如何在 NiFi 中使用计数器的值 [英] How to use value of a counter in NiFi
问题描述
在 NiFi 1.3.0 中,我创建了一个流来拆分 JSON 文件并使用名称 filenamecounter
更新计数器,以便我可以将每个拆分保存为不同的文件名.当我查看 NiFi 计数器窗格时,我看到计数器值得到更新.但是我怎样才能访问这个值?
In NiFi 1.3.0, I have created a flow to split a JSON file and update the counter with name filenamecounter
so that I can save each split into different file names. I see that the counter value gets updated when I view the NiFi counters pane. But how can I access this value?
我尝试使用计数器名称和计数器属性设置属性.像 ${filenamecounter}
和 ${filenamecounter.counter}
但不成功.
I tried setting an attribute with the counter name, and counters property. Like ${filenamecounter}
and ${filenamecounter.counter}
but unsuccessful.
推荐答案
目前计数器主要是一个监控功能,你不能真正从表达式语言中访问它们.它们习惯于回答诸如我从源 xyz 收到多少条消息?"之类的问题.
Currently counters are mostly a monitoring feature, you can't really access them from expression language. They're used to answer questions like "how many messages have I received from source xyz?".
在您的情况下,所有拆分"处理器都应该编写一组标准的片段属性:
In your case, all of the "split" processors should be writing a standard set of fragment attributes:
@WritesAttribute(attribute = "fragment.identifier",
description = "All split FlowFiles produced from the same parent FlowFile will have the same randomly generated UUID added for this attribute"),
@WritesAttribute(attribute = "fragment.index",
description = "A one-up number that indicates the ordering of the split FlowFiles that were created from a single parent FlowFile"),
@WritesAttribute(attribute = "fragment.count",
description = "The number of split FlowFiles generated from the parent FlowFile"),
所以你应该可以在你的文件名中使用 ${fragment.index}.
So you should be able to use ${fragment.index} in your filename.
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