Cannot GET Request To Flask App Localhost In Docker Container

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1 Cannot GET request to flask app localhost in Docker container

Problem Description:

i have simple app packed in container

app = Flask(__name__)


@app.route('/readiness')
@app.route('/liveness')
def health():
    return {"health_status": "running"}, 200


class StandaloneApplication(gunicorn.app.base.BaseApplication):
    def __init__(self, flask_app, gunicorn_options=None):
        self.options = gunicorn_options or {}
        self.gunicorn_app = flask_app
        super().__init__()

    def load_config(self):
        config = {key: value for key, value in self.options.items()
                  if key in self.cfg.settings and value is not None}
        for key, value in config.items():
            self.cfg.set(key.lower(), value)

    def load(self):
        return self.gunicorn_app


if __name__ == "__main__":
    options = {
        'bind': ['0.0.0.0:8080', '0.0.0.0:8090'],
        'workers': 1,
        "timeout": 60
    }
    StandaloneApplication(app, options).run()
    log.info("Server started")

The container with app running successfully

CONTAINER ID   IMAGE       COMMAND           CREATED              STATUS              PORTS                            NAMES
28a8152aa90f   embs:embs   "python app.py"   About a minute ago   Up About a minute   8080/tcp, 0.0.0.0:8080->80/tcp   determined_galois

[2022-12-06 12:48:59 +0000] [1] [INFO] Starting gunicorn 20.1.0
[2022-12-06 12:48:59 +0000] [1] [INFO] Listening at: http://0.0.0.0:8080,http://0.0.0.0:8090 (1)
[2022-12-06 12:48:59 +0000] [1] [INFO] Using worker: sync
[2022-12-06 12:48:59 +0000] [15] [INFO] Booting worker with pid: 15

When i try

 curl 0.0.0.0:8080/readiness

I got

curl: (52) Empty reply from server

when i use requests

url = '0.0.0.0:8080/readiness'
requests.get(url)

I got requests.exceptions.ConnectionError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

How can request flask app in Docker properly ?

Solution – 1

You need to publish the 8080 port.
Currently, you have 8080/tcp, 0.0.0.0:8080->80/tcp but this configuration is the 8080 port inside the container is published on port 80 from local machine.

You need 8080/tcp, 0.0.0.0:8080->8080/tcp (and same with 8090), add -p 8080:8080 to docker run command and check with docker ps.

Another detail, you can use localhost or 127.0.0.1 for get, 0.0.0.0 is not recommended.

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