Service has had a problem since forever:
- User creates a service type=LoadBalancer
- We silently allocate them a NodePort
- User changes type to ClusterIP
- We fail the operation because they did not clear NodePort
They never asked for or used the NodePort!
Dual-stack introduced some dependent fields that get auto-wiped on
updates. This carries it further.
If you squint, you can see Service as a big, messy discriminated union,
with type as the discriminator. Ignoring fields for non-selected
union-modes seems right.
This introduces the potential for an apply loop. Specifically, we will
accept YAML that we did not previously accept. Apply could see the
field in local YAML and not in the server and repeatedly try to patch it
in. But since that YAML is currently an error, it seems like a very low
risk. Almost nobody actually specifies their own NodePort values.
To mitigate this somewhat, we only auto-wipe on updates. The same YAML
would fail to create. This is a little inconsistent. We could
auto-wipe on create, too, at the risk of more potential impact.
To do this properly, we need to know the old and new values, which means
we can not do it in defaulting or conversion. So we do it in strategy.
This change also adds unit tests and updates e2e tests to rely on and
verify this behavior.
Generally try to waive away folks who see a particular event stream
and feel tempted to extrapolate and build tooling that expects the
same underlying resource transition chain to continue to produce a
similar event stream as the underlying components evolve and are
updated. New controllers should not be constrained to be
backwards-compatible with previous versions with regard to Event
emission. This is distinct from the Event type itself, which has the
usual Kubernetes-API compatibility commitments for versioned types.
The EventTTL default has been 1h since 7e258b85bd (Reduce TTL for
events in etcd from 48hrs to 1hr, 2015-03-11, #5315), and remains so
today:
$ git --no-pager log -1 --format='%h %s' origin/master
8e5c02255c Merge pull request #90942 from ii/ii-create-pod%2Bpodstatus-resource-lifecycle-test
$ git --no-pager grep EventTTL: 8e5c02255c cmd/kube-apiserver/app/options/options.go
8e5c02255cc:cmd/kube-apiserver/app/options/options.go: EventTTL: 1 * time.Hour,
In this space [1,2]:
To avoid filling up master's disk, a retention policy is enforced:
events are removed one hour after the last occurrence. To provide
longer history and aggregation capabilities, a third party solution
should be installed to capture events.
...
Note: It is not guaranteed that all events happening in a cluster
will be exported to Stackdriver. One possible scenario when events
will not be exported is when event exporter is not running
(e.g. during restart or upgrade). In most cases it's fine to use
events for purposes like setting up metrics and alerts, but you
should be aware of the potential inaccuracy.
...
To prevent disturbing your workloads, event exporter does not have
resources set and is in the best effort QOS class, which means that
it will be the first to be killed in the case of resource
starvation.
Although that's talking more about export from etcd -> external
storage, and not about cluster components submitting events to etcd.
[1]: https://kubernetes.io/docs/tasks/debug-application-cluster/events-stackdriver/
[2]: https://github.com/kubernetes/website/pull/4155/files#diff-d8eb69c5436aa38b396d4f3ed75e4792R10
* api: structure change
* api: defaulting, conversion, and validation
* [FIX] validation: auto remove second ip/family when service changes to SingleStack
* [FIX] api: defaulting, conversion, and validation
* api-server: clusterIPs alloc, printers, storage and strategy
* [FIX] clusterIPs default on read
* alloc: auto remove second ip/family when service changes to SingleStack
* api-server: repair loop handling for clusterIPs
* api-server: force kubernetes default service into single stack
* api-server: tie dualstack feature flag with endpoint feature flag
* controller-manager: feature flag, endpoint, and endpointSlice controllers handling multi family service
* [FIX] controller-manager: feature flag, endpoint, and endpointSlicecontrollers handling multi family service
* kube-proxy: feature-flag, utils, proxier, and meta proxier
* [FIX] kubeproxy: call both proxier at the same time
* kubenet: remove forced pod IP sorting
* kubectl: modify describe to include ClusterIPs, IPFamilies, and IPFamilyPolicy
* e2e: fix tests that depends on IPFamily field AND add dual stack tests
* e2e: fix expected error message for ClusterIP immutability
* add integration tests for dualstack
the third phase of dual stack is a very complex change in the API,
basically it introduces Dual Stack services. Main changes are:
- It pluralizes the Service IPFamily field to IPFamilies,
and removes the singular field.
- It introduces a new field IPFamilyPolicyType that can take
3 values to express the "dual-stack(mad)ness" of the cluster:
SingleStack, PreferDualStack and RequireDualStack
- It pluralizes ClusterIP to ClusterIPs.
The goal is to add coverage to the services API operations,
taking into account the 6 different modes a cluster can have:
- single stack: IP4 or IPv6 (as of today)
- dual stack: IPv4 only, IPv6 only, IPv4 - IPv6, IPv6 - IPv4
* [FIX] add integration tests for dualstack
* generated data
* generated files
Co-authored-by: Antonio Ojea <aojea@redhat.com>
