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Code Issues Releases Wiki Activity

🎉 Use select_for_update tag to update note balances when we save a Transaction to avoid concurrency issues

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This commit is contained in:
Yohann D'ANELLO 2020-08-15 18:57:44 +02:00
parent 242b85676d
commit d4090a4043
1 changed files with 27 additions and 26 deletions
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19
apps/note/models/transactions.py
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@ -2,6 +2,7 @@
# SPDX-License-Identifier: GPL-3.0-or-later # SPDX-License-Identifier: GPL-3.0-or-later
from django.core.exceptions import ValidationError from django.core.exceptions import ValidationError
from django.db import models, transaction from django.db import models, transaction
from django.db.models import F
from django.urls import reverse from django.urls import reverse
from django.utils import timezone from django.utils import timezone
from django.utils.translation import gettext_lazy as _ from django.utils.translation import gettext_lazy as _
@ -208,7 +209,15 @@ class Transaction(PolymorphicModel):
""" """
When saving, also transfer money between two notes When saving, also transfer money between two notes
""" """
with transaction.atomic(): if self.source.pk == self.destination.pk:
# When source == destination, no money is transferred and no transaction is created
return
# We refresh the notes with the "select for update" tag to avoid concurrency issues
self.source = Note.objects.filter(pk=self.source_id).select_for_update().get()
self.destination = Note.objects.filter(pk=self.destination_id).select_for_update().get()
# Check that the amounts stay between big integer bounds
diff_source, diff_dest = self.validate() diff_source, diff_dest = self.validate()
if not self.source.is_active or not self.destination.is_active: if not self.source.is_active or not self.destination.is_active:
@ -224,21 +233,13 @@ class Transaction(PolymorphicModel):
if not self.destination_alias: if not self.destination_alias:
self.destination_alias = str(self.destination) self.destination_alias = str(self.destination)
if self.source.pk == self.destination.pk:
# When source == destination, no money is transferred and no transaction is created
return
# We save first the transaction, in case of the user has no right to transfer money # We save first the transaction, in case of the user has no right to transfer money
super().save(*args, **kwargs) super().save(*args, **kwargs)
# Save notes # Save notes
self.source.refresh_from_db()
self.source.balance += diff_source self.source.balance += diff_source
self.source._force_save = True
self.source.save() self.source.save()
self.destination.refresh_from_db()
self.destination.balance += diff_dest self.destination.balance += diff_dest
self.destination._force_save = True
self.destination.save() self.destination.save()
def delete(self, **kwargs): def delete(self, **kwargs):