Backing up context data

Hi all,

About 2 years ago, I posted the same issue;

Still, I'm facing the same issue and I'm wondering if there are any new thoughts on this?

Let me summarize my issue. My NodeRED feeds a Telegram system with about 3000 users. The user-data is stored in object as

flow.set("aUsers", aUsers, "storeInFile");

Once a day I would like to make a backup. In the beginning (years ago) I messed up this object once and I didn't have a backup. So I inject this every 24 hours :

const aUsers = flow.get("aUsers", "storeInFile"); flow.set("aUsers_backup", aUsers);

So far, so good. But the strange thing is, that this backup somehow is allways a live copy. Even if I stop injecting the backup code, the backup allways contains the same data. And, there comes the tricky part... If I delete my aUsers, the aUsers_backup also gets lost...?

I'm running NR in docker on NGINX.

Any suggestions maybe?

Hi @Hunter,

Admittedly, I have not read the original thread.

But my hunch here, is referencing...

Javascript (like most) will pass-by-ref for objects/classes, whereas for primitive types, they are

So what may be happening here, is your backup is a reference to the original (and not a copy)
so when the original changes, so does any 'reference' to it.

Try using RED.util.cloneMessage() to see if it makes a difference

const aUsers = flow.get("aUsers", "storeInFile");
flow.set("aUsers_backup", RED.util.cloneMessage(aUsers));
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And the real issue is that your backup is not using the storeInFile type so it is only an in-memory copy which is, as stated, merely a link to the original data, not a copy.

Ideally, if you can take your Node-RED instance offline for a backup, that would ensure that the storeInFile context store was always in a valid state for the backup. Remembering that, by default, I think Node-RED only writes a file store to disk every 30 seconds.

I think that, if you really want a more robust store, it would be better to have a timed flow that manually writes the current context state to a file. Or even write a copy of inputs to a DB and restore from DB on startup. Database engines will have more robust backup processes.

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Thanks for the tip mate, but this seems to be using some kind of reference as well :frowning:

Show us what the code now is.

For such a use case, I'd go with a local SQLite database instead of using the file context. It is much more resilient regarding corruption, easy to integrate and to take backups. :thinking:

As stated.

At several points I save the user data as;

flow.set("aUsers", aUsers, "storeInFile");

As for the backup, I've tried 2 options;

const aUsers = flow.get("aUsers", "storeInFile");
flow.set("aUsers_backup", aUsers);

const aUsers = flow.get("aUsers", "storeInFile");
flow.set("aUsers_backup", RED.util.cloneMessage(aUsers));

Both ending up in the same behaviour as described.

That should work. Can you post a small example flow showing it failing?

Well, it doesn't :frowning:

When I inject this code, the backup contains the same data, as expected. I use the node.warn() to show the number of users (size of object) which are both similar, as they should be.

When I register as new member, the main aUsers object increases by one, but when I run both Object.keys(aUsers).length and Object.keys(aUsers_backup).length they are both increased by one. So the backup is not an independant object, but locked to the main object.

[quote="Hunter, post:9, topic:82260"]
when I run both Object.keys(aUsers).length and Object.keys(aUsers_backup).length

In that case the aUsers_backup variable you are using is not the one in created by
flow.set("aUsers_backup", RED.util.cloneMessage(aUsers));

That is what we need.

What do you mean by "failing"? There is no such failing message.
In fact, nothing fails. But the result is not as requested.

As long as I don't log any actions, there are no messages to be shown. So what is it you want to see?

There was no backup object present when I started this second topic. It was created by :

flow.set("aUsers_backup", RED.util.cloneMessage(aUsers));

There is no other code which can create this object...

Just a small flow export reproducing the issue - of course using dummy data :disguised_face:

Something like this possibly, but exhibiting the problem.

[{"id":"be7131e3813e4c1c","type":"inject","z":"bdd7be38.d3b55","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":120,"y":2580,"wires":[["c5f859709b461748"]]},{"id":"c5f859709b461748","type":"function","z":"bdd7be38.d3b55","name":"create context value and backup","func":"const obj = {test: 7}\nflow.set(\"obj\", obj)\nflow.set(\"obj_backup\", RED.util.cloneMessage(obj))\nreturn msg;","outputs":1,"timeout":0,"noerr":0,"initialize":"","finalize":"","libs":[],"x":340,"y":2580,"wires":[["a4503b334101f033"]]},{"id":"a4503b334101f033","type":"function","z":"bdd7be38.d3b55","name":"Fetch and test","func":"const obj = flow.get(\"obj\")\nconst objBackup = flow.get(\"obj_backup\")\nobj.newStuff = \"new stuff\"\nreturn [{payload: obj}, {payload: objBackup}];","outputs":2,"timeout":0,"noerr":0,"initialize":"","finalize":"","libs":[],"x":580,"y":2580,"wires":[["7ed33b67ec465ce3"],["907c5650d0a2951b"]]},{"id":"7ed33b67ec465ce3","type":"debug","z":"bdd7be38.d3b55","name":"debug 103","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":770,"y":2540,"wires":[]},{"id":"907c5650d0a2951b","type":"debug","z":"bdd7be38.d3b55","name":"debug 104","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":770,"y":2600,"wires":[]}]
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If your data is important, I would personally recommend a database backup. Preferably on a separate computer to avoid the inevitable file corruption. It doesn't have to be anything fancy.

As previously stated, your flow.set is not using the file store and therefore is not a backup.

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