django-health-check
This project checks for various conditions and provides reports when anomalous behavior is detected.
The following health checks are bundled with this project:
- cache
- database
- storage
- disk and memory utilization (via
psutil
) - AWS S3 storage
- Celery task queue
- RabbitMQ
Writing your own custom health checks is also very quick and easy.
We also like contributions, so don't be afraid to make a pull request.
Use Cases
The primary intended use case is to monitor conditions via HTTP(S), with responses available in HTML and JSON formats. When you get back a response that includes one or more problems, you can then decide the appropriate course of action, which could include generating notifications and/or automating the replacement of a failing node with a new one. If you are monitoring health in a high-availability environment with a load balancer that returns responses from multiple nodes, please note that certain checks (e.g., disk and memory usage) will return responses specific to the node selected by the load balancer.
Supported Versions
We officially only support the latest version of Python as well as the latest version of Django and the latest Django LTS version.
Note
The latest version to support Python 2 is 2.4.0
Installation
First install the django-health-check
package:
pip install django-health-check
Add the health checker to a URL you want to use:
urlpatterns = [
# ...
url(r'^ht/', include('health_check.urls')),
]
Add the health_check
applications to your INSTALLED_APPS
:
INSTALLED_APPS = [
# ...
'health_check', # required
'health_check.db', # stock Django health checkers
'health_check.cache',
'health_check.storage',
'health_check.contrib.celery', # requires celery
'health_check.contrib.psutil', # disk and memory utilization; requires psutil
'health_check.contrib.s3boto_storage', # requires boto and S3BotoStorage backend
'health_check.contrib.rabbitmq', # requires RabbitMQ broker
'health_check.contrib.redis', # required Redis broker
]
(Optional) If using the psutil
app, you can configure disk and memory
threshold settings; otherwise below defaults are assumed. If you want to disable
one of these checks, set its value to None
.
HEALTH_CHECK = {
'DISK_USAGE_MAX': 90, # percent
'MEMORY_MIN': 100, # in MB
}
If using the DB check, run migrations:
django-admin migrate
To use the RabbitMQ healthcheck, please make sure that there is a variable named BROKER_URL
on django.conf.settings with the required format to connect to your rabbit server. For example:
BROKER_URL = amqp://myuser:mypassword@localhost:5672/myvhost
To use the Redis healthcheck, please make sure that there is a variable named REDIS_URL
on django.conf.settings with the required format to connect to your redis server. For example:
REDIS_URL = redis://localhost:6370
Setting up monitoring
You can use tools like Pingdom or other uptime robots to monitor service status.
The /ht/
endpoint will respond a HTTP 200 if all checks passed
and a HTTP 500 if any of the tests failed.
$ curl -v -X GET -H http://www.example.com/ht/ > GET /ht/ HTTP/1.1 > Host: www.example.com > Accept: */* > < HTTP/1.1 200 OK < Content-Type: text/html; charset=utf-8 <!-- This is an excerpt --> <div class="container"> <h1>System status</h1> <table> <tr> <td class="status_1"></td> <td>CacheBackend</td> <td>working</td> </tr> <tr> <td class="status_1"></td> <td>DatabaseBackend</td> <td>working</td> </tr> <tr> <td class="status_1"></td> <td>S3BotoStorageHealthCheck</td> <td>working</td> </tr> </table> </div>
Getting machine readable JSON reports
If you want machine readable status reports you can request the /ht/
endpoint with the Accept
HTTP header set to application/json
or pass format=json
as a query parameter.
The backend will return a JSON response:
$ curl -v -X GET -H "Accept: application/json" http://www.example.com/ht/ > GET /ht/ HTTP/1.1 > Host: www.example.com > Accept: application/json > < HTTP/1.1 200 OK < Content-Type: application/json { "CacheBackend": "working", "DatabaseBackend": "working", "S3BotoStorageHealthCheck": "working" } $ curl -v -X GET http://www.example.com/ht/?format=json > GET /ht/?format=json HTTP/1.1 > Host: www.example.com > < HTTP/1.1 200 OK < Content-Type: application/json { "CacheBackend": "working", "DatabaseBackend": "working", "S3BotoStorageHealthCheck": "working" }
Writing a custom health check
Writing a health check is quick and easy:
from health_check.backends import BaseHealthCheckBackend
class MyHealthCheckBackend(BaseHealthCheckBackend):
#: The status endpoints will respond with a 200 status code
#: even if the check errors.
critical_service = False
def check_status(self):
# The test code goes here.
# You can use `self.add_error` or
# raise a `HealthCheckException`,
# similar to Django's form validation.
pass
def identifier(self):
return self.__class__.__name__ # Display name on the endpoint.
After writing a custom checker, register it in your app configuration:
from django.apps import AppConfig
from health_check.plugins import plugin_dir
class MyAppConfig(AppConfig):
name = 'my_app'
def ready(self):
from .backends import MyHealthCheckBackend
plugin_dir.register(MyHealthCheckBackend)
Make sure the application you write the checker into is registered in your INSTALLED_APPS
.
Customizing output
You can customize HTML or JSON rendering by inheriting from MainView
in health_check.views
and customizing the template_name
, get
, render_to_response
and render_to_response_json
properties:
# views.py
from health_check.views import MainView
class HealthCheckCustomView(MainView):
template_name = 'myapp/health_check_dashboard.html' # customize the used templates
def get(self, request, *args, **kwargs):
plugins = []
# ...
if 'application/json' in request.META.get('HTTP_ACCEPT', ''):
return self.render_to_response_json(plugins, status)
return self.render_to_response(plugins, status)
def render_to_response(self, plugins, status): # customize HTML output
return HttpResponse('COOL' if status == 200 else 'SWEATY', status=status)
def render_to_response_json(self, plugins, status): # customize JSON output
return JsonResponse(
{str(p.identifier()): 'COOL' if status == 200 else 'SWEATY' for p in plugins}
status=status
)
# urls.py
import views
urlpatterns = [
# ...
url(r'^ht/$', views.HealthCheckCustomView.as_view(), name='health_check_custom'),
]
Django command
You can run the Django command health_check to perform your health checks via the command line, or periodically with a cron, as follow:
django-admin health_check
This should yield the following output:
DatabaseHealthCheck ... working CustomHealthCheck ... unavailable: Something went wrong!
Similar to the http version, a critical error will case the command to quit with the exit code 1.
Other resources
- django-watchman is a package that does some of the same things in a slightly different way.
- See this weblog about configuring Django and health checking with AWS Elastic Load Balancer.