Overview

Write health checks

Write health checks just like you would write tests. The main difference is their scope: they check “production” facts instead of mocks/fakes/dummies.

Health checks are special kind of tests. Use healthcheck() decorator to differenciate health checks from tests.

Just like tests, health checks can be simple functions that perform assertions:

import sys
import hospital

@hospital.healthcheck
def test_python_version():
    """Python version >= 2."""
    assert sys.version_info[0] >= 2

You can reuse test libraries, like unittest:

import unittest
import hospital

@hospital.healthcheck
class DocumentationHealthCheck(unittest.TestCase):
    """Check `hospital` online documentation."""
    def test_ping(self):
        """`hospital` documentation server responds to ping."""
        hostname = 'hospital.readthedocs.org'
        hospital.assert_ping(hostname)

    def test_http_200(self):
        """`hospital` online documentation returns HTTP 200."""
        url = 'http://hospital.readthedocs.org/en/0.1/'
        hospital.assert_http_response(url, status_code=200)

Hospital provides a set of useful assertions and health check suites.

Recommended namespace: healthchecks

As a convention, put healthchecks in “healthchecks” namespace (i.e. module or package) inside your projects.

Just as “tests” namespace is used by convention for tests.

As an example, if your project distributes an “unbreakable” root package, then you should put healthchecks in either unbreakable/healthchecks.py module or unbreakable/healthchecks/__init__.py package.

Collect and run health checks

Run health checks to make sure everything is ok. As an example, run health checks after a deployment to verify configuration, services...

The healthcheck() decorator sets is_healthcheck attribute to True to decorated objects. Let’s use this feature to capture and run healthchecks.

Nose

With nose (here we run health checks of hospital project):

nosetests --all-modules --attr="is_healthcheck" hospital

Tip

You may want to skip health checks when you run unit/functional/integration tests. With nose, it could be:

nosetests --all-modules --attr="!is_healthcheck" hospital

Tip

–all-modules option [1] makes Nose collect tests in all modules. Without the option, it would have collected modules or packages named “tests”, and not “healthchecks”.

Other

You can use the is_healthcheck() function to verify whether an object is an healthcheck or not.

Notes & references

[1]	http://nose.readthedocs.org/en/latest/usage.html#cmdoption–all-modules