swalog/tiny-hello repository overview

⁠Main feature:

Tiny docker image providing a web-server test, which adds ONLY 18.5 kb on top of busybox.

• busybox base, i.e. usable linux box w/tools
• nweb http-webserver
• Cronjob that updates landing-page with debug information
• Access to web-server log at <SERVER>/nweb.log

Inspired by tutum/hello-world⁠, however, instead of building on top of alpine and php, this uses a modified nweb⁠ by Nigel Griffith, built to run on busybox, adding only a 18.5 kB layer, for a grand total of 1.18 MiB, a 93.4% size reduction.

⁠Example usage

docker run -d -p 8190:80 swalog/tiny-hello

curl localhost:8190

curl localhost:8190/nweb.log

⁠Server log files

These are available through he container log output, as well as the endpoint at <yourservice>/nweb.log hosted by the container.

⁠Built using:

• nweb by Nigel Griffith. See https://www.ibm.com/developerworks/systems/library/es-nweb/index.html⁠
• busybox, the minimal linux distro

⁠Changes to nweb⁠:

1. Allow serving .log files (useful for debugging)

Hit <endpoint>/nweb.log to request it from server

⁠Building docker image

Everything should be ready to build from the initial repostory clone, after initializing submodules:

git submodule init && git submodule update

Docker image is also automatically built on dockerhub: https://hub.docker.com/r/swalog/tiny-hello/⁠

⁠How-to: Rebuilding nweb webserver

Dockerfile handles building the webserver executable in a multi-build stage.

Additionally a pre-compiled version provided in server folder. Read on if you want to build it locally, on your own machine.

Run ./build-nweb.sh, this generates the compiled nweb server

This requires several tools:

• musl-gcc (musl-tools package)
• strip (binutils package)
• sstrip (from elfkickers, website⁠)
• upx (upx-ucl package)

All of these binary size reduction methods have been copied from sseemayer/mini-helloworld-httpd⁠. Thanks!

⁠Caveats

This hosts a static page with hostname information, as well as listing certain environment variables used by k8s matching regex ^(.*)_PORT_([0-9]*)_(TCP|UDP).

To mitigate this, a cron-job is installed that recreates the index.html once every minute. Takes order of 2ms to execute.

⁠TODOs

• Consider modifying nweb to generate webpage at reqest time