Docker vs HTTP Proxy

Before Docker's build command supported --build-arg, there was no easy way to build the container in both development (behind a HTTP proxy) and in production (with no HTTP proxy).

This is one (horrible) solution.

Description

Create a small perl script inside the container. The script will try to connect to a specified IP and port then exit appropriately. Fortunately almost all base containers come with perl.

RUN echo "Setup proxy" \
  && echo " \
      use Socket;\n \
      my \$sock;\n \
      socket(\$sock, AF_INET, SOCK_STREAM, getprotobyname('tcp')) or exit(1);\n \
      setsockopt(\$sock, SOL_SOCKET, SO_SNDTIMEO, pack('l!l!', 2, 0)) or exit(3);\n \
      connect(\$sock , sockaddr_in(\$port, inet_aton(\$ip))) or exit(2);\n \
      close(\$sock);\n \
      exit(0);\n" > /tmp/c.pl \

Run the perl script and if the connection to 10.0.2.2:3128 is successful the proxy environment variables are written to /etc/proxyrc then sourced. Also the apt mirror is set to one which is geographically closer.

&& if perl -s /tmp/c.pl -ip=10.0.2.2 -port=3128; then \
     echo "Proxy detected" \
     && for N in http_proxy https_proxy ftp_proxy rsync_proxy npm_config_proxy npm_config_https_proxy; \
       do echo "export $N=http://10.0.2.2:3128" >> /etc/proxyrc; done \
     && echo "export no_proxy=localhost,127.0.0.1,localaddress" >> /etc/proxyrc \
     && . /etc/proxyrc \
     && export APT_MIRROR=ftp.nz.debian.org \
   ; fi \
&& rm /tmp/c.pl \

Install a required package via apt. If the proxy is detected then the environment variables http_proxy and https_proxy will be set.

&& echo "Install packages" \
&& export DEBIAN_FRONTEND=noninteractive \
&& if [ -n "$APT_MIRROR" ]; then sed -i'' "s/deb.debian.org/$APT_MIRROR/g" /etc/apt/sources.list; fi \
&& apt-get -y update \
&& apt-get install -y \
    cowsay \

Create a local user to run the service. Use a high uid and gid so as not to collide with any users which already exist in the base docker image.

&& echo "Create user" \
&& mkdir -p /opt/service/ \
&& groupadd --gid 2000 service \
&& useradd -m --home /home/service --uid 2000 --gid service --shell /bin/bash service \

Tidy up the layer.

&& echo "Cleaning up" \
&& apt-get autoremove -y \
&& apt-get clean -y \
&& rm -rf /var/lib/apt/lists/*

Set the permissions in the service directory.

RUN echo "Permissions" \
  && chown -R service:service /opt/service \
  && echo "Done"

Switch to the local user because we're not supposed to run everything as root.
```
USER service

WORKDIR /opt/service/
```
If proxyrc exists, source it to set the proxy environment variables for the local user. Now the local user can access the internet.
```
RUN echo "Post run" \
  && if [ -f "/etc/proxyrc" ]; then echo "Proxy"; . /etc/proxyrc; fi \
  && echo "Done"
```

The command which does something useful.

ENTRYPOINT ["/usr/games/cowsay", "moo"]

literatesnow/docker-vs-http-proxy

Docker vs HTTP Proxy

Description