From 27a3a72a50cb24f25e48fad1e6e79aba2cd1bea2 Mon Sep 17 00:00:00 2001
From: 999lakhisidhu <42063995+999lakhisidhu@users.noreply.github.com>
Date: Wed, 15 Feb 2023 16:39:31 +0400
Subject: [PATCH] Support for selecting the Redis logical database. (#15034)

Note that this is only used for key-value store (cached values)
and not for the pub/sub replication used by Synapse.
---
 changelog.d/15034.feature                        | 1 +
 contrib/docker_compose_workers/README.md         | 1 +
 docs/usage/configuration/config_documentation.md | 4 ++++
 synapse/config/redis.py                          | 1 +
 synapse/server.py                                | 1 +
 5 files changed, 8 insertions(+)
 create mode 100644 changelog.d/15034.feature

diff --git a/changelog.d/15034.feature b/changelog.d/15034.feature
new file mode 100644
index 0000000000..34f320da92
--- /dev/null
+++ b/changelog.d/15034.feature
@@ -0,0 +1 @@
+Allow Synapse to use a specific Redis [logical database](https://redis.io/commands/select/) in worker-mode deployments.
diff --git a/contrib/docker_compose_workers/README.md b/contrib/docker_compose_workers/README.md
index bdd3dd32e0..d3cdfe5614 100644
--- a/contrib/docker_compose_workers/README.md
+++ b/contrib/docker_compose_workers/README.md
@@ -68,6 +68,7 @@ redis:
   enabled: true
   host: redis
   port: 6379
+  # dbid:  <redis_logical_db_id>
   # password: <secret_password>  
 ```
 
diff --git a/docs/usage/configuration/config_documentation.md b/docs/usage/configuration/config_documentation.md
index 2883f76a26..75483bfb12 100644
--- a/docs/usage/configuration/config_documentation.md
+++ b/docs/usage/configuration/config_documentation.md
@@ -3927,6 +3927,9 @@ This setting has the following sub-options:
 * `host` and `port`: Optional host and port to use to connect to redis. Defaults to
    localhost and 6379
 * `password`: Optional password if configured on the Redis instance.
+* `dbid`: Optional redis dbid if needs to connect to specific redis logical db.
+
+  _Added in Synapse 1.78.0._
 
 Example configuration:
 ```yaml
@@ -3935,6 +3938,7 @@ redis:
   host: localhost
   port: 6379
   password: <secret_password>
+  dbid: <dbid>
 ```
 ---
 ## Individual worker configuration
diff --git a/synapse/config/redis.py b/synapse/config/redis.py
index b42dd2e93a..e6a75be434 100644
--- a/synapse/config/redis.py
+++ b/synapse/config/redis.py
@@ -33,4 +33,5 @@ class RedisConfig(Config):
 
         self.redis_host = redis_config.get("host", "localhost")
         self.redis_port = redis_config.get("port", 6379)
+        self.redis_dbid = redis_config.get("dbid", None)
         self.redis_password = redis_config.get("password")
diff --git a/synapse/server.py b/synapse/server.py
index efc6b5f895..e5a3475247 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -827,6 +827,7 @@ class HomeServer(metaclass=abc.ABCMeta):
             hs=self,
             host=self.config.redis.redis_host,
             port=self.config.redis.redis_port,
+            dbid=self.config.redis.redis_dbid,
             password=self.config.redis.redis_password,
             reconnect=True,
         )