A simple django app that responds to heartbeat polls.
In a cluster of load-balanced web servers, this allows you to take a server out of service gracefully, by letting your load balancer know that the server is going down before shutting down.
To implement, add 'heartbeat' to INSTALLED_APPS in your Django settings file.
A control file is used for signalling. Use the following setting in your Django settings file to specify the path for the control file:
HEARTBEAT_FILENAME = '/etc/heartbeat'
If this file exists and contains a 0, heartbeat will respond with a 503 to let a load balancer know to stop sending new requests to the server because the server is going down for maintenance.
To set, use eg:
$ echo 0 > etc/heartbeat
Or you can use the Django management commands:
$ bin/django heartbeat down $ bin/django heartbeat up
Used with HAProxy, your HAProxy config file might contain this:
backend site
balance roundrobin
option httpchk HEAD /heartbeat/status/ HTTP/1.0
option httpclose
server web-appserver-A-1 10.0.2.2:80 check inter 5000
server web-appserver-A-2 10.0.2.3:80 check inter 5000
server web-appserver-A-3 10.0.2.4:80 check inter 5000
server web-appserver-B-1 10.0.5.2:80 check inter 5000
server web-appserver-B-2 10.0.5.3:80 check inter 5000
server web-appserver-B-3 10.0.5.4:80 check inter 5000