This repository is to provide a sample about how to create a controller to watch all events (add/update/delete) of some CRD kinds so that we can implement the Operator pattern.
The CRD kind referred here is Jinghzhu v1. Of course, you can use any other. The controller will do something like ReplicaSet against the CRD.
Assume:
- Go version > 1.9.0
- A Kubernetes cluster is available.
- Kubernetes version >= 1.18.0
There are many articles introducing the mechanism of Operator in Kubernetes community. So, I wouldn't pay too much attention on it. In short, it leverage the etcd watch mechanism to catch all events.
In the method New() at pkg/operator/types.go, we define the major components of Operator:
- queue - I implements an in-memory queue to process all events in concurrent way. By default, there is only one main goroutine to help the Operator get events from etcd and call add/update/delete handlers. Now, after receiving events, it puts them in the queue which can ensure the concurrent safe.
- lister
- informer
- event handler callback
queue := workqueue.NewRateLimitingQueue(workqueue.DefaultControllerRateLimiter())
lw := cache.NewListWatchFromClient(jinghzhuV1Client.JinghzhuV1().RESTClient(), jinghzhuv1.Plural, namespace, fields.Everything())
...
informer := cache.NewSharedIndexInformer(
lw,
&jinghzhuv1.Jinghzhu{},
0, //Skip resync
cache.Indexers{},
)
...
c.informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
AddFunc: c.onAdd,
UpdateFunc: c.onUpdate,
DeleteFunc: c.onDelete,
})For details, please see pkg/operator/operator.go and pkg/operator/worker.go.
$ go run cmd/operator/main.go
Init CRD Operator...
Ready to start CRD Operator...
Find an onAdd event
key = crd/jinghzhu-example-f7wgv
eventType = add
old = <nil>
new= Name = jinghzhu-example-f7wgv
Resource Version = 2343534
Desired = 1
Current = 0
PodList =
State = Pending
Message = Created but not processed yet
CRD Operator is synced and ready...
Ready to start CRD Operator workers...
Processing Jinghzhu instance key = crd/jinghzhu-example-f7wgv
eventType = add
old = <nil>
new= Name = jinghzhu-example-f7wgv
Resource Version = 2343534
Desired = 1
Current = 0
PodList =
State = Pending
Message = Created but not processed yet
All workers are started...
Ready to reconcile add event for Name = jinghzhu-example-f7wgv
Resource Version = 2343534
Desired = 1
Current = 0
PodList =
State = Pending
Message = Created but not processed yet
Finish reconciling add event for Name = jinghzhu-example-f7wgv
Resource Version = 2343534
Desired = 1
Current = 1
PodList = jinghzhu-worker-hl7fc
State = Running
Message = Start to run replica set
Find an onUpdate event
key = crd/jinghzhu-example-f7wgv
eventType = update
old = Name = jinghzhu-example-f7wgv
Resource Version = 2343534
Desired = 1
Current = 0
PodList =
State = Pending
Message = Created but not processed yet
new= Name = jinghzhu-example-f7wgv
Resource Version = 2347327
Desired = 1
Current = 1
PodList = jinghzhu-worker-hl7fc
State = Running
Message = Start to run replica set
Processing Jinghzhu instance key = crd/jinghzhu-example-f7wgv
eventType = update
old = Name = jinghzhu-example-f7wgv
Resource Version = 2343534
Desired = 1
Current = 0
PodList =
State = Pending
Message = Created but not processed yet
new= Name = jinghzhu-example-f7wgv
Resource Version = 2347327
Desired = 1
Current = 1
PodList = jinghzhu-worker-hl7fc
State = Running
Message = Start to run replica set
Ready to reconcile update event for Name = jinghzhu-example-f7wgv
Resource Version = 2347327
Desired = 1
Current = 1
PodList = jinghzhu-worker-hl7fc
State = Running
Message = Start to run replica set
No need to reconcile jinghzhu-example-f7wgv
Finish reconciling update event for Name = jinghzhu-example-f7wgv
Resource Version = 2347327
Desired = 1
Current = 1
PodList = jinghzhu-worker-hl7fc
State = Running
Message = Start to run replica set