Replicas should atomically update their distributions

It's not ideal for distributions to pick up replica changes at random
time intervals as various tasks complete, ideally the entire replica is
presented as updated at once (or with the smallest possible window).

closes #7333
Assisted-By: claude-opus-4.6

Author: dralley

CHANGES/7333.bugfix

@@ -0,0 +1 @@
+Pulp Replicas now present all of their distribution updates at the end of the replication process, rather than each individual repository-distribution pair being updated individually as syncs and publishes are completed.

pulpcore/app/replica.py

@@ -172,8 +172,11 @@ def distribution_extra_fields(self, repository, upstream_distribution):
         """
         Return the fields that need to be updated/cleared on distributions for idempotence.
         """
+        latest = repository.latest_version()
+        repo_version_href = get_url(repository) + "versions/{}/".format(latest.number)
         return {
-            "repository": get_url(repository),
+            "repository": None,
+            "repository_version": repo_version_href,
             "publication": None,
             "base_path": upstream_distribution["base_path"],
         }
@@ -187,7 +190,15 @@ def create_or_update_distribution(self, repository, upstream_distribution):
             )
             if not self._is_managed(distro):
                 return None
-            needs_update = self.needs_update(distribution_data, distro)
+            # Don't update repository_version here — that happens atomically in
+            # finalize_replication after all syncs complete.
+            update_data = {
+                k: v
+                for k, v in distribution_data.items()
+                if k not in ("repository_version", "repository", "publication")
+            }
+            update_data["pulp_labels"] = distribution_data["pulp_labels"]
+            needs_update = self.needs_update(update_data, distro)
             if needs_update:
                 # Update the distribution
                 dispatch(
@@ -197,7 +208,7 @@ def create_or_update_distribution(self, repository, upstream_distribution):
                     exclusive_resources=self.distros_uris,
                     args=(distro.pk, self.app_label, self.distribution_serializer_name),
                     kwargs={
-                        "data": distribution_data,
+                        "data": update_data,
                         "partial": True,
                     },
                 )

pulpcore/app/tasks/replica.py

@@ -3,11 +3,12 @@
 import sys
 from tempfile import NamedTemporaryFile
 
+from django.db import transaction
 from django.db.models import Min
 
 from pulpcore.constants import TASK_STATES
 from pulpcore.app.apps import pulp_plugin_configs, PulpAppConfig
-from pulpcore.app.models import UpstreamPulp, Task, TaskGroup
+from pulpcore.app.models import Distribution, Repository, UpstreamPulp, Task, TaskGroup
 from pulpcore.app.replica import ReplicaContext
 from pulpcore.tasking.tasks import dispatch
 
@@ -77,6 +78,7 @@ def replicate_distributions(server_pk):
                     replicator = replicator_class(ctx, task_group, tls_settings, server)
                     supported_replicators.append(replicator)
 
+    distro_repo_pairs = []
     for replicator in supported_replicators:
         distros = replicator.upstream_distributions(q=server.q_select)
         distro_names = []
@@ -90,7 +92,7 @@ def replicate_distributions(server_pk):
             # Check if there is already a repository
             repository = replicator.create_or_update_repository(remote=remote)
             if not repository:
-                # No update occured because server.policy==LABELED and there was
+                # No update occurred because server.policy==LABELED and there was
                 # an already existing local repository with the same name
                 continue
 
@@ -103,24 +105,35 @@ def replicate_distributions(server_pk):
 
             # Add name to the list of known distribution names
             distro_names.append(distro["name"])
+            distro_repo_pairs.append((distro["name"], str(repository.pk)))
 
         replicator.remove_missing(distro_names)
 
     dispatch(
         finalize_replication,
         task_group=task_group,
         exclusive_resources=[server],
-        args=[server.pk],
+        args=[server.pk, distro_repo_pairs],
     )
 
 
-def finalize_replication(server_pk):
+def finalize_replication(server_pk, distro_repo_pairs):
     task = Task.current()
     task_group = TaskGroup.current()
     server = UpstreamPulp.objects.get(pk=server_pk)
     if task_group.tasks.exclude(pk=task.pk).exclude(state=TASK_STATES.COMPLETED).exists():
         raise Exception("Replication failed.")
 
+    # Atomically update all managed distributions to point to their repo's latest version.
+    with transaction.atomic():
+        for distro_name, repo_pk in distro_repo_pairs:
+            distro = Distribution.objects.get(name=distro_name, pulp_domain=server.pulp_domain)
+            repo = Repository.objects.get(pk=repo_pk)
+            latest_version = repo.latest_version()
+            if latest_version and distro.repository_version != latest_version:
+                distro.repository_version = latest_version
+                distro.save(update_fields=["repository_version"])
+
     # Record timestamp of last successful replication.
     started_at = task_group.tasks.aggregate(Min("started_at"))["started_at__min"]
     server.set_last_replication_timestamp(started_at)

pulpcore/tests/functional/api/test_replication.py

@@ -117,6 +117,13 @@ def test_replication_idempotence(
             assert "UpstreamPulp" in obj.pulp_labels
             assert upstream_pulp.prn.split(":")[-1] == obj.pulp_labels["UpstreamPulp"]
 
+    # Verify the replica distribution uses repository_version (not repository)
+    replica_distro = file_bindings.DistributionsFileApi.list(
+        pulp_domain=replica_domain.name
+    ).results[0]
+    assert replica_distro.repository is None
+    assert replica_distro.repository_version is not None
+
     # Now replicate backwards
 
     upstream_pulp_body = {
@@ -147,7 +154,9 @@ def test_replication_idempotence(
     assert result.count == 1
     new_distribution = result.results[0]
     assert new_distribution.pulp_href == distro.pulp_href
-    assert new_distribution.repository == new_repository.pulp_href
+    assert new_distribution.repository is None
+    assert new_distribution.repository_version is not None
+    assert new_distribution.repository_version.startswith(new_repository.pulp_href)
     assert new_distribution.publication is None
     assert "UpstreamPulp" in new_distribution.pulp_labels
     assert upstream_pulp2.prn.split(":")[-1] == new_distribution.pulp_labels["UpstreamPulp"]
@@ -373,11 +382,9 @@ def _check_replication(
             assert upstream_pulp.last_replication > old_replication
 
         # check if the content was correctly replicated
-        local_version = file_bindings.RepositoriesFileApi.read(
-            distribution.repository
-        ).latest_version_href
+        assert distribution.repository_version is not None
         local_present = file_bindings.RepositoriesFileVersionsApi.read(
-            local_version
+            distribution.repository_version
         ).content_summary.present
         upstream_version = file_bindings.PublicationsFileApi.read(
             upstream_distribution.publication