[PATCH v4 1/3] models: Use database constraints to prevent split Series
Daniel Axtens
dja at axtens.net
Sun Dec 8 02:13:21 AEDT 2019
> Currently, the 'SeriesReference' object has a unique constraint on the
> two fields it has, 'series', which is a foreign key to 'Series', and
> 'msgid'. This is the wrong constraint. What we actually want to enforce
> is that a patch, cover letter or comment is referenced by a single
> series, or rather a single series per project the submission appears on.
> As such, we should be enforcing uniqueness on the msgid and the project
> that the patch, cover letter or comment belongs to.
OK, so I've been working on this and making good progress.
My fundamental issue with the current design, and this extension of it,
is that we're ignoring or working against the tools that databases
provide for concurrency. This patch is an improvement, no doubt, but I'd
really like to solve it properly.
Because we have multiple processes operating on the database - processes
without external syncronisation - we need to rely on the database to
provide the synchronisation primitive. Currently we're doing things like
asking the database to check if something exists and then creating it if
it does not. This is embeds TOCTOU problems, similar to the ones I fixed
for Person creation a while back. What we should be doing is
get_or_create style - basically more aggressively attempting to create
the thing we need and if that fails, then do the lookup for the existing
object.
This design pervades the series parser. It doesn't generally bite us
because we generally, more or less, parse in series.
I'm basically refactoring the parser to be
'try-creating-and-catch-failures' rather than
'lookup-and-create-if-missing'. It is a bit tricky but I think I'm at
least 80% of the way there.
I would be happy to leave my series parsing rework and Mete's work to a
2.3, or I'd be happy to try and grind through, get these done, and make
2.2 the final release in the 2.x series. What do you think?
Regards,
Daniel
Stephen Finucane <stephen at that.guru> writes:
>
> This requires adding a new field to the object, 'project', since it's
> not possible to do something like the following:
>
> unique_together = [('msgid', 'series__project')]
>
> This is detailed here [1]. In addition, the migration needs a precursor
> migration step to merge any broken series.
>
> [1] https://stackoverflow.com/a/4440189/613428
>
> Signed-off-by: Stephen Finucane <stephen at that.guru>
> Closes: #241
> Cc: Daniel Axtens <dja at axtens.net>
> Cc: Petr Vorel <petr.vorel at gmail.com>
> ---
> v4:
> - Further tweaks to logging
> v3:
> - Improve logging
> ---
> .../0038_unique_series_references.py | 121 +++++++++++++++++
> patchwork/models.py | 6 +-
> patchwork/parser.py | 123 +++++++++---------
> patchwork/tests/test_parser.py | 9 +-
> patchwork/tests/utils.py | 6 +-
> 5 files changed, 199 insertions(+), 66 deletions(-)
> create mode 100644 patchwork/migrations/0038_unique_series_references.py
>
> diff --git a/patchwork/migrations/0038_unique_series_references.py b/patchwork/migrations/0038_unique_series_references.py
> new file mode 100644
> index 00000000..91799020
> --- /dev/null
> +++ b/patchwork/migrations/0038_unique_series_references.py
> @@ -0,0 +1,121 @@
> +from django.db import connection, migrations, models
> +from django.db.models import Count
> +import django.db.models.deletion
> +
> +
> +def merge_duplicate_series(apps, schema_editor):
> + SeriesReference = apps.get_model('patchwork', 'SeriesReference')
> + Patch = apps.get_model('patchwork', 'Patch')
> +
> + msgid_seriesrefs = {}
> +
> + # find all SeriesReference that share a msgid but point to different series
> + # and decide which of the series is going to be the authoritative one
> + msgid_counts = (
> + SeriesReference.objects.values('msgid')
> + .annotate(count=Count('msgid'))
> + .filter(count__gt=1)
> + )
> + for msgid_count in msgid_counts:
> + msgid = msgid_count['msgid']
> + chosen_ref = None
> + for series_ref in SeriesReference.objects.filter(msgid=msgid):
> + if series_ref.series.cover_letter:
> + if chosen_ref:
> + # I don't think this can happen, but explode if it does
> + raise Exception(
> + "Looks like you've got two or more series that share "
> + "some patches but do not share a cover letter. Unable "
> + "to auto-resolve."
