Run Synapse workers in their own containers

This switches the `docker exec` method of spawning
Synapse workers inside the `matrix-synapse` container with
dedicated containers for each worker.

We also have dedicated systemd services for each worker,
so this are now:
- more consistent with everything else (we don't use systemd
instantiated services anywhere)
- we don't need the "parse systemd instance name into worker name +
port" part
- we don't need to keep track of PIDs manually
- we don't need jq (less depenendencies)
- workers dying would be restarted by systemd correctly, like any other
service
- `docker ps` shows each worker separately and we can observe resource
usage

roles/matrix-synapse/tasks/workers/setup_uninstall.yml

@@ -7,46 +7,30 @@
   service:
     name: "{{ item.key }}"
     state: stopped
-  with_dict: "{{ ansible_facts.services|default({})|dict2items|selectattr('key', 'match', 'matrix-synapse-worker@.+\\.service')|list|items2dict }}"
-
-- name: Ensure worker service symlinks are cleaned
-  file:
-    path: "{{ item.root + '/' + item.path }}"
-    state: absent
-  when:
-    - item.state == 'link'
-    - item.path is match('matrix-synapse-worker@.*\\.service')
-  with_filetree:
-    - "{{ matrix_systemd_path }}/matrix-synapse.service.wants"
-
-- name: Ensure synapse worker base service file gets removed
-  file:
-    path: "{{ matrix_systemd_path }}/matrix-synapse-worker@.service"
-    state: absent
-  register: matrix_synapse_worker_systemd_service_result
+  with_dict: "{{ ansible_facts.services|default({})|dict2items|selectattr('key', 'match', 'matrix-synapse-worker-.+\\.service')|list|items2dict }}"
 
 - name: Find worker configs to be cleaned
   find:
     path: "{{ matrix_synapse_config_dir_path }}"
     patterns: "worker.*.yaml"
     use_regex: true
-  register: worker_config_files
+  register: matrix_synapse_workers_current_config_files
 
-- name: Ensure worker configs are cleaned
+- name: Ensure previous worker configs are cleaned
   file:
     path: "{{ item.path }}"
     state: absent
-  with_items: "{{ worker_config_files.files }}"
+  with_items: "{{ matrix_synapse_workers_current_config_files.files }}"
 
-- name: Remove workers from synapse.wants list
-  set_fact:
-    matrix_synapse_systemd_wanted_services_list: "{{ matrix_synapse_systemd_wanted_services_list | reject('search', '^matrix-synapse-worker@') | list }}"
+- name: Find worker systemd services to be cleaned
+  find:
+    path: "{{ matrix_systemd_path }}"
+    patterns: "matrix-synapse-worker.*.service"
+    use_regex: true
+  register: matrix_synapse_workers_current_systemd_services
 
-- name: Ensure systemd noticed removal of worker service units
-  service:
-    daemon_reload: yes
-
-- name: Ensure matrix-synapse-worker-write-pid script is removed
+- name: Ensure previous worker systemd services are cleaned
   file:
-    path: "{{ matrix_local_bin_path }}/matrix-synapse-worker-write-pid"
+    path: "{{ item.path }}"
     state: absent
+  with_items: "{{ matrix_synapse_workers_current_systemd_services.files }}"