controllers

package
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 Go to latest Published: Apr 19, 2024 License: Apache-2.0 Imports: 14 Imported by: 10

Documentation

Overview

Example

nolint: gocritic 

package main

import (
	"fmt"
	"time"

	"go.uber.org/atomic"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/types"

	"istio.io/istio/pkg/kube"
	"istio.io/istio/pkg/kube/controllers"
	"istio.io/istio/pkg/kube/kclient"
	"istio.io/istio/pkg/log"
	"istio.io/istio/pkg/test/util/retry"
)

// Controller represents a simple example controller show best practices for correctly writing a controller
// in Istio.
// In this example, we simply print all pods.
type Controller struct {
	pods   kclient.Client[*corev1.Pod]
	queue  controllers.Queue
	events *atomic.Int32
}

// NewController creates a controller instance. A controller should typically take in a kube.Client,
// and optionally whatever other configuration is needed. When a large number of options are needed,
// prefer a struct as input.
func NewController(cl kube.Client) *Controller {
	c := &Controller{events: atomic.NewInt32(0)}
	// For each thing we watch, build a typed `client`. This encapsulates a variety of complex logic
	// that would otherwise need to be dealt with manually with Informers and Listers.
	// In general, you should *not* ever do a direct List or Get call to the api-server.
	// Each kube.Client (which, there should be one per cluster) has a shared set of watches to the API server,
	// so two controllers watching Pods will only open a single watch to the API server.
	c.pods = kclient.New[*corev1.Pod](cl)
	// Some other examples:
	// filteredPods := client.NewFiltered[*corev1.Pod](c, kclient.Filter{ObjectFilter: options.GetFilter()})
	// singlePod := client.NewFiltered[*corev1.Pod](c, kclient.Filter{FieldSelector: "metadata.name=my-pod})

	// Establish a queue. This ensures that:
	// * our event handlers are fast (simply enqueuing an item)
	// * if we have multiple resources watched, they are not handled in parallel
	// * errors can be retried
	c.queue = controllers.NewQueue("pods",
		controllers.WithReconciler(c.Reconcile),
		controllers.WithMaxAttempts(5))

	// Register a handler for pods. For each pod event, we will add it to the queue.
	c.pods.AddEventHandler(controllers.ObjectHandler(c.queue.AddObject))
	return c
}

// Reconcile is the main work function for our controller. As input, we get a name of an object; with
// this we should drive the rest of the state of the world.
func (c *Controller) Reconcile(key types.NamespacedName) error {
	// Its often useful to shadow the log one with additional K/V context
	log := log.WithLabels("resource", key)
	pod := c.pods.Get(key.Name, key.Namespace)
	if pod == nil {
		log.Infof("pod deleted")
	} else {
		c.events.Inc()
		fmt.Println("pod has IP", pod.Status.PodIP) // Just for our test, normally use log.Info
		log.Infof("pod has IP %v", pod.Status.PodIP)
	}
	// We never have an error for this controller.
	// If we did, it would be retried (with backoff), based on our controllers.WithMaxAttempts argument.
	return nil
}

// Run is called after New() but before HasSynced(). This separation allows building up the controllers
// without yet running them.
// Run should block.
func (c *Controller) Run(stop <-chan struct{}) {
	// The details here are subtle but important to get right. We want to mark our controller ready
	// only after it has processed the state of the world when we started. That is, we must have
	// Reconciled() each Pod. The queueing introduces some indirection, though - we want to make sure
	// we have fully processed each item, not simply added it to the Queue. The queue exposes a
	// HasSynced method that returns true once all items added before queue.Run() was called are complete.
	// This means we must populate the initial state into the queue *before* we run it.

	// First, wait for pods to sync. Once this is complete, we know the event handler for Pods will have
	// ran for each item and enqueued everything.
	kube.WaitForCacheSync("pod controller", stop, c.pods.HasSynced)

	// Now we can run the queue. This will block until `stop` is closed.
	c.queue.Run(stop)
	// Unregister our handler. This ensures it does not continue to run if the informer is still running
	// after the controller exits.
	// This is typically only needed for leader election controllers, as otherwise the controller lifecycle
	// is typically the same as the informer.
	c.pods.ShutdownHandlers()
}

