在定义时间后未收到消息时触发流
问题
您希望在定义时间后未收到消息时触发流。例如，您期望每 5 秒收到一个传感器读数，并且需要知道它是否未能到达。
解决方案
使用 Trigger 节点来检测在定义的时间间隔后消息是否未到达。
示例
[{"id":"6ea53ad8.2362a4","type":"debug","z":"ac14500e.2c57d","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":450,"y":1160,"wires":[]},{"id":"3da6946e.184a5c","type":"inject","z":"ac14500e.2c57d","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":100,"y":1160,"wires":[["38caaff4.03f6d","6ea53ad8.2362a4"]]},{"id":"38caaff4.03f6d","type":"trigger","z":"ac14500e.2c57d","op1":"","op2":"timeout","op1type":"nul","op2type":"str","duration":"5","extend":true,"units":"s","reset":"","bytopic":"all","name":"Watchdog","x":270,"y":1200,"wires":[["ae477709.016088"]]},{"id":"ae477709.016088","type":"debug","z":"ac14500e.2c57d","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":450,"y":1200,"wires":[]}]
讨论
在示例流中，顶部分支代表消息的正常流。它们也会被传递到流的第二个分支上的 Trigger 节点。
Trigger 节点被配置为最初不发送任何内容，然后等待 5 秒钟，然后发送一条 "timeout" 消息。还选择了如果新消息到达则延长延迟的选项。这意味着只要消息继续到达，该节点就不会做任何事情。一旦上次消息到达后经过 5 秒，它将发送 "timeout" 消息。
