Mercurial > public > mercurial-scm > hg
comparison mercurial/changelog.py @ 50316:87f0155d68aa stable
revlog: improve the robustness of the splitting process
The previous "in-place" splitting, preserving the splitting on transaction
failure had a couple of issue in case of transaction rollback:
- a race windows that could still lead to a crash and data loss
- it corrupted the `fncache`.
So instead, we use a new approach that we summarized as "we do a backup of the
inline revlog pre-split, and we restore this in case of failure".
To make readers live easier, we don't overwrite the inline index file until
transaction finalization. (once the transaction get into its finalization phase,
it is not expected to rollback, unless some crash happens).
To do so, we write the index of the split index in a temporary file that we use
until transaction finalization. We also keep a backup of the initial inline file
to be able to rollback the split if needed.
As a result, transaction rollback cancel the split and no longer corrupt
fncache. We also no longer have a small inconsistency windows where the
transaction could be unrecoverable.
| author | Pierre-Yves David <pierre-yves.david@octobus.net> |
|---|---|
| date | Mon, 20 Mar 2023 11:52:17 +0100 |
| parents | 642e31cb55f0 |
| children | c690d2cc7f36 |
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| 50315:cf6e1d535602 | 50316:87f0155d68aa |
|---|---|
| 479 fp.write(b"".join(self._delaybuf)) | 479 fp.write(b"".join(self._delaybuf)) |
| 480 fp.close() | 480 fp.close() |
| 481 self._delaybuf = None | 481 self._delaybuf = None |
| 482 self._divert = False | 482 self._divert = False |
| 483 # split when we're done | 483 # split when we're done |
| 484 self._enforceinlinesize(tr) | 484 self._enforceinlinesize(tr, side_write=False) |
| 485 | 485 |
| 486 def _writepending(self, tr): | 486 def _writepending(self, tr): |
| 487 """create a file containing the unfinalized state for | 487 """create a file containing the unfinalized state for |
| 488 pretxnchangegroup""" | 488 pretxnchangegroup""" |
| 489 if self._docket: | 489 if self._docket: |
| 510 if self._divert: | 510 if self._divert: |
| 511 return True | 511 return True |
| 512 | 512 |
| 513 return False | 513 return False |
| 514 | 514 |
| 515 def _enforceinlinesize(self, tr): | 515 def _enforceinlinesize(self, tr, side_write=True): |
| 516 if not self._delayed: | 516 if not self._delayed: |
| 517 revlog.revlog._enforceinlinesize(self, tr) | 517 revlog.revlog._enforceinlinesize(self, tr, side_write=side_write) |
| 518 | 518 |
| 519 def read(self, nodeorrev): | 519 def read(self, nodeorrev): |
| 520 """Obtain data from a parsed changelog revision. | 520 """Obtain data from a parsed changelog revision. |
| 521 | 521 |
| 522 Returns a 6-tuple of: | 522 Returns a 6-tuple of: |