async_workers.go

/*
Copyright 2022 The Katalyst 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 asyncworker

import (
	"context"
	"fmt"
	"reflect"
	"strings"
	"time"

	"k8s.io/apimachinery/pkg/util/wait"

	"github.com/kubewharf/katalyst-core/pkg/metrics"
	"github.com/kubewharf/katalyst-core/pkg/util/general"
)

func NewAsyncWorkers(name string, emitter metrics.MetricEmitter) *AsyncWorkers {
	return &AsyncWorkers{
		name:                name,
		emitter:             emitter,
		lastUndeliveredWork: make(map[string]*Work),
		workStatuses:        make(map[string]*workStatus),
	}
}

func (aws *AsyncWorkers) AddWork(workName string, work *Work, policy DuplicateWorkPolicy) error {
	aws.workLock.Lock()
	defer aws.workLock.Unlock()

	err := validateWork(work)
	if err != nil {
		return fmt.Errorf("validateWork for: %s failed with error: %v", workName, err)
	}

	general.InfoS("add work",
		"AsyncWorkers", aws.name,
		"workName", workName,
		"params", work.Params,
		"deliveredAt", work.DeliveredAt)

	status, ok := aws.workStatuses[workName]
	if !ok || status == nil {
		general.InfoS("create status for work",
			"AsyncWorkers", aws.name, "workName", workName)
		status = &workStatus{}
		aws.workStatuses[workName] = status
	} else if status.IsWorking() && policy == DuplicateWorkPolicyDiscard {
		general.InfoS("work %v already exists, discard new work", workName)
		return nil
	}

	// dispatch a request to the pod work if none are running
	if !status.IsWorking() {
		general.InfoS("status isn't working, handle work immediately",
			"AsyncWorkers", aws.name,
			"workName", workName,
			"params", work.Params,
			"deliveredAt", work.DeliveredAt)

		ctx := aws.contextForWork(workName, work)
		go aws.handleWork(ctx, workName, work)

		return nil
	}

	general.InfoS("status is working, queue work",
		"AsyncWorkers", aws.name,
		"workName", workName,
		"params", work.Params,
		"deliveredAt", work.DeliveredAt)

	if undelivered, ok := aws.lastUndeliveredWork[workName]; ok {
		general.InfoS("overwrite undelivered work",
			"AsyncWorkers", aws.name,
			"workName", workName,
			"old params", undelivered.Params,
			"old deliveredAt", undelivered.DeliveredAt,
			"new params", work.Params,
			"new deliveredAt", work.DeliveredAt)
	}

	// always set the most recent work
	aws.lastUndeliveredWork[workName] = work

	if status.cancelFn == nil {
		general.Fatalf("[AsyncWorkers: %s] %s nil cancelFn in working status", aws.name, workName)
	} else if status.work == nil {
		general.Fatalf("[AsyncWorkers: %s] %s nil work in working status", aws.name, workName)
	}

	general.InfoS("canceling current working work",
		"AsyncWorkers", aws.name,
		"workName", workName,
		"params", status.work.Params,
		"deliveredAt", status.work.DeliveredAt)
	status.cancelFn()

	return nil
}

func (aws *AsyncWorkers) handleWork(ctx context.Context, workName string, work *Work) {
	var handleErr error

	defer func() {
		if r := recover(); r != nil {
			handleErr = fmt.Errorf("recover from %v", r)

			metricErr := EmitCustomizedAsyncedMetrics(ctx,
				metricNameAsyncWorkPanic, 1,
				metrics.ConvertMapToTags(map[string]string{
					"workName": workName,
				})...)

			if metricErr != nil {
				general.Errorf("emit metric(%s:%d) failed with err: %v",
					metricNameAsyncWorkDurationMs, 1, metricErr)
			}
		}

		aws.completeWork(workName, work, handleErr)
	}()

	general.InfoS("handle work",
		"AsyncWorkers", aws.name,
		"workName", workName,
		"params", work.Params,
		"deliveredAt", work.DeliveredAt)

	funcValue := reflect.ValueOf(work.Fn)