> + )
> +
> + # if a series has a cover letter, that's the one we'll group
> + # everything under
> + chosen_ref = series_ref
> +
> + if not chosen_ref:
> + # if none of the series have cover letters, simply use the last
> + # one (hint: this relies on Python's weird scoping for for loops
> + # where 'series_ref' is still accessible outside the loop)
> + chosen_ref = series_ref
> +
> + msgid_seriesrefs[msgid] = chosen_ref
> +
> + # reassign any patches referring to non-authoritative series to point to
> + # the authoritative one, and delete the other series; we do this separately
> + # to allow us a chance to raise the exception above if necessary
> + for msgid, chosen_ref in msgid_seriesrefs.items():
> + for series_ref in SeriesReference.objects.filter(msgid=msgid):
> + if series_ref == chosen_ref:
> + continue
> +
> + # update the patches to point to our chosen series instead, on the
> + # assumption that all other metadata is correct
> + for patch in Patch.objects.filter(series=series_ref.series):
> + patch.series = chosen_ref.series
> + patch.save()
> +
> + # delete the other series (which will delete the series ref)
> + series_ref.series.delete()
> +
> +
> +def copy_project_field(apps, schema_editor):
> + if connection.vendor == 'postgresql':
> + schema_editor.execute(
> + """
> + UPDATE patchwork_seriesreference
> + SET project_id = patchwork_series.project_id
> + FROM patchwork_series
> + WHERE patchwork_seriesreference.series_id = patchwork_series.id
> + """
> + )
> + elif connection.vendor == 'mysql':
> + schema_editor.execute(
> + """
> + UPDATE patchwork_seriesreference, patchwork_series
> + SET patchwork_seriesreference.project_id = patchwork_series.project_id
> + WHERE patchwork_seriesreference.series_id = patchwork_series.id
> + """
> + ) # noqa
> + else:
> + SeriesReference = apps.get_model('patchwork', 'SeriesReference')
> +
> + for series_ref in SeriesReference.objects.all().select_related(
> + 'series'
> + ):
> + series_ref.project = series_ref.series.project
> + series_ref.save()
> +
> +
> +class Migration(migrations.Migration):
> +
> + dependencies = [('patchwork', '0037_event_actor')]
> +
> + operations = [
> + migrations.RunPython(
> + merge_duplicate_series, migrations.RunPython.noop, atomic=False
> + ),
> + migrations.AddField(
> + model_name='seriesreference',
> + name='project',
> + field=models.ForeignKey(
> + null=True,
> + on_delete=django.db.models.deletion.CASCADE,
> + to='patchwork.Project',
> + ),
> + ),
> + migrations.AlterUniqueTogether(
> + name='seriesreference', unique_together={('project', 'msgid')}
> + ),
> + migrations.RunPython(
> + copy_project_field, migrations.RunPython.noop, atomic=False
> + ),
> + migrations.AlterField(
> + model_name='seriesreference',
> + name='project',
> + field=models.ForeignKey(
> + on_delete=django.db.models.deletion.CASCADE,
> + to='patchwork.Project',
> + ),
> + ),
> + ]
> diff --git a/patchwork/models.py b/patchwork/models.py
> index 7f0efd48..dbaff024 100644
> --- a/patchwork/models.py
> +++ b/patchwork/models.py
> @@ -79,7 +79,8 @@ class Project(models.Model):
> webscm_url = models.CharField(max_length=2000, blank=True)
> list_archive_url = models.CharField(max_length=2000, blank=True)
> list_archive_url_format = models.CharField(
> - max_length=2000, blank=True,
> + max_length=2000,
> + blank=True,
> help_text="URL format for the list archive's Message-ID redirector. "
> "{} will be replaced by the Message-ID.")
> commit_url_format = models.CharField(
> @@ -787,6 +788,7 @@ class SeriesReference(models.Model):
> required to handle the case whereby one or more patches are
> received before the cover letter.
