AWS Serverless scheduler

This code is a simplified and redesigned version of @bahrmichael's repo.

Right now this repo is only capable of scheduling webhook-related tasks

Deploy

This section explains how you can deploy the service yourself. Once set up use it like shown above. The following picture shows you the structure of the service.

Prerequisites

You must have the following tools installed:

• serverless framework 1.48.3 or later
• node
• npm
• python3
• pip

Setup

1. Complete the variable names in scheduler/settings.py (based on the names that you have in serverless.yml)
2. Run scripts/init_services.py to create the complementary services (dynamo table, SQS and SNS)
3. Run npm i serverless-python-requirements for python requirments installer
4. Deploy the cloudformation stack with sls deploy

Usage

Input

To schedule a trigger you have to publish an event which follows the structure below to the ARN of the input topic. You can find the ARN in the console logs after deploying

{
  "date": "utc timestamp following ISO 8601",
  "url": "the url that will receive the scheduled request",
  "method": "http method for calling the url", 
  "payload": "any payload that your endpoint might need to receive",
  "headers": "any headers that your endpoint might need to receive",
  "cookies": "any cookies that your endpoint might need to receive",
}

date, url and method fields are mandatory.

# Python example for scheduling a telegram message 10 minutes later 
import json
import boto3
from datetime import datetime, timedelta

client = boto3.client('sns')
token = "<YOUR_TELEGRAM_BOT_TOKEN>"
chat_id="<YOUR_TELEGRAM_CHAT_ID>"
message = "Your first scheduled message!"

data = f'chat_id={chat_id}&text={message}'

date = (datetime.utcnow() + timedelta(minutes=10)).isoformat()

event = {
        "date": date,
        "url": f'https://api.telegram.org/bot{token}/sendMessage?{data}',
        "method": "post"
        }

input_topic = "arn:aws:sns:{YOUR_AWS_REGION}:{YOUR_AWS_ACCOUNT_ID}:{YOUR_INPUT_TOPIC_NAME}"
client.publish(TopicArn=input_topic, Message=json.dumps(event))

Limitations

• Events may arrive more than once
• Check your AWS Lambda concurrent execution quota, if you send too many messages at the same time you might drown your lambdas
• This approach costs more than using DynamoDB's TTL attribute. If delays of 30 minutes to 48 hours are acceptable for you, then check out this article.

Contributions

Contributions are welcome, both issues and code. Get in touch at twitter @agusmdev or create an issue.

TODOs

• Add batch processing for SQS and SNS messages
• Add an abstraction Scheduler to use this architecture without friction
• secure the PoC with test