Python MongoDB 查询请求将数据分割成块

Question

我正在编写一个 python 脚本来执行以下这些步骤。

查询一个MongoDB数据库解析和聚合结果通过 REST API

将数据上传到 ServiceNow table

脚本有效，但是数据集太大，REST 事务在 60 秒后超时（连接被目的地的 ServiceNow 服务器关闭）。

我需要将数据分成块并为每个数据块发送单独的 REST 事务，以确保通过 POST 发送完整的数据集而不会达到超时限制。

如何通过修改下面的脚本来实现该目标？

#!/usr/bin/env python

from config import *

import os, sys

mypath = os.path.dirname(os.path.realpath(__file__))
sys.path.append(os.path.join(mypath, "api-python-client"))

from apiclient.mongo import *

from pymongo import MongoClient

import json

import requests

from bson.json_util import dumps

client = MongoClient(mongo_uri)

#Create ServiceNow URL
svcnow_url = create_svcnow_url('u_imp_cmps')

#BITSDB Nmap Collection
db = client[mongo_db]

#Aggregate - RDBMS equivalent to Alias select x as y
#Rename fields to match ServiceNow field names
computers = db['computer'].aggregate([
        {"$unwind": "$hostnames"},
        {"$project" : {
                "_id":0,
                "u_hostname": "$hostnames.name",
                "u_ipv4": "$addresses.ipv4",
                "u_status": "$status.state",
                "u_updated_timestamp": "$last_seen"
        }}

])

j = dumps({"records":computers})
#print(j)


#Set proper headers
headers = {"Content-Type":"application/json","Accept":"application/json"}

#Build HTTP Request
response = requests.post(url=svcnow_url, auth=(svcnow_user, svcnow_pwd), headers=headers ,data=j)

#Check for HTTP codes other than 200
if response.status_code != 200:
        print('Status:', response.status_code, 'Headers:', response.headers, 'Response Text', response.text, 'Error Response:',response.json())
        exit()

#Decode the JSON response into a dictionary and use the data
print('Status:',response.status_code,'Headers:',response.headers,'Response:',response.json())

更新：我有一个计划，但我不确定如何准确实施。

将游标设置为每个 1000 条记录的固定批处理大小
当批次已满时，创建 JSON 输出并通过请求发送数据
在一个循环中：继续抓取新的批次并将每个批次发送到目的地，直到到达整个数据集

https://docs.mongodb.com/v3.0/reference/method/cursor.batchSize/

基本上我认为我可以通过创建批次并循环遍历批次来解决这个问题，每次调用一个新的 API。如果有人有任何想法，这是否是一个好的计划以及如何实施解决方案，请告诉我。谢谢

Answer 1

j = dumps({"records":computers}) 将 return 一个列表，因此您可以通过调用 j[x] 或遍历 for 循环轻松指向单个数据条目。这些条目中的每一个都应该被 ServiceNow 接受。

# Set proper headers (these are always the same, so this
# can be assigned outside of the for loop)
headers = {"Content-Type":"application/json","Accept":"application/json"}

for data_point in j:

    #Build HTTP Request (Note we are using data_point instead of j)
    response = requests.post(url=svcnow_url, auth=(svcnow_user, svcnow_pwd), headers=headers ,data=data_point)

    #Check for HTTP codes other than 200
    if response.status_code != 200:
        print('Status:', response.status_code, 'Headers:', response.headers, 'Response Text', response.text, 'Error Response:',response.json())
    else:
        # This is a response of success for a single record
        print('Status:',response.status_code,'Headers:',response.headers,'Response:',response.json())

exit()

如果 MongoDB 中有 100 个新条目，这将对 ServiceNow 进行 100 POST 次调用。您的 ServiceNow 实例应该能够处理负载，并且您可以非常轻松地识别未能加载的记录。

但是，如果您出于任何原因需要压缩调用次数，我建议将您的列表拆分为 'sublists'，例如 one-liner featured in this answer:

# Set proper headers (these are always the same, so this
# can be assigned outside of the for loop)
headers = {"Content-Type":"application/json","Accept":"application/json"}

# Each POST will send up to 10 records of data
split_size = 10

# Note the two places where our split_size variable is used
for data_point in [j[x:x+split_size] for x in xrange(0, len(j), split_size)]:

    #Build HTTP Request (Note we are using data_point instead of j)
    response = requests.post(url=svcnow_url, auth=(svcnow_user, svcnow_pwd), headers=headers ,data=data_point)

    #Check for HTTP codes other than 200
    if response.status_code != 200:
        print('Status:', response.status_code, 'Headers:', response.headers, 'Response Text', response.text, 'Error Response:',response.json())
    else:
        # This is a response of success for a single record
        print('Status:',response.status_code,'Headers:',response.headers,'Response:',response.json())

exit()

Python MongoDB 查询请求将数据分割成块

Python MongoDB query requests segment data into chunks

python

mongodb

rest

servicenow

chunked