Replace final image base to be alpine

[BobyMCbobs]

Goal

Currently work-in-progress.

The final container image can be reduced by ~75% by replacing the base with alpine.

plausible/analytics                       bobymcbobs          4fb17172ceb0        10 minutes ago      57.5MB
plausible/analytics                       dev                 a7d58b5d74da        16 hours ago        242MB

The size of the container image is important as:

• in some environment there may not be a lot of storage
• nodes can run out of storage and cause problems
• if it can be reduced, it should be

Changes

Please describe the changes made in the pull request here.

Below you'll find a checklist. For each item on the list, check one option and delete the other.

Tests

• Automated tests have been added
• This PR does not require tests

Changelog

• Entry has been added to changelog
• This PR does not make a user-facing change

Documentation

• Docs have been updated
• This change does not need a documentation update

[BobyMCbobs]

Currently getting the error:

/app/releases/0.0.1/../../erts-10.7.2.1/bin/erl: exec: line 12: /app/erts-10.7.2.1/bin/erlexec: not found

---

according to

/app # file erts-10.7.2.1/bin/erlexec
erts-10.7.2.1/bin/erlexec: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=ef464f52ec7d693c667eaaff8fc0b851e262ed70, with debug_info, not stripped

the binary is not statically linked, so it depends a bit on the system it was built on (being Debian).

[BobyMCbobs]

May or may not be related but at least with Erlang, it is possible to use scratch (nothing) as the base image, so it can only contain the app and nothing OS related.

https://github.com/shortishly/erlang-in-docker-from-scratch

[ukutaht]

Awesome! I'd love to reduce the final image size

[BobyMCbobs]

In the latest commit, the image size has been further reduced:

plausible/analytics                       bobymcbobs          5f0b46b91d10        5 minutes ago       29.3MB
plausible/analytics                       dev                 3eade4a07b9c        9 minutes ago       242MB
plausible/analytics                       latest              edc04495bd46        20 hours ago        258MB

[BobyMCbobs]

Note:

• Alpine doesn't use GCC by default, but it has been included (build stage)
• for some reason the ncurses package is required in at least the init stages
• some programs such as adduser have different syntax than Debian, see https://github.com/plausible/analytics/pull/353/files#diff-dd2c0eb6ea5cfc6c4bd4eac30934e2d5746747af48fef6da689e85b752f39557L67

[BobyMCbobs]

@ukutaht, this PR is ready! 😄
May I please have a review?

[ukutaht]

Looks good to me! Thanks a ton