Merge the Complement testing Docker images into a single, multi-purpose image. (#12881)

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

18 files changed, 276 insertions, 371 deletions

diff --git a/changelog.d/12881.misc b/changelog.d/12881.misc
new file mode 100644
index 0000000000..8a83182bd4
--- /dev/null
+++ b/changelog.d/12881.misc
@@ -0,0 +1 @@
+Merge the Complement testing Docker images into a single, multi-purpose image.
\ No newline at end of file
diff --git a/docker/Dockerfile-workers b/docker/Dockerfile-workers
index 24b03585f9..83db0a95b9 100644
--- a/docker/Dockerfile-workers
+++ b/docker/Dockerfile-workers
@@ -1,5 +1,6 @@
 # Inherit from the official Synapse docker image
-FROM matrixdotorg/synapse
+ARG SYNAPSE_VERSION=latest
+FROM matrixdotorg/synapse:$SYNAPSE_VERSION
 
 # Install deps
 RUN \
diff --git a/docker/README-testing.md b/docker/README-testing.md
index c38cae7530..1f0423f09b 100644
--- a/docker/README-testing.md
+++ b/docker/README-testing.md
@@ -8,79 +8,50 @@ docker images that can be run inside Complement for testing purposes.
 
 Note that running Synapse's unit tests from within the docker image is not supported.
 
-## Testing with SQLite and single-process Synapse
+## Using the Complement launch script
 
-> Note that `scripts-dev/complement.sh` is a script that will automatically build
-> and run an SQLite-based, single-process of Synapse against Complement.
+`scripts-dev/complement.sh` is a script that will automatically build
+and run Synapse against Complement.
+Consult the [contributing guide][guideComplementSh] for instructions on how to use it.
 
-The instructions below will set up Complement testing for a single-process,
-SQLite-based Synapse deployment.
 
-Start by building the base Synapse docker image. If you wish to run tests with the latest
-release of Synapse, instead of your current checkout, you can skip this step. From the
-root of the repository:
-
-```sh
-docker build -t matrixdotorg/synapse -f docker/Dockerfile .
-```
-
-This will build an image with the tag `matrixdotorg/synapse`.
-
-Next, build the Synapse image for Complement.
+[guideComplementSh]: https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#run-the-integration-tests-complement
 
-```sh
-docker build -t complement-synapse -f "docker/complement/Dockerfile" docker/complement
-```
+## Building and running the images manually
 
-This will build an image with the tag `complement-synapse`, which can be handed to
-Complement for testing via the `COMPLEMENT_BASE_IMAGE` environment variable. Refer to
-[Complement's documentation](https://github.com/matrix-org/complement/#running) for
-how to run the tests, as well as the various available command line flags.
-
-## Testing with PostgreSQL and single or multi-process Synapse
+Under some circumstances, you may wish to build the images manually.
+The instructions below will lead you to doing that.
 
-The above docker image only supports running Synapse with SQLite and in a
-single-process topology. The following instructions are used to build a Synapse image for
-Complement that supports either single or multi-process topology with a PostgreSQL
-database backend.
-
-As with the single-process image, build the base Synapse docker image. If you wish to run
-tests with the latest release of Synapse, instead of your current checkout, you can skip
-this step. From the root of the repository:
+Start by building the base Synapse docker image. If you wish to run tests with the latest
+release of Synapse, instead of your current checkout, you can skip this step. From the
+root of the repository:
 
 ```sh
 docker build -t matrixdotorg/synapse -f docker/Dockerfile .
 ```
 
-This will build an image with the tag `matrixdotorg/synapse`.
-
-Next, we build a new image with worker support based on `matrixdotorg/synapse:latest`.
-Again, from the root of the repository:
+Next, build the workerised Synapse docker image, which is a layer over the base
+image.
 
 ```sh
 docker build -t matrixdotorg/synapse-workers -f docker/Dockerfile-workers .
 ```
 
-This will build an image with the tag` matrixdotorg/synapse-workers`.
-
-It's worth noting at this point that this image is fully functional, and
-can be used for testing against locally. See instructions for using the container
-under
-[Running the Dockerfile-worker image standalone](#running-the-dockerfile-worker-image-standalone)
-below.
-
-Finally, build the Synapse image for Complement, which is based on
-`matrixdotorg/synapse-workers`.
+Finally, build the multi-purpose image for Complement, which is a layer over the workers image.
 
 ```sh
-docker build -t matrixdotorg/complement-synapse-workers -f docker/complement/SynapseWorkers.Dockerfile docker/complement
+docker build -t complement-synapse -f docker/complement/Dockerfile docker/complement
 ```
 
-This will build an image with the tag `complement-synapse-workers`, which can be handed to
+This will build an image with the tag `complement-synapse`, which can be handed to
 Complement for testing via the `COMPLEMENT_BASE_IMAGE` environment variable. Refer to
 [Complement's documentation](https://github.com/matrix-org/complement/#running) for
 how to run the tests, as well as the various available command line flags.
 
