Failing to build docker container on remote host - docker

Question

I have a set of docker containers that are generated from yml files and work ok.
I now want to deploy them to another machine. In another post here I was advised to build the container on the remote host using one of 2 options:
option1 - copy the code to the remote host and apply a modified docker-compose, and build from source using a modified docker-compose
option2 - create an image on local machine, push it to a docker repository, pull it from there, using a modified docker-compose
I'm trying to follow option1 (as a start). I copied the code into the remote host, and modified the Dockerfile, and docker-compose.yml files (snippet1)
The build goes partway through. It downloads the python and postgres images, and starts to process the Dockerfile, but it fails to install the requirements (it fails to install the first requirement - see snippet2)
What can be the problem?
snippet1 - Dockerfile.dair, and docker-compose.yml
cat /home/ubuntu/webServer/web/Dockerfile.dair
FROM python:3.6.1
MAINTAINER User4 <user4#gmail.com>
# Create the group and user to be used in this container
RUN groupadd flaskgroup && useradd -m -g flaskgroup -s /bin/bash flask
# Create the working directory (and set it as the working directory)
RUN mkdir -p /home/flask/app/web
WORKDIR /home/flask/app/web
# Install the package dependencies (this step is separated
# from copying all the source code to avoid having to
# re-install all python packages defined in requirements2.txt
# whenever any source code change is made)
COPY requirements2.txt /home/flask/app/web
RUN pip install --no-cache-dir -r requirements2.txt
# Copy the source code into the container
COPY . /home/flask/app/web
RUN chown -R flask:flaskgroup /home/flask
USER flask
EXPOSE 8000
CMD /usr/local/bin/gunicorn -w 2 -t 3600 -b :8000 project:app
ENV PYTHONUNBUFFERED=1
ENV FLASK_APP=run.py
ENV FLASK_DEBUG=1
,
cat /home/ubuntu/construction_overlay/webServer/docker-compose.dair.yml
version: '3'
services:
web:
restart: always
build:
context: ./web
dockerfile: Dockerfile.dair
volumes:
- /home/ubuntu/construction_overlay/webServer/web:/home/flask/app/web
depends_on:
- postgres
nginx:
restart: always
build: ./nginx
ports:
- "80:80"
volumes:
- /home/ubuntu/construction_overlay/webServer/web:/home/flask/app/web
depends_on:
- web
postgres:
restart: always
build: ./postgresql
volumes:
- data1:/var/lib/postgresql
expose:
- "5432"
volumes:
data1:
snippet2 - the build fails to install the requirements
cat /home/ubuntu/webServer/web/requirements.txt
alembic==0.8.8
atomicwrites==1.3.0
attrs==19.1.0
...
,
docker-compose -f /home/ubuntu/webServer/docker-compose.dair.yml up --build -d;
Building postgres
Step 1/4 : FROM postgres:11.3
---> 4e045cb8eecd
Step 2/4 : ENV POSTGRES_USER postgres_user
---> Using cache
---> 400023c58607
Step 3/4 : ENV POSTGRES_PASSWORD postgres_user
---> Using cache
---> 0cf91f314380
Step 4/4 : ENV POSTGRES_DB construction-overlay-db
---> Using cache
---> 151106ecf13b
Successfully built 151106ecf13b
Successfully tagged webserver_postgres:latest
Building web
Step 1/10 : FROM python:3.6.1
---> 955d0c3b1bb2
Step 2/10 : MAINTAINER User4 <user4#gmail.com>
---> Using cache
---> 128d55ddb4e7
Step 3/10 : RUN groupadd flaskgroup && useradd -m -g flaskgroup -s /bin/bash flask
---> Using cache
---> e2c30915fcf5
Step 4/10 : RUN mkdir -p /home/flask/app/web
---> Using cache
---> 8f44dada5953
Step 5/10 : WORKDIR /home/flask/app/web
---> Using cache
---> 04a895c3fe27
Step 6/10 : COPY requirements.txt /home/flask/app/web
---> Using cache
---> 13ab37e789f8
Step 7/10 : RUN pip install --no-cache-dir -r requirements.txt
---> Running in 61475950cd73
Collecting alembic==0.8.8 (from -r requirements.txt (line 1))
Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'NewConnectionError('<pip._vendor.requests.packages.urllib3.connection.VerifiedHTTPSConnection object at 0x7f1e979262b0>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',)': /simple/alembic/

Answer 1

The solution was to add a rule for UDP outbound at the cloud provider
After adding this rule, the pre-requirements install ok
Egress IPv4 UDP 1 - 65535 0.0.0.0/0