- 20 May, 2020 2 commits
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Jan-Jaap Driessen authored
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Jan-Jaap Driessen authored
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- 31 Mar, 2020 1 commit
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Kirill Smelkov authored
ZODB tries to avoid saving empty transactions to storage on `transaction.commit()`. The way it works is: if no objects were changed during ongoing transaction, ZODB.Connection does not join current TransactionManager, and transaction.commit() performs two-phase commit protocol only on joined DataManagers. In other words if no objects were changed, no tpc_*() methods are called at all on ZODB.Connection at transaction.commit() time. This way application servers like Zope/ZServer/ERP5/... can have something as try: # process incoming request transaction.commit() # processed ok except: transaction.abort() # problem: log + reraise in top-level code to process requests without creating many on-disk transactions with empty data changes just because read-only requests were served. Everything is working as intended. However at storage level, FileStorage currently also checks whether transaction that is being committed also comes with empty data changes, and _skips_ saving transaction into disk *at all* for such cases, even if it has been explicitly told to commit the transaction via two-phase commit protocol calls done at storage level. This creates the situation, where contrary to promise in ZODB/interfaces.py(*), after successful tpc_begin/tpc_vote/tpc_finish() calls made at storage level, transaction is _not_ made permanent, despite tid of "committed" transaction being returned to caller. In other words FileStorage, when asked to commit a transaction, even if one with empty data changes, reports "ok" and gives transaction ID to the caller, without creating corresponding transaction record on disk. This behaviour is a) redundant to application-level avoidance to create empty transaction on storage described in the beginning, and b) creates problems: The first problem is that application that works at storage-level might be interested in persisting transaction, even with empty changes to data, just because it wants to save the metadata similarly to e.g. `git commit --allow-empty`. The other problem is that an application view and data in database become inconsistent: an application is told that a transaction was created with corresponding transaction ID, but if the storage is actually inspected, e.g. by iteration, the transaction is not there. This, in particular, can create problems if TID of committed transaction is reported elsewhere and that second database client does not find the transaction it was told should exist. I hit this particular problem with wendelin.core. In wendelin.core, there is custom virtual memory layer that keeps memory in sync with data in ZODB. At commit time, the memory is inspected for being dirtied, and if a page was changed, virtual memory layer joins current transaction _and_ forces corresponding ZODB.Connection - via which it will be saving data into ZODB objects - to join the transaction too, because it would be too late to join ZODB.Connection after 2PC process has begun(+). One of the format in which data are saved tries to optimize disk space usage, and it actually might happen, that even if data in RAM were dirtied, the data itself stayed the same and so nothing should be saved into ZODB. However ZODB.Connection is already joined into transaction and it is hard not to join it because joining a DataManager when the 2PC is already ongoing does not work. This used to work ok with wendelin.core 1, but with wendelin.core 2 - where separate virtual filesystem is also connected to the database to provide base layer for arrays mappings - this creates problem, because when wcfs (the filesystem) is told to synchronize to view the database @tid of committed transaction, it can wait forever waiting for that, or later, transaction to appear on disk in the database, creating application-level deadlock. I agree that some more effort might be made at wendelin.core side to avoid committing transactions with empty data at storage level. However the most clean way to fix this problem in my view is to fix FileStorage itself, because if at storage level it was asked to commit something, it should not silently skip doing so and dropping even non-empty metadata + returning ok and committed transaction ID to the caller. As described in the beginning this should not create problems for application-level ZODB users, while at storage-level the implementation is now consistently matching interface and common sense. ---- (*) tpc_finish: Finish the transaction, making any transaction changes permanent. Changes must be made permanent at this point. ... https://github.com/zopefoundation/ZODB/blob/5.5.1-35-gb5895a5c2/src/ZODB/interfaces.py#L828-L831 (+) https://lab.nexedi.com/kirr/wendelin.core/blob/9ff5ed32/bigfile/file_zodb.py#L788-822
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- 27 Mar, 2020 1 commit
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sblondon authored
Update package links from pypi.python.org to pypi.org
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- 26 Mar, 2020 1 commit
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Stéphane Blondon authored
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- 20 Mar, 2020 1 commit
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Éloi Rivard authored
Added newtdb link
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- 17 Mar, 2020 12 commits
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Éloi Rivard authored
Removed log.ini
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Éloi Rivard authored
Use python3 for coverage
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Éloi Rivard authored
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Éloi Rivard authored
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Éloi Rivard authored
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Éloi Rivard authored
Some documentation love
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Éloi Rivard authored
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Éloi Rivard authored
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Éloi Rivard authored
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Éloi Rivard authored
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Éloi Rivard authored
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Éloi Rivard authored
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- 06 Mar, 2020 1 commit
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Jason Madden authored
Simplify appveyor.yml.
