python-panopticon 0.4.0

A collection of healthcheck and monitoring helpers.

Panopticon is a collection of health check and monitoring helpers that we use at Mobify for our services.

Installation

The easiest way to install it is from PyPI:

$ pip install python-panopticon

You can also install it straight from the repo:

$ pip install https://github.com/elbaschid/python-panopticon/archive/master.zip

Setup with Django

panopticon comes with a Django integration app that simplifies the setup. Make sure you have the python-panopticon package installed.

Add the panopticon.django app into you INSTALLED_APPS settings and configure the API key for Datadog by specifying DATADOG_API_KEY in your settings. You are all done!

If you want your healthcheck to be automatically exposed on /healthcheck/ you can simply add the following line to your main project urls.py:

#urls.py
urlpatterns = [
    # all your other URLs

    url(r'', include('panopticon.django.urls', namespace='panopticon')),
]

Using this view at this point requires django-rest-framework (DRF) to be installed as a dependency. We’ll probably changes it in the future but for now, we are using DRF in our projects and it provides some additional features.

If you don’t hook up panopticon.urls, you can simply build your own view and ignore this dependency.

Available Settings

• DATADOG_STATS_ENABLED : Enables or disables the Datadog wrapper in panopticon. If you disable panopticon, it’ll use a mock.Mock object as the stats client. It is disabled by default.

• DATADOG_STATS_PREFIX : The prefix used for all Datadog metrics when submitted to the Datadog API. The default is panopticon.

Adding a custom healthcheck in Django

If you are using the Django app to integrate it with Django, adding new health checks is easy. Every application in INSTALLED_APPS will be checked for a healthchecks.py module on startup. Loading each of these modules will automatically register all health checks in that module. This is similar to how models.py and tasks.py (Celery) work.

Let’s assume we have a monitoring Django app that should contain some simple health checks. The first thing to do is creating a healthchecks.py file. Within this file, we can now create a simple function that test the database connection. All we have to do to hook it up is register it as a health check and provide details about its success:

from django.db import connection, DatabaseError

@HealthCheck.register_healthcheck
def database(data):
    cursor = connection.cursor()

    healthy = True
    status = 'database is available.'

    try:
        cursor.execute('SELECT 1;')
    except DatabaseError as exc:
        status = 'error connecting to the database: {}'.format(str(exc))
    finally:
        cursor.close()

    data[HealthCheck.HEALTHY] = healthy
    data[HealthCheck.STATUS_MESSAGE] = status

    return data

The name of the function, i.e. database in this case, will be used as the component name for the health check result as defined in the response format below.

The Response Format

The health check format that we use makes sure that all health checks return an agreed upon JSON response. This ensure that certain properties are always present and can be relied upon for external processing, e.g. service_healthy, timestamp, components and healthy within each of the components.

{
    // This represents the overall health of the service
    // If all of the components are healthy this should be true, false otherwise.
    "service_healthy": true,

    // The instant when the response was generated. This is useful to determine
    // if the health check response is up to date or stale, for example because it
    // was cached. This is in ISO8601 format.
    "timestamp": "2014-09-03T23:09:38.702Z",

    // We also expose the health status for each internal component
    // of the service. Besides a “healthy” flag this can also include
    // metadata like the number of queued jobs or average processing times.
    // We expose this information in a list so that monitoring tools can parse
    // and visualize this information easily.
    "components": {
        "database": {
            "healthy":  true,
            "response_time": 0.00123,
            "friendly_status": "The database is working awesomely great!"
        },
        "background_jobs": {
            "healthy":  true,
            "response_time": 0.00123,
            "queued_jobs": 423
        }
    }
}

Setup Development

The development setup is using tox for testing against various versions of Python. Running tox tests is quit simple for a given Python version that you have installed locally. For instance running tox for Python 3.5:

$ tox -e py35

If you prefer to install and run the tests inside a virtualenv, you can install all the test and release requirements inside a virtualenv using:

$ pip install -e ".[test]"
$ pip install -e ".[dev]"

Creating a Release

Creating a new release is simple. We use bumpversion which ensures that naming tags and updating all version numbers in the Python code is ensured. To create a new version specify the type of version bump (either major, minor or patch) and bumpversion will do the rest. For a patch it looks like this:

$ bumpversion patch

This will do the following:

• Change all version strings defined in bumpversion.cfg.

• Create a new commit.

• Create a new tag with the given version number.

Note A new release should only be created on the master branch after one or more changes have been merged and tested.

After releasing a new version, the commit and tag have to be pushed to github:

$ git push
$ git push --tags

You can now release this version to PyPI using the Makefile. This requires the password for the mobify user to be exported in your shell. You can find it in LastPass:

$ PYPI_PASSWORD=<the password> make release

License

This code is licensed under the MIT License.