ktor-health-check

Simple, opinionated ktor health and readiness checks made for Kubernetes.

import ktor_health_check.Health

fun main(args: Array<String>) {
    embeddedServer(Netty, 80) {
        // Install the middleware...
        install(Health)
    }.start(wait = true)
}

... and boom, the your application now exposes a /healthz and /readyz endpoint for use with for example Kubernetes. For a simple application this is all you configuration you will ever need. In a more complicated application we might want to our readycheck to start failing if the database goes down.

fun main(args: Array<String>) {
    embeddedServer(Netty, 80) {
        install(Health) {
            readyCheck("database") { myDatabase.ping() }
        }
    }.start(wait = true)
}

And now getting /readyz returns:

HTTP/1.1 200 OK
Content-Type: application/json; charset=UTF-8
Content-Length: 17

{"database":true}

Lets add another check

install(Health) {
            readyCheck("database") { myDatabase.ping() }
            readyCheck("redis") { redis.ping() }
}

Now lets say someone tripped on the cord for our Redis server.

HTTP/1.1 500 Internal Server Error
Content-Type: application/json; charset=UTF-8
Content-Length: 31

{"database":true,"redis":false}

The database check is still returning true, but redis has turned false. If any single check is down, as is the case here, the result of the entire request becomes 500, indicating that the service isn't operational.

For some use-cases you may want to expose checks on URLs other than /healthz and /readyz. In that case we need to use customCheck

customCheck("/smoketest", "database") { database.test() }

And the smoketest should now be avaliable on /smoketest