Resolve shared Synapse worker unit values once per run

The worker systemd service template is rendered once per worker, and
Ansible re-evaluates every variable it references (and every variable
those depend on) on each render. Most of these values are identical for
all workers, e.g. the Redis/Valkey and Postgres socket settings, which
fan out into chains like matrix_playbook_synapse_uses_managed_valkey ->
valkey_enabled -> matrix_bridge_hookshot_*.

Resolve the worker-independent values once in setup_install.yml, before
the per-worker loop, and have the template read them from a single fact.
The per-worker-type argument selection becomes a lookup, so a render no
longer evaluates all 12 type-specific argument lists.

Rendered units are byte-identical. With the specialized-workers preset
(19 workers), the systemd service tasks went from 28.8s to ~13.5s on
ansible-core 2.20.1 (connection=local), close to the ~0.6s-per-task cost
of templating a static file. Deployments whose inventory makes these
variables more expensive to evaluate gain proportionally more.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

roles/custom/matrix-synapse/tasks/synapse/workers/setup_install.yml

@@ -59,6 +59,50 @@
   with_items: "{{ matrix_synapse_workers_current_label_files.files }}"
   when: "not ansible_check_mode and (item.path | basename | replace ('worker.', '') | replace('.labels', '')) not in matrix_synapse_enabled_worker_names"
 
+# Ansible re-evaluates every variable a template references (and all variables those depend on) each time the template is rendered.
+# The worker systemd service template is rendered once per worker and mostly references values that are the same for all workers,
+# so we resolve those once here instead of re-deriving them for every worker.
+- name: Resolve worker-independent values for the worker systemd service template
+  ansible.builtin.set_fact:
+    matrix_synapse_worker_systemd_shared:
+      config_dir_path: "{{ matrix_synapse_config_dir_path }}"
+      base_path: "{{ matrix_synapse_base_path }}"
+      storage_path: "{{ matrix_synapse_storage_path }}"
+      uid: "{{ matrix_synapse_uid }}"
+      gid: "{{ matrix_synapse_gid }}"
+      tmp_directory_size_mb: "{{ matrix_synapse_tmp_directory_size_mb }}"
+      container_image_final: "{{ matrix_synapse_container_image_final }}"
+      container_network: "{{ matrix_synapse_container_network }}"
+      container_additional_networks: "{{ matrix_synapse_container_additional_networks }}"
+      container_additional_volumes: "{{ matrix_synapse_container_additional_volumes }}"
+      container_arguments: "{{ matrix_synapse_container_arguments }}"
+      container_worker_arguments_by_type:
+        room_worker: "{{ matrix_synapse_workers_room_workers_container_arguments }}"
+        sync_worker: "{{ matrix_synapse_workers_sync_workers_container_arguments }}"
+        client_reader: "{{ matrix_synapse_workers_client_reader_workers_container_arguments }}"
+        federation_reader: "{{ matrix_synapse_workers_federation_reader_workers_container_arguments }}"
+        generic_worker: "{{ matrix_synapse_workers_generic_workers_container_arguments }}"
+        stream_writer: "{{ matrix_synapse_workers_stream_writers_container_arguments }}"
+        federation_sender: "{{ matrix_synapse_workers_federation_sender_workers_container_arguments }}"
+        pusher: "{{ matrix_synapse_workers_pusher_workers_container_arguments }}"
+        appservice: "{{ matrix_synapse_workers_appservice_workers_container_arguments }}"
+        user_dir: "{{ matrix_synapse_workers_user_dir_workers_container_arguments }}"
+        background: "{{ matrix_synapse_workers_background_workers_container_arguments }}"
+        media_repository: "{{ matrix_synapse_workers_media_repository_workers_container_arguments }}"
+      workers_enabled: "{{ matrix_synapse_workers_enabled }}"
+      workers_container_host_bind_address: "{{ matrix_synapse_workers_container_host_bind_address }}"
+      redis_path_enabled: "{{ matrix_synapse_redis_path_enabled }}"
+      redis_path: "{{ matrix_synapse_redis_path }}"
+      redis_path_host: "{{ matrix_synapse_redis_path_host }}"
+      database_socket_enabled: "{{ matrix_synapse_database_socket_enabled }}"
+      database_socket_path: "{{ matrix_synapse_database_socket_path }}"
+      database_socket_path_host: "{{ matrix_synapse_database_socket_path_host }}"
+      systemd_path: "{{ devture_systemd_docker_base_systemd_path }}"
+      systemd_unit_home_path: "{{ devture_systemd_docker_base_systemd_unit_home_path }}"
+      host_command_sh: "{{ devture_systemd_docker_base_host_command_sh }}"
+      host_command_docker: "{{ devture_systemd_docker_base_host_command_docker }}"
+      container_stop_grace_time_seconds: "{{ devture_systemd_docker_base_container_stop_grace_time_seconds }}"
+
 - name: Ensure creation of worker systemd service files and configuration files
   ansible.builtin.include_tasks: "{{ role_path }}/tasks/synapse/workers/util/setup_files_for_worker.yml"
   with_items: "{{ matrix_synapse_workers_enabled_list }}"

