Re: detecting server down

From: Ulric Eriksson (
Date: Wed Apr 09 2003 - 23:31:34 CEST

On Tue, 1 Apr 2003, Caffeinate The World wrote:

> How does pen detect a server is unavailable?

The built-in mechanism is to blacklist servers that don't respond at all,
i.e. connection refused or timeout.

> How does it detect when the server comes backup?

After some period of time, 30 seconds by default, the server is put back
in the selection mechanism. If it fails the next time it is supposed to
accept a client, it is blacklisted again. The -b option can be used to
change the blacklist time. See man page.

It isn't always sufficient to just check if the server responds. For
example, a web server can respond with nothing but error messages or empty
pages and Pen will think it's working fine. It is possible to use more
advanced tests, see for an example.


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