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From: donn@MILTON.U.WASHINGTON.EDU (Donn Cave)
Newsgroups: comp.windows.x
Subject: R5 wish list -- client recovery
Message-ID: <9011191810.AA01979@milton.u.washington.edu>
Date: 19 Nov 90 18:10:38 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 31

excerpts from <6220@lanl.gov> (Dale Carstensen):

>  ... with X11R3 and X11R4 ... if the server dies ... remote clients that
> had been connected to it continue to run, usually.

Even if you wanted to use xdm, it isn't a complete cure for this one, since
it only gets the clients directly descended from it - not clients started from
the shell command line, not clients running on other hosts.

We were able to install a fairly trivial patch to Xlib, so that the socket
is created with a keep-alive option.  Clients that would normally accept
prolonged inactivity on the connection, now fail at some point when the
keep-alive comes up.  Since the twm client seems to be particularly hardy
in disconnected state I'm now running a test twm client linked with the
revised Xlib routine, and at least with some TCPs it seems to fix Problem 1.
Unfortunately, it seems to slightly aggravate Problem 2:

> On the other hand, unreliability in the network connection between client
> and server can terminate clients while the server is still running.

We get a lot of "Network down" (E_NETDOWN) errors, particularly on one host
whose Ethernet hardware is not the industry's best.  These errors tend to
afflict only one client at a time, rather than shutting down everyone at
once, and they don't seem bother ftp or telnet in the least.  I'm told that
ftp and telnet re-try when they encounter these conditions - would such
re-trying be another trivial modification to Xlib?  Are there fundamental
reasons why X should give up immediately when it encounters this network error?

		Donn Cave
		University Computing Services, University of Washington
		donn@cac.washington.edu