HAProxy Enterprise Documentation 2.5r1

HTTP Health Checks

An HTTP-layer health check sends an HTTP OPTIONS request to the server and expects to get a successful response. To enable it, add option httpchk to the backend section:

backend be_myapp
   option httpchk
   server srv1 192.168.1.5:80 check

Checks are sent using GET to the URL / by default.

You can change the HTTP method and URL by specifying them on the option httpchk line. In the following example, checks are sent using GET to the URL /healthz:

backend be_myapp
   option httpchk GET /healthz
   server srv1 10.0.0.1:80 check
   server srv2 10.0.0.2:80 check

If the response status code is in the 2xx or 3xx range, the server is healthy.

Customizing the HTTP check with the send directive

Another way to change the HTTP method and URL is by adding the http-check send line and specifying the new values there. In the following example, checks are sent using GET to the URL /healthz:

backend be_myapp
   option httpchk
   http-check send meth HEAD uri /healthz ver HTTP/1.1 hdr Host test.local
   server srv1 192.168.1.5:80 check

You can send POST requests, too:

backend be_myapp
   option httpchk
   http-check send meth POST uri /health hdr Content-Type "application/json;charset=UTF-8" hdr Host www.mwebsite.com body "{\"id\": 1, \"field\": \"value\"}"
   server srv1 192.168.1.5:80 check

For the complete list of parameters that can be specified on the send line, see http-check send.

Multiple HTTP endpoints

Additional power comes from the ability to query several endpoints during a single health check. In the following example, we make requests to two distinct services: one listening on port 8080 and the other on port 8081. We also use different URIs. If either endpoint fails to respond, the entire health check fails.

backend servers
    option httpchk

    http-check connect port 8080
    http-check send meth HEAD uri /health

    http-check connect port 8081
    http-check send meth HEAD uri /up

    server server1 127.0.0.1:80 check

Next up

Health Check Interval