Flask POST request is causing server to crash

python json api rest flask

105,363

Solution 1

First what you want to do is enable debug mode so Flask will actually tell you what the error is. (And you get the added benefit of flask reloading every time you modify your code!)

if __name__ == '__main__':
    app.debug = True
    app.run()

Then we find out our error:

TypeError: 'dict' object is not callable

You're returning request.json, which is a dictionary. You need to convert it into a string first. It's pretty easy to do:

def api_response():
    from flask import jsonify
    if request.method == 'POST':
        return jsonify(**request.json)

There you are! :)

Solution 2

The server is overloaded because the default port(5000) or port explicitly mentioned by a user(eg:app.run(port=7000)) may be using some other processes in the background, so we need to kill the processes which are being used by that port.

You can see the process id's(PIDS) which are using that port by using the following command: netstat -o -a in command prompt *Look into the respective PID for the port

Then kill all the Processes(PIDS) for the port you want to use using the following command: Taskkill /PID 30832 /F Here I used the PID 30832 for port 127.0.0.1:7000 which is giving the overloaded error. After that problem is solved.

105,363

zallarak

Updated on January 11, 2022

Comments

zallarak over 2 years

I am trying to make a simple api in Flask, the first step being getting the POST json data. (I just want to print it for now) This is my code and when I request /api with json data, it returns a 500 error. Any thoughts on why this is happening?

from flask import Flask, request, Response
app = Flask(__name__)

@app.route('/')
def root_response():
    return "Hello World."

@app.route('/api', methods=['POST', 'GET'])
def api_response():
    if request.method == 'POST':
        return request.json

if __name__ == '__main__':
    app.run()

The curl command:

$ curl -H "Content-Type: application/json" --data @body.json http://127.0.0.1:5000/api
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<title>500 Internal Server Error</title>
<h1>Internal Server Error</h1>
<p>The server encountered an internal error and was unable to complete your request.  Either the server is overloaded or there is an error in the application.</p>

body.json:

{
"please": "print",
"me": "now"
}

BoJack Horseman almost 9 years

That debug mode saved me a lot of time :D
disruptive over 8 years

Are the other settings for debug, because I find that despite having debug set to True, I don't get the error messages on screen.
alisa over 7 years

I actually realized that all error messages were output to the terminal where I was running my server. Yet the debug mode turned out to be helpful for other testings (and it prints right where you run your curl command)