+See [the Complement image README](./complement/README.md) for information about the
+expected environment variables.
+
+
 ## Running the Dockerfile-worker image standalone
 
 For manual testing of a multi-process Synapse instance in Docker,
@@ -113,6 +84,9 @@ docker run -d --name synapse \
 ...substituting `POSTGRES*` variables for those that match a postgres host you have
 available (usually a running postgres docker container).
 
+
+### Workers
+
 The `SYNAPSE_WORKER_TYPES` environment variable is a comma-separated list of workers to
 use when running the container. All possible worker names are defined by the keys of the
 `WORKERS_CONFIG` variable in [this script](configure_workers_and_start.py), which the
@@ -125,8 +99,11 @@ type, simply specify the type multiple times in `SYNAPSE_WORKER_TYPES`
 (e.g `SYNAPSE_WORKER_TYPES=event_creator,event_creator...`).
 
 Otherwise, `SYNAPSE_WORKER_TYPES` can either be left empty or unset to spawn no workers
-(leaving only the main process). The container is configured to use redis-based worker
-mode.
+(leaving only the main process).
+The container will only be configured to use Redis-based worker mode if there are
+workers enabled.
+
+### Logging
 
 Logs for workers and the main process are logged to stdout and can be viewed with
 standard `docker logs` tooling. Worker logs contain their worker name
@@ -136,3 +113,21 @@ Setting `SYNAPSE_WORKERS_WRITE_LOGS_TO_DISK=1` will cause worker logs to be writ
 `<data_dir>/logs/<worker_name>.log`. Logs are kept for 1 week and rotate every day at 00:
 00, according to the container's clock. Logging for the main process must still be
 configured by modifying the homeserver's log config in your Synapse data volume.
+
+
+### Application Services
+
+Setting the `SYNAPSE_AS_REGISTRATION_DIR` environment variable to the path of
+a directory (within the container) will cause the configuration script to scan
+that directory for `.yaml`/`.yml` registration files.
+Synapse will be configured to load these configuration files.
+
+
+### TLS Termination
+
+Nginx is present in the image to route requests to the appropriate workers,
+but it does not serve TLS by default.
+
+You can configure `SYNAPSE_TLS_CERT` and `SYNAPSE_TLS_KEY` to point to a
+TLS certificate and key (respectively), both in PEM (textual) format.
+In this case, Nginx will additionally serve using HTTPS on port 8448.
diff --git a/docker/complement/Dockerfile b/docker/complement/Dockerfile
index 4823ce7364..50684c956d 100644
--- a/docker/complement/Dockerfile
+++ b/docker/complement/Dockerfile
@@ -1,22 +1,45 @@
-# A dockerfile which builds an image suitable for testing Synapse under
-# complement.
-
+# This dockerfile builds on top of 'docker/Dockerfile-workers' in matrix-org/synapse
+# by including a built-in postgres instance, as well as setting up the homeserver so
+# that it is ready for testing via Complement.
+#
+# Instructions for building this image from those it depends on is detailed in this guide:
+# https://github.com/matrix-org/synapse/blob/develop/docker/README-testing.md#testing-with-postgresql-and-single-or-multi-process-synapse
 ARG SYNAPSE_VERSION=latest
+FROM matrixdotorg/synapse-workers:$SYNAPSE_VERSION
+
+# Install postgresql
+RUN apt-get update && \
+  DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y postgresql-13
+
+# Configure a user and create a database for Synapse
+RUN pg_ctlcluster 13 main start &&  su postgres -c "echo \
+ \"ALTER USER postgres PASSWORD 'somesecret'; \
+ CREATE DATABASE synapse \
+  ENCODING 'UTF8' \
+  LC_COLLATE='C' \
+  LC_CTYPE='C' \
+  template=template0;\" | psql" && pg_ctlcluster 13 main stop
+
+# Extend the shared homeserver config to disable rate-limiting,
+# set Complement's static shared secret, enable registration, amongst other
+# tweaks to get Synapse ready for testing.
+# To do this, we copy the old template out of the way and then include it
+# with Jinja2.
+RUN mv /conf/shared.yaml.j2 /conf/shared-orig.yaml.j2
+COPY conf/workers-shared-extra.yaml.j2 /conf/shared.yaml.j2
 
