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From:Tuc at T-B-O-H Date:September 5 2005 1:43pm
Subject:Re: Connections with bad DNS cause lockups
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Hi,

	Ok. Is there a way to get a timestamp in the file too? If
this happens while I'm not near a machine I want to make sure I can
find the right time frame in the file.

		Thanks, Tuc

> 
> Hello.
> 
> When I suggested to create a trace file, I wanted to find the place
> where mysqld hangs. In my opinion, it is possible. You  should
> research the last entries at the end of the trace file (using tail,
> for example) after mysql has hung. I'm not sure if we are able to find
> any clues in the trace files when using clients with a good reverse.
> 
> 
> Tuc at T-B-O-H <ml@stripped> wrote:
> > Hi,
> > 
> >        I hacked the Makefile so that it would recompile it with
> > -debug on the version. I started it with "--debug" as part of the 
> > extra args passed to safe_mysqld. It started, and created a 
> > /tmp/mysqld.trace where its logging to.
> > 
> >        So far, no one with a broken reverse DNS has tried to
> > contact the server.... However, me with a good reverse but no
> > authority via the /etc/hosts.allow has gone against it 5 or
> > 6 times, and the log doesn't even show any evidence. 
> > 
> >        If it isn't showing any sort of logging of my illegal
> > attempt, I'm concerned it will not show any attempts from the 
> > hosts that are causing the problems.
> > 
> >                Thanks, Tuc
> > 
> >> 
> >> Hello.
> >> 
> >> 
> >> To make the suggestions, we should have enough amount of information.
> >> If your MySQL server isn't heavy loaded, create a trace file and find
> >> out the place where the new connections hang. See:
> >>   http://dev.mysql.com/doc/mysql/en/making-trace-files.html
> >> 
> >> 
> >> 
> >> Tuc at T-B-O-H <ml@stripped> wrote:
> >> >> 
> >> >> Hello.
> >> >> 
> >> >> In my opinion, we're a little kinked in this issue. Let's start
> over.
> >> >>
> >> >        :( Sorry. I've been told by the GF that I have a habit of
> >> > doing it to her too. 
> >> >>
> >> >> In one of your posts you mentioned that the server runs lots
> >> >> of other services besides the database. 
> >> >>
> >> >        Yes, according to my runbook, the server :
> >> > 
> >> >        1) Is an NFS server to 4 other servers for web traffic
> >> > and logging. 
> >> >        2) Is the primary MX server for 7 domains (About 100
> >> > emails a day)
> >> >        3) Runs a Listproc for 4 mailing lists (About 5 messages
> >> > a day to 60 people)
> >> >        4) Runs MySQL (Approx 98 queries per hour)
> >> >        5) Runs Seti@Home (2 processes)
> >> >        6) Runs an IMAP Server for 1 user who logs on 5-10 
> >> > minutes a day
> >> > 
> >> >        The server pushes about 120kb/s a second 
> >> > according to MRTG for all that.
> >> >>
> >> >> Why do you think that
> >> >> the cause of the server's weird behavior is MySQL?
> >> >>
> >> >        Maybe I wasn't clear about it. The server is running
> >> > perfectly. I'm running SETI on it since its normally bored out
> >> > of its ever loving mind. When someone with a missing or bad
> >> > reverse DNS (PTR) record attempts to connect to the MySQL
> >> > server, any other connection via either the socket or the
> >> > TCP socket ends up blocking and waiting. Every other service
> >> > on the machine is fine, but MySQL becomes completely
> >> > unresponsive. When I said "DOS", I meant only against MySQL.
> >> > The rest of the machine is fine to process anything it wants.
> >> >>
> >> >> Is server still
> >> >> working, but you are unable to reach it through the network, or it
> >> >> is completely hung?
> >> >>
> >> >        No other services are affected, only attempts to connect
> >> > to MySQL via the socket or TCP. This makes what little access there
> >> > is to the database (A searchable orchid database) stop, and monitoring
> >> > detects it down and pages out. 
> >> > 
> >> > 
> >> >                Thanks, Tuc 
> >> >> 
> >> >> >> 
> >> >> >> 
> >> >> >        So if thats the way (FreeBSD ports), then besides the
> already suggested
> >> >> > changing to pure IP, is there any other ways to stop the DOS?
> >> >> > 
> >> >> >                Thanks, Tuc
> >> >> > 

Thread
Connections with bad DNS cause lockupsTuc at T-B-O-H30 Aug
  • Re: Connections with bad DNS cause lockupsGleb Paharenko31 Aug
    • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H1 Sep
      • Re: Connections with bad DNS cause lockupsSGreen1 Sep
        • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H1 Sep
          • Re: Connections with bad DNS cause lockupsSGreen1 Sep
            • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H1 Sep
      • Re: Connections with bad DNS cause lockupsGleb Paharenko2 Sep
        • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H2 Sep
          • Re: Connections with bad DNS cause lockupsGleb Paharenko3 Sep
            • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H3 Sep
              • Re: Connections with bad DNS cause lockupsGleb Paharenko3 Sep
                • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H3 Sep
                  • Re: Connections with bad DNS cause lockupsGleb Paharenko5 Sep
                    • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H5 Sep
                      • Re: Connections with bad DNS cause lockupsGleb Paharenko5 Sep
                        • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H5 Sep
                    • Re: Connections with bad DNS cause lockupsTuc at T-B-O-H14 Sep