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 or documentation] Need to be able to add metadata to DB data blocks. Need to update block checksum, etc. when this is done. 5) Use block metadata (above) to add process_id to each modified block, and later clear process_id. This is done in or near Genezzo::BufCa::DirtyScalar::STORE. May need to register callback on different routine to prevent endless recursion. 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). Also need to be able to release single blocks on demand -- this would be used when async-callback lock request support is added. 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. 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. 99) After the above, complete rest of development per Design Document: a) Detect blocks needing recovery via process_id in block b) Recover dead processes c) etc... 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 rollins@acm.org