Route a Message Based on a Context Value

Problem

You want to route a message to different flows according to the current value of a flow context property.

Solution

Use the Switch node to check the value of a flow context property against different values corresponding to different outputs of the node.

Example

Flow JSON

[{"id":"a62d8cdf.1bd82","type":"inject","z":"ac14500e.2c57d","name":"Inject","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":600,"wires":[["b8bbbc41.f272"]]},{"id":"b8bbbc41.f272","type":"switch","z":"ac14500e.2c57d","name":"Context based routing","property":"state","propertyType":"flow","rules":[{"t":"eq","v":"1","vt":"num"},{"t":"eq","v":"2","vt":"num"},{"t":"eq","v":"3","vt":"num"}],"checkall":"true","repair":false,"outputs":3,"x":320,"y":600,"wires":[["9aa9c6b2.18a8e8"],["6ba4ec46.476794"],["a2e806c8.ffa168"]]},{"id":"9aa9c6b2.18a8e8","type":"debug","z":"ac14500e.2c57d","name":"Output 1","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","x":560,"y":540,"wires":[]},{"id":"6ba4ec46.476794","type":"debug","z":"ac14500e.2c57d","name":"Output 2","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","x":560,"y":600,"wires":[]},{"id":"a2e806c8.ffa168","type":"debug","z":"ac14500e.2c57d","name":"Output 3","active":true,"tosidebar":true,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","x":560,"y":660,"wires":[]},{"id":"8aabdb51.e8b538","type":"inject","z":"ac14500e.2c57d","name":"Set state 0","topic":"","payload":"0","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":680,"wires":[["e46083e4.1f17b"]]},{"id":"d1722dee.48db4","type":"inject","z":"ac14500e.2c57d","name":"Set state 1","topic":"","payload":"1","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":720,"wires":[["e46083e4.1f17b"]]},{"id":"4bdb08de.706328","type":"inject","z":"ac14500e.2c57d","name":"Set state 2","topic":"","payload":"2","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":760,"wires":[["e46083e4.1f17b"]]},{"id":"220ce0a6.cf81e","type":"inject","z":"ac14500e.2c57d","name":"Set state 3","topic":"","payload":"3","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":120,"y":800,"wires":[["e46083e4.1f17b"]]},{"id":"e46083e4.1f17b","type":"change","z":"ac14500e.2c57d","name":"Set flow.state","rules":[{"t":"set","p":"state","pt":"flow","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":340,"y":720,"wires":[[]]}]

Discussion

In the example flow, the top flow represents the stream of messages that need to be routed to one of the three outputs by the Switch node.

The bottom flow provides a set of Inject nodes to change the current value of the flow.state context property.

This shows how the routing in one flow can be changed by a separate flow.