controller.go

/*
Copyright (c) 2016-2017 Bitnami

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controller

import (
	"errors"
	"fmt"
	"time"

	"github.com/Sirupsen/logrus"
	k8sErrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/fields"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/pkg/api"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/util/workqueue"

	"github.com/kubeless/kubeless/pkg/spec"
	"github.com/kubeless/kubeless/pkg/utils"
)

const (
	crdName    = "function.k8s.io"
	maxRetries = 5
	funcKind   = "Function"
	funcAPI    = "k8s.io"
)

var (
	errVersionOutdated = errors.New("Requested version is outdated in apiserver")
	initRetryWaitTime  = 30 * time.Second
)

// Controller object
type Controller struct {
	logger    *logrus.Entry
	clientset kubernetes.Interface
	crdclient rest.Interface
	Functions map[string]*spec.Function
	queue     workqueue.RateLimitingInterface
	informer  cache.SharedIndexInformer
}

// Config contains k8s client of a controller
type Config struct {
	KubeCli   kubernetes.Interface
	CRDClient rest.Interface
}

// New initializes a controller object
func New(cfg Config) *Controller {
	lw := cache.NewListWatchFromClient(cfg.CRDClient, "functions", api.NamespaceAll, fields.Everything())

	queue := workqueue.NewRateLimitingQueue(workqueue.DefaultControllerRateLimiter())

	informer := cache.NewSharedIndexInformer(
		lw,
		&spec.Function{},
		0,
		cache.Indexers{},
	)

	informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			key, err := cache.MetaNamespaceKeyFunc(obj)
			if err == nil {
				queue.Add(key)
			}
		},
		UpdateFunc: func(old, new interface{}) {
			key, err := cache.MetaNamespaceKeyFunc(new)
			if err == nil {
				queue.Add(key)
			}
		},
		DeleteFunc: func(obj interface{}) {
			key, err := cache.DeletionHandlingMetaNamespaceKeyFunc(obj)
			if err == nil {
				queue.Add(key)
			}
		},
	})

	return &Controller{
		logger:    logrus.WithField("pkg", "controller"),
		clientset: cfg.KubeCli,
		crdclient: cfg.CRDClient,
		informer:  informer,
		queue:     queue,
	}
}

// Run starts the kubeless controller
func (c *Controller) Run(stopCh <-chan struct{}) {
	defer utilruntime.HandleCrash()
	defer c.queue.ShutDown()

	c.logger.Info("Starting kubeless controller")

	go c.informer.Run(stopCh)

	if !cache.WaitForCacheSync(stopCh, c.HasSynced) {
		utilruntime.HandleError(fmt.Errorf("Timed out waiting for caches to sync"))
		return
	}

	c.logger.Info("Kubeless controller synced and ready")

	// run one round of GC at startup to detect orphaned objects from the last time
	c.garbageCollect()

	wait.Until(c.runWorker, time.Second, stopCh)
}

// HasSynced is required for the cache.Controller interface.
func (c *Controller) HasSynced() bool {
	return c.informer.HasSynced()
}

// LastSyncResourceVersion is required for the cache.Controller interface.
func (c *Controller) LastSyncResourceVersion() string {
	return c.informer.LastSyncResourceVersion()
}

func (c *Controller) runWorker() {
	for c.processNextItem() {
		// continue looping
	}
}

func (c *Controller) processNextItem() bool {
	key, quit := c.queue.Get()
	if quit {
		return false
	}
	defer c.queue.Done(key)

	err := c.processItem(key.(string))
	if err == nil {
		// No error, reset the ratelimit counters
		c.queue.Forget(key)
	} else if c.queue.NumRequeues(key) < maxRetries {
		c.logger.Errorf("Error processing %s (will retry): %v", key, err)
		c.queue.AddRateLimited(key)
	} else {
		// err != nil and too many retries
		c.logger.Errorf("Error processing %s (giving up): %v", key, err)
		c.queue.Forget(key)
		utilruntime.HandleError(err)
	}

	return true
}

// ensureK8sResources creates/updates k8s objects (deploy, svc, configmap) for the function
func (c *Controller) ensureK8sResources(funcObj *spec.Function) error {
	if len(funcObj.Metadata.Labels) == 0 {
		funcObj.Metadata.Labels = make(map[string]string)
	}
	funcObj.Metadata.Labels["function"] = funcObj.Metadata.Name

	t := true
	or := []metav1.OwnerReference{
		{
			Kind:               "Function",
			APIVersion:         "k8s.io",
			Name:               funcObj.Metadata.Name,
			UID:                funcObj.Metadata.UID,
			BlockOwnerDeletion: &t,
		},
	}

	err := utils.EnsureFuncConfigMap(c.clientset, funcObj, or)
	if err != nil {
		return err
	}

	err = utils.EnsureFuncService(c.clientset, funcObj, or)
	if err != nil {
		return err
	}

	err = utils.EnsureFuncDeployment(c.clientset, funcObj, or)
	if err != nil {
		return err
	}

	if funcObj.Spec.Type == "Scheduled" {
		err = utils.EnsureFuncCronJob(c.clientset, funcObj, or)
		if err != nil {
			return err
		}
	}

	return nil
}

// deleteK8sResources removes k8s objects of the function
func (c *Controller) deleteK8sResources(ns, name string) error {
	//check if func is scheduled or not
	_, err := c.clientset.BatchV2alpha1().CronJobs(ns).Get(fmt.Sprintf("trigger-%s", name), metav1.GetOptions{})
	if err == nil {
		err = c.clientset.BatchV2alpha1().CronJobs(ns).Delete(fmt.Sprintf("trigger-%s", name), &metav1.DeleteOptions{})
		if err != nil && !k8sErrors.IsNotFound(err) {
			return err
		}
	}

