Re: lynx-dev HTDoRead() HTTCP.c possible bug - retry limit set too high?

[Klaus Weide]

On Fri, 7 Jul 2000, Vlad Harchev wrote:
> On Thu, 6 Jul 2000, jtnews wrote:
> 
> > I use lynx to dump URL text pages using lynx -dump and
> > occasionally, lynx hangs in the following section of code...
> > 
> > HTTCP.c:
> >     while (!ready) {
> >         /*
> >         **  Protect against an infinite loop.
> >         */
> > =>      if (tries++ >= 180000) {
> >             HTAlert(gettext("Socket read failed for 180,000 tries."));
> > 
> > I'm using lynx 2.8.4dev4.
> > I also ran into a similar situation using 2.8.3 also.
> > 
> > With the timeout in select set to 100000 microseconds   The call will
> > only timeout
> > after 180000 * 100000 / 1000000 = 18000 seconds or 5 hours.

What's wrong with that?  It is not a bug that lynx tries for a long time.

Ok, I can guess that you would like a shorter timeout.  But it's not
lynx that is broken here - it's the network connection (or maybe the
server).

>   Thanks for reporting this.
> 
>   Seems we should add new lynx.cfg setting READ_TIMEOUT to control this (there
> already exists CONNECT_TIMEOUT). Does anybody object against it? 

As long as you keep the current behavior by default...

But this isn't really the best solution for the problem, if the problem
is really: 'Non-interactive lynx processes hang around for too long
under some conditions'.  The best solution, because it should always
work, is: kill the process from the outside if it runs for too long.
Shortening the read timeout, together with a short connect timeout,
will still not apply to all situations.  I am thinking about some
situations in the FTP protocol (if we are blocked in listen(), neither
of the timeout applies), or reading a "local" file that is actually
on an NFS-mounted filesystem that is unavailable, or some other special
local files.

Better learn how to kill a process so that it *never* can run longer
than a max time.  Take the shell script below as a starting point.
(It should be improved for real use, see for example documentation
of {bash,ksh} builtin 'wait' command.) 

   Klaus

----------------   tolynx   ---------------------
#! /bin/sh
LYNX="./src/lynx"  # change this, e.g. to "lynx"
if [ $# -lt 2 ]; then
  echo "tolynx - invoke lynx with timeout." >&2
  echo "Usage: $0 TIMEOUT LYNXOPTIONS URL" >&2
  echo "       LYNXOPTIONS should include -dump." >&2
  exit 1
fi
TIMEOUT=$1
shift
$LYNX "$@" &
CHILDPID=$!
sleep $TIMEOUT
kill -0 $CHILDPID 2>/dev/null && kill $CHILDPID
exit 0



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