nodejs async loop with delay

Question

I'm trying to get a loop working with a longer delay, when the task takes longer as planned.

currently I'm using this code for the loop:

async function doSomeStuff() {
    // do some stuff
    // sometimes this action may take longer than 5 seconds
    // after finishing wait 5 seconds
    console.log('task completed, waiting 5 seconds for next run...');
}

setInterval(doSomeStuff, 5000);

works like a charm, but the delay is fixed at 5 seconds, even if the tasks takes longer as planned, so that sometimes the new loop starts only 1 second after finishing the last one instead of waiting 5 seconds.

unfortunately, I was not able to solve it myself by looking at the other questions.

I am grateful for any help.

Best regards Paedda

Estus Flask · Accepted Answer · 2018-12-23 15:24:52Z

6

async functions shouldn't be used with API that ignores a promise that it returns such as setInterval, in case it's expected that a promise should be chained.

This can be done with recursive async function:

(async function doSomeStuff() {
    await new Promise(resolve => setTimeout(resolve, 5000));
    // do some stuff
    await doSomeStuff();
})();

Or infinite loop:

(async function doSomeStuff() {
    while (true) {
        await new Promise(resolve => setTimeout(resolve, 5000));
        // do some stuff
    }
})();

Function body can be wrapped with try..catch if needed to handle errors.

edited Dec 23, 2018 at 15:24

answered Dec 23, 2018 at 15:19

Estus Flask

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Comments

nikksan · Accepted Answer · 2018-12-23 15:54:50Z

0

You were almost there

async function doSomeStuff() {
    // do some stuff
    // sometimes this action may take longer than 5 seconds
    // after finishing wait 5 seconds
    console.log('task completed, waiting 5 seconds for next run...');
    setTimeout(doSomeStuff, 5000);
}

answered Dec 23, 2018 at 15:54

nikksan

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