Use django-safemigrate for migrations

docs/dev/index.rst

@@ -25,6 +25,7 @@ or taking the open source Read the Docs codebase for your own custom installatio
    style-guide
    front-end
    i18n
+   migrations
    server-side-search
    search-integration
    subscriptions

docs/dev/migrations.rst

@@ -0,0 +1,133 @@
+Database migrations
+===================
+
+We use `Django migrations <https://docs.djangoproject.com/en/4.2/topics/migrations/>`__ to manage database schema changes,
+and the `django-safemigrate <https://github.com/aspiredu/django-safemigrate>`__ package to ensure that migrations are run in a given order to avoid downtime.
+
+To make sure that migrations don't cause downtime,
+the following rules should be followed for each case.
+
+Adding a new field
+------------------
+
+When adding a new field to a model, it should be nullable.
+This way, the database can be migrated without downtime, and the field can be populated later.
+Don't forget to make the field non-nullable in a separate migration after the data has been populated.
+You can achieve this by following these steps:
+
+- #. Set the new field as ``null=True`` and ``blank=True`` in the model.
+
+     .. code-block:: python
+
+        class MyModel(models.Model):
+            new_field = models.CharField(
+                max_length=100, null=True, blank=True, default="default"
+            )
+
+- #. Make sure that the field is always populated with a proper value in the new code,
+     and the code handles the case where the field is null.
+
+     .. code-block:: python
+
+        if my_model.new_field in [None, "default"]:
+            pass
+
+
+        # If it's a boolean field, make sure that the null option is removed from the form.
+        class MyModelForm(forms.ModelForm):
+            def __init__(self, *args, **kwargs):
+                super().__init__(*args, **kwargs)
+                self.fields["new_field"].widget = forms.CheckboxInput()
+                self.fields["new_field"].empty_value = False
+
+- #. Create the migration file (let's call this migration ``app 0001``),
+     and mark it as ``Safe.before_deploy``.
+
+     .. code-block:: python
+
+        from django.db import migrations, models
+        from django_safemigrate import Safe
+
+
+        class Migration(migrations.Migration):
+            safe = Safe.before_deploy
+
+- #. Create a data migration to populate all null values of the new field with a proper value (let's call this migration ``app 0002``),
+     and mark it as ``Safe.after_deploy``.
+
+     .. code-block:: python
+
+         from django.db import migrations
+
+
+         def migrate(apps, schema_editor):
+             MyModel = apps.get_model("app", "MyModel")
+             MyModel.objects.filter(new_field=None).update(new_field="default")
+
+
+         class Migration(migrations.Migration):
+             safe = Safe.after_deploy
+
+             operations = [
+                 migrations.RunPython(migrate),
+             ]
+
+- #. After the deploy has been completed, create a new migration to set the field as non-nullable (let's call this migration ``app 0003``).
+     Run this migration on a new deploy, you can mark it as ``Safe.before_deploy`` or ``Safe.always``.
+- #. Remove any handling of the null case from the code.
+
+At the end, the deploy should look like this:
+
+- Deploy web-extra.
+- Run ``django-admin safemigrate`` to run the migration ``app 0001``.
+- Deploy the webs
+- Run ``django-admin migrate`` to run the migration ``app 0002``.
+- Create a new migration to set the field as non-nullable,
+  and apply it on the next deploy.
+
+Removing a field
+----------------
+
+When removing a field from a model,
+all usages of the field should be removed from the code before the field is removed from the model,
+and the field should be nullable.
+You can achieve this by following these steps:
+
+- #. Remove all usages of the field from the code.
+- #. Set the field as ``null=True`` and ``blank=True`` in the model.
+
+     .. code-block:: python
+
+        class MyModel(models.Model):
+            field_to_delete = models.CharField(max_length=100, null=True, blank=True)
+
+- #. Create the migration file (let's call this migration ``app 0001``),
+     and mark it as ``Safe.before_deploy``.
+
+     .. code-block:: python
+
+        from django.db import migrations, models
+        from django_safemigrate import Safe
+
+
+        class Migration(migrations.Migration):
+            safe = Safe.before_deploy
+
+- #. Create a migration to remove the field from the database (let's call this migration ``app 0002``),
+     and mark it as ``Safe.after_deploy``.
+
+     .. code-block:: python
+
+        from django.db import migrations, models
+        from django_safemigrate import Safe
+
+
+        class Migration(migrations.Migration):
+            safe = Safe.after_deploy
+
+At the end, the deploy should look like this:
+
+- Deploy web-extra.
+- Run ``django-admin safemigrate`` to run the migration ``app 0001``.
+- Deploy the webs
+- Run ``django-admin migrate`` to run the migration ``app 0002``.

readthedocs/builds/migrations/0057_migrate_timestamp_fields.py

@@ -0,0 +1,32 @@
+# Generated by Django 4.2.9 on 2024-02-01 20:29
+
+import datetime
+
+from django.db import migrations
+from django_safemigrate import Safe
+
+
+def migrate(apps, schema_editor):
+    """
+    Migrate the created and modified fields of the Version model to have a non-null value.
+
+    This date corresponds to the release date of 5.6.5,
+    when the created field was added to the Version model
+    at https://github.com/readthedocs/readthedocs.org/commit/d72ee6e27dc398b97e884ccec8a8cf135134faac.
+    """
+    Version = apps.get_model("builds", "Version")
+    date = datetime.datetime(2020, 11, 23, tzinfo=datetime.timezone.utc)
+    Version.objects.filter(created=None).update(created=date)
+    Version.objects.filter(modified=None).update(modified=date)
+
+
+class Migration(migrations.Migration):
+    safe = Safe.before_deploy
+
+    dependencies = [
+        ("builds", "0056_alter_versionautomationrule_priority"),
+    ]
+
+    operations = [
+        migrations.RunPython(migrate),
+    ]

readthedocs/builds/migrations/0058_alter_version_created_alter_version_modified.py

