feat(docker): update alpine linux to v.3.5 and add dumb-init

[ellerbrock]

Update for Node.js Alpine Linux

• Update Alpine Linux to Version 3.5
• Add dumb-init to prevent zombie processes

[tianon]

See also #298 (especially the discussion and linked threads over there) and moby/moby#26061 / moby/moby#28037 (was released in Docker 1.13.0 this week; not something to necessarily discourage adding a zombie-reaper, but something to be aware of).

Additionally, in the case of a language stack, I wouldn't recommend adding a zombie reaper directly unless Node.js itself lends itself to poorly-reaping applications (ie, the differentiator for me is whether this is a problem that everyone will encounter with Node.js applications, or whether "it depends" -- if Node.js applications can be written to handle SIGCHLD and reap their own children appropriately, this is probably something best left to consumers of this image to add, rather than something added by default, since once the space is added to the base, consumers of the image can't ever reclaim that space if they don't need it due to not needing it due to their application not requiring it or due to using Docker's own --init flag).

(Simply my thoughts as an upstream official-images reviewer -- I'm not a direct maintainer of the Node.js Docker images.)

[chorrell]

👎

See #298. We're only going to bump the version of Alpine for the upcoming Node.js v8.x.x release. I consider the upgrade from 3.4 to 3.5 to be a breaking change (like the switch from OpenSSL to LibreSSL for example...)

A few thoughts about dum-init:

• It would be better to have non-trivial changes like adding dum-init etc. in it's own PR for discussion.
• I also think adding a zombie reaper is something best left to consumers of this repo
• I'm generally against including it, but these kinds of changes should be considered for all images not just the Alpine variant to keep things consistent.

[chorrell]

Closing this in favour of switching to Alpine 3.5 for the v8 release only.