Node-RED UI does not show up

General
1

Hi Community,

I guess I need your support: How to start Node-RED-UI without flows running from the beginning?

I changed an existing flow and after a restart of Node-RED the Node-RED-UI won’t show up anymore. Using IP-address (192.168.x.x:1880) the browser shows “busy” and some minutes later only a blank page. Using Home Assistant’s Node-RED side bar it's the same. All other functions of Home Assistant are up and running.

Restart of Node-RED or of the whole system won’t change the behavoir. The logs doesn’t show any untipical entries. Status monitor of the system shows that Node-RED causes 28% of the CPU load! (RPi4).

That leads me to the assumption that I may generated an infinit loop with the last edit of one of the flows (I somehow looped back an output signal to input). I guess Node-RED could be too busy to start the UI? While Node-RED-UI won’t show up I can’t change the flow to solve the issue.

Any ideas how to avoid Node-RED is running the flows from the beginning?
I won't loose the latest changes.

Best regards - Marco

2

You should be able to start using the --safe flag. Eg

node-red --safe

3

Thanks for you reply dceejay!

I'm using Node-RED as an add-on in Home Assistant. I don't know how/where to add the parameter "--safe".

Are the flow information completly stored in the file flows.json? In this file I found segments containing "disabled":false.

..."type":"tab","label":"<my_tab_name>","disabled":false,"info":...

What is the meaning of this "disabled"? Is it just that the TAB is not displayed or will the flows inside also not been processed?

4

Disabled will mean not running. Sorry I don’t use HA, so yes careful hand editing of the flow may be a way out. But back it up first.

5

Thanks dceejay. That helped to solve the problem. For others who might have the same problem some more information:

ROOT CAUSE
By mistake I created an infinite loop inside a Node-RED flow (connected output from nodeA to input of nodeB and output of nodeB to input of nodeA). After deploying the change this infinite loop caused a high CPU load on my RPi4. After a restart of the Node-RED add-on the user interface in Home Assistant never came up again. The add-on showed 28% CPU load instead of the normal approx. 1%.

SOLUTION

I disabled the tab with the infinite-loop-flow manually and restarted the Node-RED add-on. The userinterface showed up again. Afterwards I could repair the flow and activate the tab again. - DONE :+1:

I used SAMBA to access the right folder (\\config\node-red\flows.json and opend the flows.json with an text editor (e.g. notepad++). At the very beginning I found
...,"type":"tab","label":"<YOUR TAB NAME>","disabled":false,...
I replaced the false with true to disable the tab, saved the file and restarted the Node-RED add-on.

The deactivated tab means that the flow will not be processed.

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