how do POST API requests use parallel processing in python? requests.exceptions.ConnectionError:

Question

I have code like this:

import requests
import multiprocessing as mp
import json
import time

BASE_URL = 'http://127.0.0.1:3000/employees'

with open('data.json', 'r') as f:
    array = json.load(f)

def internet_resource_getter(post_data):
    stuff_got = []
    response = requests.post(BASE_URL, json=post_data)
    stuff_got.append(response.json())
    print(stuff_got)
    time.sleep(1)
    return stuff_got

if __name__ == '__main__':
    # freeze_support() here if program needs to be frozen  
    start=time.time()
    with mp.Pool(mp.cpu_count()) as pool:
        pool.map(internet_resource_getter, array)
    elapsed = (time.time() - start)  
    print("\n","time elapsed is :", elapsed)

in file data.json contains 500 records, for example:

[{"first_name":"John","last_name":"Swen"},{"first_name":"Ricard","last_name":"Candra"}]

in BASE_URL there is data like this:

[
  {
    "id": 1,
    "first_name": "Sebastian",
    "last_name": "Eschweiler"
  },
  {
    "id": 2,
    "first_name": "Steve",
    "last_name": "Palmer"
  },
  {
    "id": 3,
    "first_name": "Ann",
    "last_name": "Smith"
  }
]

expected output after POST API:

[
  {
    "id": 1,
    "first_name": "Sebastian",
    "last_name": "Eschweiler"
  },
  {
    "id": 2,
    "first_name": "Steve",
    "last_name": "Palmer"
  },
  {
    "id": 3,
    "first_name": "Ann",
    "last_name": "Smith"
  },
 {
    "id": 4,
    "first_name": "John",
    "last_name": "Swen"
  },
{
    "id": 5,
    "first_name": "Ricard",
    "last_name": "Candra"
  },
]

with my code above, the data that enters the url is only 420 records, even though my data.json is 500 records. how do I solve this so that I post 500 records to url. I don't know why only 400 data are processed. I have an error like this:

multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 699, in urlopen
    httplib_response = self._make_request(
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 445, in _make_request
    six.raise_from(e, None)
  File "<string>", line 3, in raise_from
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 440, in _make_request
    httplib_response = conn.getresponse()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\http\client.py", line 1347, in getresponse
    response.begin()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\http\client.py", line 307, in begin
    version, status, reason = self._read_status()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\http\client.py", line 276, in _read_status
    raise RemoteDisconnected("Remote end closed connection without"
http.client.RemoteDisconnected: Remote end closed connection without response

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\requests\adapters.py", line 439, in send
    resp = conn.urlopen(
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 755, in urlopen
    retries = retries.increment(
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\util\retry.py", line 531, in increment
    raise six.reraise(type(error), error, _stacktrace)
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\packages\six.py", line 734, in reraise
    raise value.with_traceback(tb)
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 699, in urlopen
    httplib_response = self._make_request(
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 445, in _make_request
    six.raise_from(e, None)
  File "<string>", line 3, in raise_from
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\site-packages\urllib3\connectionpool.py", line 440, in _make_request
    httplib_response = conn.getresponse()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\http\client.py", line 1347, in getresponse
    response.begin()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\http\client.py", line 307, in begin
    version, status, reason = self._read_status()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\http\client.py", line 276, in _read_status
    raise RemoteDisconnected("Remote end closed connection without"
urllib3.exceptions.ProtocolError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "paralel_pro.py", line 28, in <module>
    pool.map(internet_resource_getter, array)
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\multiprocessing\pool.py", line 364, in map
    return self._map_async(func, iterable, mapstar, chunksize).get()
  File "C:\Users\admin\AppData\Local\Programs\Python\Python38\lib\multiprocessing\pool.py", line 771, in get
    raise self._value
requests.exceptions.ConnectionError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

Answer 1

To get your answer, check your server logs. I suspect bad data and/or server not handling unexpected data gracefully.

Client-Side Check

See if the 80 records are always the same 80 records.

Server-Side Check

Can you find the logs for your server that is running on http://127.0.0.1:3000/employees ? It looks like it is running on your same machine. The server's application or service logs should have the smoking gun.