	// filling up parameters for the passed functions
	paramValues := make([]reflect.Value, 1, len(work.Params)+1)
	paramValues[0] = reflect.ValueOf(ctx)
	for _, param := range work.Params {
		paramValues = append(paramValues, reflect.ValueOf(param))
	}

	startTime := time.Now()
	funcRets := funcValue.Call(paramValues)
	workDurationMs := time.Since(startTime).Milliseconds()

	if len(funcRets) != 1 {
		handleErr = fmt.Errorf("work Fn returns invalid number: %d of return values", len(funcRets))
	} else if funcRets[0].Interface() != nil {
		var ok bool
		handleErr, ok = funcRets[0].Interface().(error)

		if !ok {
			handleErr = fmt.Errorf("work Fn returns return value: %v of invalid type", funcRets[0].Interface())
		}
	}

	metricErr := EmitCustomizedAsyncedMetrics(ctx,
		metricNameAsyncWorkDurationMs, workDurationMs,
		metrics.ConvertMapToTags(map[string]string{
			"workName": workName,
		})...)

	if metricErr != nil {
		general.Errorf("emit metric(%s:%d) failed with err: %v",
			metricNameAsyncWorkDurationMs, workDurationMs, metricErr)
	}
}

func (aws *AsyncWorkers) completeWork(workName string, completedWork *Work, workErr error) {
	// TODO: support retrying if workErr != nil
	general.InfoS("complete work",
		"AsyncWorkers", aws.name,
		"workName", workName,
		"params", completedWork.Params,
		"deliveredAt", completedWork.DeliveredAt,
		"workErr", workErr)

	aws.workLock.Lock()
	defer aws.workLock.Unlock()

	if work, exists := aws.lastUndeliveredWork[workName]; exists {

		ctx := aws.contextForWork(workName, work)

		go aws.handleWork(ctx, workName, work)
		delete(aws.lastUndeliveredWork, workName)
	} else {
		aws.resetWorkStatus(workName)
	}
}

// contextForWork returns or initializes the appropriate context for a known
// work. And point status.work to the work. If the current context is expired, it is reset.
// It should be called in function protected by aws.workLock.
func (aws *AsyncWorkers) contextForWork(workName string, work *Work) context.Context {
	if work == nil {
		general.Fatalf("[AsyncWorkers: %s] contextForWork: %s got nil work", aws.name, workName)
	}

	status, ok := aws.workStatuses[workName]
	if !ok || status == nil {
		general.Fatalf("[AsyncWorkers: %s] contextForWork: %s got no status", aws.name, workName)
	}
	if status.ctx == nil || status.ctx.Err() == context.Canceled {
		ctx := context.Background()
		if names := strings.Split(workName, WorkNameSeperator); len(names) > 0 {
			ctx = context.WithValue(ctx, contextKeyMetricName, names[len(names)-1])
			ctx = context.WithValue(ctx, contextKeyMetricEmitter, aws.emitter)
		}
		status.ctx, status.cancelFn = context.WithCancel(ctx)

	}
	status.working = true
	status.work = work
	status.startedAt = time.Now()
	return status.ctx
}

// resetWorkStatus resets work status corresponding to workName,
// when there is no work of workName to do.
// It should be called in function protected by aws.workLock.
func (aws *AsyncWorkers) resetWorkStatus(workName string) {
	status, ok := aws.workStatuses[workName]
	if !ok || status == nil {
		general.Fatalf("[AsyncWorkers: %s] contextForWork: %s got no status",
			aws.name, workName)
	}

	status.working = false
	status.work = nil
	status.startedAt = time.Time{}
}

func (aws *AsyncWorkers) Start(stopCh <-chan struct{}) error {
	go wait.Until(aws.cleanupWorkStatus, 10*time.Second, stopCh)
	return nil
}

// cleanupWorkStatus cleans up work status not in working
func (aws *AsyncWorkers) cleanupWorkStatus() {
	aws.workLock.Lock()
	defer aws.workLock.Unlock()

	for workName, status := range aws.workStatuses {
		if status == nil {
			general.Errorf("[AsyncWorkers: %s] nil status for %s, clean it", aws.name, workName)
			delete(aws.workStatuses, workName)
		} else if !status.working {
			general.Errorf("[AsyncWorkers: %s] status for %s not in working, clean it", aws.name, workName)
			delete(aws.workStatuses, workName)
		}
	}
}

func (aws *AsyncWorkers) WorkExists(workName string) bool {
	aws.workLock.Lock()
	defer aws.workLock.Unlock()

	status, hasRunningWork := aws.workStatuses[workName]
	if hasRunningWork && status.IsWorking() {
		return true
	}

	_, hasUndeliveredWork := aws.lastUndeliveredWork[workName]
	if hasUndeliveredWork {
		return true
	}

	return false
}