CHANGES.txt

================
 Change History
================

3.9.0 (2008-??-??)
====================

New Features
------------

- The connection now estimates the object size based on its pickle size
  and informs the cache about size changes.

  The database got additional configurations options (`cache-size-bytes`
  and `historical-cache-size-bytes`) to limit the
  cache size based on the estimated total size of cached objects.
  The default values are 0 which has the interpretation "do not limit
  based on the total estimated size".
  There are corresponding methods to read and set the new configuration
  parameters.

  XXX There are known issues with this implementation that need to be
  sorted out before it is "released".

3.9.0a8 (2008-12-15)
====================

New Features
------------

- Made ZEO Client Blob Cache control a bit more rational.  Now, when
  checking the cache size, the target is::

     blob-cache-size * (100 - blob-cache-size-check) / 100

  The makes it far more likely (but doesn't guarantee) that the blob
  cache size will remain under the maximum.  

  The blob-cache-size check was reduced to 10%.

Bugs Fixed
----------

- Fixed a bug in the logic to reduce the blob cache size.

3.9.0a7 (2008-12-05)
====================

New Features
------------

- The Blob open method now supports a new mode, 'c', to open committed
  data for reading as an ordinary file, rather than as a blob file.
  The ordinary file may be used outside the current transaction and
  even after the blob's database connection has been closed.

- ClientStorage now provides blob cache management. When using
  non-shared blob directories, you can set a target cache size and the
  cache will periodically be reduced to the target size.

  The client blob directory layout has changed.  If you have existing
  non-shared blob directories, you will have to remove them. 

Bugs Fixed
----------

- Starting ClientStorages sometimes failed with non-new but empty
  cache files.

3.9.0a6 (2008-11-30)
====================

New Features
------------

- ZODB 3.9 ZEO clients can connect to ZODB 3.8 servers.

Bug Fixes
---------

- ZODB 3.8 clients couldn't talk to  ZODB 3.9 servers.

- The history method on ZEO clients failed.


3.9.0a5 (2008-11-21)
====================

New Features
------------

- When a ZEO cache is stale and would need verification, a
  ZEO.interfaces.StaleCache event is published (to zope.event).
  Applications may handle this event and take action such as exiting
  the application without verifying the cache or starting cold.

- There's a new convenience function, ZEO.DB, for creating databases
  using ZEO Client Storages.  Just call ZEO.DB with the same arguments
  you would otherwise pass to ZEO.ClientStorage.ClientStorage::

    import ZEO
    db = ZEO.DB(('some_host', 8200)) 

- Object saves are a little faster

- The previous (ZODB 3.8) ZEO client-cache format is supported.
  The newer cache format introduced in ZODB 3.9.0a1 is no-longer
  supported. Cache files can still be larger than 4G.  Cache file
  sizes can now be changed.

- When configuring storages in a storage server, the storage name now
  defaults to "1".  In the overwhelmingly common case that a single
  storage, the name can now be ommitted.

Bug Fixes
---------

- ZEO client transaction iterators weren't properly handled after on
  disconnects.

- The code to drop a ZEO client cache rather than verifying didn't
  drop it and didn't leave the client storage in a valid state.

3.9.0a4 (2008-11-06)
====================

Bug Fixes
---------

- DemoStorage could sometimes hand out the same new object id more
  than once.

3.9.0a3 (2008-11-04)
====================

New Features
------------

- FileStorage now provides optional garbage collection.  A 'gc'
  keyword option can be passed to the pack method.  A false value
  prevents garbage collection.

- The FileStorage constructor now provides a boolean pack_gc option,
  which defaults to True, to control whether garbage collection is
  performed when packing by default. This can be overridden with the
  gc option to the pack method.

  The ZConfig configuration for FileStorage now includes a pack-gc
  option, corresponding to the pack_gc constructor argument.

- The FileStorage constructor now has a packer keyword argument that
  allows an alternative packer to be supplied.

  The ZConfig configuration for FileStorage now includes a packer
  option, corresponding to the packer constructor argument.

