Created
February 20, 2017 03:52
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Serverless async task via SNS
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import os | |
import json | |
import importlib | |
import inspect | |
import boto3 | |
SNS_ARN = os.environ.get('SNS_ARN', None) | |
def import_and_get_task(task_path): | |
""" | |
Given a modular path to a function, import that module | |
and return the function. | |
""" | |
module, function = task_path.rsplit('.', 1) | |
app_module = importlib.import_module(module) | |
app_function = getattr(app_module, function) | |
return app_function | |
def route_task(event, context): | |
""" | |
Gets SNS Message, deserialises the message, | |
imports the function, calls the function with args | |
""" | |
record = event['Records'][0] | |
message = json.loads( | |
record['Sns']['Message'] | |
) | |
func = import_and_get_task( | |
message['task_path']) | |
return func( | |
*message['args'], **message['kwargs'] | |
) | |
def send_async_task(task_path, *args, **kwargs): | |
""" | |
Send a SNS message to a specified SNS topic | |
Serialise the func path and arguments | |
""" | |
client = boto3.client('sns') | |
message = { | |
'task_path': task_path, | |
'args': args, | |
'kwargs': kwargs | |
} | |
return client.publish( | |
TargetArn=SNS_ARN, | |
Message=json.dumps(message), | |
) | |
def task(): | |
""" | |
Async task decorator for a function. | |
Serialises and dispatches the task to SNS. | |
Lambda subscribes to SNS topic and gets this message | |
Lambda routes the message to the same function | |
Example: | |
@task() | |
def my_async_func(*args, **kwargs): | |
dosomething() | |
my_async_func.delay(*args, **kwargs) | |
""" | |
def _delay(func): | |
def _delay_inner(*args, **kwargs): | |
module_path = inspect.getmodule(func).__name__ | |
task_path = '{module_path}.{func_name}'.format( | |
module_path=module_path, | |
func_name=func.__name__ | |
) | |
if SNS_ARN: | |
return send_async_task(task_path, *args, **kwargs) | |
return func(*args, **kwargs) | |
return _delay_inner | |
def _wrap(func): | |
func.delay = _delay(func) | |
return func | |
return _wrap |
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