Introducing backend healthchecking plugin

[Piotr Sikora]

Hello Jack,

> To redeem the module, I checked over your config and it was missing the 
> "Host:" header in your healthcheck_send.  Try using something similar to 
> the sample config:
>
>    healthcheck_send "GET /health HTTP/1.1" 'Host: www.ahost.com' 
> 'Connection: close';

No, it wasn't. Missing header wouldn't yield timeout. But just for the sake 
of it, I tested it with the above line and it didn't help.

Like I said yesterday, I don't really have time to fully investigate this 
right now, but I'll try to narrow down / fix the problem over the weekend.

Best regards,
Piotr Sikora < piotr.sikora at frickle.com >