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From Jim Albert <...@netrition.com>
Subject Re: automatically restart httpd
Date Tue, 23 Apr 2013 19:23:52 GMT
On 4/23/2013 3:09 PM, Jim Albert wrote:
> On 4/23/2013 2:33 PM, Ryan Perry wrote:
>>
>>
>>
>> On Tue, Apr 23, 2013 at 12:47 PM, Jim Albert <jim@netrition.com
>> <mailto:jim@netrition.com>> wrote:
>>
>>     On 4/23/2013 1:36 PM, Ryan Perry wrote:
>>
>>
>>
>>
>>         On Tue, Apr 23, 2013 at 12:23 PM, Jim Albert <jim@netrition.com
>>         <mailto:jim@netrition.com>
>>         <mailto:jim@netrition.com <mailto:jim@netrition.com>>> wrote:
>>
>>              On 4/23/2013 1:08 PM, Ryan Perry wrote:
>>
>>                  I've considered doing it daily via cron, but if there's
>>         a way to
>>                  do when
>>                  I hit this error I'd prefer that.
>>
>>
>>                  On Tue, Apr 23, 2013 at 12:02 PM, Jim Albert
>>         <jim@netrition.com <mailto:jim@netrition.com>
>>                  <mailto:jim@netrition.com <mailto:jim@netrition.com>>
>>                  <mailto:jim@netrition.com <mailto:jim@netrition.com>
>>         <mailto:jim@netrition.com <mailto:jim@netrition.com>>>>
wrote:
>>
>>                       On 4/23/2013 11:49 AM, Ryan Perry wrote:
>>
>>                           I've been plagued by some bug that makes a
>>         call to LWP
>>                  stop working:
>>                           "Can't connect to 192.168.0.222 (Bad hostname)"
>>
>>                           I haven't been able to figure out why, but a
>>         simple httpd
>>                           restart fixes
>>                           it for a day or 2.
>>
>>                           Since I can't figure out a real fix, I'm
>>         wondering if
>>                  there is a
>>                           way for
>>                           me to automatically restart httpd whenever
>> the bug
>>                  hits.  Maybe
>>                           whenever
>>                           it appears in the httpd-error.log?  What are
>>         my options?
>>
>>
>>                       Without more to go on to the actual cause of the
>>         problem...
>>
>>                       Restarting apache daily isn't a bad idea in
>>         general if even
>>                  just a
>>                       graceful restart.
>>                       kill -USR1 `cat /var/run/httpd.pid`
>>                       which I believe should be safe any time of day.
>>
>>                       If a complete restart, maybe early morning off
>> hours
>>                  assuming your
>>                       server requires a high degree of availability?
>>
>>                       Jim
>>
>>
>>              Try to remember not to top-post, please. It makes it hard
>>         for others
>>              to read the thread.
>>
>>              I don't know, but it kind of has a DNS feel to it,
>>         possibly. Nothing
>>              concrete to go on, just past experience when I see network
>>         and I
>>              know the network is fine... I think DNS. Maybe reverse
>>         resolution of
>>              your private IP address space assuming your requests are
>>         being made
>>              to/from private addresses? That's really just a shot in the
>>         dark
>>              because we don't have much to go on. I'd start thinking
>>         network and
>>              DNS, put in some debug, see what if anything is timing out.
>>
>>              Jim
>>
>>
>>         Sorry about the top post.
>>
>>         I've done the debugging on DNS.  If it try changing the
>>         IP/hostname I
>>         still get the error.  I think it's per-process though.  Once it
>>         starts
>>         to happen it's intermittent and gets worse, making me think
>>         depending
>>         which process I hit it will work or not until all processes are
>>         affected.
>>
>>         This is on FreeBSD using a jailed (virtualized) host.  I read
>> about
>>         apache/jails on OpenBSD having a config issue with DNS but it
>> seemed
>>         different than this.
>>
>>         It only seems to affect httpd, I can log in and ping from the
>> server
>>         just fine.
>>
>>
>>     Also, please reply to the list, not personal email addresses so
>>     everyone else gets the benefit of the thread, and maybe you get a
>>     better answer from someone other than me. :)
>>
>>     I'm not so sure you've eliminated DNS, yet.
>>
>>     What if from 192.168.0.222 you:
>>     dig -x 192.168.0.x
>>
>>     where 192.168.0.x is the IP addressing making the connection to
>>     192.168.0.222
>>
>>     Do you have reverse resolvers for your private address space or are
>>     the requests handled by the top level root servers?
>>
>>     Who is answering for that reverse resolution request?
>>     dig -x 192.168.0.x
>>     Is it your resolver or a root level like prisoner.iana.org
>>     <http://prisoner.iana.org>
>>
>>     Jim
>>
>>
>> Interesting, but it seems hard to believe that would be it.  I don't
>> have any other suspects though...
>>
>>
>> ; <<>> DiG 9.8.3-P3 <<>> -x 192.168.0.200
>> ;; global options: +cmd
>> ;; Got answer:
>> ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 20209
>> ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
>>
>> ;; QUESTION SECTION:
>> ;200.0.168.192.in-addr.arpa.INPTR
>>
>> ;; AUTHORITY SECTION:
>> 168.192.in-addr.arpa.10800INSOAlocalhost. nobody.invalid. 1 3600 1200
>> 604800 10800
>>
>> ;; Query time: 6 msec
>> ;; SERVER: 4.2.2.1#53(4.2.2.1)
>> ;; WHEN: Tue Apr 23 18:28:37 2013
>> ;; MSG SIZE  rcvd: 103
> You're using a public resolver... 4.2.2.1
> I'm not saying that's your problem, but I've had problems in the past
> where connections were slow or timed out doing a reverse lookup of my
> private address space. The problem went away after configuring my own
> resolvers to handle reverse lookups on my private address space.
>
> If you want to continue to use 4.2.2.1 or any public resolver as your
> resolver, that's not an option.
>
> If you have your own resolvers, this might help:
> http://www.sendmail.com/sm/open_source/tips/private_dns/
>
> Again... I'm still kind of shooting in the dark, so my confidence level
> on where I'm going with this is not high.
>
> You really should put some debug in or maybe a packet trace... is your
> server actually getting the request is where I would start.
>
> Does your ISP provide a resolver? Is there a reason you want to use
> 4.2.2.1 rather than your ISP's or your own or maybe at least Google's at
> 8.8.8.8?
>
> Jim
>

As a test, you could configure 192.168.0.200 in 192.168.0.222's /etc/hosts
Offhand, you could just make up a name for it.
192.168.0.200	just_testing

That might help confirm if reverse resolution is the issue as in normal 
configuration /etc/hosts is the first level of resolution prior to DNS 
being queried.

Jim

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