Saving context variable to the localfilesystem immediately on change

General
1

Hi,

I have my node-red flow configured to use localfilesystem as contextStorage. I know that for every 30 seconds context variables are saved to the file system.

Is there a way to save these immediately to the file system as and when they are created,updated or deleted?

Regards,
Kushan

2

You can configure the flush time as per the docs.. But I have to ask why ?

3

Yes I understand that the flush time can be configured. But my need is to preserve context data in case of sudden restart of the server.

4

However rapidly you attempt to update it it can never be instantaneous, there will always be a window after it is changed before it is saved to disk during which the power may fail. That is true even if there were a flag you could set that said that immediately after updating a variable it is to be flushed to disc. The power could still fail in the gap between update and flush.

5

I am ok to loose data for a second or two and I don't want the flush interval to be too short as well. A flag or some other way for immediate update is what I am looking for.

6

Again as per the docs you can also set cache to false which should turn it off.

2 Likes
7

Oh really, I didn't noticed that. That is the solution.
Great thanks.

8

Just be aware that if you turn off the cache, the store becomes a asynchronous store, which means you cannot do:

var a = flow.get("foo");

You have to use the version with a callback function:

flow.get("foo", function(err, a) {
});
1 Like
9

Thank you for your valuable advice for saving my time. I was just noticing breaking my flow after cache=false.

Hope it affects to change nodes too.

10

Now I am a bit confused, if you turn of the cache it gets a synchronous store? You mean asynchronous?
And shouldn't the callback for the get have at least two parameters, because the first one is the error?

11

Yup - you are quite right, will edit my post. Need more tea.

3 Likes