@@ -0,0 +1,37 @@
+# Generated by Django 4.2.9 on 2024-02-01 20:38
+
+import django.utils.timezone
+import django_extensions.db.fields
+from django.db import migrations
+from django_safemigrate import Safe
+
+
+class Migration(migrations.Migration):
+    safe = Safe.after_deploy
+
+    dependencies = [
+        ("builds", "0057_migrate_timestamp_fields"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="version",
+            name="created",
+            field=django_extensions.db.fields.CreationDateTimeField(
+                auto_now_add=True,
+                default=django.utils.timezone.now,
+                verbose_name="created",
+            ),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name="version",
+            name="modified",
+            field=django_extensions.db.fields.ModificationDateTimeField(
+                auto_now=True,
+                default=django.utils.timezone.now,
+                verbose_name="modified",
+            ),
+            preserve_default=False,
+        ),
+    ]

readthedocs/builds/models.py

@@ -13,7 +13,6 @@
 from django.utils import timezone
 from django.utils.translation import gettext
 from django.utils.translation import gettext_lazy as _
-from django_extensions.db.fields import CreationDateTimeField, ModificationDateTimeField
 from django_extensions.db.models import TimeStampedModel
 from polymorphic.models import PolymorphicModel
 
@@ -92,19 +91,6 @@ class Version(TimeStampedModel):
 
     """Version of a ``Project``."""
 
-    # Overridden from TimeStampedModel just to allow null values.
-    # TODO: remove after deploy.
-    created = CreationDateTimeField(
-        _('created'),
-        null=True,
-        blank=True,
-    )
-    modified = ModificationDateTimeField(
-        _('modified'),
-        null=True,
-        blank=True,
-    )
-
     project = models.ForeignKey(
         Project,
         verbose_name=_('Project'),

readthedocs/integrations/migrations/0013_set_timestamp_fields_as_no_null.py

@@ -0,0 +1,37 @@
+# Generated by Django 4.2.9 on 2024-02-01 20:10
+
+import django.utils.timezone
+import django_extensions.db.fields
+from django.db import migrations
+from django_safemigrate import Safe
+
+
+class Migration(migrations.Migration):
+    safe = Safe.always
+
+    dependencies = [
+        ("integrations", "0012_migrate_timestamp_fields"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="integration",
+            name="created",
+            field=django_extensions.db.fields.CreationDateTimeField(
+                auto_now_add=True,
+                default=django.utils.timezone.now,
+                verbose_name="created",
+            ),
+            preserve_default=False,
+        ),
+        migrations.AlterField(
+            model_name="integration",
+            name="modified",
+            field=django_extensions.db.fields.ModificationDateTimeField(
+                auto_now=True,
+                default=django.utils.timezone.now,
+                verbose_name="modified",
+            ),
+            preserve_default=False,
+        ),
+    ]

readthedocs/integrations/models.py

@@ -9,7 +9,6 @@
 from django.utils.crypto import get_random_string
 from django.utils.safestring import mark_safe
 from django.utils.translation import gettext_lazy as _
-from django_extensions.db.fields import CreationDateTimeField, ModificationDateTimeField
 from django_extensions.db.models import TimeStampedModel
 from pygments import highlight
 from pygments.formatters import HtmlFormatter
@@ -278,19 +277,6 @@ class Integration(TimeStampedModel):
 
     INTEGRATIONS = WEBHOOK_INTEGRATIONS
 
-    # Overridden from TimeStampedModel just to allow null values.
-    # TODO: remove after deploy.
-    created = CreationDateTimeField(
-        _("created"),
-        null=True,
-        blank=True,
-    )
-    modified = ModificationDateTimeField(
-        _("modified"),
-        null=True,
-        blank=True,
-    )
-
     project = models.ForeignKey(
         Project,
         related_name="integrations",

readthedocs/projects/fixtures/test_data.json

@@ -888,8 +888,8 @@
     "model": "builds.version",
     "pk": 1,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 1,
         "type": "unknown",
         "identifier": "2ff3d36340fa4d3d39424e8464864ca37c5f191c",
@@ -912,8 +912,8 @@
     "model": "builds.version",
     "pk": 2,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 1,
         "type": "unknown",
         "identifier": "354456a7dba2a75888e2fe91f6d921e5fe492bcd",
@@ -936,8 +936,8 @@
     "model": "builds.version",
     "pk": 3,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 1,
         "type": "unknown",
         "identifier": "master",
@@ -960,8 +960,8 @@
     "model": "builds.version",
     "pk": 4,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 1,
         "type": "unknown",
         "identifier": "not_ok",
@@ -984,8 +984,8 @@
     "model": "builds.version",
     "pk": 8,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 1,
         "type": "unknown",
         "identifier": "awesome",
@@ -1008,8 +1008,8 @@
     "model": "builds.version",
     "pk": 18,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 6,
         "type": "tag",
         "identifier": "2404a34eba4ee9c48cc8bc4055b99a48354f4950",
@@ -1032,8 +1032,8 @@
     "model": "builds.version",
     "pk": 19,
     "fields": {
-        "created": null,
-        "modified": null,
+        "created": "2022-02-22T10:55:46.784Z",
+        "modified": "2022-02-22T10:55:46.784Z",
         "project": 6,
         "type": "tag",
         "identifier": "f55c28e560c92cafb6e6451f8084232b6d717603",