Creating a loop

General
1

Hi

We have NodeRed running in a docker and as part of teh process I need to send a file to a windows machine which processes the file and then outputs a new file. I need to build a process in NodeRed which outputs the file and then monitors a folder waiting for it to come back, it needs to time out after 1 hour and error if it hasn't come back

In our previous solutuion I did this by having a script which had a for loop in for 60 instances and sleep for 1 minute so it just checked the folder using the FileSystemObject and if it was there then it broke out of the for loop and continued processing. However I have been advised that I can't install the FileSystemObject libary as there are security concerns?!?!

So I'm trying to figure out how to create somethign similar using nodeRed nodes and would appreciate any ideas

2

Perhaps you can use the Watch node to watch for changes on the folder.

3

There's no timeout on that unfortunatley so if the job faield on the other process the job would just sit there

4

Do the timeout separately. You can probably use a Trigger node, usually that is the one to use for timeouts.

5

This is not a good way to do things in JavaScript. If you really need a periodic check, you should use a setInterval. That will clear the process loop until the appropriate time (in milliseconds) has passed. This can be used in a function node but you have to keep a context variable reference to it so it doesn't get recreated each time a msg hits it.

However, as Colin has said, the "Node-RED way" would be a watch node which will trigger when the folder is updated and a trigger node to handle the timeout. Set the trigger node to extend the time if another msg is received.

6

Set the trigger node to Send Nothing then Wait 1 hour, then send the timeout message. Send it a message when you send the file. When the Watch node sees the response then send the Trigger a message with msg.reset true, which will reset it so it doesn't send the error message.

For this application you don't want Extend Delay set.

7

This flow will check for the existence of a file, at 5 second intervals, for a maximum of 5 tries.

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