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queue.go
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queue.go
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// Copyright 2017 Istio Authors
//
// 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 kube
import (
"os"
"strconv"
"sync"
"time"
"k8s.io/client-go/util/flowcontrol"
"istio.io/istio/pilot/pkg/model"
"istio.io/istio/pkg/log"
)
const (
// enableQueueThrottleEnv is an environment variable that can be set to re-enable the
// throttling, in case problems are discovered. This is not a flag - it would cause too
// many changes, and it is only intended as a short term fail-safe and A/B testing.
// TODO: remove in 0.7 after more testing without the throttle.
enableQueueThrottleEnv = "PILOT_THROTTLE"
)
// Queue of work tickets processed using a rate-limiting loop
type Queue interface {
// Push a ticket
Push(Task)
// Run the loop until a signal on the channel
Run(<-chan struct{})
}
// Handler specifies a function to apply on an object for a given event type
type Handler func(obj interface{}, event model.Event) error
// Task object for the event watchers; processes until handler succeeds
type Task struct {
handler Handler
obj interface{}
event model.Event
}
// NewTask creates a task from a work item
func NewTask(handler Handler, obj interface{}, event model.Event) Task {
return Task{handler: handler, obj: obj, event: event}
}
type queueImpl struct {
delay time.Duration
queue []Task
lock sync.Mutex
closing bool
}
// NewQueue instantiates a queue with a processing function
func NewQueue(errorDelay time.Duration) Queue {
return &queueImpl{
delay: errorDelay,
queue: make([]Task, 0),
closing: false,
lock: sync.Mutex{},
}
}
func (q *queueImpl) Push(item Task) {
q.lock.Lock()
if !q.closing {
q.queue = append(q.queue, item)
}
q.lock.Unlock()
}
func (q *queueImpl) Run(stop <-chan struct{}) {
go func() {
<-stop
q.lock.Lock()
q.closing = true
q.lock.Unlock()
}()
rate := os.Getenv(enableQueueThrottleEnv)
rateLimit := 100
if len(rate) > 0 {
r, err := strconv.Atoi(rate)
if err == nil {
rateLimit = r
}
}
// Throttle processing up to smoothed 10 qps with bursts up to 100 qps
var rateLimiter flowcontrol.RateLimiter
if rateLimit > 0 {
rateLimiter = flowcontrol.NewTokenBucketRateLimiter(float32(rateLimit), 10*rateLimit)
}
var item Task
for {
if rateLimit > 0 {
rateLimiter.Accept()
}
q.lock.Lock()
if q.closing {
q.lock.Unlock()
return
} else if len(q.queue) == 0 {
q.lock.Unlock()
} else {
item, q.queue = q.queue[0], q.queue[1:]
q.lock.Unlock()
for {
err := item.handler(item.obj, item.event)
if err != nil {
log.Infof("Work item failed (%v), repeating after delay %v", err, q.delay)
time.Sleep(q.delay)
} else {
break
}
}
}
}
}
// ChainHandler applies handlers in a sequence
type ChainHandler struct {
funcs []Handler
}
// Apply is the handler function
func (ch *ChainHandler) Apply(obj interface{}, event model.Event) error {
for _, f := range ch.funcs {
if err := f(obj, event); err != nil {
return err
}
}
return nil
}
// Append a handler as the last handler in the chain
func (ch *ChainHandler) Append(h Handler) {
ch.funcs = append(ch.funcs, h)
}