Path: utzoo!attcan!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!ames!think!barmar
From: barmar@think.COM (Barry Margolin)
Newsgroups: comp.windows.x
Subject: Re: Why does X not use SO_KEEPALIVE?
Message-ID: <20663@news.Think.COM>
Date: 24 May 89 19:06:32 GMT
References: <7992@boring.cwi.nl> <8905241247.AA00833@expire.lcs.mit.edu>
Sender: news@Think.COM
Reply-To: barmar@kulla.think.com.UUCP (Barry Margolin)
Organization: Thinking Machines Corporation, Cambridge, MA
Lines: 30

In article <8905241247.AA00833@expire.lcs.mit.edu> rws@EXPO.LCS.MIT.EDU writes:
>"indiscriminant" use (e.g. automatically in all X connections) is evil.

Agreed.  xperfmon, xclock, and other clients that produce frequent
automatic output don't need keepalives, but xterm, emacs, and most
other event-driven applications generally do.  Servers probably don't
need to use keepalives, either.

>	A TCP keep-alive mechanism should only be invoked in
>	network servers that might otherwise hang indefinitely
>	and consume resources unnecessarily if a client crashes
>	or aborts a connection during a network partition.

Since only the client application knows its interaction style, only it
knows whether it needs keepalives.  This implies that there needs to
be an option to the X stream-creation routine to specify this.  If
this doesn't fit into the current Xlib design, then it could be done
with a new Xlib function to turn keepalives on and off.  Needless to
say, this option would be advisory only, since not all OSes and
transport protocols may support this notion.

I definitely think that this is a case where keepalives are warranted.
I'm getting sick of having to hunt down all my xterms whenever my
server crashes.

Barry Margolin
Thinking Machines Corp.

barmar@think.com
{uunet,harvard}!think!barmar