Slow Down Messages Passing Through a Flow

Problem

You want to slow down the messages passing through a flow. For example, you have a message containing an array of values that you split into a stream of messages and want to process each message in that stream at a rate of one per second.

Solution

Use a Delay node configured to rate limit the messages passing through it.

Example

Flow JSON

[{"id":"1fccc223.7ba87e","type":"inject","z":"ac14500e.2c57d","name":"Inject Array","topic":"","payload":"[0,1,2,3,4,5,6,7,8,9]","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":1280,"wires":[["b2837466.e02a38"]]},{"id":"b2837466.e02a38","type":"split","z":"ac14500e.2c57d","name":"","splt":"\\n","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"","x":250,"y":1280,"wires":[["bd97c8ed.a5c8d8"]]},{"id":"bd97c8ed.a5c8d8","type":"delay","z":"ac14500e.2c57d","name":"","pauseType":"rate","timeout":"5","timeoutUnits":"seconds","rate":"1","nbRateUnits":"1","rateUnits":"second","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"x":390,"y":1280,"wires":[["bd66f03e.bdf0c"]]},{"id":"bd66f03e.bdf0c","type":"debug","z":"ac14500e.2c57d","name":"Debug","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":530,"y":1280,"wires":[]}]

Discussion

The rate limiting mode of the Delay node can be used to change the rate of messages passing through it. It is configured with the desired number of messages to pass through the node per time interval. It will evenly spread the delivery of messages across the time period.