Kala

Not battle-tested. Use at your own risk.

Kala is a simplistic, modern, and performant job scheduler written in Go. It lives in a single binary and does not have any dependencies.

Kala was inspired by the desire for a simpler Chronos (developed by Airbnb). Kala is Chronos for the rest of us.

It has a simple JSON over HTTP API, so it is language agnostic. It has Job Stats, Configurable Retries, uses ISO 8601 Date and Interval
notation, Dependant Jobs, and is Persistent (using BoltDB). Eventually it will have a Web UI.

I need [fault tolerance, distributed-features, this to work at scale]

I recommend checking out Chronos. This is designed to be the Chronos for start-ups.

Installing Kala

Kala uses Go Modules

1. Get Kala

   go get github.com/ajvb/kala
   

2. Run Kala

   kala run
   

Getting Started

Once you have installed Kala onto the machine you would like to use, you can follow the below steps to start using it.

To Run Kala:

$ kala run
INFO[0000] Preparing cache
INFO[0000] Starting server on port :8000

$ kala run -p 2222
INFO[0000] Preparing cache
INFO[0000] Starting server on port :2222

Kala uses BoltDB by default for the job database
use Redis by using the jobDB and jobDBAddress params:

kala run --jobDB=redis --jobDBAddress=127.0.0.1:6379

use Consul by using the jobDB and jobDBAddress params:

kala run --jobDB=consul --jobDBAddress=127.0.0.1:8500

use Mongo by using the jobDB, jobDBAddress, jobDBUsername, and jobDBPassword params:

kala run --jobDB=mongo --jobDBAddress=server1.example.com,server2.example.com --jobDBUsername=admin --jobDBPassword=password

use Postgres by using the jobDB, jobDBAddress params:

kala run --jobDB=postgres --jobDBAddress=server1.example.com/kala --jobDBUsername=admin --jobDBPassword=password

Kala runs on 127.0.0.1:8000 by default. You can easily test it out by curling the metrics path.

$ curl http://127.0.0.1:8000/api/v1/stats/
{"Stats":{"ActiveJobs":2,"DisabledJobs":0,"Jobs":2,"ErrorCount":0,"SuccessCount":0,"NextRunAt":"2015-06-04T19:25:16.82873873-07:00","LastAttemptedRun":"0001-01-01T00:00:00Z","CreatedAt":"2015-06-03T19:58:21.433668791-07:00"}}

Once it's up in running, you can utilize curl or the official go client to interact with Kala. Also check out the examples directory.

Examples of Usage

There are more examples in the examples directory within this repo. Currently its pretty messy. Feel free to submit a new example if you have one.

Deployment

Supervisord

After installing supervisord, open its config file (/etc/supervisor/supervisord.conf is the default usually) and add something like:

[program:kala]
command=kala run
autorestart=true
stdout_logfile=/var/log/kala.stdout.log
stderr_logfile=/var/log/kala.stderr.log

Docker

If you have docker installed, you can build the dockerfile in this directory with
docker build -t kala .
and run it as a daemon with:
docker run -it -d -p 8000:8000 kala

API v1 Docs

All routes have a prefix of /api/v1

Client Libraries

Official:

• Go - Docs: http://godoc.org/github.com/ajvb/kala/client

  go get github.com/ajvb/kala/client
  

Contrib:

• Node.js

  npm install kala-node
  

• Python

  pip install git+https://github.com/dmajere/kala-python.git
  

Job Data Struct

Docs can be found here

Things to Note

• If schedule is omitted, the job will run immediately.