-FROM matrixdotorg/synapse:${SYNAPSE_VERSION}
-
-ENV SERVER_NAME=localhost
-
-COPY conf/* /conf/
+WORKDIR /data
 
-# generate a signing key
-RUN generate_signing_key -o /conf/server.signing.key
+COPY conf/postgres.supervisord.conf /etc/supervisor/conf.d/postgres.conf
 
-WORKDIR /data
+# Copy the entrypoint
+COPY conf/start_for_complement.sh /
 
+# Expose nginx's listener ports
 EXPOSE 8008 8448
 
-ENTRYPOINT ["/conf/start.sh"]
+ENTRYPOINT ["/start_for_complement.sh"]
 
+# Update the healthcheck to have a shorter check interval
 HEALTHCHECK --start-period=5s --interval=1s --timeout=1s \
-    CMD curl -fSs http://localhost:8008/health || exit 1
+    CMD /bin/sh /healthcheck.sh
diff --git a/docker/complement/README.md b/docker/complement/README.md
index e075418e4a..37c39e2dfc 100644
--- a/docker/complement/README.md
+++ b/docker/complement/README.md
@@ -1 +1,32 @@
-Stuff for building the docker image used for testing under complement.
+# Unified Complement image for Synapse
+
+This is an image for testing Synapse with [the *Complement* integration test suite][complement].
+It contains some insecure defaults that are only suitable for testing purposes,
+so **please don't use this image for a production server**.
+
+This multi-purpose image is built on top of `Dockerfile-workers` in the parent directory
+and can be switched using environment variables between the following configurations:
+
+- Monolithic Synapse with SQLite (`SYNAPSE_COMPLEMENT_DATABASE=sqlite`)
+- Monolithic Synapse with Postgres (`SYNAPSE_COMPLEMENT_DATABASE=postgres`)
+- Workerised Synapse with Postgres (`SYNAPSE_COMPLEMENT_DATABASE=postgres` and `SYNAPSE_COMPLEMENT_USE_WORKERS=true`)
+
+The image is self-contained; it contains an integrated Postgres, Redis and Nginx.
+
+
+## How to get Complement to pass the environment variables through
+
+To pass these environment variables, use [Complement's `COMPLEMENT_SHARE_ENV_PREFIX`][complementEnv]
+variable to configure an environment prefix to pass through, then prefix the above options
+with that prefix.
+
+Example:
+```
+COMPLEMENT_SHARE_ENV_PREFIX=PASS_ PASS_SYNAPSE_COMPLEMENT_DATABASE=postgres
+```
+
+Consult `scripts-dev/complement.sh` in the repository root for a real example.
+
+
+[complement]: https://github.com/matrix-org/complement
+[complementEnv]: https://github.com/matrix-org/complement/pull/382
diff --git a/docker/complement/SynapseWorkers.Dockerfile b/docker/complement/SynapseWorkers.Dockerfile
deleted file mode 100644
index 99a09cbc2b..0000000000
--- a/docker/complement/SynapseWorkers.Dockerfile
+++ /dev/null
@@ -1,40 +0,0 @@
-# This dockerfile builds on top of 'docker/Dockerfile-worker' in matrix-org/synapse
-# by including a built-in postgres instance, as well as setting up the homeserver so
-# that it is ready for testing via Complement.
-#
-# Instructions for building this image from those it depends on is detailed in this guide:
-# https://github.com/matrix-org/synapse/blob/develop/docker/README-testing.md#testing-with-postgresql-and-single-or-multi-process-synapse
-FROM matrixdotorg/synapse-workers
-
-# Install postgresql
-RUN apt-get update && \
-  DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y postgresql-13
-
-# Configure a user and create a database for Synapse
-RUN pg_ctlcluster 13 main start &&  su postgres -c "echo \
- \"ALTER USER postgres PASSWORD 'somesecret'; \
- CREATE DATABASE synapse \
-  ENCODING 'UTF8' \
-  LC_COLLATE='C' \
-  LC_CTYPE='C' \
