AWS Node Scheduled Weather Example

This is an example of creating a function that runs as a cron job using the serverless schedule event. It retrieves weather information at 10am (UTC) and emails it to a predefined recipient. For more information on schedule event check out the Serverless docs on schedule.

Cron syntax

cron(Minutes Hours Day-of-month Month Day-of-week Year)

All fields are required and time zone is UTC only.

Field	Values	Wildcards
Minutes	0-59	, - * /
Hours	0-23	, - * /
Day-of-month	1-31	, - * ? / L W
Month	1-12 or JAN-DEC	, - * /
Day-of-week	1-7 or SUN-SAT	, - * ? / L #
Year	192199	, - * /

Read the AWS cron expression syntax docs for more info on how to setup cron

Setup

DarkSky

Please visit https://darksky.net/dev/ to register for a free API token.

Postmark

Please visit https://postmarkapp.com to register for a free Postmark account.

Configuration

Upon setting up access to both external services, you'll be required to update the environment variables in serverless.yml:

environment:
  RECIPIENT: tom@carrotcreative.com
  DARK_SKY_API_KEY: abc123
  POSTMARK_API_KEY: abc123
  POSTMARK_SENDER: devops@carrotcreative.com
  LATITUDE: 40.702637
  LONGITUDE: -73.989406

Deploy

In order to deploy the you endpoint simply run

serverless deploy

The expected result should be similar to:

Serverless: Packaging service...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading service .zip file to S3 (1.87 MB)...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
...........
Serverless: Stack update finished...
Serverless: Removing old service versions...
Service Information
service: scheduled-weather-example
stage: dev
region: us-east-1
api keys:
  None
endpoints:
  None
functions:
  scheduled-weather-example-dev-weather: arn:aws:lambda:us-east-1:219106525755:function:scheduled-weather-example-dev-weather

There is no additional step required. Your defined schedule becomes active right away after deployment.

Usage

To test your function remotely:

sls invoke -f weather

The expected result should be similar to:

{
  "success": true
}

Additonal Resources

For more information on running cron with Serverless check out the Tutorial: Serverless Scheduled Tasks by Parallax.