> """
> + project = models.ForeignKey(Project, on_delete=models.CASCADE)
> series = models.ForeignKey(Series, related_name='references',
> related_query_name='reference',
> on_delete=models.CASCADE)
> @@ -796,7 +798,7 @@ class SeriesReference(models.Model):
> return self.msgid
>
> class Meta:
> - unique_together = [('series', 'msgid')]
> + unique_together = [('project', 'msgid')]
>
>
> class Bundle(models.Model):
> diff --git a/patchwork/parser.py b/patchwork/parser.py
> index c424729b..c0084cc0 100644
> --- a/patchwork/parser.py
> +++ b/patchwork/parser.py
> @@ -16,6 +16,7 @@ import re
>
> from django.contrib.auth.models import User
> from django.db.utils import IntegrityError
> +from django.db import transaction
> from django.utils import six
>
> from patchwork.models import Comment
> @@ -256,16 +257,9 @@ def _find_series_by_references(project, mail):
> for ref in refs:
> try:
> return SeriesReference.objects.get(
> - msgid=ref[:255], series__project=project).series
> + msgid=ref[:255], project=project).series
> except SeriesReference.DoesNotExist:
> continue
> - except SeriesReference.MultipleObjectsReturned:
> - # FIXME: Open bug: this can happen when we're processing
> - # messages in parallel. Pick the first and log.
> - logger.error("Multiple SeriesReferences for %s in project %s!" %
> - (ref[:255], project.name))
> - return SeriesReference.objects.filter(
> - msgid=ref[:255], series__project=project).first().series
>
>
> def _find_series_by_markers(project, mail, author):
> @@ -1092,47 +1086,65 @@ def parse_mail(mail, list_id=None):
> except IntegrityError:
> raise DuplicateMailError(msgid=msgid)
>
> - # if we don't have a series marker, we will never have an existing
> - # series to match against.
> - series = None
> - if n:
> - series = find_series(project, mail, author)
> + for attempt in range(1, 11): # arbitrary retry count
> + try:
> + with transaction.atomic():
> + # if we don't have a series marker, we will never have an
> + # existing series to match against.
> + series = None
> + if n:
> + series = find_series(project, mail, author)
> + else:
> + x = n = 1
> +
> + # We will create a new series if:
> + # - there is no existing series to assign this patch to, or
> + # - there is an existing series, but it already has a patch
> + # with this number in it
> + if not series or Patch.objects.filter(
> + series=series, number=x).count():
> + series = Series.objects.create(
> + project=project,
> + date=date,
> + submitter=author,
> + version=version,
> + total=n)
> +
> + # NOTE(stephenfin) We must save references for series.
> + # We do this to handle the case where a later patch is
> + # received first. Without storing references, it would
> + # not be possible to identify the relationship between
> + # patches as the earlier patch does not reference the
> + # later one.
> + for ref in refs + [msgid]:
> + ref = ref[:255]
> + # we don't want duplicates
> + try:
> + # we could have a ref to a previous series.
> + # (For example, a series sent in reply to
> + # another series.) That should not create a
> + # series ref for this series, so check for the
> + # msg-id only, not the msg-id/series pair.
> + SeriesReference.objects.get(
> + msgid=ref, project=project)
> + except SeriesReference.DoesNotExist:
> + SeriesReference.objects.create(
> + msgid=ref, project=project, series=series)
> + break
> + except IntegrityError:
> + # we lost the race so go again
> + logger.warning('Conflict while saving series. This is '
> + 'probably because multiple patches belonging '
> + 'to the same series have been received at '
> + 'once. Trying again (attempt %02d/10)',
> + attempt)
> else:
> - x = n = 1
> -
> - # We will create a new series if:
> - # - there is no existing series to assign this patch to, or
> - # - there is an existing series, but it already has a patch with this
> - # number in it
> - if not series or Patch.objects.filter(series=series, number=x).count():
> - series = Series.objects.create(
> - project=project,
> - date=date,
> - submitter=author,
> - version=version,
> - total=n)
> -
> - # NOTE(stephenfin) We must save references for series. We
> - # do this to handle the case where a later patch is
> - # received first. Without storing references, it would not
> - # be possible to identify the relationship between patches
> - # as the earlier patch does not reference the later one.
