使用数据库中的映射每隔X秒运行一次代码

Question

Using golang's time.NewTicker, I am trying to run each record from a database (consisting of text and a timer, i.e the number of seconds before it repeats) but it is only repeating the first record it grabs

func LoadTimedCommands() map[string]time.Duration {
    database := InitializeDB()

    rows, _ := database.Query("SELECT TimedResponse, Timer from timedcommands")

    com := make(map[string]time.Duration)
    for rows.Next() {
        var TimedResponse string
        var Timer time.Duration
        rows.Scan(&TimedResponse, &Timer)
        com[TimedResponse] = Timer
    }
    return com
}

func TimedCommands(conn net.Conn, channel string, name string) {
    timedcoms := LoadTimedCommands()
    for k, v := range timedcoms {
        for range time.NewTicker(v * time.Second).C {
            BotSendMsg(conn, channel, k, name)
        }
    }
}

So if I have two records to use from: Sqlite data

Then the code should run the first record every 15 seconds, and the second every 10. But again, only the first one that is loaded into the map is run.

Answer 1

Your problem is in this function:

func TimedCommands(conn net.Conn, channel string, name string) {
    timedcoms := LoadTimedCommands()
    for k, v := range timedcoms {
        for range time.NewTicker(v * time.Second).C {
            BotSendMsg(conn, channel, k, name)
        }
    }
}

In this section, where you range over the channel time.NewTicker(...).C:

for range time.NewTicker(v * time.Second).C {
    BotSendMsg(conn, channel, k, name)
}

This will try and read values from this one ticker until the channel C is closed. This means that the outer loop only does one iteration, then we block on the inner loop until C is closed. And we never create more than one Ticker at once.

You could get around this by creating tickers in their own goroutines:

for k, v := range timedcoms {
    go func(conn net.Conn, channel, name, k string, v time.Duration) {
        for range time.NewTicker(v * time.Second).C {
            BotSendMsg(conn, channel, k, name)
        }
    }(conn, channel, k, v)
}

But you will probably want to include some synchronisation to ensure that you can stop the goroutines that you start, or to ensure that BotSendMsg(...) can be called from multiple goroutines at the same time etc.