100% CPU load : how to investigate?

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  • Vincent Delporte
    #1

    100% CPU load : how to investigate?

    Hello

    Someone I know is running some Web 2.0-type web site that lives on a
    shared host, and is experiencing 100% CPU load after a few hours. At
    this point, his provider couldn't tell if it's due to a DoS attack, or
    a bug in his application.

    1. For the DoS thing, I assume looking at the log files should be
    enough to tell if it's the problem is due to a suspicious rise in the
    number of connections at some point.

    2. As for bugs, are there tools available for PHP that can monitor an
    application and reveal bugs that could explain this CPU load?

    Thank you.
    Tags: None
    • Erwin Moller
      #2
      Re: 100% CPU load : how to investigate?

      Vincent Delporte wrote:
      Hello
      >
      Someone I know is running some Web 2.0-type web site that lives on a
      shared host, and is experiencing 100% CPU load after a few hours. At
      this point, his provider couldn't tell if it's due to a DoS attack, or
      a bug in his application.
      Web2. A very vague description. :P
      >
      1. For the DoS thing, I assume looking at the log files should be
      enough to tell if it's the problem is due to a suspicious rise in the
      number of connections at some point.
      Yes.
      Simply check the number of requests. A DDos should be found easily (before
      crashing).
      >
      2. As for bugs, are there tools available for PHP that can monitor an
      application and reveal bugs that could explain this CPU load?
      Yes. A few debuggers/profilers are out there.
      just type 'debugger php' in google to get them.
      A very well known one is the DBG debugger.

      I understood Zend has a good one, but you have to buy it.
      I didn't buy Zend Studio (yet), but am considering it. I hear only good
      things from people in here. :)

      or check here: http://drupal.org/node/1466

      Regards,
      Erwin Moller
      >
      Thank you.

        Comment

        • Vincent Delporte
          #3
          Re: 100% CPU load : how to investigate?

          On Tue, 13 Mar 2007 15:52:25 +0100, Erwin Moller
          <since_humans_r ead_this_I_am_s pammed_too_much @spamyourself.c omwrote:
          >Web2. A very vague description. :P
          Some kind of social site :-)
          >Simply check the number of requests. A DDos should be found easily (before
          >crashing).
          Will do.
          >Yes. A few debuggers/profilers are out there.
          >just type 'debugger php' in google to get them.
          >A very well known one is the DBG debugger.
          Thanks for the info. I assume it's more a profiler than a debugger.
          Hopefully, they're easy to add to a production site without breaking
          anything, and that it will easily show what is causing this surge in
          CPU load after hours of normal operation.

            Comment

            • Toby A Inkster
              #4
              Re: 100% CPU load : how to investigate?

              Vincent Delporte wrote:
              Someone I know is running some Web 2.0-type web site that lives on a
              shared host, and is experiencing 100% CPU load after a few hours.
              I would suggest that the number one thing to check is:

              /usr/bin/top

              to establish exactly what process is causing the big CPU usage. Your next
              stage of investigation will depend on what "top" tells you.

              --
              Toby A Inkster BSc (Hons) ARCS
              Contact Me ~ http://tobyinkster.co.uk/contact
              Geek of ~ HTML/SQL/Perl/PHP/Python*/Apache/Linux

              * = I'm getting there!

                Comment

                • Toby A Inkster
                  #5
                  Re: 100% CPU load : how to investigate?

                  Vincent Delporte wrote:
                  Some kind of social site
                  These sorts of things usually develop into having some pretty big database
                  tables.

                  Do you have any "big" tables (say, 2000 rows or more)? Which columns do
                  you routinely query those big tables by, or join them on? Are those columns
                  indexed?

                  Are you using inappropriate data types? (e.g. Storing dates in a varchar
                  field, which although possible, is very inefficient for queries.)

                  Do you unnecessarily use "SELECT * FROM ..." when "SELECT x, y FROM ..."
                  would suffice?

                  --
                  Toby A Inkster BSc (Hons) ARCS
                  Contact Me ~ http://tobyinkster.co.uk/contact
                  Geek of ~ HTML/SQL/Perl/PHP/Python*/Apache/Linux

                  * = I'm getting there!

                    Comment

                    • Vincent Delporte
                      #6
                      Re: 100% CPU load : how to investigate?

                      On Tue, 13 Mar 2007 15:16:49 +0000, Toby A Inkster
                      <usenet200703@t obyinkster.co.u kwrote:
                      >These sorts of things usually develop into having some pretty big database
                      >tables.
                      Will forward your suggestions, including "top" (although it's a shared
                      host, so probably no shell).

                      FWIW, it works fine for hours at a time, and poof. At this point, it
                      is unknown if it's a DoS or some bug in the code that would only show
                      after... a while.

                        Comment

                        • Toby A Inkster
                          #7
                          Re: 100% CPU load : how to investigate?

                          Vincent Delporte wrote:
                          although it's a shared host, so probably no shell
                          If it's a shared host, then what makes you think that it's your friend's
                          site that is using all the CPU? It could be another customer's site on the
                          same server.

                          --
                          Toby A Inkster BSc (Hons) ARCS
                          Contact Me ~ http://tobyinkster.co.uk/contact
                          Geek of ~ HTML/SQL/Perl/PHP/Python*/Apache/Linux

                          * = I'm getting there!

                            Comment

                            • Vincent Delporte
                              #8
                              Re: 100% CPU load : how to investigate?

                              On Tue, 13 Mar 2007 17:51:09 +0000, Toby A Inkster
                              <usenet200703@t obyinkster.co.u kwrote:
                              >If it's a shared host, then what makes you think that it's your friend's
                              >site that is using all the CPU? It could be another customer's site on the
                              >same server.
                              According to the hoster, it's his site that's causing the problem. I
                              assume they have monitoring tools that tells them whose processes are
                              using the host's resources.

                                Comment

                                • Kimmo Laine
                                  #9
                                  Re: 100% CPU load : how to investigate?

                                  Erwin Moller kirjoitti:
                                  Vincent Delporte wrote:
                                  >
                                  >Hello
                                  >>
                                  >Someone I know is running some Web 2.0-type web site that lives on a
                                  >shared host, and is experiencing 100% CPU load after a few hours. At
                                  >this point, his provider couldn't tell if it's due to a DoS attack, or
                                  >a bug in his application.
                                  >
                                  Web2. A very vague description. :P
                                  I suppose the performance hit comes from the extrem popularity of the
                                  website, after all, it's web 2.0 for crying out loud! ;)


                                  --
                                  "En ole paha ihminen, mutta omenat ovat elinkeinoni." -Perttu Sirviö
                                  spam@outolempi. net | Gedoon-S @ IRCnet | rot13(xvzzb@bhg byrzcv.arg)

                                    Comment

                                    • Vincent Delporte
                                      #10
                                      Re: 100% CPU load : how to investigate?

                                      On Tue, 13 Mar 2007 21:00:58 +0200, Kimmo Laine <spam@outolempi .net>
                                      wrote:
                                      >I suppose the performance hit comes from the extrem popularity of the
                                      >website, after all, it's web 2.0 for crying out loud! ;)
                                      Nope. The same site would crawl to a snail's space with about 40
                                      concurrent users, while it can easily handle 200 users after being
                                      moved to an hoster, even though both servers where shared. Guess it
                                      was due to configuration.

                                      We still have to investigate why the new host sometimes ends up using
                                      100% CPU time, though.

                                        Comment

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