Question about watch node?

General
1

I am not sure I understand the following...

Note: The directory or file must exist in order to be watched. If the file or directory gets deleted it may no longer be monitored even if it gets re-created.

If I have a flow that creates a file, I can't use a watch node to get the file size of the file I just created? That is what the above note implies to me. Can someone clarify if a watch node will or will not work correctly on a file just created?

2

It means what it says... It can't get a handle on something that doesn't exist. So to watch for files being created you need to watch the directory they are in - not the filename you think they will be created as.

3

What is the mechanism that is used? The inode? Something else? If the file exists, the watch node created, then the file is deleted and created again, this works. I have a flow right now that has never failed that matches the scenario I just noted.

You can watch for the flows file to be recreated on a deployment with a watch node for example. So I am trying to understand what the circumstances are for failure of a watch node, when right now, I have an example, where it does not fail. The 'may' wording needs some qualification in context of my question.

Per my understanding the flows file is a safe-save model, so could that be contributing factor? Fie content is replaced but file (handle) is not actually removed from the file system?

4

it uses fs.stat (I think). I'm sure there was once a situation where on some OS they did not all behave the same. (maybe those without inodes)

5

Cool. thanks for the info. Gives me a place to start. :slight_smile: Right, usually when something is qualified, similar to this, OS specific limits can come into scope. Fortunately, I only have Linux/Pi based infrastructure. But I want to have at least one Windows based system for reference at some point as well.

6

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