roles/custom/matrix-synapse/tasks/synapse/workers/util/setup_files_for_worker.yml

@@ -32,5 +32,5 @@
 - name: Ensure systemd service exists for {{ matrix_synapse_worker_systemd_service_name }}
   ansible.builtin.template:
     src: "{{ role_path }}/templates/synapse/systemd/matrix-synapse-worker.service.j2"
-    dest: "{{ devture_systemd_docker_base_systemd_path }}/{{ matrix_synapse_worker_systemd_service_name }}.service"
+    dest: "{{ matrix_synapse_worker_systemd_shared.systemd_path }}/{{ matrix_synapse_worker_systemd_service_name }}.service"
     mode: '0644'

roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse-worker.service.j2

@@ -1,100 +1,75 @@
 #jinja2: lstrip_blocks: True
 [Unit]
 Description=Synapse worker ({{ matrix_synapse_worker_container_name }})
-AssertPathExists={{ matrix_synapse_config_dir_path }}/{{ matrix_synapse_worker_config_file_name }}
+AssertPathExists={{ matrix_synapse_worker_systemd_shared.config_dir_path }}/{{ matrix_synapse_worker_config_file_name }}
 After=matrix-synapse.service
 Requires=matrix-synapse.service
 
-{% set matrix_synapse_container_worker_arguments = [] %}
+{% set matrix_synapse_container_worker_arguments = matrix_synapse_worker_systemd_shared.container_worker_arguments_by_type[matrix_synapse_worker_type] | default([]) %}
 
-{% if matrix_synapse_worker_type == "room_worker" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_room_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "sync_worker" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_sync_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "client_reader" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_client_reader_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "federation_reader" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_federation_reader_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "generic_worker" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_generic_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "stream_writer" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_stream_writers_container_arguments %}
-{% elif matrix_synapse_worker_type == "federation_sender" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_federation_sender_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "pusher" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_pusher_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "appservice" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_appservice_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "user_dir" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_user_dir_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "background" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_background_workers_container_arguments %}
-{% elif matrix_synapse_worker_type == "media_repository" %}
-	{% set matrix_synapse_container_worker_arguments = matrix_synapse_workers_media_repository_workers_container_arguments %}
-{% endif %}
 
 [Service]
 Type=simple
-Environment="HOME={{ devture_systemd_docker_base_systemd_unit_home_path }}"
+Environment="HOME={{ matrix_synapse_worker_systemd_shared.systemd_unit_home_path }}"
 
-ExecStartPre=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} stop -t {{ devture_systemd_docker_base_container_stop_grace_time_seconds }} {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
-ExecStartPre=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} rm {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
+ExecStartPre=-{{ matrix_synapse_worker_systemd_shared.host_command_sh }} -c '{{ matrix_synapse_worker_systemd_shared.host_command_docker }} stop -t {{ matrix_synapse_worker_systemd_shared.container_stop_grace_time_seconds }} {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
+ExecStartPre=-{{ matrix_synapse_worker_systemd_shared.host_command_sh }} -c '{{ matrix_synapse_worker_systemd_shared.host_command_docker }} rm {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
 
-ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} create \
+ExecStartPre={{ matrix_synapse_worker_systemd_shared.host_command_docker }} create \
 			--rm \
 			--name={{ matrix_synapse_worker_container_name }} \
 			--log-driver=none \
-			--user={{ matrix_synapse_uid }}:{{ matrix_synapse_gid }} \
+			--user={{ matrix_synapse_worker_systemd_shared.uid }}:{{ matrix_synapse_worker_systemd_shared.gid }} \
 			--cap-drop=ALL \
 			--read-only \
-			--tmpfs=/tmp:rw,noexec,nosuid,size={{ matrix_synapse_tmp_directory_size_mb }}m \
-			--network={{ matrix_synapse_container_network }} \
+			--tmpfs=/tmp:rw,noexec,nosuid,size={{ matrix_synapse_worker_systemd_shared.tmp_directory_size_mb }}m \
+			--network={{ matrix_synapse_worker_systemd_shared.container_network }} \
 			{% if matrix_synapse_worker_details.port != 0 and matrix_synapse_worker_details.webserving %}
 			--health-cmd 'curl -fSs http://localhost:{{ matrix_synapse_worker_details.port }}/health || exit 1' \
 			{% else %}
 			--no-healthcheck \
 			{% endif %}
-			{% if matrix_synapse_workers_enabled and matrix_synapse_workers_container_host_bind_address %}
+			{% if matrix_synapse_worker_systemd_shared.workers_enabled and matrix_synapse_worker_systemd_shared.workers_container_host_bind_address %}
 			{% if matrix_synapse_worker_details.port != 0 %}
-			-p {{ '' if matrix_synapse_workers_container_host_bind_address == '*' else (matrix_synapse_workers_container_host_bind_address + ':') }}{{ matrix_synapse_worker_details.port }}:{{ matrix_synapse_worker_details.port }} \
+			-p {{ '' if matrix_synapse_worker_systemd_shared.workers_container_host_bind_address == '*' else (matrix_synapse_worker_systemd_shared.workers_container_host_bind_address + ':') }}{{ matrix_synapse_worker_details.port }}:{{ matrix_synapse_worker_details.port }} \
 			{% endif %}
 			{% if matrix_synapse_worker_details.metrics_port != 0 %}
-			-p {{ '' if matrix_synapse_workers_container_host_bind_address == '*' else (matrix_synapse_workers_container_host_bind_address + ':') }}{{ matrix_synapse_worker_details.metrics_port }}:{{ matrix_synapse_worker_details.metrics_port }} \
+			-p {{ '' if matrix_synapse_worker_systemd_shared.workers_container_host_bind_address == '*' else (matrix_synapse_worker_systemd_shared.workers_container_host_bind_address + ':') }}{{ matrix_synapse_worker_details.metrics_port }}:{{ matrix_synapse_worker_details.metrics_port }} \
 			{% endif %}
 			{% endif %}
-			--mount type=bind,src={{ matrix_synapse_config_dir_path }},dst=/data,ro \
-			--mount type=bind,src={{ matrix_synapse_storage_path }},dst=/matrix-media-store-parent,bind-propagation=slave \
-			{% for volume in matrix_synapse_container_additional_volumes %}
+			--mount type=bind,src={{ matrix_synapse_worker_systemd_shared.config_dir_path }},dst=/data,ro \
+			--mount type=bind,src={{ matrix_synapse_worker_systemd_shared.storage_path }},dst=/matrix-media-store-parent,bind-propagation=slave \
+			{% for volume in matrix_synapse_worker_systemd_shared.container_additional_volumes %}
 			--mount type={{ volume.type | default('bind' if '/' in volume.src else 'volume') }},src={{ volume.src }},dst={{ volume.dst }}{{ (',' + volume.options) if volume.options else '' }} \
 			{% endfor %}
-			{% if matrix_synapse_redis_path_enabled %}
-			--mount type=bind,src={{ matrix_synapse_redis_path_host }},dst={{ matrix_synapse_redis_path }} \
+			{% if matrix_synapse_worker_systemd_shared.redis_path_enabled %}
+			--mount type=bind,src={{ matrix_synapse_worker_systemd_shared.redis_path_host }},dst={{ matrix_synapse_worker_systemd_shared.redis_path }} \
 			{% endif %}
-			{% if matrix_synapse_database_socket_enabled %}
-			--mount type=bind,src={{ matrix_synapse_database_socket_path_host }},dst={{ matrix_synapse_database_socket_path }} \
+			{% if matrix_synapse_worker_systemd_shared.database_socket_enabled %}
+			--mount type=bind,src={{ matrix_synapse_worker_systemd_shared.database_socket_path_host }},dst={{ matrix_synapse_worker_systemd_shared.database_socket_path }} \
 			{% endif %}
-			--label-file={{ matrix_synapse_base_path }}/{{ matrix_synapse_worker_labels_file_name }} \
-			{% for arg in matrix_synapse_container_arguments %}
+			--label-file={{ matrix_synapse_worker_systemd_shared.base_path }}/{{ matrix_synapse_worker_labels_file_name }} \
+			{% for arg in matrix_synapse_worker_systemd_shared.container_arguments %}
 			{{ arg }} \
 			{% endfor %}
 			{% for arg in matrix_synapse_container_worker_arguments %}
 			{{ arg }} \
 			{% endfor %}
-			{{ matrix_synapse_container_image_final }} \
+			{{ matrix_synapse_worker_systemd_shared.container_image_final }} \
 			run -m synapse.app.{{ matrix_synapse_worker_details.app }} -c /data/homeserver.yaml -c /data/{{ matrix_synapse_worker_config_file_name }}
 