-  template=template0;\" | psql" && pg_ctlcluster 13 main stop
-
-# Modify the shared homeserver config with postgres support, certificate setup
-# and the disabling of rate-limiting
-COPY conf-workers/workers-shared.yaml /conf/workers/shared.yaml
-
-WORKDIR /data
-
-COPY conf-workers/postgres.supervisord.conf /etc/supervisor/conf.d/postgres.conf
-
-# Copy the entrypoint
-COPY conf-workers/start-complement-synapse-workers.sh /
-
-# Expose nginx's listener ports
-EXPOSE 8008 8448
-
-ENTRYPOINT ["/start-complement-synapse-workers.sh"]
-
-# Update the healthcheck to have a shorter check interval
-HEALTHCHECK --start-period=5s --interval=1s --timeout=1s \
-    CMD /bin/sh /healthcheck.sh
diff --git a/docker/complement/conf-workers/start-complement-synapse-workers.sh b/docker/complement/conf-workers/start-complement-synapse-workers.sh
deleted file mode 100755
index b7e2444000..0000000000
--- a/docker/complement/conf-workers/start-complement-synapse-workers.sh
+++ /dev/null
@@ -1,61 +0,0 @@
-#!/bin/bash
-#
-# Default ENTRYPOINT for the docker image used for testing synapse with workers under complement
-
-set -e
-
-function log {
-    d=$(date +"%Y-%m-%d %H:%M:%S,%3N")
-    echo "$d $@"
-}
-
-# Set the server name of the homeserver
-export SYNAPSE_SERVER_NAME=${SERVER_NAME}
-
-# No need to report stats here
-export SYNAPSE_REPORT_STATS=no
-
-# Set postgres authentication details which will be placed in the homeserver config file
-export POSTGRES_PASSWORD=somesecret
-export POSTGRES_USER=postgres
-export POSTGRES_HOST=localhost
-
-# Specify the workers to test with
-export SYNAPSE_WORKER_TYPES="\
-    event_persister, \
-    event_persister, \
-    background_worker, \
-    frontend_proxy, \
-    event_creator, \
-    user_dir, \
-    media_repository, \
-    federation_inbound, \
-    federation_reader, \
-    federation_sender, \
-    synchrotron, \
-    appservice, \
-    pusher"
-
-# Add Complement's appservice registration directory, if there is one
-# (It can be absent when there are no application services in this test!)
-if [ -d /complement/appservice ]; then
-    export SYNAPSE_AS_REGISTRATION_DIR=/complement/appservice
-fi
-
-# Generate a TLS key, then generate a certificate by having Complement's CA sign it
-# Note that both the key and certificate are in PEM format (not DER).
-openssl genrsa -out /conf/server.tls.key 2048
-
-openssl req -new -key /conf/server.tls.key -out /conf/server.tls.csr \
-  -subj "/CN=${SERVER_NAME}"
-
-openssl x509 -req -in /conf/server.tls.csr \
-  -CA /complement/ca/ca.crt -CAkey /complement/ca/ca.key -set_serial 1 \
-  -out /conf/server.tls.crt
-
-export SYNAPSE_TLS_CERT=/conf/server.tls.crt
-export SYNAPSE_TLS_KEY=/conf/server.tls.key
-
-# Run the script that writes the necessary config files and starts supervisord, which in turn
-# starts everything else
-exec /configure_workers_and_start.py
diff --git a/docker/complement/conf/homeserver.yaml b/docker/complement/conf/homeserver.yaml
deleted file mode 100644
index e2be540bbb..0000000000
--- a/docker/complement/conf/homeserver.yaml
+++ /dev/null
@@ -1,129 +0,0 @@
-## Server ##
-
-server_name: SERVER_NAME
-log_config: /conf/log_config.yaml
-report_stats: False
-signing_key_path: /conf/server.signing.key
-trusted_key_servers: []
-enable_registration: true
-enable_registration_without_verification: true
-
-## Listeners ##
-
-tls_certificate_path: /conf/server.tls.crt
-tls_private_key_path: /conf/server.tls.key
