When scaling down a ReplicaSet, delete doubled up replicas first, where a
"doubled up replica" is defined as one that is on the same node as an
active replica belonging to a related ReplicaSet. ReplicaSets are
considered "related" if they have a common controller (typically a
Deployment).
The intention of this change is to make a rolling update of a Deployment
scale down the old ReplicaSet as it scales up the new ReplicaSet by
deleting pods from the old ReplicaSet that are colocated with ready pods of
the new ReplicaSet. This change in the behavior of rolling updates can be
combined with pod affinity rules to preserve the locality of a Deployment's
pods over rollout.
A specific scenario that benefits from this change is when a Deployment's
pods are exposed by a Service that has type "LoadBalancer" and external
traffic policy "Local". In this scenario, the load balancer uses health
checks to determine whether it should forward traffic for the Service to a
particular node. If the node has no local endpoints for the Service, the
health check will fail for that node. Eventually, the load balancer will
stop forwarding traffic to that node. In the meantime, the service proxy
drops traffic for that Service. Thus, in order to reduce risk of dropping
traffic during a rolling update, it is desirable preserve node locality of
endpoints.
* pkg/controller/controller_utils.go (ActivePodsWithRanks): New type to
sort pods using a given ranking.
* pkg/controller/controller_utils_test.go (TestSortingActivePodsWithRanks):
New test for ActivePodsWithRanks.
* pkg/controller/replicaset/replica_set.go
(getReplicaSetsWithSameController): New method. Given a ReplicaSet, return
all ReplicaSets that have the same owner.
(manageReplicas): Call getIndirectlyRelatedPods, and pass its result to
getPodsToDelete.
(getIndirectlyRelatedPods): New method. Given a ReplicaSet, return all
pods that are owned by any ReplicaSet with the same owner.
(getPodsToDelete): Add an argument for related pods. Use related pods and
the new getPodsRankedByRelatedPodsOnSameNode function to take into account
whether a pod is doubled up when sorting pods for deletion.
(getPodsRankedByRelatedPodsOnSameNode): New function. Return an
ActivePodsWithRanks value that wraps the given slice of pods and computes
ranks where each pod's rank is equal to the number of active related pods
that are colocated on the same node.
* pkg/controller/replicaset/replica_set_test.go (newReplicaSet): Set
OwnerReferences on the ReplicaSet.
(newPod): Set a unique UID on the pod.
(byName): New type to sort pods by name.
(TestGetReplicaSetsWithSameController): New test for
getReplicaSetsWithSameController.
(TestRelatedPodsLookup): New test for getIndirectlyRelatedPods.
(TestGetPodsToDelete): Augment the "various pod phases and conditions, diff
= len(pods)" test case to ensure that scale-down still selects doubled-up
pods if there are not enough other pods to scale down. Add a "various pod
phases and conditions, diff = len(pods), relatedPods empty" test case to
verify that getPodsToDelete works even if related pods could not be
determined. Add a "ready and colocated with another ready pod vs not
colocated, diff < len(pods)" test case to verify that a doubled-up pod gets
preferred for deletion. Augment the "various pod phases and conditions,
diff < len(pods)" test case to ensure that not-ready pods are preferred
over ready but doubled-up pods.
* pkg/controller/replicaset/BUILD: Regenerate.
* test/e2e/apps/deployment.go
(testRollingUpdateDeploymentWithLocalTrafficLoadBalancer): New end-to-end
test. Create a deployment with a rolling update strategy and affinity
rules and a load balancer with "Local" external traffic policy, and verify
that set of nodes with local endponts for the service remains unchanged
during rollouts.
(setAffinity): New helper, used by
testRollingUpdateDeploymentWithLocalTrafficLoadBalancer.
* test/e2e/framework/service/jig.go (GetEndpointNodes): Factor building the
set of node names out...
(GetEndpointNodeNames): ...into this new method.
The code was already 99% similar between RC and RS.
This is a wild idea to try to deduplicate the two controllers
in a type-safe manner without adding tons of boilerplate,
and without using code generation.
They are still separate resources. This is a refactor that isn't
intended to change any behavior.
Prevent too-large replicas from generating enormous numbers
of events by creating only a few pods at a time, then increasing
the batch size when pod creations succeed. Stop creating batches
of pods when any pod creation errors are encountered.
The GC expects that once it sees a controller with a non-nil
DeletionTimestamp, that controller will not attempt any adoption.
There was a known race condition that could cause a controller to
re-adopt something orphaned by the GC, because the controller is using a
cached value of its own spec from before DeletionTimestamp was set.
This fixes that race by doing an uncached quorum read of the controller
spec just before the first adoption attempt. It's important that this
read occurs after listing potential orphans. Note that this uncached
read is skipped if no adoptions are attempted (i.e. at steady state).
To prepare for implementing ControllerRef across all controllers,
this pushes the common adopt/orphan logic into ControllerRefManager
so each controller doesn't have to duplicate it.
This also shares the adopt/orphan logic between Pods and ReplicaSets,
so it lives in only one place.
