Dockerfile Build, Certificate Generation, and Health Check

[InAnimaTe]

This PR provides the following:

• A multi-stage Dockerfile which builds echo-server and then ships that to the final from scratch image for execution.
• Generation of a self-signed certificate on docker build and colocated with echo-server for SSL support.
  • PORT and SSLPORT variables define the ports to use for each.
• Updated logging to output UserAgent.
• Example health endpoint implementation. Future iterations will utilize something intelligent like this from Heptio!
• Dockerfile Build with Docker Hub Registry: https://cloud.docker.com/repository/docker/inanimate/echo-server/tags
• Removal of old un-needed files (pre-built binary and certificate keys).

Run yourself!

docker run -ti -p 80:8080 -p 443:8443 inanimate/echo-server:dockerfile-update

Health Check Example:

┌[mloria@odyssey] [dockerfile-update] 
└[~/exercise/echo-server]> httpstat -k https://localhost:443/health
Connected to 127.0.0.1:443 from 127.0.0.1:57402

HTTP/2 200 
content-type: application/json
content-length: 15
date: Fri, 25 Oct 2019 21:45:47 GMT

Body stored in: /var/folders/bm/n1j83h5n0zl89k53v41byb_80000gn/T/tmpsSHGSx

  DNS Lookup   TCP Connection   Server Processing   Content Transfer
[     4ms    |       0ms      |        2ms        |        0ms       ]
             |                |                   |                  |
    namelookup:4ms            |                   |                  |
                        connect:4ms               |                  |
                                      starttransfer:30ms             |
                                                                 total:30ms   

speed_download: 0.5 KiB/s, speed_upload: 0.0 KiB/s
┌[mloria@odyssey] [dockerfile-update] 
└[~/exercise/echo-server]> cat /var/folders/bm/n1j83h5n0zl89k53v41byb_80000gn/T/tmpsSHGSx
───────┬──────────────────────────────────────────────────────────────────────────────────────────────
       │ File: /var/folders/bm/n1j83h5n0zl89k53v41byb_80000gn/T/tmpsSHGSx
───────┼──────────────────────────────────────────────────────────────────────────────────────────────
   1   │ {"Status":"ok"}
───────┴──────────────────────────────────────────────────────────────────────────────────────────────

And the stdout:

┌[mloria@odyssey] [dockerfile-update ⚡] 
└[~/exercise/echo-server]> docker run -ti -p 80:8080 -p 443:8443 testbuild10
Echo server listening on ssl port :8443.
Echo server listening on port :8080.
172.17.0.1:41570 | curl/7.54.0 | GET /health