-bcrypt_rounds: 4
-registration_shared_secret: complement
-
-listeners:
-  - port: 8448
-    bind_addresses: ['::']
-    type: http
-    tls: true
-    resources:
-      - names: [federation]
-
-  - port: 8008
-    bind_addresses: ['::']
-    type: http
-
-    resources:
-      - names: [client]
-
-## Database ##
-
-database:
-  name: "sqlite3"
-  args:
-    # We avoid /data, as it is a volume and is not transferred when the container is committed,
-    # which is a fundamental necessity in complement.
-    database: "/conf/homeserver.db"
-
-## Federation ##
-
-# trust certs signed by the complement CA
-federation_custom_ca_list:
-- /complement/ca/ca.crt
-
-# unblacklist RFC1918 addresses
-ip_range_blacklist: []
-
-# Disable server rate-limiting
-rc_federation:
-  window_size: 1000
-  sleep_limit: 10
-  sleep_delay: 500
-  reject_limit: 99999
-  concurrent: 3
-
-rc_message:
-  per_second: 9999
-  burst_count: 9999
-
-rc_registration:
-  per_second: 9999
-  burst_count: 9999
-
-rc_login:
-  address:
-    per_second: 9999
-    burst_count: 9999
-  account:
-    per_second: 9999
-    burst_count: 9999
-  failed_attempts:
-    per_second: 9999
-    burst_count: 9999
-
-rc_admin_redaction:
-  per_second: 9999
-  burst_count: 9999
-
-rc_joins:
-  local:
-    per_second: 9999
-    burst_count: 9999
-  remote:
-    per_second: 9999
-    burst_count: 9999
-
-rc_3pid_validation:
-  per_second: 1000
-  burst_count: 1000
-
-rc_invites:
-  per_room:
-    per_second: 1000
-    burst_count: 1000
-  per_user:
-    per_second: 1000
-    burst_count: 1000
-
-federation_rr_transactions_per_room_per_second: 9999
-
-## API Configuration ##
-
-# A list of application service config files to use
-#
-app_service_config_files:
-AS_REGISTRATION_FILES  
-
-## Experimental Features ##
-
-experimental_features:
-  # Enable spaces support
-  spaces_enabled: true
-  # Enable history backfilling support
-  msc2716_enabled: true
-  # server-side support for partial state in /send_join responses
-  msc3706_enabled: true
-  # client-side support for partial state in /send_join responses
-  faster_joins: true
-  # Enable jump to date endpoint
-  msc3030_enabled: true
-
-server_notices:
-  system_mxid_localpart: _server
-  system_mxid_display_name: "Server Alert"
-  system_mxid_avatar_url: ""
-  room_name: "Server Alert"
diff --git a/docker/complement/conf/log_config.yaml b/docker/complement/conf/log_config.yaml
deleted file mode 100644
index c33fd6cd00..0000000000
--- a/docker/complement/conf/log_config.yaml
+++ /dev/null
@@ -1,24 +0,0 @@
-version: 1
-
-formatters:
-  precise:
-   format: '%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(request)s - %(message)s'
-
-filters:
-  context:
-    (): synapse.logging.context.LoggingContextFilter
-    request: ""
-
-handlers:
-  console:
-    class: logging.StreamHandler
-    formatter: precise
-    filters: [context]
-    # log to stdout, for easier use with 'docker logs'
-    stream: 'ext://sys.stdout'
-
-root:
-    level: INFO
-    handlers: [console]
-
-disable_existing_loggers: false
diff --git a/docker/complement/conf-workers/postgres.supervisord.conf b/docker/complement/conf/postgres.supervisord.conf
index 5608342d1a..5dae3e6330 100644
--- a/docker/complement/conf-workers/postgres.supervisord.conf
+++ b/docker/complement/conf/postgres.supervisord.conf
@@ -1,6 +1,9 @@
 [program:postgres]
 command=/usr/local/bin/prefix-log /usr/bin/pg_ctlcluster 13 main start --foreground
 
