Nextdoor Scheduler

ndscheduler is a flexible python library for building your own cron-like system to schedule jobs, which is to run a tornado process to serve REST APIs and a web ui.

Check out our blog post - We Don't Run Cron Jobs at Nextdoor

ndscheduler currently supports Python 2 & 3 on Mac OS X / Linux.

Table of contents

• Key Abstractions
• Try it NOW
• How to build Your own cron-replacement
  • Install ndscheduler
  • Three things
  • Reference Implementation
• Contribute code to ndscheduler
• REST APIs
• Web UI

Key Abstractions

• CoreScheduler: encapsulates all core scheduling functionality, and consists of:
  • Datastore: manages database connections and makes queries; could support Postgres, MySQL, and sqlite.
    • Job: represents a schedule job and decides how to run a paricular job.
    • Execution: represents an instance of job execution.
    • AuditLog: logs when and who runs what job.
  • ScheduleManager: access Datastore to manage jobs, i.e., schedule/modify/delete/pause/resume a job.
• Server: a tornado server that runs ScheduleManager and provides REST APIs and serves UI.
• Web UI: a single page HTML app; this is a default implementation.

Note: corescheduler can also be used independently within your own service if you use a different Tornado server / Web UI.

Try it NOW

From source code:

git clone https://github.com/Nextdoor/ndscheduler.git
cd ndscheduler
make simple

Or use docker:

docker run -it -p 8888:8888 wenbinf/ndscheduler

Open your browser and go to localhost:8888.

Demo (Click for fullscreen play)

How to build Your own cron-replacement

Install ndscheduler

Using pip (from GitHub repo)

#
# Put this in requirements.txt, then run
#    pip install -r requirements.txt
#

# If you want the latest build
git+https://github.com/Nextdoor/ndscheduler.git#egg=ndscheduler

# Or put this if you want a specific commit
git+https://github.com/Nextdoor/ndscheduler.git@5843322ebb440d324ca5a66ba55fea1fd00dabe8

# Or put this if you want a specific tag version
git+https://github.com/Nextdoor/ndscheduler.git@v0.1.0#egg=ndscheduler

#
# Run from command line
#

pip install -e git+https://github.com/Nextdoor/ndscheduler.git#egg=ndscheduler

(We'll upload the package to PyPI soon.)

Three things

You have to implement three things for your scheduler, i.e., Settings, Server, and Jobs.

Settings

In your implementation, you need to provide a settings file to override default settings (e.g., settings in simple_scheduler). You need to specify the python import path in the environment variable NDSCHEDULER_SETTINGS_MODULE before running the server.

All available settings can be found in default_settings.py file.

Server

You need to have a server file to import and run ndscheduler.server.server.SchedulerServer.

Jobs

Each job should be a standalone class that is a subclass of ndscheduler.job.JobBase and put the main logic of the job in run() function.

After you set up Settings, Server and Jobs, you can run the whole thing like this:

NDSCHEDULER_SETTINGS_MODULE=simple_scheduler.settings \
PYTHONPATH=.:$(PYTHONPATH) \
	    python simple_scheduler/scheduler.py

Upgrading

It is best practice to backup your database before doing any upgrade. ndscheduler relies on apscheduler to serialize jobs to the database, and while it is usually backwards-compatible (i.e. jobs created with an older version of apscheduler will continue to work after upgrading apscheduler) this is not guaranteed, and it is known that downgrading apscheduler can cause issues. See this PR comment for more details.

Reference Implementation

See code in the simple_scheduler/ directory for inspiration :)

Run it

make simple

Access the web ui via localhost:8888

The reference implementation also comes with several sample jobs.

• AwesomeJob: it just prints out 2 arguments you pass in.
• SlackJob: it sends a slack message periodically, for example, team standup reminder.
• ShellJob: it runs an executable command, for example, run curl to crawl web pages.
• CurlJob: it's like running curl periodically.

And it's dockerized.

Contribute code to ndscheduler

Install dependencies

# Each time we introduce a new dependency in setup.py, you have to run this
make install

Run unit tests

make test

Clean everything and start from scratch

make clean

Finally, send pull request. Please make sure the CI passes for your PR.

REST APIs

Please see README.md in ndscheduler/server/handlers.

Web UI

We provide a default implementation of web ui. You can replace the default web ui by overwriting these settings

STATIC_DIR_PATH = :static asset directory paths:
TEMPLATE_DIR_PATH = :template directory path:
APP_INDEX_PAGE = :the file name of the single page app's html:

The default web ui

List of jobs

List of executions

Audit Logs

Modify a job