Complete & Split: is the value wrong?

Core Development
1

Hi There,

and sorry to go with this complete node topic but ....

Screenshot 2025-04-20 at 10.03.04
Screenshot 2025-04-20 at 10.03.041149Ă—565 21 KB

[{"id":"801126629e8ab7c2","type":"inject","z":"14ef36ad590a7fe8","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[1,2,3,4]","payloadType":"json","x":540,"y":740,"wires":[["43e9c21fa8e74c31"]]},{"id":"50914d4efa31df6e","type":"complete","z":"14ef36ad590a7fe8","name":"","scope":["43e9c21fa8e74c31"],"uncaught":false,"x":1008,"y":495,"wires":[["fa1a47e2ee058fb1"]]},{"id":"fa1a47e2ee058fb1","type":"debug","z":"14ef36ad590a7fe8","name":"debug 394","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"","statusType":"counter","x":1350,"y":336,"wires":[]},{"id":"3ed5963b7a8e8f57","type":"join","z":"14ef36ad590a7fe8","name":"","mode":"custom","build":"array","property":"","propertyType":"full","key":"topic","joiner":"\\n","joinerType":"str","useparts":false,"accumulate":false,"timeout":"","count":"4","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"","reduceFixup":"","x":1014,"y":740,"wires":[["ef44b9d6ea93685b"]]},{"id":"43e9c21fa8e74c31","type":"split","z":"14ef36ad590a7fe8","name":"","splt":"\\n","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"","property":"payload","x":792,"y":605,"wires":[["3ed5963b7a8e8f57"]]},{"id":"ef44b9d6ea93685b","type":"debug","z":"14ef36ad590a7fe8","name":"debug 395","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"","statusType":"counter","x":1322,"y":588,"wires":[]}]

This time the complete is listening to the split node which receives a message with [1,2,3,4] array of four values. It sends out four messages to the join. It also sends a message to the complete node but instead of sending the original array, it sends the value '4' i.e. the last value in the array:

Screenshot 2025-04-20 at 10.04.58
Screenshot 2025-04-20 at 10.04.58441Ă—180 9.26 KB

Shouldn't that be the content of the original message, i.e. [1,2,3,4] since that's the message with which the split has completed with?

2

hmm - possibly/probably yes. The idea of the complete node was to aid transactionality of flows - so that if either something broke halfway through or if a flow was asked to stop then you could possibly how far it had got and take steps to recover from that point... BUT that gets tricky around these case where a node does more than one thing... when is it really complete ? and indeed there are no doubt some inconsistencies in the existing implementations that could be thought through a bit more.

In this specific case I would need to check if it was sending 4 for the last item value or 4 for the number of items processed...

1 Like
3

I added ten to the list and got 10 as complete message ... :wink:

EDIT: I didn't add ten elements just the number 10 :wink:

1 Like
4

yes - I see that - net is that I think I agree with you that in this case the complete node should really send the original input payload. I can raise a PR - but need to check with @knolleary where we raise it as it is a potentially breaking change (for someone).

4 Likes
5

This edge case has a finer edge to it than any good Japanese Samurai sword ...

... and then the world bank collapses because they were checking the last value in an array.

6

Even using a Complete node with a Split would be a very unusual thing to do I think. It is mostly of use with async nodes.

7

Not if you had a query that returned an array of financial trades for example. You would want to split and track progress of each one.

8

folks do strange things and in particular banks.

I could well imagine someone asking how to get the last value of an array in a visual fbp way ... well if we send the array to the split and then have a complete node listening to it we get the last value - 10 points for creativity, 0 for correctness!

EDIT: I'm definitely not questioning the usefulness of the complete node, just that one use case with split ....

9

Having worked in a couple of large UK banks on their IT, mostly there are only a couple of people in the bank who actually know how the financial processing actually works! :slight_smile: And those people are not financial people! I several times found myself with more knowledge than bank staff simply because I'd done some homework.

10

Pull request raised Let split node send original msg to complete node by dceejay · Pull Request #5113 · node-red/node-red · GitHub

11

Btw I found the same issue with the status node - it filters direct nodes from which it will ignore status updates but if I put a change in-between the status and the node producing the status update, I've got an endless loop.

I.e. this setup:

Screenshot 2025-04-21 at 14.53.56
Screenshot 2025-04-21 at 14.53.56811Ă—559 21 KB

If I enable the change node and then trigger one of the injects, loop is created. Especially since the status is ever changing in the debug node 398 - it's a message counter, status each time now, status all sends out message, debug 398 counts that message, new status, status all captchas that status update and sends out a message, debug 398 counts that message, updates its status, status all captchas that update .... and I'm dizzy.

1 Like
12

Good shout - will apply same "simple" fix to status node.