+# Only start if START_POSTGRES=1
+autostart=%(ENV_START_POSTGRES)s
+
 # Lower priority number = starts first
 priority=1
 
diff --git a/docker/complement/conf/start.sh b/docker/complement/conf/start.sh
deleted file mode 100755
index 5d8d0fe016..0000000000
--- a/docker/complement/conf/start.sh
+++ /dev/null
@@ -1,30 +0,0 @@
-#!/bin/sh
-
-set -e
-
-sed -i "s/SERVER_NAME/${SERVER_NAME}/g" /conf/homeserver.yaml
-
-# Add the application service registration files to the homeserver.yaml config
-for filename in /complement/appservice/*.yaml; do
-  [ -f "$filename" ] || break
-
-  as_id=$(basename "$filename" .yaml)
-
-  # Insert the path to the registration file and the AS_REGISTRATION_FILES marker after 
-  # so we can add the next application service in the next iteration of this for loop
-  sed -i "s/AS_REGISTRATION_FILES/  - \/complement\/appservice\/${as_id}.yaml\nAS_REGISTRATION_FILES/g" /conf/homeserver.yaml
-done
-# Remove the AS_REGISTRATION_FILES entry
-sed -i "s/AS_REGISTRATION_FILES//g" /conf/homeserver.yaml
-
-# generate an ssl key and cert for the server, signed by the complement CA
-openssl genrsa -out /conf/server.tls.key 2048
-
-openssl req -new -key /conf/server.tls.key -out /conf/server.tls.csr \
-  -subj "/CN=${SERVER_NAME}"
-openssl x509 -req -in /conf/server.tls.csr \
-  -CA /complement/ca/ca.crt -CAkey /complement/ca/ca.key -set_serial 1 \
-  -out /conf/server.tls.crt
-
-exec python -m synapse.app.homeserver -c /conf/homeserver.yaml "$@"
-
diff --git a/docker/complement/conf/start_for_complement.sh b/docker/complement/conf/start_for_complement.sh
new file mode 100755
index 0000000000..b9c97ab687
--- /dev/null
+++ b/docker/complement/conf/start_for_complement.sh
@@ -0,0 +1,90 @@
+#!/bin/bash
+#
+# Default ENTRYPOINT for the docker image used for testing synapse with workers under complement
+
+set -e
+
+echo "Complement Synapse launcher"
+echo "  Args: $@"
+echo "  Env: SYNAPSE_COMPLEMENT_DATABASE=$SYNAPSE_COMPLEMENT_DATABASE SYNAPSE_COMPLEMENT_USE_WORKERS=$SYNAPSE_COMPLEMENT_USE_WORKERS"
+
+function log {
+    d=$(date +"%Y-%m-%d %H:%M:%S,%3N")
+    echo "$d $@"
+}
+
+# Set the server name of the homeserver
+export SYNAPSE_SERVER_NAME=${SERVER_NAME}
+
+# No need to report stats here
+export SYNAPSE_REPORT_STATS=no
+
+
+case "$SYNAPSE_COMPLEMENT_DATABASE" in
+  postgres)
+    # Set postgres authentication details which will be placed in the homeserver config file
+    export POSTGRES_PASSWORD=somesecret
+    export POSTGRES_USER=postgres
+    export POSTGRES_HOST=localhost
+
+    # configure supervisord to start postgres
+    export START_POSTGRES=true
+    ;;
+
+  sqlite)
+    # Configure supervisord not to start Postgres, as we don't need it
+    export START_POSTGRES=false
+    ;;
+
+  *)
+    echo "Unknown Synapse database: SYNAPSE_COMPLEMENT_DATABASE=$SYNAPSE_COMPLEMENT_DATABASE" >&2
+    exit 1
+    ;;
+esac
+
+
+if [[ -n "$SYNAPSE_COMPLEMENT_USE_WORKERS" ]]; then
+  # Specify the workers to test with
+  export SYNAPSE_WORKER_TYPES="\
+      event_persister, \
+      event_persister, \
+      background_worker, \
+      frontend_proxy, \
+      event_creator, \
+      user_dir, \
+      media_repository, \
+      federation_inbound, \
+      federation_reader, \
+      federation_sender, \
+      synchrotron, \
+      appservice, \
+      pusher"
+else
+  # Empty string here means 'main process only'
+  export SYNAPSE_WORKER_TYPES=""
+fi
+
+
+# Add Complement's appservice registration directory, if there is one
+# (It can be absent when there are no application services in this test!)
+if [ -d /complement/appservice ]; then
+    export SYNAPSE_AS_REGISTRATION_DIR=/complement/appservice
+fi
+
+# Generate a TLS key, then generate a certificate by having Complement's CA sign it
+# Note that both the key and certificate are in PEM format (not DER).
+openssl genrsa -out /conf/server.tls.key 2048
+
+openssl req -new -key /conf/server.tls.key -out /conf/server.tls.csr \
+  -subj "/CN=${SERVER_NAME}"
+
+openssl x509 -req -in /conf/server.tls.csr \
+  -CA /complement/ca/ca.crt -CAkey /complement/ca/ca.key -set_serial 1 \
+  -out /conf/server.tls.crt
+
+export SYNAPSE_TLS_CERT=/conf/server.tls.crt
+export SYNAPSE_TLS_KEY=/conf/server.tls.key
+
+# Run the script that writes the necessary config files and starts supervisord, which in turn
+# starts everything else
+exec /configure_workers_and_start.py
diff --git a/docker/complement/conf-workers/workers-shared.yaml b/docker/complement/conf/workers-shared-extra.yaml.j2
index cd7b50c65c..a5b1b6bb8b 100644
--- a/docker/complement/conf-workers/workers-shared.yaml
+++ b/docker/complement/conf/workers-shared-extra.yaml.j2
@@ -1,3 +1,11 @@
+{#
+  This file extends the default 'shared' configuration file (from the 'synapse-workers'
+  docker image) with Complement-specific  tweak.
+
+  The base configuration is moved out of the default path to `shared-orig.yaml.j2`
+  in the Complement Dockerfile and below we include that original file.
+#}
+
 ## Server ##
 report_stats: False
 trusted_key_servers: []
@@ -76,10 +84,16 @@ federation_rr_transactions_per_room_per_second: 9999
 ## Experimental Features ##
 