Bug Fixes
---------

- DemoStorage could sometimes hand out the same new object id more
  than once.

3.9.0a2 (2008-10-31)
====================

Bug Fixes
---------

- MappingStorage hung when committing a transaction *after* committing
  an empty transaction.

3.9.0a1 (2008-10-29)
====================

New Features
------------

- MappingStorage now supports multi-version concurrency control and
  iteration and provides a better storage implementation example.

- DemoStorage has a number of new features:

  - The ability to use a separate storage, such as a file storage to
    store changes

  - Blob support

  - Multi-version concurrency control and iteration

  - Explicit support dfor demo-storage stacking via push and pop methods.

- Wen calling ZODB.DB to create a database, you can now pass a file
  name, rather than a storage to use a file storage.

- Added support for copying and recovery of blob storages:

  - Added a helper function, ZODB.blob.is_blob_record for testing whether
    a data record is for a blob.  This can be used when iterating over a
    storage to detect blob records so that blob data can be copied.

    In the future, we may want to build this into a blob-aware
    iteration interface, so that records get blob file attributes
    automatically.

  - Added the IBlobStorageRestoreable interfaces for blob storages
    that support recovery via a restoreBlob method.

  - Updated ZODB.blob.BlobStorage to implement
    IBlobStorageRestoreable and to have a copyTransactionsFrom method
    that also copies blob data.

- New `ClientStorage` configuration option `drop_cache_rather_verify`.
  If this option is true then the ZEO client cache is dropped instead of
  the long (unoptimized) verification. For large caches, setting this
  option can avoid effective downtimes in the order of hours when
  the connection to the ZEO server was interrupted for a longer time.

- Cleaned-up the storage iteration API and provided an iterator implementation
  for ZEO.

- Versions are no-longer supported.

- ZEO cache files can be larger than 4G. Note that older ZEO cache
  files are not supported.

- Document conflict resolution (see ZODB/ConflictResolution.txt).

- Support multidatabase references in conflict resolution.

- Make it possible to examine oid and (in some situations) database
  name of persistent object references during conflict resolution.

- Moved 'transaction' module out of ZODB.
  ZODB depends upon this module, but it must be installed separately.

- ZODB installation now requires setuptools.

- Added `offset` information to output of `fstail`
  script. Added test harness for this script.

- Added support for read-only, historical connections based
  on datetimes or serials (TIDs).  See
  src/ZODB/historical_connections.txt.

- Removed the ThreadedAsync module.

- Now depend on zc.lockfile

Bugs Fixed
----------

- Fix for bug #251037: Make packing of blob storages non-blocking.

- Fix for bug #220856: Completed implementation of ZEO authentication.

- Fix for bug #184057: Make initialisation of small ZEO client file cache
  sizes not fail.

- Fix for bug #184054: MappingStorage used to raise a KeyError during `load`
  instead of a POSKeyError.

- Fixed bug in Connection.TmpStore: load() would not defer to the backend
  storage for loading blobs.

- Fix for bug #181712: Make ClientStorage update `lastTransaction` directly
  after connecting to a server, even when no cache verification is necessary.

- Fixed bug in blob filesystem helper: the `isSecure` check was inversed.

- Fixed bug in transaction buffer: a tuple was unpacked incorrectly in
  `clear`.

- Bugfix the situation in which comparing persistent objects (for
  instance, as members in BTree set or keys of BTree) might cause data
  inconsistency during conflict resolution.

- Fixed bug 153316: persistent and BTrees were using `int`
  for memory sizes which caused errors on x86_64 Intel Xeon machines
  (using 64-bit Linux).
  
- Fixed small bug that the Connection.isReadOnly method didn't
  work after a savepoint.

- Bug #98275: Made ZEO cache more tolerant when invalidating current
  versions of objects.

- Fixed a serious bug that could cause client I/O to stop
  (hang). This was accomonied by a critical log message along the
  lines of: "RuntimeError: dictionary changed size during iteration".

