agones.dev/agones@v1.53.0/cmd/processor/main.go

// Copyright 2025 Google LLC All Rights Reserved.
//
// 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.

// Processor
package main

import (
	"context"
	"os"
	"strings"
	"time"

	"agones.dev/agones/pkg"
	"agones.dev/agones/pkg/util/httpserver"
	"agones.dev/agones/pkg/util/runtime"
	"agones.dev/agones/pkg/util/signals"

	"github.com/google/uuid"
	"github.com/heptiolabs/healthcheck"
	"github.com/sirupsen/logrus"
	"github.com/spf13/pflag"
	"github.com/spf13/viper"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	leaderelection "k8s.io/client-go/tools/leaderelection"
	"k8s.io/client-go/tools/leaderelection/resourcelock"
)

const (
	logLevelFlag       = "log-level"
	leaderElectionFlag = "leader-election"
	podNamespace       = "pod-namespace"
	leaseDurationFlag  = "lease-duration"
	renewDeadlineFlag  = "renew-deadline"
	retryPeriodFlag    = "retry-period"
)

var (
	logger = runtime.NewLoggerWithSource("main")
)

type processorConfig struct {
	LogLevel       string
	LeaderElection bool
	PodNamespace   string
	LeaseDuration  time.Duration
	RenewDeadline  time.Duration
	RetryPeriod    time.Duration
}

func parseEnvFlags() processorConfig {
	viper.SetDefault(logLevelFlag, "Info")
	viper.SetDefault(leaderElectionFlag, false)
	viper.SetDefault(podNamespace, "")
	viper.SetDefault(leaseDurationFlag, 15*time.Second)
	viper.SetDefault(renewDeadlineFlag, 10*time.Second)
	viper.SetDefault(retryPeriodFlag, 2*time.Second)

	pflag.String(logLevelFlag, viper.GetString(logLevelFlag), "Log level")
	pflag.Bool(leaderElectionFlag, viper.GetBool(leaderElectionFlag), "Enable leader election")
	pflag.String(podNamespace, viper.GetString(podNamespace), "Pod namespace")
	pflag.Duration(leaseDurationFlag, viper.GetDuration(leaseDurationFlag), "Leader election lease duration")
	pflag.Duration(renewDeadlineFlag, viper.GetDuration(renewDeadlineFlag), "Leader election renew deadline")
	pflag.Duration(retryPeriodFlag, viper.GetDuration(retryPeriodFlag), "Leader election retry period")
	pflag.Parse()

	viper.SetEnvKeyReplacer(strings.NewReplacer("-", "_"))
	viper.AutomaticEnv()
	_ = viper.BindPFlags(pflag.CommandLine)

	return processorConfig{
		LogLevel:       viper.GetString(logLevelFlag),
		LeaderElection: viper.GetBool(leaderElectionFlag),
		PodNamespace:   viper.GetString(podNamespace),
		LeaseDuration:  viper.GetDuration(leaseDurationFlag),
		RenewDeadline:  viper.GetDuration(renewDeadlineFlag),
		RetryPeriod:    viper.GetDuration(retryPeriodFlag),
	}
}

func main() {
	ctx, cancelCtx := context.WithCancel(context.Background())
	defer cancelCtx()

	conf := parseEnvFlags()

	logger.WithField("version", pkg.Version).WithField("processorConf", conf).
		WithField("featureGates", runtime.EncodeFeatures()).
		Info("Starting agones-processor")

	logger.WithField("logLevel", conf.LogLevel).Info("Setting LogLevel configuration")
	level, err := logrus.ParseLevel(strings.ToLower(conf.LogLevel))
	if err == nil {
		runtime.SetLevel(level)
	} else {
		logger.WithError(err).Info("Specified wrong Logging. Setting default loglevel - Info")
		runtime.SetLevel(logrus.InfoLevel)
	}

	healthserver := &httpserver.Server{Logger: logger}
	health := healthcheck.NewHandler()

	config, err := rest.InClusterConfig()
	if err != nil {
		logger.WithError(err).Fatal("Failed to create in-cluster config")
		panic("Failed to create in-cluster config: " + err.Error())
	}
	kubeClient, err := kubernetes.NewForConfig(config)
	if err != nil {
		logger.WithError(err).Fatal("Failed to create Kubernetes client")
		panic("Failed to create Kubernetes client: " + err.Error())
	}

	go func() {
		healthserver.Handle("/", health)
		_ = healthserver.Run(context.Background(), 0)
	}()

	signals.NewSigTermHandler(func() {
		logger.Info("Pod shutdown has been requested, failing readiness check")
		cancelCtx()
		os.Exit(0)
	})

	whenLeader(ctx, cancelCtx, logger, conf, kubeClient, func(ctx context.Context) {
		logger.Info("Starting processor work as leader")

		// Simulate processor work (to ensure the leader is working)
		// TODO: implement processor work
		ticker := time.NewTicker(5 * time.Second)
		defer ticker.Stop()

		for {
			select {
			case <-ctx.Done():
				logger.Info("Processor work completed")
				return
			case <-ticker.C:
				logger.Info("Processor is active as leader")
			}
		}
	})

	logger.Info("Processor exited gracefully.")
}

func whenLeader(ctx context.Context, cancel context.CancelFunc, logger *logrus.Entry,
	conf processorConfig, kubeClient *kubernetes.Clientset, start func(_ context.Context)) {
	if !conf.LeaderElection {
		start(ctx)
		return
	}

	id := uuid.New().String()

	lock := &resourcelock.LeaseLock{
		LeaseMeta: metav1.ObjectMeta{
			Name:      "agones-processor-lock",
			Namespace: conf.PodNamespace,
		},
		Client: kubeClient.CoordinationV1(),
		LockConfig: resourcelock.ResourceLockConfig{
			Identity: id,
		},
	}

	logger.WithField("id", id).Info("Leader Election ID")

	leaderelection.RunOrDie(ctx, leaderelection.LeaderElectionConfig{
		Lock: lock,
		// IMPORTANT: you MUST ensure that any code you have that
		// is protected by the lease must terminate **before**
		// you call cancel. Otherwise, you could have a background
		// loop still running and another process could
		// get elected before your background loop finished, violating
		// the stated goal of the lease.
		ReleaseOnCancel: true,
		LeaseDuration:   conf.LeaseDuration,
		RenewDeadline:   conf.RenewDeadline,
		RetryPeriod:     conf.RetryPeriod,
		Callbacks: leaderelection.LeaderCallbacks{
			OnStartedLeading: start,
			OnStoppedLeading: func() {
				logger.WithField("id", id).Info("Leader Lost")
				cancel()
				os.Exit(0)
			},
			OnNewLeader: func(identity string) {
				if identity == id {
					return
				}
				logger.WithField("id", id).Info("New Leader Elected")
			},
		},
	})
}