package main

import (
	"github.com/lib/pq"
	"database/sql"
	"fmt"
	"log"
	"time"
)

const connInfo = "host=/var/run/postgresql sslmode=disable"

func listener(i int) {
	l := pq.NewListener(connInfo, time.Second, time.Second, nil)
	err := l.Listen(fmt.Sprintf("channel%d", i))
	if err != nil {
		log.Fatal(err)
	}
	for {
		<-l.Notify
	}
}

func notifier(dbh *sql.DB, i int) {
	for {
		_, err := dbh.Exec(fmt.Sprintf("NOTIFY channel%d", i))
		if err != nil {
			log.Fatal(err)
		}
		time.Sleep(750 * time.Millisecond)
	}
}

func main() {
	openDb := func() *sql.DB {
		db, _ := sql.Open("postgres", connInfo)
		err := db.Ping()
		if err != nil {
			log.Fatal(err)
		}
		db.SetMaxIdleConns(2)
		db.SetMaxOpenConns(2)
		return db
	}

	for i := 0; i < 50; i++ {
		go listener(i)
		go notifier(openDb(), i)
		time.Sleep(20 * time.Millisecond)
	}
	select{}
}