NiFi 中的 Python ExecuteScript：轉換流文件屬性和內容

Question

我正在嘗試在 NiFi 中創建一個 Python 腳本：

1. 從傳入的流文件中讀取一些屬性
2. 讀取流文件的 json 內容並提取特定字段
3. 將屬性寫入傳出流文件
4. 用腳本中創建的新內容覆蓋傳入的流文件（例如，返回新 json 的 API 調用）並將其發送到 SUCCESS 關系或刪除舊的流文件並使用所需內容創建新的流文件

到目前為止我所做的：

import json
import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback,InputStreamCallback, OutputStreamCallback

class OutputWrite(OutputStreamCallback, obj):

def __init__(self):
    self.obj = obj

def process(self, outputStream):

    outputStream.write(bytearray(json.dumps(self.obj).encode('utf')))

###end class###

flowfile = session.get()

if flowfile != None:

**#1) Get flowfile attributes**

    headers = {
        'Accept-Encoding': 'gzip, deflate, br',
        'Accept': 'application/json, text/plain, */*',
        'Cache-Control': 'no-cache',
        'Ocp-Apim-Trace': 'true',
        'Authorization': flowfile.getAttribute('Authorization')
    }

    collection = flowfile.getAttribute('collection')
    dataset = flowfile.getAttribute('dataset')

    **#2)Get flowfile content**

    stream_content = session.read(flowfile)
    text_content = IOUtils.toString(stream_content, StandardCharsets.UTF_8)
    json_content = json.loads(text_content)

    records = json_content['result']['count']
    pages = records/10000

    **#3) Write flowfile attributes**

    flowfile = session.putAttribute(flowfile, 'collection', collection)
    flowfile = session.putAttribute(flowfile, 'dataset', dataset)

    **#API operations: output_json with desired data**

    output_json = {some data}

    **#4) Write final JSON data to output flowfile**

    flowfile = session.write(flowfile, OutputWrite(output_json))

    session.transfer(flowfile, REL_SUCCESS)
    session.commit()

我的問題是我找不到將所需 output_json 對象的引用作為參數傳遞給 OutputStreamCallback 類的方法。 關於如何解決這個問題或更好的方法的任何想法？

在這種情況下，在類的 process 函數中執行所有 API 操作是否可能更容易，但是我如何訪問 process 函數中的傳入流文件屬性（需要會話或流文件對象）？

非常感謝任何幫助！

Answer 1

你可以試試這樣的——

import json
import sys
import traceback
from java.nio.charset import StandardCharsets
from org.apache.commons.io import IOUtils
from org.apache.nifi.processor.io import StreamCallback
from org.python.core.util import StringUtil

class TransformCallback(StreamCallback):
    def __init__(self):
        pass

    def process(self, inputStream, outputStream):
        try:
            # Read input FlowFile content
            input_text = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
            input_obj = json.loads(input_text)
            # Transform content
            output_obj = input_obj   #your input content

            #perform Data tranformation on output_obj

            # Write output content
            output_text = json.dumps(outputJson)
            outputStream.write(StringUtil.toBytes(output_text))
        except:
            traceback.print_exc(file=sys.stdout)
            raise


flowFile = session.get()
if flowFile != None:
    flowFile = session.write(flowFile, TransformCallback())

    # Finish by transferring the FlowFile to an output relationship
    session.transfer(flowFile, REL_SUCCESS)

Answer 2

我在下面包含了示例 Python 代碼，該代碼允許自定義PyStreamCallback類，該類實現邏輯以轉換來自Matt Burgess 的關於該主題的博客文章的流文件內容中的 JSON，但我鼓勵您考慮使用本機處理器進行UpdateAttribute和EvaluateJSONPath執行相關活動，並且僅在特別需要執行 NiFi 無法立即處理的任務時才使用自定義代碼。

import json
import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback

class PyStreamCallback(StreamCallback):
  def __init__(self):
        pass
  def process(self, inputStream, outputStream):
    text = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
    obj = json.loads(text)
    newObj = {
          "Range": 5,
          "Rating": obj['rating']['primary']['value'],
          "SecondaryRatings": {}
        }
    for key, value in obj['rating'].iteritems():
      if key != "primary":
        newObj['SecondaryRatings'][key] = {"Id": key, "Range": 5, "Value": value['value']}

    outputStream.write(bytearray(json.dumps(newObj, indent=4).encode('utf-8'))) 

flowFile = session.get()
if (flowFile != None):
  flowFile = session.write(flowFile,PyStreamCallback())
  flowFile = session.putAttribute(flowFile, "filename", flowFile.getAttribute('filename').split('.')[0]+'_translated.json')
  session.transfer(flowFile, REL_SUCCESS)

更新：

要在回調中訪問流文件的屬性，只需將其作為參數傳遞給構造函數，將其存儲為字段，並在process方法中引用它。 這是一個非常簡單的示例，它將屬性my_attr的值連接到傳入的流文件內容並將其寫回：

import json
import java.io
from org.apache.commons.io import IOUtils
from java.nio.charset import StandardCharsets
from org.apache.nifi.processor.io import StreamCallback

class PyStreamCallback(StreamCallback):
    def __init__(self, flowfile):
        self.ff = flowfile
        pass
    def process(self, inputStream, outputStream):
        text = IOUtils.toString(inputStream, StandardCharsets.UTF_8)
        text += self.ff.getAttribute('my_attr')
        outputStream.write(bytearray(text.encode('utf-8')))

flowFile = session.get()
if (flowFile != None):
    flowFile = session.write(flowFile,PyStreamCallback(flowFile))
    session.transfer(flowFile, REL_SUCCESS)

傳入流文件：

--------------------------------------------------
Standard FlowFile Attributes
Key: 'entryDate'
    Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'lineageStartDate'
    Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'fileSize'
    Value: '30'
FlowFile Attribute Map Content
Key: 'filename'
    Value: '1690494181462176'
Key: 'my_attr'
    Value: 'This is an attribute value.'
Key: 'path'
    Value: './'
Key: 'uuid'
    Value: 'dc93b715-50a0-43ce-a4db-716bd9ec3205'
--------------------------------------------------
This is some flowfile content.

傳出流文件：

--------------------------------------------------
Standard FlowFile Attributes
Key: 'entryDate'
    Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'lineageStartDate'
    Value: 'Tue Mar 13 13:10:48 PDT 2018'
Key: 'fileSize'
    Value: '57'
FlowFile Attribute Map Content
Key: 'filename'
    Value: '1690494181462176'
Key: 'my_attr'
    Value: 'This is an attribute value.'
Key: 'path'
    Value: './'
Key: 'uuid'
    Value: 'dc93b715-50a0-43ce-a4db-716bd9ec3205'
--------------------------------------------------
This is some flowfile content.This is an attribute value.