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Healtchecks for Django

Project description

django-alive 🕺

tests coverage PyPI Python Versions

Provides two healthcheck endpoints for your Django application:

Alive

Verifies the WSGI server is responding.

  • Default URL: /-/alive/
  • Success:
    • status code: 200
    • content: ok
  • Failure: This view never returns a failure. A failure would mean your WSGI server is not running.

Health

Verifies services are ready.

  • Default URL: /-/health/
  • Success:
    • status_code: 200
    • content: {"healthy": true}
  • Failure:
    • status_code: 503
    • content: {"healthy": false, "errors": ["error 1", "error 2"]}

By default the health endpoint will test the database connection, but can be configured to check the cache, staticfiles, or any additional custom checks.

Supports Django 1.10+ on both Python 2 & 3.

Install

pip install django-alive

Configure

Add this to your project's urlpatterns:

path("-/", include("django_alive.urls"))

For versions before Django 2.0, use:

url(r"-/", include("django_alive.urls"))

If you wish to use the healthcheck management command, add django_alive to the INSTALLED_APPS.

Enabling Checks

The default "health" endpoint will test a simple SELECT 1 query on the database. Additional checks can be enabled in your Django settings.

Use the ALIVE_CHECKS setting to configure the checks to include. It is a dictionary with the path to a Python function as a key and any keyword arguments to pass to that function as a value. A full example:

ALIVE_CHECKS = {
    "django_alive.checks.check_database": {},
    "django_alive.checks.check_staticfile": {
        "filename": "img/favicon.ico",
    },
    "django_alive.checks.check_cache": {
        "cache": "session",
        "key": "test123",
    },
    "django_alive.checks.check_migrations": {},
}

Built-in Checks

Defined in django_alive.checks.

def check_cache(key="django-alive", cache="default")

Fetch a cache key against the specified cache.

Parameters:

  • key (str): Cache key to fetch (does not need to exist)
  • cache (str): Cache alias to execute against

def check_database(query="SELECT 1", database="default")

Run a SQL query against the specified database.

Parameters:

  • query (str): SQL to execute
  • database (str): Database alias to execute against

def check_migrations(alias=None)

Verify all defined migrations have been applied

Parameters:

  • alias (str): An optional database alias (default: check all defined databases)

def check_staticfile(filename)

Verify a static file is reachable

Parameters:

  • filename (str): static file to verify

Management Command

In addition to the view, the configured healthchecks can also be run via a management command with manage.py healthcheck. This will exit with an error code if all the healthchecks do not pass.

Custom Checks

django-alive is designed to easily extend with your own custom checks. Simply define a function which performs your check and raises a django_alive.HealthcheckFailure exception in the event of a failure. See checks.py for some examples on how to write a check.

Disabling ALLOWED_HOSTS for Healthchecks

Often, load balancers will not pass a Host header when probing a healthcheck endpoint. This presents a problem for Django's host header validation. A middleware is included that will turn off the host checking only for the healthcheck endpoints. This is safe since these views never do anything with the Host header.

Enable the middleware by inserting this at the beginning of your MIDDLEWARE:

MIDDLEWARE = [
    "django_alive.middleware.healthcheck_bypass_host_check",
    # ...
]

Handling SECURE_SSL_REDIRECT

If your load balancer is doing HTTPS termination and you have SECURE_SSL_REDIRECT=True in your settings, you want to make sure that your healtcheck URLs are not also redirected to HTTPS. In that case, add the following to your settings:

SECURE_REDIRECT_EXEMPT = [r"^-/"]  # django-alive URLs

1.1.0 (2019-11-06)

  • Added healthcheck management command
  • Added optional check_migrations healthcheck

1.0.1 (2018-09-10)

  • Documentation improvements
  • Python 3.7 support

1.0.0 (2018-08-21)

  • Initial release

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