Serve previously published artifacts for 3 days

fixes pulp#911

CHANGES/911.feature

@@ -0,0 +1,3 @@
+Added feature to serve published artifacts from previous publications for 3 days.
+This fulfills the apt-by-hash/acquire-by-hash spec by allowing by-hash files to be cached for a
+period of time.

pulp_deb/app/migrations/0029_distributedpublication.py

@@ -0,0 +1,48 @@
+# Generated by Django 4.2.2 on 2023-10-25 17:07
+
+from django.db import migrations, models
+import django.db.models.deletion
+import django_lifecycle.mixins
+import pulpcore.app.models.base
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("deb", "0028_sourcepackage_sourcepackagereleasecomponent_and_more"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="DistributedPublication",
+            fields=[
+                (
+                    "pulp_id",
+                    models.UUIDField(
+                        default=pulpcore.app.models.base.pulp_uuid,
+                        editable=False,
+                        primary_key=True,
+                        serialize=False,
+                    ),
+                ),
+                ("pulp_created", models.DateTimeField(auto_now_add=True)),
+                ("pulp_last_updated", models.DateTimeField(auto_now=True, null=True)),
+                (
+                    "distribution",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE, to="deb.aptdistribution"
+                    ),
+                ),
+                (
+                    "publication",
+                    models.ForeignKey(
+                        on_delete=django.db.models.deletion.CASCADE, to="deb.aptpublication"
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+            },
+            bases=(django_lifecycle.mixins.LifecycleModelMixin, models.Model),
+        ),
+    ]

pulp_deb/app/models/publication.py

@@ -1,6 +1,10 @@
+from datetime import timedelta
+
 from django.db import models
+from django.utils import timezone
+from django_lifecycle import hook, AFTER_CREATE, AFTER_SAVE
 
-from pulpcore.plugin.models import Publication, Distribution
+from pulpcore.plugin.models import BaseModel, Distribution, Publication, PublishedArtifact
 
 from pulp_deb.app.models.signing_service import AptReleaseSigningService
 
@@ -17,6 +21,11 @@ class VerbatimPublication(Publication):
 
     TYPE = "verbatim-publication"
 
+    @hook(AFTER_CREATE)
+    def set_distributed_publication(self):
+        for distro in AptDistribution.objects.filter(repository__pk=self.repository.pk):
+            DistributedPublication(distribution=distro, publication=self).save()
+
     class Meta:
         default_related_name = "%(app_label)s_%(model_name)s"
 
@@ -36,6 +45,11 @@ class AptPublication(Publication):
         AptReleaseSigningService, on_delete=models.PROTECT, null=True
     )
 
+    @hook(AFTER_CREATE)
+    def set_distributed_publication(self):
+        for distro in AptDistribution.objects.filter(repository__pk=self.repository.pk):
+            DistributedPublication(distribution=distro, publication=self).save()
+
     class Meta:
         default_related_name = "%(app_label)s_%(model_name)s"
 
@@ -47,5 +61,42 @@ class AptDistribution(Distribution):
 
     TYPE = "apt-distribution"
 
+    PUBLICATION_CACHE_DURATION = timedelta(days=3)
+
+    @hook(AFTER_SAVE, when="publication", has_changed=True)
+    def set_distributed_publication(self):
+        if self.publication:
+            DistributedPublication(distribution=self, publication=self.publication).save()
+
+    def content_handler(self, path):
+        recent_publications = (
+            self.distributedpublication_set.filter(
+                pulp_created__gte=timezone.now() - self.PUBLICATION_CACHE_DURATION
+            )
+            .order_by("pulp_created")
+            .values_list("publication", flat=True)
+        )
+        for publication in recent_publications:
+            pa = (
+                PublishedArtifact.objects.filter(relative_path=path, publication__pk=publication)
+                .select_related(
+                    "content_artifact",
+                    "content_artifact__artifact",
+                )
+                .first()
+            )
+            if pa:
+                return pa.content_artifact
+        return
+
     class Meta:
         default_related_name = "%(app_label)s_%(model_name)s"
+
+
+class DistributedPublication(BaseModel):
+    """
+    A history of previously distributed publications.
+    """
+
+    distribution = models.ForeignKey(AptDistribution, on_delete=models.CASCADE)
+    publication = models.ForeignKey(AptPublication, on_delete=models.CASCADE)