Python 3 - Flask Restful API to restart another API

Question

I created a python REST web-service, and it will execute a series of subprocess commands to restart another python REST webservice. But the problem is it doesn't really start my other REST service after I call it.

Here is my code for the REST API :

from flask import Flask, jsonify, request, make_response
from flask_restful import fields, reqparse, abort, Api, Resource
import sqlalchemy
from sqlalchemy.sql import table, column, select, update, insert, delete, func
from sqlalchemy.orm import sessionmaker
import requests
import time
import traceback
import subprocess
import os

app = Flask(__name__)
api = Api(app)

class RestartPython(Resource):
    def get(self):

        command1 = 'fuser -k 9876/tcp'
        proc1 = subprocess.Popen(command1, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
        proc1.wait()

        print('kill python process done')

        command2 = 'source activate envpy3'
        proc2 = subprocess.Popen(command2, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
        proc2.wait()

        print('switch python env done')

        command3 = 'python ReceiveCall.py'
        print(command3)
        proc3 = subprocess.Popen(command3, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
        proc3.wait()

        print('ReceiveCall started')

        return make_response(jsonify({'message': 'Python webservice is restarted', 'status': 'Ok'}), 200)

    api.add_resource(RestartPython, '/restart')

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8082, debug=True)

This will works if I just run it without wrapping them in web-service

import subprocess

if __name__ == '__main__':
    command1 = 'fuser -k 9876/tcp'
    proc1 = subprocess.Popen(command1, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
    proc1.wait()

    print('kill python process done')

    command2 = 'source activate envpy3'
    proc2 = subprocess.Popen(command2, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
    proc2.wait()

    print('switch python env done')

    command3 = 'python ReceiveCall.py'
    print(command3)
    proc3 = subprocess.Popen(command3, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
    proc3.wait()

    print('ReceiveCall started')

Any ideas?

what are the output,error you are getting after running each Popen instance , use below link to get the output and error stackoverflow.com/questions/1996518/… — pankaj mishra
– pankaj mishra, Commented Dec 6, 2017 at 9:42
if my answer solves your issue, can you accept it? a right tick mark below down vote button — pankaj mishra
– pankaj mishra, Commented Dec 6, 2017 at 9:55

pankaj mishra · Accepted Answer · 2017-12-06 10:38:28Z

1

instead of wait() i would recommend to use communicate() . communicate is used to avoid deadlock wherever pipe is used . Let me know if below modification works for you

from flask import Flask, jsonify, request, make_response
from flask_restful import fields, reqparse, abort, Api, Resource
import sqlalchemy
from sqlalchemy.sql import table, column, select, update, insert, delete, func
from sqlalchemy.orm import sessionmaker
import requests
import time
import traceback
import subprocess
from subprocess import PIPE,Popen
import os

app = Flask(__name__)
api = Api(app)

class RestartPython(Resource):
    def get(self):

        command1 = 'fuser -k 9876/tcp'
        proc1 = subprocess.Popen(command1, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
        #proc1.wait()
        (stdout, stderr) = proc1.communicate()

        print '.'.join(stdout)
        print '.'.join(stderr)

        print('kill python process done')

        command2 = 'source activate envpy3'
        proc2 = subprocess.Popen(command2, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
        #proc2.wait()
        proc2.communicate()

        print('switch python env done')

        command3 = 'python ReceiveCall.py'
        print(command3)
        proc3 = subprocess.Popen(command3, stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT, shell=True)
        #proc3.wait()
         proc3.communicate()

        print('ReceiveCall started')

        return make_response(jsonify({'message': 'Python webservice is restarted', 'status': 'Ok'}), 200)

    api.add_resource(RestartPython, '/restart')

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8082, debug=True)

edited Dec 6, 2017 at 10:38

answered Dec 6, 2017 at 9:50

pankaj mishra

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10 Comments

pankaj mishra Over a year ago

what is the problem you are facing and expected output?

Abc123 Over a year ago

I expect my other REST API will be started after I run it, "ReceiveCall.py" is my another python REST API.

Abc123 Over a year ago

And if I run those subprocess commands without calling it as a web-service, it will works.

pankaj mishra Over a year ago

did not get your last comment "...calling as a web-service"

pankaj mishra Over a year ago

run the code as it is , i have made some modification, just wanted to check even the subprocess Popen is called or not

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