Dalga

Dalga is a job scheduler. It's like cron-as-a-service.

• Can schedule periodic or one-off jobs.
• Stores jobs in a MySQL table with location info.
• Has an HTTP interface for scheduling and cancelling jobs.
• Makes a POST request to the endpoint defined in config on the job's execution time.
• Retries failed jobs with constant or exponential backoff.
• Multiple instances can be run for high availability and scaling out.

Install

Use pre-built Docker image:

$ docker run -e DALGA_MYSQL_HOST=mysql.example.com cenkalti/dalga

or download the latest binary from releases page.

Usage

See example config file for configuration options. TOML and YAML file formats are supported. Configuration values can also be set via environment variables with DALGA_ prefix.

First, you must create the table for storing jobs:

$ dalga -config dalga.toml -create-tables

Then, run the server:

$ dalga -config dalga.toml

Schedule a new job to run every 60 seconds:

$ curl -i -X PUT 'http://127.0.0.1:34006/jobs/check_feed/1234?interval=60'
HTTP/1.1 201 Created
Content-Type: application/json; charset=utf-8
Date: Tue, 11 Nov 2014 22:10:40 GMT
Content-Length: 83

{"path":"check_feed","body":"1234","interval":60,"next_run":"2014-11-11T22:11:40Z"}

PUT always returns 201. If there is an existing job with path and body, it will be rescheduled.

There are 4 options that you can pass to Schedule but not every combination is valid:

60 seconds later, Dalga makes a POST to your endpoint defined in config:

Path: <config.baseurl>/<job.path>
Body: <job.body>

The endpoint must return 200 if the job is successful.

The endpoint may return 204 if job is invalid. In this case Dalga will remove the job from the table.

Anything other than 200 or 204 makes Dalga to retry the job indefinitely with an exponential backoff.

Get the status of a job:

$ curl -i -X GET 'http://127.0.0.1:34006/jobs/check_feed/1234'
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Date: Tue, 11 Nov 2014 22:12:21 GMT
Content-Length: 83

{"path":"check_feed","body":"1234","interval":60,"next_run":"2014-11-11T22:12:41Z"}

GET may return 404 if job is not found.

Cancel previously scheduled job:

$ curl -i -X DELETE 'http://127.0.0.1:34006/jobs/check_feed/1234'
HTTP/1.1 204 No Content
Date: Tue, 11 Nov 2014 22:13:35 GMT