NodeJS SetInterval 与 Async/Await [英] NodeJS SetInterval with Async/Await

问题描述

我使用以下代码和 websocket 从数据库中抓取数据并返回给用户.它返回聊天消息、用户状态和其他内容.代码按预期工作(在测试中)，但我有几个问题.

I'm using the following code with a websocket to scrape data from a DB and return to users. It returns chat messages, users status and other things. The code works as expected (in testing) but I have a couple of questions.

                setInterval(async () => {
                    if (connectedUserIDs.length > 0) {
                        logger.info("short loop...")
                        await eventsHelper.extractEvents(db, connectedUserIDs, connectedSockets, ws)
                    }
                }, 5000)

问题 1. SetInterval 是否会等待await"?还是每 5 秒触发一次?我假设它会每 5 秒触发一次.

Question 1. Will the SetInterval wait for the the "await" or will it just fire every 5 seconds? I assume it will fire every 5 seconds regardless.

如果是这样.

问题 2. 有没有办法重复上述任务，但确保仅在前一次运行完成且最短时间为 5 秒时才重新运行?我想避免同时运行多个查询的情况.也许每次都可以取消并重新启动 setInterval...

Question 2. Is there a way to repeat a task like above but ensure it only re-runs if the previous run as completed with a minimum time of 5 seconds? I want to avoid a situation where I get multiple queries running at the same time. Maybe the setInterval could be cancelled and restarted each time...

谢谢亚当

推荐答案

问题 1. SetInterval 是否会等待await"?还是每 5 秒触发一次?我假设它会每 5 秒触发一次.

Question 1. Will the SetInterval wait for the the "await" or will it just fire every 5 seconds? I assume it will fire every 5 seconds regardless.

是的，它会天真地每 5 秒重新运行一次

Yes it will naively re-run every 5s

问题 2. 有没有办法重复上述任务，但确保仅在前一次运行至少 5 秒内完成时才重新运行

Question 2. Is there a way to repeat a task like above but ensure it only re-runs if the previous run as completed with a minimum time of 5 seconds

防止冲突的最简单方法是在等待之后设置下一次运行:

Easiest way to prevent collisions is to set the next run after the await:

let timeoutId;
const extractEvents = async () => {
  if (connectedUserIDs.length > 0) {
    logger.info("short loop...");
    await eventsHelper.extractEvents(db, connectedUserIDs, connectedSockets, ws);
  }
  timeoutId = setTimeout(extractEvents, 5000);
};
timeoutId = setTimeout(extractEvents, 5000);

存储 timeoutId 以便稍后清除

Storing timeoutId so you can clear it later

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