Genezzo-Contrib-Clustered
=========================

Shared data cluster support for Genezzo

Genezzo is an extensible database with SQL and DBI.  It is written in Perl.
Basic routines inside Genezzo are overridden via Havok SysHooks.  Override
routines provide support for shared data clusters.  Routines
provide transactions, distributed locking, undo, and recovery.

INSTALLATION

To install this module type the following:

  perl Makefile.PL
  make
  make test
  make install

To prepare for use of Genezzo::Clustered

 genprepundo.pl

 gendba.pl
 >@havok.sql
 >@syshook.sql
 >@clustered.sql

LIMITATIONS

 This is pre-alpha software; don't use it to store any data you hope
 to see again!

 Transactions, Rollback, etc. are not fully implemented.  Process death
 and necessary cleanup is not detected.

DEPENDENCIES

This module requires these other modules and libraries:

 Genezzo
 FreezeThaw

 OpenDLM

SEE ALSO

 For more information, please visit the Genezzo homepage
 at http://www.genezzo.com

 also
 http://eric_rollins.home.mindspring.com/genezzo/ClusteredGenezzoDesign.html
 http://eric_rollins.home.mindspring.com/genezzo/cluster.html
 http://opendlm.sourceforge.net/

TODO

 1)   [Genezzo fix done]

 2)   [Genezzo update] Need a exception mechanism when SQL is run to catch
      errors such as running out of disk space.  Currently multi-row
      SQL statements can result in partial results on disk when system
      runs out of disk space.

 3)   Use new exception mechanism (above) to handle deadlock with DLM.
      Currently program exits on any error from OpenDLM.  Need to modify
      inline::C interface to provide deadlock return code distinct from
      other errors.  Need to modify GLock Perl code to throw SQL exception.

 4)   [Genezzo update done]

 5)   done.

 6)   [Genezzo update] Need way to invalidate entire buffer cache.
      Simply release all blocks, don't write them to disk (disk write
      should already have been done in commit case).

 7)   Invalidate buffer cache (using new mechanism above) before releasing
      all locks on commit or rollback.  Actually only invalidate
      non-system tablespace portion, see below.

 8)   [Genezzo update done]

 9)   done

 10)  [Genezzo fix] fix "mystery" writes.  These bogus writes create
      unnecessary write locks,  generate unnecessary undo, and confuse
      rollback code.  Solution may be to attach syshook to new attachment
      point instead of Genezzo::BufCa::DirtyScalar::STORE.  Yes, some of
      the writes are not "mysteries".  They occur when a pre-existing
      buffer cache block is reused -- the reloading of new data from disk
      or memory into the block triggers the STORE callback.  The cure
      is to attach the syshook in a more intelligent location that is
      aware of the different cases.

 11)  [Genezzo update] complete tablespace support.

 12)  Use tablespace support (above) to restrict locking to non-system
      tablespace tables.  Otherwise we need to lock additional blocks
      (for system tables) already read at startup prior to syshook
      initialization.  And locking system tables prevents other
      instances from running in parallel.  [this may not solve problems...]

 13)  [Genezzo update] add pre-havok command line param which specifies
      routine to run prior to opening database.

 14)  Use pre-havok (above) to perform recovery prior to opening database.
      Havok/syshook routines won't run if database cannot be opened due
      to corruption.  Also unlocked startup reads create race conditions.

 13)  [Genezzo redesign] Storing table directory and free space list in
      block zero of each tablespace prevents any concurrency of writes
      with reads.  Also cached structures become invalid whenever block
      zero is written.

 14)  [Genezzo refactoring done]

 15)  Done.

 99)  After the above, complete rest of development per Design Document:
  a)  [Done] Detect blocks needing recovery via process_id in block.
  b)  [Done] Recover dead processes
  c)  etc...

 100) Recognize incomplete undo blocks and read buddy block instead.

COPYRIGHT AND LICENCE

   Copyright (C) 2005 by Eric Rollins.  All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

Address bug reports and comments to [email protected]

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