Azure webapp running "docker run" twice and fails to deploy - azure

Question

I am trying to deploy my web app on azure using docker. On my local machine it works fine, but when I deploy it in azure I can see that it is running docker run twice (why twice?)
2019-10-02 11:15:26.257 INFO - Status: Image is up to date for *******.azurecr.io/****_****:v2.11
2019-10-02 11:15:26.266 INFO - Pull Image successful, Time taken: 0 Minutes and 1 Seconds
2019-10-02 11:15:26.297 INFO - Starting container for site
2019-10-02 11:15:26.298 INFO - docker run -d -p 27757:8000 --name **********-dv_0_a70e438e -e WEBSITES_ENABLE_APP_SERVICE_STORAGE=false -e WEBSITES_PORT=8000 -e WEBSITE_SITE_NAME=********-dv -e WEBSITE_AUTH_ENABLED=True -e WEBSITE_ROLE_INSTANCE_ID=0 -e WEBSITE_HOSTNAME=********-dv.azurewebsites.net -e WEBSITE_INSTANCE_ID=************************* -e HTTP_LOGGING_ENABLED=1 ********.azurecr.io/*****_*****:v2.11 init.sh
2019-10-02 11:15:28.069 INFO - Starting container for site
2019-10-02 11:15:28.070 INFO - docker run -d -p 6078:8081 --name **********_middleware -e WEBSITES_ENABLE_APP_SERVICE_STORAGE=false -e WEBSITES_PORT=8000 -e WEBSITE_SITE_NAME=******-dv -e WEBSITE_AUTH_ENABLED=True -e WEBSITE_ROLE_INSTANCE_ID=0 -e WEBSITE_HOSTNAME=********** -e WEBSITE_INSTANCE_ID=******73***** -e HTTP_LOGGING_ENABLED=1 appsvc/middleware:1907112318 /Host.ListenUrl=http://0.0.0.0:8081 /Host.DestinationHostUrl=http://172.16.1.3:8000 /Host.UseFileLogging=true
This leads to an error later :
2019-10-02 11:15:30.410 INFO - Initiating warmup request to container drillx-stuckpipe-dv_0_a70e438e for site *********-dv
2019-10-02 11:19:38.791 ERROR - Container *******-dv_0_a70e438e for site ********-dv did not start within expected time limit. Elapsed time = 248.3813377 sec
In the logs stream of the app I can see that the web app has started but du to the fact that the port 8000 is not accessible I get this error :
2019-10-02 11:43:55.827 INFO - Container ********-dv_0_33e8d6cc_middleware for site ********-dv initialized successfully and is ready to serve requests.
2019-10-02 11:43:55.881 ERROR - Container ********-dv_0_33e8d6cc didn't respond to HTTP pings on port: 8000, failing site start. See container logs for debugging.
In my Dockerfile I do have at end EXPOSE 8000. I do not know what I am missing here...
FROM python:3.6
# ssh
ENV SSH_PASSWD "root:PWD!"
RUN apt-get update \
&& apt-get -y install \
apt-transport-https \
apt-utils \
curl \
openssh-server \
&& apt-get clean \
&& echo "$SSH_PASSWD" | chpasswd
RUN curl https://packages.microsoft.com/keys/microsoft.asc | apt-key add - \
&& curl https://packages.microsoft.com/config/debian/9/prod.list > /etc/apt/sources.list.d/mssql-release.list \
&& apt-get update \
&& ACCEPT_EULA=Y apt-get -y install \
msodbcsql17 \
unixodbc-dev \
libxmlsec1-dev \
&& apt-get clean
RUN mkdir /code
WORKDIR code
ADD requirements.txt /code/
RUN pip install -r requirements.txt
COPY . /code/
WORKDIR /code/
RUN ls -ltr
COPY sshd_config /etc/ssh/
COPY init.sh /usr/local/bin/
RUN chmod u+x /usr/local/bin/init.sh
EXPOSE 8000
ENTRYPOINT ["init.sh"]
Init.sh :
#!/bin/bash
set -e
echo "Starting SSH ..."
service ssh start
gunicorn --bind 0.0.0.0:8000 wsgi

Answer 1

If we correctly look at the logs, its actually not running twice. The docker run logs are for different images.
Your application image
Middleware - "appsvc/middleware" is the image used to handle Easy Auth/MSI/CORS on Web App Linux.
https://hajekj.net/2019/01/21/exploring-app-service-authentication-on-linux/
Now coming to the actual issue, if we take a look at the second set of logs. It states that your application failed to start in expected time limit.
This is by default 230 seconds on Web App Linux and can be increased using WEBSITES_CONTAINER_START_TIME_LIMIT application setting. Maximum value can be upto 1800 seconds.
How does Azure verify that application has started or not? : Azure will ping to a PORT and will wait for a HTTP response. If it receives one, then container will be started otherwise docker run will be executed again and process continues.
Which PORT: https://blogs.msdn.microsoft.com/waws/2017/09/08/things-you-should-know-web-apps-and-linux/#NoPing