> - for ref in refs + [msgid]:
> - ref = ref[:255]
> - # we don't want duplicates
> - try:
> - # we could have a ref to a previous series. (For
> - # example, a series sent in reply to another
> - # series.) That should not create a series ref
> - # for this series, so check for the msg-id only,
> - # not the msg-id/series pair.
> - SeriesReference.objects.get(msgid=ref,
> - series__project=project)
> - except SeriesReference.DoesNotExist:
> - SeriesReference.objects.create(series=series, msgid=ref)
> - except SeriesReference.MultipleObjectsReturned:
> - logger.error("Multiple SeriesReferences for %s"
> - " in project %s!" % (ref, project.name))
> + # we failed to save the series so return the series-less patch
> + logger.warning('Failed to save series. Your patch with message ID '
> + '%s has been saved but this should not happen. '
> + 'Please report this as a bug and include logs',
> + msgid)
> + return patch
>
> # add to a series if we have found one, and we have a numbered
> # patch. Don't add unnumbered patches (for example diffs sent
> @@ -1170,14 +1182,9 @@ def parse_mail(mail, list_id=None):
> # message
> try:
> series = SeriesReference.objects.get(
> - msgid=msgid, series__project=project).series
> + msgid=msgid, project=project).series
> except SeriesReference.DoesNotExist:
> series = None
> - except SeriesReference.MultipleObjectsReturned:
> - logger.error("Multiple SeriesReferences for %s"
> - " in project %s!" % (msgid, project.name))
> - series = SeriesReference.objects.filter(
> - msgid=msgid, series__project=project).first().series
>
> if not series:
> series = Series.objects.create(
> @@ -1190,12 +1197,8 @@ def parse_mail(mail, list_id=None):
> # we don't save the in-reply-to or references fields
> # for a cover letter, as they can't refer to the same
> # series
> - try:
> - SeriesReference.objects.get_or_create(series=series,
> - msgid=msgid)
> - except SeriesReference.MultipleObjectsReturned:
> - logger.error("Multiple SeriesReferences for %s"
> - " in project %s!" % (msgid, project.name))
> + SeriesReference.objects.create(
> + msgid=msgid, project=project, series=series)
>
> try:
> cover_letter = CoverLetter.objects.create(
> diff --git a/patchwork/tests/test_parser.py b/patchwork/tests/test_parser.py
> index 0bf71585..0edbd87a 100644
> --- a/patchwork/tests/test_parser.py
> +++ b/patchwork/tests/test_parser.py
> @@ -421,17 +421,20 @@ class SeriesCorrelationTest(TestCase):
> msgids = [make_msgid()]
> project = create_project()
> series_v1 = create_series(project=project)
> - create_series_reference(msgid=msgids[0], series=series_v1)
> + create_series_reference(msgid=msgids[0], series=series_v1,
> + project=project)
>
> # ...and three patches
> for i in range(3):
> msgids.append(make_msgid())
> - create_series_reference(msgid=msgids[-1], series=series_v1)
> + create_series_reference(msgid=msgids[-1], series=series_v1,
> + project=project)
>
> # now create a new series with "cover letter"
> msgids.append(make_msgid())
> series_v2 = create_series(project=project)
> - ref_v2 = create_series_reference(msgid=msgids[-1], series=series_v2)
> + ref_v2 = create_series_reference(msgid=msgids[-1], series=series_v2,
> + project=project)
>
> # ...and the "first patch" of this new series
> msgid = make_msgid()
> diff --git a/patchwork/tests/utils.py b/patchwork/tests/utils.py
> index 577183d0..4ead1781 100644
> --- a/patchwork/tests/utils.py
> +++ b/patchwork/tests/utils.py
> @@ -282,8 +282,12 @@ def create_series(**kwargs):
>
> def create_series_reference(**kwargs):
> """Create 'SeriesReference' object."""
> + project = kwargs.pop('project', create_project())
> + series = kwargs.pop('series', create_series(project=project))
> +
> values = {
> - 'series': create_series() if 'series' not in kwargs else None,
> + 'series': series,
> + 'project': project,
> 'msgid': make_msgid(),
> }
> values.update(**kwargs)
> --
> 2.23.0
More information about the Patchwork
mailing list