How to capture output of Flask CLI command in supervisord and redirect it to stdout?

Question

This is my Flask CLI script. It awaits for messages from rabbitmq and prints them out.

import pika
import click
from app import app_queue
from app import RABBITMQ_USER
from app import RABBITMQ_HOST
from app import RABBITMQ_PASSWORD
from app import RABBITMQ_PASSWORD
from app import RABBITMQ_PORT
from app import RABBITMQ_VHOST
from flask import current_app
from flask.cli import with_appcontext
from threading import Event

credentials = pika.PlainCredentials(RABBITMQ_USER, RABBITMQ_PASSWORD)
parameters = pika.ConnectionParameters(RABBITMQ_HOST, RABBITMQ_PORT, RABBITMQ_VHOST, credentials)
connection = pika.BlockingConnection(parameters)
channel = connection.channel()


@app_queue.command("listen", help="Listen to default queue.")
@click.argument("queue", required=False)
@with_appcontext
def consume_message(queue):
    queue = queue if queue else 'results'
    print(f'Command is listening for "{queue}" queue.', flush=True)

    channel.queue_declare(queue, durable=True, exclusive=False)
    channel.basic_consume(queue=queue, on_message_callback=process_results)

    print(f'[*] Waiting for messages. from "{queue}" queue. To exit press CTRL+C', flush=True)
    channel.start_consuming()

    Event().wait()


def process_results(ch, method, properties, body):
    print(" [x] Received %r" % body, flush=True)
    ch.basic_ack(delivery_tag = method.delivery_tag)

The script is executed by supervisord which triggers flask queue listen command.

[program:app_rabbitmq]
user=root
numprocs=1
directory=/src
autostart=true
autorestart=true
process_name=%(program_name)s
redirect_stderr=true
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
command=flask queue listen

How can I redirect output of Flask CLI command to stdout so I can see it with docker logs <my_container> command?

Answer 1

I found solution. Here are three things that I did.

• Instead redirecting my log to /dev/stdout I redirected it to /proc/1/fd/1

• I started supervisord in nodaemon mode supervisord -n

• I set these two environment variables in my docker image export PYTHONUNBUFFERED=True and export PYTHONIOENCODING=UTF-8