Job JSON Example

{
        "name":"test_job",
        "id":"93b65499-b211-49ce-57e0-19e735cc5abd",
        "command":"bash /home/ajvb/gocode/src/github.com/ajvb/kala/examples/example-kala-commands/example-command.sh",
        "owner":"",
        "disabled":false,
        "dependent_jobs":null,
        "parent_jobs":null,
        "schedule":"R2/2015-06-04T19:25:16.828696-07:00/PT10S",
        "retries":0,
        "epsilon":"PT5S",
        "success_count":0,
        "last_success":"0001-01-01T00:00:00Z",
        "error_count":0,
        "last_error":"0001-01-01T00:00:00Z",
        "last_attempted_run":"0001-01-01T00:00:00Z",
        "next_run_at":"2015-06-04T19:25:16.828794572-07:00"
}

Breakdown of schedule string. (ISO 8601 Notation)

Example schedule string:

R2/2017-06-04T19:25:16.828696-07:00/PT10S

This string can be split into three parts:

Number of times to repeat/Start Datetime/Interval Between Runs

Number of times to repeat

This is designated with a number, prefixed with an R. Leave out the number if it should repeat forever.

Examples:

• R - Will repeat forever
• R1 - Will repeat once
• R231 - Will repeat 231 times.

Start Datetime

This is the datetime for the first time the job should run.

Kala will return an error if the start datetime has already passed.

Examples:

• 2017-06-04T19:25:16
• 2017-06-04T19:25:16.828696
• 2017-06-04T19:25:16.828696-07:00
• 2017-06-04T19:25:16-07:00

To Note: It is recommended to include a timezone within your schedule parameter.

Interval Between Runs

This is defined by the ISO8601 Interval Notation.

It starts with a P, then you can specify years, months, or days, then a T, preceded by hours, minutes, and seconds.

Lets break down a long interval: P1Y2M10DT2H30M15S

• P - Starts the notation
• 1Y - One year
• 2M - Two months
• 10D - Ten days
• T - Starts the time second
• 2H - Two hours
• 30M - Thirty minutes
• 15S - Fifteen seconds

Now, there is one alternative. You can optionally use just weeks. When you use the week operator, you only get that. An example of using the week operator for an interval of every two weeks is P2W.

Examples:

• P1DT1M - Interval of one day and one minute
• P1W - Interval of one week
• PT1H - Interval of one hour.

More Information on ISO8601

• Wikipedia's Article

Overview of routes, Task, Method, Route, ---, ---, ---, Creating a Job, POST, /api/v1/job/, Getting a list of all Jobs, GET, /api/v1/job/, Getting a Job, GET, /api/v1/job/{id}/, Deleting a Job, DELETE, /api/v1/job/{id}/, Deleting all Jobs, DELETE, /api/v1/job/all/, Getting metrics about a certain Job, GET, /api/v1/job/stats/{id}/, Starting a Job manually, POST, /api/v1/job/start/{id}/, Disabling a Job, POST, /api/v1/job/disable/{id}/, Enabling a Job, POST, /api/v1/job/enable/{id}/, Getting app-level metrics, GET, /api/v1/stats/, ## /job

This route accepts both a GET and a POST. Performing a GET request will return a list of all currently running jobs.
Performing a POST (with the correct JSON) will create a new Job.

Note: When creating a Job, the only fields that are required are the Name and the Command field. But, if you omit the Schedule field, the job will be ran immediately.

Example:

$ curl http://127.0.0.1:8000/api/v1/job/
{"jobs":{}}
$ curl http://127.0.0.1:8000/api/v1/job/ -d '{"epsilon": "PT5S", "command": "bash /home/ajvb/gocode/src/github.com/ajvb/kala/examples/example-kala-commands/example-command.sh", "name": "test_job", "schedule": "R2/2017-06-04T19:25:16.828696-07:00/PT10S"}'
{"id":"93b65499-b211-49ce-57e0-19e735cc5abd"}
$ curl http://127.0.0.1:8000/api/v1/job/
{
    "jobs":{
        "93b65499-b211-49ce-57e0-19e735cc5abd":{
            "name":"test_job",
            "id":"93b65499-b211-49ce-57e0-19e735cc5abd",
            "command":"bash /home/ajvb/gocode/src/github.com/ajvb/kala/examples/example-kala-commands/example-command.sh",
            "owner":"",
            "disabled":false,
            "dependent_jobs":null,
            "parent_jobs":null,
            "schedule":"R2/2017-06-04T19:25:16.828696-07:00/PT10S",
            "retries":0,
            "epsilon":"PT5S",
            "success_count":0,
            "last_success":"0001-01-01T00:00:00Z",
            "error_count":0,
            "last_error":"0001-01-01T00:00:00Z",
            "last_attempted_run":"0001-01-01T00:00:00Z",
            "next_run_at":"2017-06-04T19:25:16.828794572-07:00"
        }
    }
}

/job/{id}

This route accepts both a GET and a DELETE, and is based off of the id of the Job. Performing a GET request will return a full JSON object describing the Job.
Performing a DELETE will delete the Job.

