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I want to execute a particular line of code at timed intervals. The line will be res.write(""), to keep a connection alive.

This is similar to hardware interrupts in embedded systems.

Is it possible to have a function that inside will run my code, but at 20 seconds period to execute one particular line of code?

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  • 2
    You might want to take a look at web sockets. Commented Sep 18, 2018 at 13:01
  • Do they offer this functionality? Commented Sep 18, 2018 at 13:01
  • take a look to setInterval() function Commented Sep 18, 2018 at 13:02

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The code res.write("") not necessary will send something to the wire, since the payload is empty. What you might need is TCP keepalive functionality.

 res.connection.setKeepAlive(true, 20000)
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4 Comments

My code consists of a function that takes a lot of time to finish and Heroku throws an H12 timeout error for more than 30 seconds of not serving a response. I hope this line will trick Heroku. Thanks a lot!
The link you provided, does not contain any res.connection.setKeepAlive() function. It only caontains, socket.setKeepAlive([enable][, initialDelay]). Is this the one you are referring to?
Sure, res.connection is just my guess how one can access the underlying socket object having a reference to a request. You can also try req.connection or look for the information about accessing of the connection in the framework you use.
So you wrote res.connection.setKeepAlive(true, 20000), instead of socket.setKeepAlive(true, 5000);, because i am using the express framework. Is my assumption correct?
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You can use setInterval

https://developer.mozilla.org/fr/docs/Web/API/WindowTimers/setInterval

setInterval(() => res.write(""), 20000);
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3 Comments

While not 'wrong' per se, this really isn't a great way to keep a connection alive.
I absolutely agree to that. I was responding more to the beginning of the question which is I want to execute a code, but at timed intervals
If you decide to go with setInterval, don’t forget to close interval after sending the response.

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