- Fixed bug #127182: Blobs were subclassable which was not desired.

- Fixed bug #126007: tpc_abort had untested code path that was
  broken.

- Fixed bug #129921: getSize() function in BlobStorage could not
  deal with garbage files

- Fixed bug in which MVCC would not work for blobs.

- Fixed bug in ClientCache that occurred with objects larger than the total
  cache size.

3.8.1b9 (2008-??-??)
====================

Bugs Fixed:

- When an error occured attempting to lock a file and logging of said error was
  enabled.

3.8.1b8 (2008-09-22
====================

Bugs Fixed:

- FileStorages previously saved indexes after a certain
  number of writes.  This was done during the last phase of two-phase
  commit, which made this critical phase more subject to errors than
  it should have been.  Also, for large databases, saves were done so
  infrequently as to be useless.  The feature was removed to reduce
  the chance for errors during the last phase of two-phase commit.

- File storages previously kept an internal object id to
  transaction id mapping as an optimization. This mapping caused
  excessive memory usage and failures during the last phase of
  two-phase commit. This optimization has been removed.

- Refactored handling of invalidations on ZEO clients to fix
  a possible ordering problem for invalidation messages.

- An ZEO cache internal data structure can get out of sync
  with the data in a way that prevents data from being loaded into the
  cache. We don't yet know why, but added an exception handler to
  prevent this error from being fatal.

- Fixed setup.py use of setuptools vs distutils, so .c and .h
  files are included in the bdist_egg.

- On many systems, it was impossible to create more than 32K
  blobs. Added a new blob-directory layout to work around this
  limitation.


3.8.1b7 (2008-08-23)
====================

Bugs Fixed:

- Fixed a bug, introduced in an earlier beta, that allowed
  clients to connect to out of date servers.

- Fixed bug that could lead to memory errors due to the use
  of a Python dictionary for a mapping that can grow large.

- Fixed bug #251037: Made packing of blob storages non-blocking.

3.8.1b6 (2008-07-24)
====================

Bugs Fixed:

- Fixed a bug that could cause InvalidObjectReference errors
  for objects that were explicitly added to a database if the object
  was modified after a savepoint that added the object.

3.8.1b5 (2008-07-14)
====================

Bugs Fixed:

- Fixed several bugs that caused ZEO cache corruption when connecting
  to servers. These bugs affected both persistent and non-persistent caches. 

- Improved the the ZEO client shutdown support to try to
  avoid spurious errors on exit, especially for scripts, such as zeopack.

3.8.1b4 (2008-05-23)
====================

Bugs Fixed:

- Packing failed for databases containing cross-database references.

3.8.1b3 (2008-05-14)
====================

Bugs Fixed:

- Cross-database references to databases with empty names
  weren't constructed properly.

3.8.1b2 (2008-05-13)
====================

Bugs Fixed:

- The cache used an excessive amount of memory, causing applications
  with large caches to exhaust available memory. 

3.8.1b1 (2008-05-08)
====================

Bugs Fixed:

- Fixed a number of bugs in the handling of persistent ZEO caches:

  - Cache records are written in several steps.  If a process exits
    after writing begins and before it is finishes, the cache will be
    corrupt on restart.  The way records are writted was changed to
    make cache record updates atomic.

  - There was no lock file to prevent opening a cache multiple times
    at once, which would lead to corruption.  Persistent caches now
    use lock files, in the same way that file storages do.

  - A bug in the cache-opening logic led to cache failure in the
    unlikely event that a cache has no free blocks.

- When using ZEO Client Storages, Errors occured when trying to store
  objects too big to fit in the ZEO cache file.

- Fixed bug in blob filesystem helper: the `isSecure` check was inversed.

- Fixed bug in transaction buffer: a tuple was unpacked incorrectly in
  `clear`.

- Fixed bug in Connection.TmpStore: load() would not defer to the
  backend storage for loading blobs.

- Fixed bug #190884: Wrong reference to `POSKeyError` caused NameError.

- Completed implementation of ZEO authentication. This fixes issue 220856.