From 0c40a03efce77c7afb726c094e18dac5404176c8 Mon Sep 17 00:00:00 2001
From: Aine <aine@etke.cc>
Date: Sun, 8 Mar 2026 07:24:33 +0000
Subject: [PATCH] allow synapse to use redis unix socket instead of tcp

---
 group_vars/matrix_servers                                | 4 ++++
 roles/custom/matrix-synapse/defaults/main.yml            | 9 +++++++--
 .../matrix-synapse/templates/synapse/homeserver.yaml.j2  | 5 +++++
 .../synapse/systemd/matrix-synapse-worker.service.j2     | 3 +++
 .../templates/synapse/systemd/matrix-synapse.service.j2  | 3 +++
 5 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/group_vars/matrix_servers b/group_vars/matrix_servers
index e3dda9acd..4294aca39 100755
--- a/group_vars/matrix_servers
+++ b/group_vars/matrix_servers
@@ -4844,6 +4844,10 @@ matrix_synapse_redis_enabled: "{{ valkey_enabled }}"
 matrix_synapse_redis_host: "{{ valkey_identifier if valkey_enabled else '' }}"
 matrix_synapse_redis_password: "{{ valkey_connection_password if valkey_enabled else '' }}"
 
+matrix_synapse_redis_path_enabled: false # temporarily, then switch to true by default once properly tested
+matrix_synapse_redis_path: "{{ '/tmp/redis.sock' if valkey_enabled else '' }}" # default value for Synapse
+matrix_synapse_redis_path_host: "{{ valkey_run_path+'/valkey.sock' if valkey_enabled else '' }}" # path on the host
+
 matrix_synapse_container_extra_arguments_auto: "{{ matrix_homeserver_container_extra_arguments_auto }}"
 matrix_synapse_app_service_config_files_auto: "{{ matrix_homeserver_app_service_config_files_auto }}"
 
diff --git a/roles/custom/matrix-synapse/defaults/main.yml b/roles/custom/matrix-synapse/defaults/main.yml
index bd46a2e2b..336d1824a 100644
--- a/roles/custom/matrix-synapse/defaults/main.yml
+++ b/roles/custom/matrix-synapse/defaults/main.yml
@@ -1241,11 +1241,16 @@ matrix_synapse_instance_map: |
 
 # Redis information
 matrix_synapse_redis_enabled: false
-matrix_synapse_redis_host: ""
-matrix_synapse_redis_port: 6379
 matrix_synapse_redis_password: ""
 matrix_synapse_redis_dbid: 0
 matrix_synapse_redis_use_tls: false
+# Connection option 1: TCP
+matrix_synapse_redis_host: ""
+matrix_synapse_redis_port: 6379
+# Connection option 2: Unix socket (takes precedence over TCP if `matrix_synapse_redis_path` is set)
+matrix_synapse_redis_path_enabled: false
+matrix_synapse_redis_path: "" # the path to the redis socket inside the container, e.g. "/var/run/redis.sock"
+matrix_synapse_redis_path_host: "" # the path to the redis socket on the host, e.g. "/matrix/valkey/run/valkey.sock"
 
 # Controls whether Synapse starts a replication listener necessary for workers.
 #
diff --git a/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2 b/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
index 61c306ef3..84ed4e5fa 100644
--- a/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
+++ b/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
@@ -2932,6 +2932,11 @@ redis:
   host: {{ matrix_synapse_redis_host | to_json }}
   port: {{ matrix_synapse_redis_port | to_json }}
 
+  # The full path to a local Unix socket file. If this is used, host and port are ignored.
+  {% if matrix_synapse_redis_path_enabled %}
+  path: {{ matrix_synapse_redis_path | to_json }}
+  {% endif %}
+
   # Optional database ID to connect to. Defaults to 0.
   dbid: {{ matrix_synapse_redis_dbid | to_json }}
 
diff --git a/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse-worker.service.j2 b/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse-worker.service.j2
index 54558dc39..086fe287b 100644
--- a/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse-worker.service.j2
+++ b/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse-worker.service.j2
@@ -67,6 +67,9 @@ ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} create \
 			{% for volume in matrix_synapse_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 }} \
+			{% endif %}
 			--label-file={{ matrix_synapse_base_path }}/{{ matrix_synapse_worker_labels_file_name }} \
 			{% for arg in matrix_synapse_container_arguments %}
 			{{ arg }} \
diff --git a/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse.service.j2 b/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse.service.j2
index a3bcc0bc0..ecf09a64b 100644
--- a/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse.service.j2
+++ b/roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse.service.j2
@@ -51,6 +51,9 @@ ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} create \
 			{% 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 \
+			{% if matrix_synapse_redis_path_enabled %}
+			--mount type=bind,src={{ matrix_synapse_redis_path_host }},dst={{ matrix_synapse_redis_path }} \
+			{% endif %}
 			--label-file={{ matrix_synapse_base_path }}/labels \
 			{% for volume in matrix_synapse_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 '' }} \