-{% if matrix_synapse_container_network != 'host' %}
-{% for network in matrix_synapse_container_additional_networks %}
-ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} network connect {{ network }} {{ matrix_synapse_worker_container_name }}
+{% if matrix_synapse_worker_systemd_shared.container_network != 'host' %}
+{% for network in matrix_synapse_worker_systemd_shared.container_additional_networks %}
+ExecStartPre={{ matrix_synapse_worker_systemd_shared.host_command_docker }} network connect {{ network }} {{ matrix_synapse_worker_container_name }}
 {% endfor %}
 {% endif %}
 
-ExecStart={{ devture_systemd_docker_base_host_command_docker }} start --attach {{ matrix_synapse_worker_container_name }}
+ExecStart={{ matrix_synapse_worker_systemd_shared.host_command_docker }} start --attach {{ matrix_synapse_worker_container_name }}
 
-ExecStop=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} stop -t {{ devture_systemd_docker_base_container_stop_grace_time_seconds }} {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
-ExecStop=-{{ devture_systemd_docker_base_host_command_sh }} -c '{{ devture_systemd_docker_base_host_command_docker }} rm {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
+ExecStop=-{{ matrix_synapse_worker_systemd_shared.host_command_sh }} -c '{{ matrix_synapse_worker_systemd_shared.host_command_docker }} stop -t {{ matrix_synapse_worker_systemd_shared.container_stop_grace_time_seconds }} {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
+ExecStop=-{{ matrix_synapse_worker_systemd_shared.host_command_sh }} -c '{{ matrix_synapse_worker_systemd_shared.host_command_docker }} rm {{ matrix_synapse_worker_container_name }} 2>/dev/null || true'
 
-ExecReload={{ devture_systemd_docker_base_host_command_docker }} exec {{ matrix_synapse_worker_container_name }} /bin/sh -c 'kill -HUP 1'
+ExecReload={{ matrix_synapse_worker_systemd_shared.host_command_docker }} exec {{ matrix_synapse_worker_container_name }} /bin/sh -c 'kill -HUP 1'
 Restart=always
 RestartSec=30
 SyslogIdentifier={{ matrix_synapse_worker_container_name }}