 experimental_features:
-  # Enable history backfilling support
-  msc2716_enabled: true
   # Enable spaces support
   spaces_enabled: true
+  # Enable history backfilling support
+  msc2716_enabled: true
+  # server-side support for partial state in /send_join responses
+  msc3706_enabled: true
+  {% if not workers_in_use %}
+  # client-side support for partial state in /send_join responses
+  faster_joins: true
+  {% endif %}
   # Enable jump to date endpoint
   msc3030_enabled: true
 
@@ -88,3 +102,5 @@ server_notices:
   system_mxid_display_name: "Server Alert"
   system_mxid_avatar_url: ""
   room_name: "Server Alert"
+
+{% include "shared-orig.yaml.j2" %}
diff --git a/docker/conf-workers/shared.yaml.j2 b/docker/conf-workers/shared.yaml.j2
index 644ed788f3..92d25386dc 100644
--- a/docker/conf-workers/shared.yaml.j2
+++ b/docker/conf-workers/shared.yaml.j2
@@ -3,8 +3,10 @@
 # configure_workers_and_start.py uses and amends to this file depending on the workers
 # that have been selected.
 
+{% if enable_redis %}
 redis:
     enabled: true
+{% endif %}
 
 {% if appservice_registrations is not none %}
 ## Application Services ##
diff --git a/docker/conf-workers/supervisord.conf.j2 b/docker/conf-workers/supervisord.conf.j2
index ca1f7aef8e..7afab05133 100644
--- a/docker/conf-workers/supervisord.conf.j2
+++ b/docker/conf-workers/supervisord.conf.j2
@@ -28,6 +28,9 @@ stderr_logfile_maxbytes=0
 username=redis
 autorestart=true
 
+# Redis can be disabled if the image is being used without workers
+autostart={{ enable_redis }}
+
 [program:synapse_main]
 command=/usr/local/bin/prefix-log /usr/local/bin/python -m synapse.app.homeserver --config-path="{{ main_config_path }}" --config-path=/conf/workers/shared.yaml
 priority=10
@@ -41,4 +44,4 @@ autorestart=unexpected
 exitcodes=0
 
 # Additional process blocks
-{{ worker_config }}
\ No newline at end of file
+{{ worker_config }}
diff --git a/docker/configure_workers_and_start.py b/docker/configure_workers_and_start.py
index f7dac90222..64697e0354 100755
--- a/docker/configure_workers_and_start.py
+++ b/docker/configure_workers_and_start.py
@@ -37,8 +37,8 @@ import sys
 from pathlib import Path
 from typing import Any, Dict, List, Mapping, MutableMapping, NoReturn, Set
 
-import jinja2
 import yaml
+from jinja2 import Environment, FileSystemLoader
 
 MAIN_PROCESS_HTTP_LISTENER_PORT = 8080
 
@@ -236,12 +236,13 @@ def convert(src: str, dst: str, **template_vars: object) -> None:
         template_vars: The arguments to replace placeholder variables in the template with.
     """
     # Read the template file
-    with open(src) as infile:
-        template = infile.read()
+    # We disable autoescape to prevent template variables from being escaped,
+    # as we're not using HTML.
+    env = Environment(loader=FileSystemLoader(os.path.dirname(src)), autoescape=False)
+    template = env.get_template(os.path.basename(src))
 
-    # Generate a string from the template. We disable autoescape to prevent template
-    # variables from being escaped.
-    rendered = jinja2.Template(template, autoescape=False).render(**template_vars)
+    # Generate a string from the template.
+    rendered = template.render(**template_vars)
 
     # Write the generated contents to a file
     #
@@ -378,8 +379,8 @@ def generate_worker_files(
     nginx_locations = {}
 
     # Read the desired worker configuration from the environment
-    worker_types_env = environ.get("SYNAPSE_WORKER_TYPES")
-    if worker_types_env is None:
+    worker_types_env = environ.get("SYNAPSE_WORKER_TYPES", "").strip()
+    if not worker_types_env:
         # No workers, just the main process
         worker_types = []
     else:
@@ -506,12 +507,16 @@ def generate_worker_files(
             if reg_path.suffix.lower() in (".yaml", ".yml")
         ]
 
