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#!/usr/bin/env python

# Copyright 2016 Google Inc. All Rights Reserved.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""This application demonstrates how to perform basic operations on

subscriptions with the Cloud Pub/Sub API.

For more information, see the README.md under /pubsub and the documentation

at https://cloud.google.com/pubsub/docs.

"""

import argparse

import time

from google.cloud import pubsub_v1

def list_subscriptions(project, topic_name):

"""Lists all subscriptions for a given topic."""

subscriber = pubsub_v1.SubscriberClient()

topic_path = subscriber.topic_path(project, topic_name)

for subscription in subscriber.list_subscriptions(topic_path):

print(subscription.name)

def create_subscription(project, topic_name, subscription_name):

"""Create a new pull subscription on the given topic."""

subscriber = pubsub_v1.SubscriberClient()

topic_path = subscriber.topic_path(project, topic_name)

subscription_path = subscriber.subscription_path(

project, subscription_name)

subscription = subscriber.create_subscription(

subscription_path, topic_path)

print('Subscription created: {}'.format(subscription))

def delete_subscription(project, subscription_name):

"""Deletes an existing Pub/Sub topic."""

subscriber = pubsub_v1.SubscriberClient()

subscription_path = subscriber.subscription_path(

project, subscription_name)

subscriber.delete_subscription(subscription_path)

print('Subscription deleted: {}'.format(subscription_path))

def receive_messages(project, subscription_name):

"""Receives messages from a pull subscription."""

subscriber = pubsub_v1.SubscriberClient()

subscription_path = subscriber.subscription_path(

project, subscription_name)

def callback(message):

print('Received message: {}'.format(message))

message.ack()

subscriber.subscribe(subscription_path, callback=callback)

# The subscriber is non-blocking, so we must keep the main thread from

# exiting to allow it to process messages in the background.

print('Listening for messages on {}'.format(subscription_path))

while True:

time.sleep(60)

def receive_messages_with_flow_control(project, subscription_name):

"""Receives messages from a pull subscription with flow control."""

subscriber = pubsub_v1.SubscriberClient()

subscription_path = subscriber.subscription_path(

project, subscription_name)

def callback(message):

print('Received message: {}'.format(message))

message.ack()

# Limit the subscriber to only have ten outstanding messages at a time.

flow_control = pubsub_v1.types.FlowControl(max_messages=10)

subscriber.subscribe(

subscription_path, callback=callback, flow_control=flow_control)

# The subscriber is non-blocking, so we must keep the main thread from

# exiting to allow it to process messages in the background.

print('Listening for messages on {}'.format(subscription_path))

while True:

time.sleep(60)

if __name__ == '__main__':

parser = argparse.ArgumentParser(

description=__doc__,

formatter_class=argparse.RawDescriptionHelpFormatter

)

parser.add_argument('project', help='Your Google Cloud project ID')

subparsers = parser.add_subparsers(dest='command')

list_parser = subparsers.add_parser(

'list', help=list_subscriptions.__doc__)

list_parser.add_argument('topic_name')

create_parser = subparsers.add_parser(

'create', help=create_subscription.__doc__)

create_parser.add_argument('topic_name')

create_parser.add_argument('subscription_name')

delete_parser = subparsers.add_parser(

'delete', help=delete_subscription.__doc__)

delete_parser.add_argument('subscription_name')

receive_parser = subparsers.add_parser(

'receive', help=receive_messages.__doc__)

receive_parser.add_argument('subscription_name')

receive_with_flow_control_parser = subparsers.add_parser(

'receive-flow-control',

help=receive_messages_with_flow_control.__doc__)

receive_with_flow_control_parser.add_argument('subscription_name')

args = parser.parse_args()

if args.command == 'list':

list_subscriptions(args.project, args.topic_name)

elif args.command == 'create':

create_subscription(

args.project, args.topic_name, args.subscription_name)

elif args.command == 'delete':

delete_subscription(

args.project, args.subscription_name)

elif args.command == 'receive':

receive_messages(args.project, args.subscription_name)

elif args.command == 'receive-flow-control':

receive_messages_with_flow_control(

args.project, args.subscription_name)