synapse-workers docker: copy nginx and redis in from base images (#13447)

Part of my continuing quest to make the docker images build quicker: copy nginx and redis in from base docker images, rather than apt installing each time.

changelog.d/13447.misc

+Improve rebuild speed for the "synapse-workers" docker image.

docker/Dockerfile-workers

 # syntax=docker/dockerfile:1
-# Inherit from the official Synapse docker image
-ARG SYNAPSE_VERSION=latest
-FROM matrixdotorg/synapse:$SYNAPSE_VERSION
-
-# Install deps
-RUN \
-   --mount=type=cache,target=/var/cache/apt,sharing=locked \
-   --mount=type=cache,target=/var/lib/apt,sharing=locked \
-  apt-get update -qq && \
-  DEBIAN_FRONTEND=noninteractive apt-get install -yqq --no-install-recommends \
-     redis-server nginx-light
-
-# Install supervisord with pip instead of apt, to avoid installing a second
-# copy of python.
-RUN --mount=type=cache,target=/root/.cache/pip \
-    pip install supervisor~=4.2
-
-# Disable the default nginx sites
-RUN rm /etc/nginx/sites-enabled/default
 
-# Copy Synapse worker, nginx and supervisord configuration template files
-COPY ./docker/conf-workers/* /conf/
-
-# Copy a script to prefix log lines with the supervisor program name
-COPY ./docker/prefix-log /usr/local/bin/
-
-# Expose nginx listener port
-EXPOSE 8080/tcp
+ARG SYNAPSE_VERSION=latest
 
-# A script to read environment variables and create the necessary
-# files to run the desired worker configuration. Will start supervisord.
-COPY ./docker/configure_workers_and_start.py /configure_workers_and_start.py
-ENTRYPOINT ["/configure_workers_and_start.py"]
+# first of all, we create a base image with an nginx which we can copy into the
+# target image. For repeated rebuilds, this is much faster than apt installing
+# each time.
+
+FROM debian:bullseye-slim AS deps_base
+    RUN \
+       --mount=type=cache,target=/var/cache/apt,sharing=locked \
+       --mount=type=cache,target=/var/lib/apt,sharing=locked \
+      apt-get update -qq && \
+      DEBIAN_FRONTEND=noninteractive apt-get install -yqq --no-install-recommends \
+          redis-server nginx-light
+
+# Similarly, a base to copy the redis server from.
+#
+# The redis docker image has fewer dynamic libraries than the debian package,
+# which makes it much easier to copy (but we need to make sure we use an image
+# based on the same debian version as the synapse image, to make sure we get
+# the expected version of libc.
+FROM redis:6-bullseye AS redis_base
+
+# now build the final image, based on the the regular Synapse docker image
+FROM matrixdotorg/synapse:$SYNAPSE_VERSION
 
-# Replace the healthcheck with one which checks *all* the workers. The script
-# is generated by configure_workers_and_start.py.
-HEALTHCHECK --start-period=5s --interval=15s --timeout=5s \
-    CMD /bin/sh /healthcheck.sh
+    # Install supervisord with pip instead of apt, to avoid installing a second
+    # copy of python.
+    RUN --mount=type=cache,target=/root/.cache/pip \
+        pip install supervisor~=4.2
+    RUN mkdir -p /etc/supervisor/conf.d
+
+    # Copy over redis and nginx
+    COPY --from=redis_base /usr/local/bin/redis-server /usr/local/bin
+
+    COPY --from=deps_base /usr/sbin/nginx /usr/sbin
+    COPY --from=deps_base /usr/share/nginx /usr/share/nginx
+    COPY --from=deps_base /usr/lib/nginx /usr/lib/nginx
+    COPY --from=deps_base /etc/nginx /etc/nginx
+    RUN rm /etc/nginx/sites-enabled/default
+    RUN mkdir /var/log/nginx /var/lib/nginx
+    RUN chown www-data /var/log/nginx /var/lib/nginx
+
+    # Copy Synapse worker, nginx and supervisord configuration template files
+    COPY ./docker/conf-workers/* /conf/
+
+    # Copy a script to prefix log lines with the supervisor program name
+    COPY ./docker/prefix-log /usr/local/bin/
+
+    # Expose nginx listener port
+    EXPOSE 8080/tcp
+
+    # A script to read environment variables and create the necessary
+    # files to run the desired worker configuration. Will start supervisord.
+    COPY ./docker/configure_workers_and_start.py /configure_workers_and_start.py
+    ENTRYPOINT ["/configure_workers_and_start.py"]
+
+    # Replace the healthcheck with one which checks *all* the workers. The script
+    # is generated by configure_workers_and_start.py.
+    HEALTHCHECK --start-period=5s --interval=15s --timeout=5s \
+        CMD /bin/sh /healthcheck.sh

docker/conf-workers/supervisord.conf.j2

@@ -19,7 +19,7 @@ username=www-data
 autorestart=true
 
 [program:redis]
-command=/usr/local/bin/prefix-log /usr/bin/redis-server /etc/redis/redis.conf --daemonize no
+command=/usr/local/bin/prefix-log /usr/local/bin/redis-server
 priority=1
 stdout_logfile=/dev/stdout
 stdout_logfile_maxbytes=0