+    workers_in_use = len(worker_types) > 0
+
     # Shared homeserver config
     convert(
         "/conf/shared.yaml.j2",
         "/conf/workers/shared.yaml",
         shared_worker_config=yaml.dump(shared_config),
         appservice_registrations=appservice_registrations,
+        enable_redis=workers_in_use,
+        workers_in_use=workers_in_use,
     )
 
     # Nginx config
@@ -531,6 +536,7 @@ def generate_worker_files(
         "/etc/supervisor/supervisord.conf",
         main_config_path=config_path,
         worker_config=supervisord_config,
+        enable_redis=workers_in_use,
     )
 
     # healthcheck config
diff --git a/docs/development/contributing_guide.md b/docs/development/contributing_guide.md
index 2b3714df66..c2f04a3905 100644
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -304,6 +304,11 @@ To run a specific test, you can specify the whole name structure:
 COMPLEMENT_DIR=../complement ./scripts-dev/complement.sh -run TestImportHistoricalMessages/parallel/Historical_events_resolve_in_the_correct_order
 ```
 
+The above will run a monolithic (single-process) Synapse with SQLite as the database. For other configurations, try:
+
+- Passing `POSTGRES=1` as an environment variable to use the Postgres database instead.
+- Passing `WORKERS=1` as an environment variable to use a workerised setup instead. This option implies the use of Postgres.
+
 
 ### Access database for homeserver after Complement test runs.
 
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
index 3c472c576e..ffd399c39d 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -43,17 +43,29 @@ fi
 # Build the base Synapse image from the local checkout
 docker build -t matrixdotorg/synapse -f "docker/Dockerfile" .
 
+# Build the workers docker image (from the base Synapse image we just built).
+docker build -t matrixdotorg/synapse-workers -f "docker/Dockerfile-workers" .
+
+# Build the unified Complement image (from the worker Synapse image we just built).
+docker build -t complement-synapse \
+  -f "docker/complement/Dockerfile" "docker/complement"
+
+export COMPLEMENT_BASE_IMAGE=complement-synapse
+
 extra_test_args=()
 
 test_tags="synapse_blacklist,msc2716,msc3030,msc3787"
 
-# If we're using workers, modify the docker files slightly.
+# All environment variables starting with PASS_ will be shared.
+# (The prefix is stripped off before reaching the container.)
+export COMPLEMENT_SHARE_ENV_PREFIX=PASS_
+
 if [[ -n "$WORKERS" ]]; then
-  # Build the workers docker image (from the base Synapse image).
-  docker build -t matrixdotorg/synapse-workers -f "docker/Dockerfile-workers" .
+  # Use workers.
+  export PASS_SYNAPSE_COMPLEMENT_USE_WORKERS=true
 
-  export COMPLEMENT_BASE_IMAGE=complement-synapse-workers
-  COMPLEMENT_DOCKERFILE=SynapseWorkers.Dockerfile
+  # Workers can only use Postgres as a database.
+  export PASS_SYNAPSE_COMPLEMENT_DATABASE=postgres
 
   # And provide some more configuration to complement.
 
@@ -65,17 +77,18 @@ if [[ -n "$WORKERS" ]]; then
   # ... and it takes longer than 10m to run the whole suite.
   extra_test_args+=("-timeout=60m")
 else
-  export COMPLEMENT_BASE_IMAGE=complement-synapse
-  COMPLEMENT_DOCKERFILE=Dockerfile
+  export PASS_SYNAPSE_COMPLEMENT_USE_WORKERS=
+  if [[ -n "$POSTGRES" ]]; then
+    export PASS_SYNAPSE_COMPLEMENT_DATABASE=postgres
+  else
+    export PASS_SYNAPSE_COMPLEMENT_DATABASE=sqlite
+  fi
 
   # We only test faster room joins on monoliths, because they are purposefully
   # being developed without worker support to start with.
   test_tags="$test_tags,faster_joins"
 fi
 
-# Build the Complement image from the Synapse image we just built.
-docker build -t $COMPLEMENT_BASE_IMAGE -f "docker/complement/$COMPLEMENT_DOCKERFILE" "docker/complement"
-
 # Run the tests!
 echo "Images built; running complement"
 cd "$COMPLEMENT_DIR"