Trigger a Flow When a Node Throws an Error

Problem

You want to trigger a flow when a node throws an error.

Solution

Use the Catch node to receive the error and trigger a flow.

Example

Flow JSON

[{"id":"2bd6810d.e22ece","type":"catch","z":"fc046f99.4be08","name":"","scope":["2c94a22c.91012e"],"uncaught":false,"x":130,"y":160,"wires":[["d16b9fac.8212a"]]},{"id":"2c94a22c.91012e","type":"function","z":"fc046f99.4be08","name":"Throw Error","func":"node.error(\"an example error\", msg);   ","outputs":1,"noerr":0,"x":310,"y":100,"wires":[[]]},{"id":"d16b9fac.8212a","type":"debug","z":"fc046f99.4be08","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"error","targetType":"msg","x":300,"y":160,"wires":[]},{"id":"c5ee9670.5dbbd8","type":"inject","z":"fc046f99.4be08","name":"Trigger error","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":100,"wires":[["2c94a22c.91012e"]]}]

Discussion

The Catch node can be configured to catch errors from specific nodes in the flow or from any node. This allows you to create different error handling flows for different nodes.

The Catch node sends on the message that was logged with the error. It also sets msg.error with details of the error and which node triggered it.

Note that this requires nodes to properly log their errors so that they can be caught.