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，我创建了一个流程来拆分JSON文件并更新名称为filenamecounter的计数器，以便可以将每个拆分保存为不同的文件名.我在查看"NiFi计数器"窗格时看到计数器值得到更新.但是我该如何获取该值?

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counters属性设置属性.类似于${filenamecounter}和${filenamecounter.counter}，但没有成功.

I tried setting an attribute with the counter name, and counters property. Like ${filenamecounter} and ${filenamecounter.counter} but unsuccessful.

推荐答案

当前计数器主要是一种监视功能，您不能真正从表达式语言访问它们.它们通常用于回答我从来源xyz收到了多少条消息?"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?".

对于您而言，所有拆分"处理器都应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"),

因此，您应该可以在文件名中使用$ {fragment.index}.

So you should be able to use ${fragment.index} in your filename.

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