错误后自动重试操作
问题
您希望在抛出错误后重试操作。
解决方案
使用 Catch 节点接收错误，并将其连接回需要重试操作的节点。
示例
[{"id":"27e61f12.c1a15","type":"inject","z":"fc046f99.4be08","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":100,"y":320,"wires":[["d7d08440.31b678"]]},{"id":"d7d08440.31b678","type":"function","z":"fc046f99.4be08","name":"Random error","func":"// Randomly throw an error rather than\n// pass on message.\nif (Math.random() < 0.5) {\n node.error(\"a random error\", msg);\n} else {\n return msg;\n}","outputs":1,"noerr":0,"x":320,"y":320,"wires":[["f22b1e9a.5d89b"]]},{"id":"f22b1e9a.5d89b","type":"debug","z":"fc046f99.4be08","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":510,"y":320,"wires":[]},{"id":"2166290d.98d736","type":"delay","z":"fc046f99.4be08","name":"","pauseType":"delay","timeout":"2","timeoutUnits":"seconds","rate":"1","nbRateUnits":"1","rateUnits":"second","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":false,"x":240,"y":380,"wires":[["d7d08440.31b678"]]},{"id":"139b836e.7950ed","type":"catch","z":"fc046f99.4be08","name":"","scope":["d7d08440.31b678"],"uncaught":false,"x":90,"y":380,"wires":[["2166290d.98d736","9c8ab214.0ecaa"]]},{"id":"9c8ab214.0ecaa","type":"debug","z":"fc046f99.4be08","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"error","targetType":"msg","x":240,"y":440,"wires":[]}]
讨论
有些错误是暂时性的，只需简单重试操作即可成功。另外，可能需要先采取一些补救措施再重试。
在示例流程中，一个 Function 模拟一个随机错误——它有 50% 的几率抛出错误而不是传递消息。
Catch 接收错误，然后将消息传回 Function 节点以重试。它还包含一个 Delay 节点，因为在某些情况下，等待一小段时间再重试是合适的。
