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-   -   If gethostbyname fails it never recovers (http://www.velocityreviews.com/forums/t374192-if-gethostbyname-fails-it-never-recovers.html)

Andrew DeFaria 10-05-2006 12:56 PM

If gethostbyname fails it never recovers
 
I've been having problems with my ISP. One way it seems to manifest
itself is that I can not reach or contact my ISP's DNS servers. IOW a
simply nslookup google.com will fail.

So I tried writing a script that would monitor this. The script calls
gethostbyname for google.com every 15 minutes and logs the status. When
gethostbyname fails however it never comes back. My ISP and internet
connection may come back and nslookup at the command line will work
fine. But my script will report failure at the next and following 15
minute intervals. This is very unexpected. What am I doing wrong and is
there a way to "reset" things so that it will start working again.

Here's a snippet:

sub CheckDNS {
my $host = shift;

my @ipaddrs = gethostbyname $host;
my $status = $?;

if ($status ne 0 and $debug) {
debug "Host: $host ($status)";
} # if

return $status
} # CheckDNS

CheckDNS is called every 15 minutes with "google.com" as a parm. When a
failure happens $status = 2 and remains = 2 forever.

--

Andrew DeFaria <http://defaria.com>
Dain bramaged.


Randal L. Schwartz 10-05-2006 02:10 PM

Re: If gethostbyname fails it never recovers
 
>>>>> "Andrew" == Andrew DeFaria <Andrew@DeFaria.com> writes:

Andrew> So I tried writing a script that would monitor this. The script calls
Andrew> gethostbyname for google.com every 15 minutes and logs the status. When
Andrew> gethostbyname fails however it never comes back. My ISP and internet
Andrew> connection may come back and nslookup at the command line will work fine. But
Andrew> my script will report failure at the next and following 15 minute
Andrew> intervals. This is very unexpected. What am I doing wrong and is there a way
Andrew> to "reset" things so that it will start working again.

Andrew> Here's a snippet:

Andrew> sub CheckDNS {
Andrew> my $host = shift;

Andrew> my @ipaddrs = gethostbyname $host;
Andrew> my $status = $?;

Andrew> if ($status ne 0 and $debug) {
Andrew> debug "Host: $host ($status)";
Andrew> } # if

Andrew> return $status
Andrew> } # CheckDNS

Andrew> CheckDNS is called every 15 minutes with "google.com" as a parm. When a
Andrew> failure happens $status = 2 and remains = 2 forever.

$? is not set for a gethostbyname failure. In fact, I'm not sure
anything is actually set.

And now a word from our Usenet manager...

If you can see this message, you are reading a group that is not
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What this means TO YOU is that your question won't be answered
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STOP POSTING HERE. POST TO COMP.LANG.PERL.MISC

And send email to your news server administrator to PLEASE DELETE THIS
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--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
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--
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Andrew DeFaria 10-06-2006 01:45 AM

Re: If gethostbyname fails it never recovers
 
Randal L. Schwartz wrote:
> $? is not set for a gethostbyname failure. In fact, I'm not sure
> anything is actually set.

Actually, at least on my system... it is! If I change $host = "bogus"
gethostbyname sets $? to 1. Try it!
> And now a word from our Usenet manager...
>
> If you can see this message, you are reading a group that is not
> officially carried, and therefore doesn't get the propogation or
> readership that the official comp.lang.perl.misc group gets.
>
> What this means TO YOU is that your question won't be answered to the
> same expert level that an official group will get. You'll get answers
> that are wrong (and not noticed to be wrong), or no answer at all.
>
> STOP POSTING HERE. POST TO COMP.LANG.PERL.MISC
>
> And send email to your news server administrator to PLEASE DELETE THIS
> GROUP.

Thanks. I had no idea. I will post there...

--

Andrew DeFaria <http://defaria.com>
I got a new shadow. I had to get rid of the other one -- it wasn't doing
what I was doing.



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