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- 05 Mar, 2020 4 commits
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Jason Madden authored
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Jason Madden authored
Fixes issues with zc.buildout and version pins (https://github.com/zopefoundation/ZODB/pull/295#issuecomment-593805066)
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Jason Madden authored
Fix test compatibility with persistent 4.6; test CPython with PURE_PYTHON
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Jason Madden authored
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- 23 Jan, 2020 1 commit
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Julien Muchembled authored
Fixes #290
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- 16 Jan, 2020 1 commit
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Jens W. Klein authored
fix #292 improve volatile attribute documentation
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- 02 Jan, 2020 1 commit
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Jens W. Klein authored
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- 30 Dec, 2019 1 commit
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Jens W. Klein authored
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- 12 Dec, 2019 1 commit
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Jason Madden authored
Fix tests with transaction 3.0.
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- 11 Dec, 2019 1 commit
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Jason Madden authored
Only test changes were required, no production code changes.
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- 09 Dec, 2019 1 commit
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Tim Gates authored
Closes #287
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- 21 Nov, 2019 1 commit
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Jürgen Gmach authored
* Add support for Python 3.8. modified: .travis.yml modified: CHANGES.rst modified: setup.py modified: tox.ini modified: appveyor.yml
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- 27 Sep, 2019 3 commits
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Jason Madden authored
Tests: Always pass bytes for the previous serial param of storage.store
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Jason Madden authored
This is consistent with what persistent.Persistent and Connection actually do. RelStorage previously had a special case just for these tests.
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Jason Madden authored
Make TmpStore implement its own getSize
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- 26 Sep, 2019 1 commit
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Jason Madden authored
This is consistent with its __len__ and provides a better figure for existing logging. Fixes #282
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- 23 Sep, 2019 2 commits
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Julien Muchembled authored
IStorage implementations used to do this task themselves which leads to code duplication and sometimes bugs (one was fixed recently in NEO). Like for object serialization, this should be done by the upper layer (Connection). This commit also provides a way to get raw extensions data while iterating over transactions (this is actually the original purpose[2]). So far, extension data could only be retrieved unpickled, which caused several problems: - tools like `zodb dump` [1] cannot dump data exactly as stored on a storage. This makes database potentially not bit-to-bit identical to its original after restoring from such dump. - `zodb dump` output could be changing from run to run on the same database. This comes from the fact that e.g. python dictionaries are unordered and so when pickling a dict back to bytes the result could be not the same as original. ( this problem can be worked-around partly to work reliably for e.g. dict with str keys - by always emitting items in key sorted order, but it is hard to make it work reliably for arbitrary types ) Both issues make it hard to verify integrity of database at the lowest possible level after restoration, and make it hard to verify bit-to-bit compatibility with non-python ZODB implementations. For this, TransactionMetaData gets a new 'extension_bytes' attribute and and common usage becomes: * Application committing a transaction: - 'extension' is set with a dictionary - the storage gets the bytes via 'extension_bytes' * Iteration: - the storage passes bytes as 'extension' parameter of TransactionMetaData - the application can get extension data either as bytes ('extension_bytes') or deserialized ('extension'): in the former case, no deserialization happens and the returned value is exactly what was passed by the storage [1] https://lab.nexedi.com/nexedi/zodbtools [2] https://github.com/zopefoundation/ZODB/pull/183Co-Authored-By: Kirill Smelkov <kirr@nexedi.com>
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Julien Muchembled authored
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- 20 Sep, 2019 2 commits
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Jason Madden authored
TransactionalUndo closes storages it opens.
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Jason Madden authored
Fixes #268.
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- 09 May, 2019 1 commit
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Jason Madden authored
Fix ResourceWarnings seen during testing, and a testrunner orphaned thread warning
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