Docker ADD folder during build and then expose to VOLUME - docker

Question

I am using docker-compose for a basic web app. When the image is built, it copies the static JS files in (ADD) and then builds them.
I then want to expose that directory to other containers, using VOLUME.
E.g.
Dockerfile
ADD ./site/static /site/static
WORKDIR /site/static
RUN gulp
docker-compose.yml
app:
build: .
volumes:
- /site/static
http:
image: nginx
volumes_from:
- app
nginx.conf
location /static {
alias /site/static
}
(Note, this is just an example)
The problem is that it seems to work the first time (i.e. when the volume does not exist), but is then never overwritten by the modified image. If I was using purely a Dockerfile, I could achieve this by putting VOLUME after ADD.
Is there a way to allow this, or am I approaching it completely wrong?
Thanks

Answer 1

Possible solution 1
I might be wrong, but I think the trouble is that when (and if) you do
docker-compose down && docker-compose up
your containers are recreated, and new "anonymous" volume is created.
You can check my guess running:
docker volume ls
I would try to use named volume, like so:
version: "2"
volumes:
app-volume: ~
services:
app:
build: .
volumes:
- app-volume:/site/static
http:
image: nginx
volumes:
- app-volume:/site/static
You need docker-compose 1.6.0+ and require a Docker Engine of version 1.10.0+ for usinng version 2 of docker-compose file.
Possible solution 2
just
app:
build: .
volumes:
- ./site/static:/site/static # maps host directory `./site/static` (relative to docker-compose.yml) to /site/static inside container
http:
image: nginx
volumes_from:
- app
And remove
ADD ./site/static /site/static
from your Dockerfile