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Quite a lot of unit tests set up informers with a fake client, do
informerFactory.WaitForCacheSync, then create or modify objects. Such tests
suffered from a race: because the fake client only delivered objects to the
watch after the watch has been created, creating an object too early caused
that object to not get delivered to the informer.
Usually the timing worked out okay because WaitForCacheSync typically slept a
bit while polling, giving the Watch call time to complete, but this race has
also gone wrong occasionally. Now with WaitForCacheSync returning more promptly
without polling (work in progress), the race goes wrong more often.
Instead of working around this in unit tests it's better to improve the fake
client such that List+Watch works reliably, regardless of the timing. The fake
client has traditionally not touched ResourceVersion in stored objects and
doing so now might break unit tests, so the added support for ResourceVersion
is intentionally limited to List+Watch.
The test simulates "real" usage of informers. It runs in a synctest bubble and
completes quickly:
go test -v .
=== RUN TestListAndWatch
listandwatch_test.go:67: I0101 01:00:00.000000] Listed configMaps="&ConfigMapList{ListMeta:{ 1 <nil>},Items:[]ConfigMap{ConfigMap{ObjectMeta:{cm1 default 0 0001-01-01 00:00:00 +0000 UTC <nil> <nil> map[] map[] [] [] []},Data:map[string]string{},BinaryData:map[string][]byte{},Immutable:nil,},},}" err=null
listandwatch_test.go:79: I0101 01:00:00.000000] Delaying Watch...
listandwatch_test.go:90: I0101 01:00:00.100000] Caches synced
listandwatch_test.go:107: I0101 01:00:00.100000] Created second ConfigMap
listandwatch_test.go:81: I0101 01:00:00.100000] Continuing Watch...
--- PASS: TestListAndWatch (0.00s)
PASS
ok k8s.io/client-go/testing/internal 0.009s
Some users of the fake client need to be updated to avoid test failures:
- ListMeta comparisons have to be updated.
- Optional: pass ListOptions into tracker.Watch. It's optional because
the implementation behaves as before when options are missing,
but the List+Watch race fix only works when options are passed.
Kubernetes-commit: 56448506075c3db1d16b5bbf0c581b833a4646f1
client-go Examples
This directory contains examples that cover various use cases and functionality for client-go.
Auth plugins
Client configuration is typically loaded from kubeconfig files containing server and credential configuration. Several plugins for obtaining credentials from external sources are available, but are not loaded by default. To enable these plugins in your program, import them in your main package.
You can load all auth plugins:
import _ "k8s.io/client-go/plugin/pkg/client/auth"
Or you can load specific auth plugins:
import _ "k8s.io/client-go/plugin/pkg/client/auth/azure"
import _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
import _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
Configuration
- Authenticate in cluster: Configure a client while running inside the Kubernetes cluster.
- Authenticate out of cluster: Configure a client to access a Kubernetes cluster from outside.
Basics
- Managing resources with API: Create, get, update, delete a Deployment resource.
Advanced Concepts
- Work queues: Create a hotloop-free controller with the rate-limited workqueue and the informer framework.
- Custom Resource Definition (CRD): Register a custom resource type with the API, create/update/query this custom type, and write a controller that drives the cluster state based on the changes to the custom resources.
- Leader election: Demonstrates the use of the leader election package, which can be used to implement HA controllers.
Testing
- Fake Client: Use a fake client in tests.