// HasSynced asserts we have "synced", meaning we have processed the initial state.
func (c *Controller) HasSynced() bool {
	// We could check `c.pods` as well, but it is redundant due to the Run() implementation.
	// Instead, just check `c.queue`.
	return c.queue.HasSynced()
}

// nolint: gocritic
func main() {
	// Setup our fake client. This can be pre-populated with items.
	c := kube.NewFakeClient(&corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{Name: "test1"},
		Status:     corev1.PodStatus{PodIP: "127.0.0.1"},
	})
	// When the test is done, terminate the client. This ensures all informers are closed.
	// This usually doesn't matter, but can be useful when mutating global state with test.SetForTest, etc.
	defer c.Shutdown() // Normally: t.Cleanup(c.Shutdown)

	// Build our controller
	controller := NewController(c)
	// Ensure our queue finished processing events
	defer func() {
		// Normally: assert.NoError(t, ...)
		controller.queue.WaitForClose(time.Second)
	}()

	stop := make(chan struct{}) // Normally: test.NewStop(t), in tests
	defer func() { close(stop) }()

	// Note: the order of the defer/t.Cleanup matters
	// We should close the stop (which will start the queue and informers shutdown process)
	// then wait for the queue and informers to shutdown

	// *After* we build the controller, we need to start all informers. The order here matters, as NewController
	// if the thing that registers them.
	c.RunAndWait(stop)

	// Now run our controller (in goroutine)
	go controller.Run(stop)
	// Wait for it to be ready
	kube.WaitForCacheSync("test", stop, controller.HasSynced)

	// In a test, we can also use a wrapped client that calls t.Fatal on errors
	// pods := clienttest.Wrap(t, controller.pods)
	_, _ = controller.pods.Create(&corev1.Pod{
		ObjectMeta: metav1.ObjectMeta{Name: "test2"},
		Status:     corev1.PodStatus{PodIP: "127.0.0.2"},
	})
	// There is no guarantee that test2 would be processed before the controller exits, so wait for events insert
	_ = retry.Until(func() bool {
		return controller.events.Load() == 2
	})
	// In a typical test, using helpers like assert.EventuallyEqual or retry.UntilSuccessOrFail are preferred
	// assert.EventuallyEqual(t, controller.events.Load, 2)

}

Output:

pod has IP 127.0.0.1
pod has IP 127.0.0.2

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func EnqueueForParentHandler 

func EnqueueForParentHandler(q Queue, kind config.GroupVersionKind) func(obj Object)

EnqueueForParentHandler returns a handler that will enqueue the parent (by ownerRef) resource

func Extract 

func Extract[T Object](obj any) T

Extract pulls a T from obj, handling tombstones. This will return nil if the object cannot be extracted.

func FilteredObjectHandler 

func FilteredObjectHandler(handler func(o Object), filter func(o Object) bool) cache.ResourceEventHandler

FilteredObjectHandler returns a handler that will act on the latest version of an object This means Add/Update/Delete are all handled the same and are just used to trigger reconciling. If filters are set, returning 'false' will exclude the event. For Add and Deletes, the filter will be based on the new or old item. For updates, the item will be handled if either the new or the old object is updated.

func FilteredObjectSpecHandler 

func FilteredObjectSpecHandler(handler func(o Object), filter func(o Object) bool) cache.ResourceEventHandler

FilteredObjectSpecHandler returns a handler that will act on the latest version of an object This means Add/Update/Delete are all handled the same and are just used to trigger reconciling. Unlike FilteredObjectHandler, the handler is only trigger when the resource spec changes (ie resourceVersion) If filters are set, returning 'false' will exclude the event. For Add and Deletes, the filter will be based on the new or old item. For updates, the item will be handled if either the new or the old object is updated.

func FromEventHandler 

func FromEventHandler(handler func(o Event)) cache.ResourceEventHandler

func IgnoreNotFound 

func IgnoreNotFound(err error) error

IgnoreNotFound returns nil on NotFound errors. All other values that are not NotFound errors or nil are returned unmodified.

func IsNil 

func IsNil[O ComparableObject](o O) bool

IsNil works around comparing generic types

func ObjectHandler 

func ObjectHandler(handler func(o Object)) cache.ResourceEventHandler

ObjectHandler returns a handler that will act on the latest version of an object This means Add/Update/Delete are all handled the same and are just used to trigger reconciling.

func ObjectToGVR 

func ObjectToGVR(u Object) (schema.GroupVersionResource, error)

