synapse workers: define and expose METRICS port for each worker

As seen on TV:
https://github.com/matrix-org/synapse/blob/master/docs/metrics-howto.md#monitoring-workers

roles/matrix-synapse/defaults/main.yml

@@ -281,19 +281,19 @@ matrix_synapse_workers_enabled: false
 # - no endpoints / doesn't need port mapping if port ends on 0
 # - single-instance-only if 2nd last digit of port number is 0
 matrix_synapse_workers_enabled_list:
-  - { type: generic_worker, port: 18111 }
-  - { type: generic_worker, port: 18112 }
-  - { type: generic_worker, port: 18113 }
-  - { type: generic_worker, port: 18114 }
-  - { type: generic_worker, port: 18115 }
-  - { type: generic_worker, port: 18116 }
-  - { type: pusher, port: 00 }
-  - { type: appservice, port: 00 }
-  - { type: federation_sender, port: 0 }
-  - { type: media_repository, port: 18221 }
+  - { type: generic_worker, port: 18111, metrics_port: 19111 }
+  - { type: generic_worker, port: 18112, metrics_port: 19112 }
+  - { type: generic_worker, port: 18113, metrics_port: 19113 }
+  - { type: generic_worker, port: 18114, metrics_port: 19114 }
+  - { type: generic_worker, port: 18115, metrics_port: 19115 }
+  - { type: generic_worker, port: 18116, metrics_port: 19116 }
+  - { type: pusher, port: 00, metrics_port: 19200 }
+  - { type: appservice, port: 00, metrics_port: 19300 }
+  - { type: federation_sender, port: 0, metrics_port: 19400 }
+  - { type: media_repository, port: 18551, metrics_port: 19551 }
 # disable until https://github.com/matrix-org/synapse/issues/8787 resolved
-# - { type: user_dir, port: 18331 }
-  - { type: frontend_proxy, port: 18441 }
+# - { type: user_dir, port: 18661, metrics_port: 19661 }
+  - { type: frontend_proxy, port: 18771, metrics_port: 19771 }
 
 # Redis information
 matrix_synapse_redis_enabled: false

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

@@ -43,14 +43,18 @@ ExecStart={{ matrix_host_command_docker }} run --rm --name matrix-synapse \
 			{% if matrix_synapse_manhole_enabled and matrix_synapse_container_manhole_api_host_bind_port %}
 			-p {{ matrix_synapse_container_manhole_api_host_bind_port }}:9000 \
 			{% endif %}
-			{% if matrix_synapse_workers_enabled and not matrix_nginx_proxy_enabled|default(False) %}
-			{# Expose worker (by default 18xxx range) ports on host if not using internal nginx proxy #}
 			{% for worker in matrix_synapse_workers_enabled_list %}
+			{% if matrix_synapse_workers_enabled and not matrix_nginx_proxy_enabled|default(False) %}
+			{# Expose worker ports (by default 18xxx range) on host if not using internal nginx proxy #}
 			{% if worker.port != 0 %}
 			-p {{ worker.port }}:{{ worker.port }} \
 			{% endif %}
-			{% endfor %}
 			{% endif %}
+			{# Expose worker metrics ports on host if defined #}
+			{% if worker.metrics_port != 0 %}
+			-p {{ worker.metrics_port }}:{{ worker.metrics_port }} \
+			{% endif %}
+			{% endfor %}
 			--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 %}

roles/matrix-synapse/templates/synapse/worker.yaml.j2

@@ -21,6 +21,10 @@ worker_listeners:
 {% endif %}
 {% endif %}
 
+  - type: metrics
+    bind_address: ''
+    port: {{ item.metrics_port }}
+
 {% if item.type == 'frontend_proxy' %}
 worker_main_http_uri: http://127.0.0.1:8008
 {% endif %}