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Re: $Session object

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  • Josh Chamas
    ... Helmut is correct. I would like to add that since mod_perl & Apache are multi-process, they don t share memory, so all this session state is stored to
    Message 1 of 6 , Feb 4, 2004
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      Helmut Zeilinger wrote:
      > Hi Chris,
      >
      > the reason for the data size limit is, that the SDBM hash size
      > limit is 1024 bytes for the key + the value.
      >
      > You can store more data if you use DB_File or MLDBM::Sync::SDBM_File
      > for storing the data.
      >
      > But see "man Apache::ASP", Section "State Management" (StateDB).
      >
      > Regards
      >
      > Helmut
      >

      Helmut is correct. I would like to add that since mod_perl & Apache
      are multi-process, they don't share memory, so all this session state
      is stored to disk to allow multi-process data sharing. So basically,
      you want to keep the data going to disk lighter, and only store enough
      to allow your objects to be recreated in memory each request via
      constructors, & not serialize the object to disk/$Session fully each
      request/read/write.

      Consider that each time one does:

      $Session->{object} = {};

      you just wrote to disk. Though DB_File holds more than SDBM_File,
      it is much slower to do basic read/write operations for smaller
      bits of data, and accessing large blocks of data is obviously slow.

      Definitely read the MLDBM::Sync man page for a further analysis of this
      which is the internal state manager used for Apache::ASP.

      Regards,

      Josh

      ________________________________________________________________
      Josh Chamas, Founder phone:925-552-0128
      Chamas Enterprises Inc. http://www.chamas.com
      NodeWorks Link Checker http://www.nodeworks.com


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    • Chris Marschall
      Gentlemen, Thanks for the prompt feedback. Of course, the lack of shared memory (multi-threading) explains why it would have to commit all state information
      Message 2 of 6 , Feb 4, 2004
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        Gentlemen,

        Thanks for the prompt feedback.

        Of course, the lack of shared memory (multi-threading) explains why it
        would have to commit all state information for each request.

        Thanks also for the DB_File information.

        Much appreciated.

        Regards,

        Chris.

        On Wed, 4 Feb 2004, Josh Chamas wrote:

        > Helmut Zeilinger wrote:
        > > Hi Chris,
        > >
        > > the reason for the data size limit is, that the SDBM hash size
        > > limit is 1024 bytes for the key + the value.
        > >
        > > You can store more data if you use DB_File or MLDBM::Sync::SDBM_File
        > > for storing the data.
        > >
        > > But see "man Apache::ASP", Section "State Management" (StateDB).
        > >
        > > Regards
        > >
        > > Helmut
        > >
        >
        > Helmut is correct. I would like to add that since mod_perl & Apache
        > are multi-process, they don't share memory, so all this session state
        > is stored to disk to allow multi-process data sharing. So basically,
        > you want to keep the data going to disk lighter, and only store enough
        > to allow your objects to be recreated in memory each request via
        > constructors, & not serialize the object to disk/$Session fully each
        > request/read/write.
        >
        > Consider that each time one does:
        >
        > $Session->{object} = {};
        >
        > you just wrote to disk. Though DB_File holds more than SDBM_File,
        > it is much slower to do basic read/write operations for smaller
        > bits of data, and accessing large blocks of data is obviously slow.
        >
        > Definitely read the MLDBM::Sync man page for a further analysis of this
        > which is the internal state manager used for Apache::ASP.
        >
        > Regards,
        >
        > Josh
        >
        > ________________________________________________________________
        > Josh Chamas, Founder phone:925-552-0128
        > Chamas Enterprises Inc. http://www.chamas.com
        > NodeWorks Link Checker http://www.nodeworks.com
        >

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