def num_tasks(self):
return (self.transport_options.get('num_tasks') or
self.default_num_tasks)
@cached_property
def lease_secs(self):
return (self.transport_options.get('lease_secs') or
self.default_lease_secs)
class Transport(virtual.Transport):
Channel = Channel
polling_interval = 1.0
default_port = None
connection_errors = (StdConnectionError, HttpError, socket.error)
channel_errors = (HttpError, StdChannelError)
driver_type = 'appengine_taskqueue'
driver_name = 'appengine_taskqueue'
def authenticate_main():
"""
Authenticate using OAuth with the Task Queue API.
"""
import sys
import argparse
from oauth2client import tools
from oauth2client.client import flow_from_clientsecrets
if len(sys.argv) > 1 and sys.argv[0] == 'python':
argv = sys.argv[2:]
else:
argv = sys.argv[1:]
parser = argparse.ArgumentParser(description=__doc__,
formatter_class=argparse.RawDescriptionHelpFormatter,
parents=[tools.argparser])
parser.add_argument('client_secrets', metavar='SECRETS',
help='Path to the client_secrets.json.')
parser.add_argument('credentials', metavar='CREDENTIALS',
help='Path where the credentials will be stored.')
flags = parser.parse_args(argv)
tools.run_flow(
flow_from_clientsecrets(flags.client_secrets, scope="https://www.googleapis.com/auth/taskqueue"),
storage=Storage(flags.credentials),
flags=flags,
)
print('Saved credentials to %s' % flags.credentials)