Example:

$ curl http://127.0.0.1:8000/api/v1/job/93b65499-b211-49ce-57e0-19e735cc5abd/
{"job":{"name":"test_job","id":"93b65499-b211-49ce-57e0-19e735cc5abd","command":"bash /home/ajvb/gocode/src/github.com/ajvb/kala/examples/example-kala-commands/example-command.sh","owner":"","disabled":false,"dependent_jobs":null,"parent_jobs":null,"schedule":"R2/2017-06-04T19:25:16.828696-07:00/PT10S","retries":0,"epsilon":"PT5S","success_count":0,"last_success":"0001-01-01T00:00:00Z","error_count":0,"last_error":"0001-01-01T00:00:00Z","last_attempted_run":"0001-01-01T00:00:00Z","next_run_at":"2017-06-04T19:25:16.828737931-07:00"}}
$ curl http://127.0.0.1:8000/api/v1/job/93b65499-b211-49ce-57e0-19e735cc5abd/ -X DELETE
$ curl http://127.0.0.1:8000/api/v1/job/93b65499-b211-49ce-57e0-19e735cc5abd/

/job/stats/{id}

Example:

$ curl http://127.0.0.1:8000/api/v1/job/stats/5d5be920-c716-4c99-60e1-055cad95b40f/
{"job_stats":[{"JobId":"5d5be920-c716-4c99-60e1-055cad95b40f","RanAt":"2017-06-03T20:01:53.232919459-07:00","NumberOfRetries":0,"Success":true,"ExecutionDuration":4529133}]}

/job/start/{id}

Example:

$ curl http://127.0.0.1:8000/api/v1/job/start/5d5be920-c716-4c99-60e1-055cad95b40f/ -X POST

/job/disable/{id}

Example:

$ curl http://127.0.0.1:8000/api/v1/job/disable/5d5be920-c716-4c99-60e1-055cad95b40f/ -X POST

/job/enable/{id}

Example:

$ curl http://127.0.0.1:8000/api/v1/job/enable/5d5be920-c716-4c99-60e1-055cad95b40f/ -X POST

/stats

Example:

$ curl http://127.0.0.1:8000/api/v1/stats/
{"Stats":{"ActiveJobs":2,"DisabledJobs":0,"Jobs":2,"ErrorCount":0,"SuccessCount":0,"NextRunAt":"2017-06-04T19:25:16.82873873-07:00","LastAttemptedRun":"0001-01-01T00:00:00Z","CreatedAt":"2017-06-03T19:58:21.433668791-07:00"}}

Debugging Jobs

There is now a command within Kala called run_command which will immediately run a command as Kala would run it live, and then gives you a response on whether it was successful or not. Allows for easier and quicker debugging of commands.

$ kala run_command "ruby /home/user/ruby/my_ruby_script.rb"
Command Succeeded!
$ kala run_command "ruby /home/user/other_dir/broken_script.rb"
FATA[0000] Command Failed with err: exit status 1

Dependent Jobs

How to add a dependent job

Check out this example for how to add dependent jobs within a python script.

Notes on Dependent Jobs

• Dependent jobs follow a rule of First In First Out
• A child will always have to wait until a parent job finishes before it runs
• A child will not run if its parent job does not.
• If a child job is disabled, it's parent job will still run, but it will not.
• If a child job is deleted, it's parent job will continue to stay around.
• If a parent job is deleted, unless its child jobs have another parent, they will be deleted as well.

Original Contributors and Contact

Original Author and Core Maintainer:

• AJ Bahnken / @ajvbahnken / aj@ajvb.me

Original Reviewers:

• Sam Dolan / @samdolan
• Steve Phillips / @elimisteve

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