[erlang-questions] Erlang and Docker

[Ameretat Reith]

> Some day in the far future, we may reach a point where Erlang is the
> only language we're running (or at least the only one on a particular
> server) and then it might be attractive to un-containerize it. On the
> other hand, maybe not. Adding another layer of virtualization in the
> form of Docker has cost us very little so far.

It happened to us.  We have provided -and still doing- network
solutions written in C and executed in containers; at first we used
Docker but after putting much energy in struggling over It's bugs for
our high load environment, switched to very very more stable lxc.  I
can summarize our reasons for using containers into two:

1. We didn't like our users -about 3K for each service- interrupt for
an update.  So we would make another container, zero load to previous
one and remove It when Its users gone.

2. Our softwares would not natively scale that much to use all cores
in an efficient manner,  they won't scale linear with more powerful
hardware.

We made same software with Erlang an as we did we dropped using lxc
to.  We write -sometime time consuming- relups and update while service
is running.  We don't need to wait 1 day to all users of a lxc image go
and It make very good sense.

And about scalability, Erlang based software scales better than
linear!  It's CPU usage per task drops after feeding more tasks to
it and It's not slower than our legacy solutions.

Ease of deployment not changed very much after using Erlang, we used
DevOps tools -Canonical's Juju- to start container images which needed a
well written script to build in ci server; now we just execute that
shell scripts in host environment.