ObjectToGVR extracts the GVR of an unstructured resource. This is useful when using dynamic clients.

func ShutdownAll 

func ShutdownAll(s ...Shutdowner)

ShutdownAll is a simple helper to shutdown all informers

func UnstructuredToGVR 

func UnstructuredToGVR(u unstructured.Unstructured) (schema.GroupVersionResource, error)

UnstructuredToGVR extracts the GVR of an unstructured resource. This is useful when using dynamic clients.

func WithGenericReconciler 

func WithGenericReconciler(f func(key any) error) func(q *Queue)

WithGenericReconciler defines the handler function to handle items in the queue that can handle any type

func WithMaxAttempts 

func WithMaxAttempts(n int) func(q *Queue)

WithMaxAttempts allows defining a custom max attempts for the queue. If not set, items will not be retried

func WithName 

func WithName(name string) func(q *Queue)

WithName sets a name for the queue. This is used for logging

func WithRateLimiter 

func WithRateLimiter(r workqueue.RateLimiter) func(q *Queue)

WithRateLimiter allows defining a custom rate limiter for the queue

func WithReconciler 

func WithReconciler(f ReconcilerFn) func(q *Queue)

WithReconciler defines the handler function to handle items in the queue.

Types

type ComparableObject 

type ComparableObject interface {
	comparable
	Object
}

type Event 

type Event struct {
	Old   Object
	New   Object
	Event EventType
}

func (Event) Latest 

func (e Event) Latest() Object

type EventHandler 

type EventHandler[T Object] struct {
	AddFunc         func(obj T)
	AddExtendedFunc func(obj T, initialSync bool)
	UpdateFunc      func(oldObj, newObj T)
	DeleteFunc      func(obj T)
}

EventHandler mirrors ResourceEventHandlerFuncs, but takes typed T objects instead of any.

func (EventHandler[T]) OnAdd 

func (e EventHandler[T]) OnAdd(obj interface{}, initialSync bool)

func (EventHandler[T]) OnDelete 

func (e EventHandler[T]) OnDelete(obj interface{})

func (EventHandler[T]) OnUpdate 

func (e EventHandler[T]) OnUpdate(oldObj, newObj interface{})

type EventType 

type EventType int

EventType represents a registry update event 

const (
	// EventAdd is sent when an object is added
	EventAdd EventType = iota

	// EventUpdate is sent when an object is modified
	// Captures the modified object
	EventUpdate

	// EventDelete is sent when an object is deleted
	// Captures the object at the last known state
	EventDelete
)

func (EventType) String 

func (event EventType) String() string

type Object 

type Object interface {
	metav1.Object
	runtime.Object
}

Object is a union of runtime + meta objects. Essentially every k8s object meets this interface. and certainly all that we care about.

func ExtractObject 

func ExtractObject(obj any) Object

type Queue 

type Queue struct {
	// contains filtered or unexported fields
}

Queue defines an abstraction around Kubernetes' workqueue. Items enqueued are deduplicated; this generally means relying on ordering of events in the queue is not feasible.

func NewQueue 

func NewQueue(name string, options ...func(*Queue)) Queue

NewQueue creates a new queue

func (Queue) Add 

func (q Queue) Add(item any)

Add an item to the queue.

func (Queue) AddObject 

func (q Queue) AddObject(obj Object)

AddObject takes an Object and adds the types.NamespacedName associated.

func (Queue) Closed 

func (q Queue) Closed() <-chan struct{}

Closed returns a chan that will be signaled when the Instance has stopped processing tasks.

func (Queue) HasSynced 

func (q Queue) HasSynced() bool

HasSynced returns true if the queue has 'synced'. A synced queue has started running and has processed all events that were added prior to Run() being called Warning: these items will be processed at least once, but may have failed.

func (Queue) Run 

func (q Queue) Run(stop <-chan struct{})

Run the queue. This is synchronous, so should typically be called in a goroutine.

func (Queue) WaitForClose 

func (q Queue) WaitForClose(timeout time.Duration) error

WaitForClose blocks until the Instance has stopped processing tasks or the timeout expires. If the timeout is zero, it will wait until the queue is done processing. WaitForClose an error if the timeout expires.

type ReconcilerFn 

type ReconcilerFn func(key types.NamespacedName) error

type Shutdowner 

type Shutdowner interface {
	ShutdownHandlers()
}

Source Files

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