	// delete deployment
	deletePolicy := metav1.DeletePropagationBackground
	err = c.clientset.Extensions().Deployments(ns).Delete(name, &metav1.DeleteOptions{PropagationPolicy: &deletePolicy})
	if err != nil && !k8sErrors.IsNotFound(err) {
		return err
	}
	// delete svc
	err = c.clientset.Core().Services(ns).Delete(name, &metav1.DeleteOptions{})
	if err != nil && !k8sErrors.IsNotFound(err) {
		return err
	}

	// delete cm
	err = c.clientset.Core().ConfigMaps(ns).Delete(name, &metav1.DeleteOptions{})
	if err != nil && !k8sErrors.IsNotFound(err) {
		return err
	}

	return nil
}

func (c *Controller) processItem(key string) error {
	c.logger.Infof("Processing change to Function %s", key)

	ns, name, err := cache.SplitMetaNamespaceKey(key)
	if err != nil {
		return err
	}

	obj, exists, err := c.informer.GetIndexer().GetByKey(key)
	if err != nil {
		return fmt.Errorf("Error fetching object with key %s from store: %v", key, err)
	}

	if !exists {
		err := c.deleteK8sResources(ns, name)
		if err != nil {
			c.logger.Errorf("Can't delete function: %v", err)
			return err
		}
		c.logger.Infof("Deleted Function %s", key)
		return nil
	}

	funcObj := obj.(*spec.Function)

	err = c.ensureK8sResources(funcObj)
	if err != nil {
		c.logger.Errorf("Function can not be created/updated: %v", err)
		return err
	}

	c.logger.Infof("Updated Function %s", key)
	return nil
}

func (c *Controller) garbageCollect() error {
	err := c.collectServices()
	if err != nil {
		return err
	}
	err = c.collectDeployment()
	if err != nil {
		return err
	}
	err = c.collectConfigMap()
	if err != nil {
		return err
	}
	return nil
}

func (c *Controller) collectServices() error {
	srvs, err := c.clientset.CoreV1().Services(api.NamespaceAll).List(metav1.ListOptions{})
	if err != nil {
		return err
	}

	for _, srv := range srvs.Items {
		if len(srv.OwnerReferences) == 0 {
			continue
		}
		// Include the derived key from existing svc owner reference to the workqueue
		// This will make sure the controller can detect the non-existing function and
		// react to delete its belonging objects
		// Assumption: a service has ownerref Kind = "Function" and APIVersion = "k8s.io" is assumed
		// to be created by kubeless controller
		if (srv.OwnerReferences[0].Kind == funcKind) && (srv.OwnerReferences[0].APIVersion == funcAPI) {
			//service and its function are deployed in the same namespace
			key := fmt.Sprintf("%s/%s", srv.Namespace, srv.OwnerReferences[0].Name)
			c.queue.Add(key)
		}
	}

	return nil
}

func (c *Controller) collectDeployment() error {
	ds, err := c.clientset.AppsV1beta1().Deployments(api.NamespaceAll).List(metav1.ListOptions{})
	if err != nil {
		return err
	}

	for _, d := range ds.Items {
		if len(d.OwnerReferences) == 0 {
			continue
		}
		// Assumption: a deployment has ownerref Kind = "Function" and APIVersion = "k8s.io" is assumed
		// to be created by kubeless controller
		if (d.OwnerReferences[0].Kind == funcKind) && (d.OwnerReferences[0].APIVersion == funcAPI) {
			key := fmt.Sprintf("%s/%s", d.Namespace, d.OwnerReferences[0].Name)
			c.queue.Add(key)
		}
	}

	return nil
}

func (c *Controller) collectConfigMap() error {
	cm, err := c.clientset.CoreV1().ConfigMaps(api.NamespaceAll).List(metav1.ListOptions{})
	if err != nil {
		return err
	}

	for _, m := range cm.Items {
		if len(m.OwnerReferences) == 0 {
			continue
		}
		// Assumption: a configmap has ownerref Kind = "Function" and APIVersion = "k8s.io" is assumed
		// to be created by kubeless controller
		if (m.OwnerReferences[0].Kind == funcKind) && (m.OwnerReferences[0].APIVersion == funcAPI) {
			key := fmt.Sprintf("%s/%s", m.Namespace, m.OwnerReferences[0].Name)
			c.queue.Add(key)
		}
	}

	return nil
}