Split caddy and php-fpm in different images

[pwFoo]

Split php-fpm to a independent image and change fastcgi destination from 127.0.0.1 to an environment variabne with default (set by dockerfile) for example "php"?

So with docker swarm a second service with name "php" (or without swarm docker linked container) is used to forward php requests to?

[pwFoo]

I test a custom dockerfile / build with build-arg for caddy plugins and alpine packages. Caddyfile generated by ENV.

dockerfile

#
# Builder
#
FROM    abiosoft/caddy:builder as builder

ARG     version="1.0.0"
ARG     plugins=""
ARG     enable_telemetry="false"

RUN     VERSION=${version} PLUGINS=${plugins} ENABLE_TELEMETRY=${enable_telemetry} /bin/sh /usr/bin/builder.sh

# validate build
RUN     /install/caddy -version    
RUN     /install/caddy -plugins    

#
# Final stage
#
FROM    alpine:3.9

ARG     version="1.0.0"
LABEL   caddy_version="$version"

# Telemetry Stats
ENV     ENABLE_TELEMETRY="$enable_telemetry"

ARG     packages=""
RUN     [ ! -z "$packages" ] && apk --update --no-cache add $packages || true

EXPOSE  80 443 2015
WORKDIR /srv

# base Caddyfile config
ENV     CADDYCONF="0.0.0.0\nlog stdout\nerrors stdout"

# install caddy
COPY    --from=builder /install/caddy /usr/bin/caddy
COPY    files/ /

# entrypoint generate the Caddyfile during startup
ENTRYPOINT ["entrypoint-caddy"]
CMD ["caddy", "--conf", "/etc/Caddyfile", "--log", "stdout"]

files/usr/local/bin/entrypoint-caddy

#!/bin/sh

printf "$CADDYCONF" > /etc/Caddyfile

exec $@