# Flask-PubSubDecorator
Decorates publisher functions and subscriber routes creating topics/subscriptions if necessary.
## Installation
Add this line to your application's requirements.txt
```python
Flask-PubSubDecorator
```
And then execute:
$ pip install -r requirements.txt
Or install it yourself as:
$ pip install Flask-PubSubDecorator
## Usage
Using PubSubDecorator is dead simple. First set your GOOGLE_APPLICATION_CREDENTIALS environment variable to point at a valid JSON creds file.
$ export GOOGLE_APPLICATION_CREDENTIALS=/path/to/creds.json
The following snippet should get you coding
```python
from flask import Flask, request
from PubSubDecorator import PubSubDecorator
import base64
import json
app = Flask(__name__)
# blueprint can optionally be passed in for registering subscribers in a blueprint endpoint
app.pubsub = PubSubDecorator(app)
# publisher decorator will inject publisher client and topic path
@app.pubsub.publisher(topic='user_confirmed')
def user_confirmed(publisher, topic, user):
publisher.publish(topic, data=json.dumps({
'user_id': user.id
}))
# subscriber decorator will register the Flask route, prefixing /_ah/push-handlers
# subscriber decorator will parse and inject pubsub message
@app.pubsub.subscriber(
subscription='process_user_confirmation',
topic='user_confirmed',
route='/process_user_confirmation',
methods=['POST']
)
def process_user_confirmation(message, *args, **kwargs):
try:
user_id = message.get('user_id')
# do some async work here!
except Exception:
_logger.exception(
'An unexpected error occurred processing subscription "{0}": {1}'.format(
kwargs.get('__subscription__'), request.data
)
)
# Unexpected failure, do not ack message
return '', 422
return '', 200
```
## Security
PubSub push subscriptions are inherently public facing and should therefore be secured. Googles recommended solution
is to attach a secret key to a registered subscription pushEndpoint. PubSubDecorator handles this for you if any of
the following is provided:
1. OS Environment Variable `PUBSUB_DECORATOR_API_KEY`
2. Flask App Config `PUBSUB_DECORATOR_API_KEY`
3. api_key is passed into PubSubDecorator constructor.
Best Practice: encrypt your key with GCloud KMS, store it in GCloud Datastore, and export to OS environment variable
at runtime.
## Logging
Decorators will log to 'flask-pubsub-decorator' namespace.
```python
import sys
import logging
import logging.handlers
logger = logging.getLogger('flask-pubsub-decorator')
logger.setLevel(logging.DEBUG)
log_file = logging.handlers.RotatingFileHandler(
'log_file_name.log', maxBytes=5 * 1024 * 1024, backupCount=10
)
logger.addHandler(log_file)
```
# Testing
$ pytest -s tests.py
