go-redis/example/pubsub/main.go

package main

import (
	"context"
	"fmt"
	"log"
	"sync"
	"time"

	"github.com/redis/go-redis/v9"
	"github.com/redis/go-redis/v9/hitless"
)

var ctx = context.Background()

// This example is not supposed to be run as is. It is just a test to see how pubsub behaves in relation to pool management.
// It was used to find regressions in pool management in hitless mode.
// Please don't use it as a reference for how to use pubsub.
func main() {
	wg := &sync.WaitGroup{}
	rdb := redis.NewClient(&redis.Options{
		Addr: ":6379",
		HitlessUpgradeConfig: &redis.HitlessUpgradeConfig{
			Mode: hitless.MaintNotificationsEnabled,
		},
	})
	_ = rdb.FlushDB(ctx).Err()

	go func() {
		for {
			time.Sleep(2 * time.Second)
			fmt.Printf("pool stats: %+v\n", rdb.PoolStats())
		}
	}()
	err := rdb.Ping(ctx).Err()
	if err != nil {
		panic(err)
	}
	if err := rdb.Set(ctx, "publishers", "0", 0).Err(); err != nil {
		panic(err)
	}
	if err := rdb.Set(ctx, "subscribers", "0", 0).Err(); err != nil {
		panic(err)
	}
	if err := rdb.Set(ctx, "published", "0", 0).Err(); err != nil {
		panic(err)
	}
	if err := rdb.Set(ctx, "received", "0", 0).Err(); err != nil {
		panic(err)
	}
	fmt.Println("published", rdb.Get(ctx, "published").Val())
	fmt.Println("received", rdb.Get(ctx, "received").Val())
	subCtx, cancelSubCtx := context.WithCancel(ctx)
	pubCtx, cancelPublishers := context.WithCancel(ctx)
	for i := 0; i < 10; i++ {
		wg.Add(1)
		go subscribe(subCtx, rdb, "test", i, wg)
	}
	time.Sleep(time.Second)
	cancelSubCtx()
	time.Sleep(time.Second)
	subCtx, cancelSubCtx = context.WithCancel(ctx)
	for i := 0; i < 10; i++ {
		if err := rdb.Incr(ctx, "publishers").Err(); err != nil {
			panic(err)
		}
		wg.Add(1)
		go floodThePool(pubCtx, rdb, wg)
	}

	for i := 0; i < 500; i++ {
		if err := rdb.Incr(ctx, "subscribers").Err(); err != nil {
			panic(err)
		}
		wg.Add(1)
		go subscribe(subCtx, rdb, "test2", i, wg)
	}
	time.Sleep(5 * time.Second)
	fmt.Println("canceling publishers")
	cancelPublishers()
	time.Sleep(10 * time.Second)
	fmt.Println("canceling subscribers")
	cancelSubCtx()
	wg.Wait()
	published, err := rdb.Get(ctx, "published").Result()
	received, err := rdb.Get(ctx, "received").Result()
	publishers, err := rdb.Get(ctx, "publishers").Result()
	subscribers, err := rdb.Get(ctx, "subscribers").Result()
	fmt.Printf("publishers: %s\n", publishers)
	fmt.Printf("published: %s\n", published)
	fmt.Printf("subscribers: %s\n", subscribers)
	fmt.Printf("received: %s\n", received)
	publishedInt, err := rdb.Get(ctx, "published").Int()
	subscribersInt, err := rdb.Get(ctx, "subscribers").Int()
	fmt.Printf("if drained = published*subscribers: %d\n", publishedInt*subscribersInt)

	time.Sleep(2 * time.Second)
}

func floodThePool(ctx context.Context, rdb *redis.Client, wg *sync.WaitGroup) {
	defer wg.Done()
	for {
		select {
		case <-ctx.Done():
			return
		default:
		}
		err := rdb.Publish(ctx, "test2", "hello").Err()
		if err != nil {
			// noop
			//log.Println("publish error:", err)
		}

		err = rdb.Incr(ctx, "published").Err()
		if err != nil {
			// noop
			//log.Println("incr error:", err)
		}
		time.Sleep(10 * time.Nanosecond)
	}
}

func subscribe(ctx context.Context, rdb *redis.Client, topic string, subscriberId int, wg *sync.WaitGroup) {
	defer wg.Done()
	rec := rdb.Subscribe(ctx, topic)
	recChan := rec.Channel()
	for {
		select {
		case <-ctx.Done():
			rec.Close()
			return
		default:
			select {
			case <-ctx.Done():
				rec.Close()
				return
			case msg := <-recChan:
				err := rdb.Incr(ctx, "received").Err()
				if err != nil {
					log.Println("incr error:", err)
				}
				_ = msg // Use the message to avoid unused variable warning
			}
		}
	}
}