I am facing a strange problem with logging when I set up a network of three docker containers each running a small flask app.
My python application looks as follows:
from flask import Flask, request
import sys
import logging
import logging.handlers
import os
app = Flask(__name__)
logger = logging.getLogger('Logger')
logger.setLevel(logging.DEBUG)
log_handler = logging.StreamHandler(sys.stdout)
logger.addHandler(log_handler)
service_name=""
if 'SERVICE_NAME' in os.environ:
service_name = os.environ['SERVICE_NAME']
logger = logging.LoggerAdapter(logger, {"serviceName" : service_name})
@app.route("/ping")
def ping():
logger.info(f'answering ping request')
return f'{service_name} OK'
if __name__ == "__main__":
logger.info("Started")
app.run(debug=True, host='0.0.0.0')
I start three instances of this in a docker network behind nginx:
docker network create tNet
docker run -it -d -p 24224:24224 -v `pwd`:/fluentd/etc -e FLUENTD_CONF=fluentd.conf --name=fluentd_logging fluent/fluentd
docker run -d --log-driver=fluentd --name ms1 -e SERVICE_NAME="ms1" --network tNet testflask
docker run -d --log-driver=fluentd --name ms2 -e SERVICE_NAME="ms2" --network tNet testflask
docker run -d --log-driver=fluentd --name ms3 -e SERVICE_NAME="ms3" --network tNet testflask
docker run -d --name=nginx --network tNet --volume `pwd`/nginx.conf:/etc/nginx/conf.d/default.conf -p 2000:2000 -p 3000:3000 nginx
The nginx configuration is as follows:
upstream app {
server ms1:5000;
server ms2:5000;
server ms3:5000;
}
server {
listen 2000;
location / {
proxy_pass http://app;
}
}
My fluent configuration looks as follows:
<source>
@type forward
</source>
<match>
@type stdout
</match>
When I use curl I can see that each instance of the service is responding:
curl localhost:2000/ping
ms1 OK
curl localhost:2000/ping
ms2 OK
curl localhost:2000/ping
ms3 OK
When I however inspect the logs I can only see logs from the 3rd instance of the service:
docker logs <fluent container ID> | grep -Eis "answering ping"
19-08-06 15:34:46.000000000 +0000 be338a3d5aa0: {"container_id":"be338a3d5aa0b8920366fdf1ba2a267082cee47e681adcea16b6c51c9c82cf0d","container_name":"/ms3","source":"stdout","log":"answering ping request"}
Has anyone an idea? Thank you in advance.
