Why can't you use multiple processes

[li yun]

I try to perform multi-process analysis in the code to analyze the data of a certain file, but the code cannot perform the join normally, and there is no method to perform multiprocessing.Process. May I ask what I did wrong, please forgive me for not knowing how to format in the google group So I formatted it manually. Thank you very much for reading my question. Below is my test code

#coding:utf-8
from prometheus_client import generate_latest, CollectorRegistry
from prometheus_client.core import CollectorRegistry
from flask import Response,Flask
import multiprocessing
class CustomCollector(object):
       def get_data(self,data):
              print(data)

      def collect(self):
             plist = []

             for x in range(30):

                   p = multiprocessing.Process(target=self.get_data,args=("test",))
                   plist.append(p)
                   p.start()

             for p in plist:
                   p.join()
                   print('Process close')

def rundata():
      REGISTRY = CollectorRegistry(auto_describe=False)
      REGISTRY.register(CustomCollector())
      coll = CustomCollector()
      coll.collect()
      return Response(generate_latest(REGISTRY), mimetype="text/plain")

rundata()