Re: Hour long timeout to ssh/telnet/ftp to down host?

[Ben Greear <greearb@candelatech.com>]

Rob Landley wrote:
> 
> I have scripts that ssh into large numbers of boxes, which are sometimes
> down.  The timeout for figuring out the box is down is over an hour.  This is
> just insane.
> 
> Telnet and ftp behave similarly, or at least tthey lasted the 5 minutes I was
> willing to wait, anyway.  Basically anything that calls connect().  If the
> box doesn't respond in 15 seconds, I want to give up.
> 
> Is this a problem with the kernel or with glibc?  If it's the kernel, I'd
> expect a /proc entry where I can set this, but I can't seem to find one.  Is
> there one?  What would be involved in writing one?
> 

You can tune things by setting the tcp-timeout probably..I don't
know exactly where to set this..

You probably don't want all tcp to time out at 15 seconds anyway, so
I'd suggest either using non-blocking connect (if you have the code
that does the connect), or just set a timer (or use sigalarm) when you
start the attempt, and fail the attempt if the timer or alarm signal
goes off.

> If it's glibc I'm probably better off writing a wrapper to ping the
> destination before trying to connect, or killing the connection after a
> timeout with no traffic.  But both of those are really ugly solutions.

Ugly is relative, and don't use ping because there is still a race condition
(ping worked, but by the time you try tcp, the box is down.)

> 
> Anybody have any light to shed on the situation?
> 
> Rob
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-- 
Ben Greear <greearb@candelatech.com>          <Ben_Greear@excite.com>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear