Dockerfile-workers: reduce the amount we install (#12464)

This is an attempt to reduce the rebuild time. In short, we reduce the amount
of stuff that the dockerfile installs, so as to give a faster startup.

1 files changed, 14 insertions, 3 deletions

diff --git a/docker/Dockerfile-workers b/docker/Dockerfile-workers
index 6fb1cdbfb0..9ccb2b22a7 100644
--- a/docker/Dockerfile-workers
+++ b/docker/Dockerfile-workers
@@ -2,10 +2,19 @@
 FROM matrixdotorg/synapse
 
 # Install deps
-RUN apt-get update
-RUN apt-get install -y supervisor redis nginx
+RUN \
+   --mount=type=cache,target=/var/cache/apt,sharing=locked \
+   --mount=type=cache,target=/var/lib/apt,sharing=locked \
+  apt-get update && \
+  DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+     redis-server nginx-light
 
-# Remove the default nginx sites
+# 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
@@ -19,5 +28,7 @@ EXPOSE 8080/tcp
 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