Here is a simple example just using a delay node in rate limit mode...
[{"id":"48d660b3a4109400","type":"inject","z":"d5b4a507fb8086e8","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":160,"y":150,"wires":[["e0f9e206681f3504"]]},{"id":"e0f9e206681f3504","type":"delay","z":"d5b4a507fb8086e8","name":"","pauseType":"rate","timeout":"5","timeoutUnits":"seconds","rate":"1","nbRateUnits":"1","rateUnits":"minute","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"allowrate":false,"outputs":1,"x":395,"y":150,"wires":[["e470f1d794e1bef9"]]},{"id":"943543cf7a1958e4","type":"change","z":"d5b4a507fb8086e8","name":"","rules":[{"t":"set","p":"flush","pt":"msg","to":"1","tot":"num"},{"t":"delete","p":"payload","pt":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":485,"y":270,"wires":[["e0f9e206681f3504"]]},{"id":"e470f1d794e1bef9","type":"function","z":"d5b4a507fb8086e8","name":"Do something that takes a while","func":"\n\nsetTimeout(function() { node.send(msg)}, 3000)\nreturn null;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":680,"y":180,"wires":[["943543cf7a1958e4","690a432132f0cc08"]]},{"id":"690a432132f0cc08","type":"debug","z":"d5b4a507fb8086e8","name":"debug 1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":850,"y":105,"wires":[]}]