Merge pull request #180135 from kevincox/redis-save

nixos.redis: Fix disabling of RDB persistence.

nixos/doc/manual/from_md/release-notes/rl-2211.section.xml

@@ -285,6 +285,13 @@
           <literal>hardware.saleae-logic.package</literal>.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          The Redis module now disables RDB persistence when
+          <literal>services.redis.servers.&lt;name&gt;.save = []</literal>
+          instead of using the Redis default.
+        </para>
+      </listitem>
       <listitem>
         <para>
           Matrix Synapse now requires entries in the

nixos/doc/manual/release-notes/rl-2211.section.md

@@ -110,6 +110,8 @@ Use `configure.packages` instead.
 
 - A new module was added for the Saleae Logic device family, providing the options `hardware.saleae-logic.enable` and `hardware.saleae-logic.package`.
 
+- The Redis module now disables RDB persistence when `services.redis.servers.<name>.save = []` instead of using the Redis default.
+
 - Matrix Synapse now requires entries in the `state_group_edges` table to be unique, in order to prevent accidentally introducing duplicate information (for example, because a database backup was restored multiple times). If your Synapse database already has duplicate rows in this table, this could fail with an error and require manual remediation.
 
 - memtest86+ was updated from 5.00-coreboot-002 to 6.00-beta2. It is now the upstream version from https://www.memtest.org/, as coreboot's fork is no longer available.

nixos/modules/services/databases/redis.nix

@@ -166,7 +166,11 @@ in {
             save = mkOption {
               type = with types; listOf (listOf int);
               default = [ [900 1] [300 10] [60 10000] ];
-              description = "The schedule in which data is persisted to disk, represented as a list of lists where the first element represent the amount of seconds and the second the number of changes.";
+              description = mdDoc ''
+                The schedule in which data is persisted to disk, represented as a list of lists where the first element represent the amount of seconds and the second the number of changes.
+
+                If set to the empty list (`[]`) then RDB persistence will be disabled (useful if you are using AOF or don't want any persistence).
+              '';
             };
 
             slaveOf = mkOption {
@@ -268,7 +272,11 @@ in {
               syslog-enabled = config.syslog;
               databases = config.databases;
               maxclients = config.maxclients;
-              save = map (d: "${toString (builtins.elemAt d 0)} ${toString (builtins.elemAt d 1)}") config.save;
+              save = if config.save == []
+                then ''""'' # Disable saving with `save = ""`
+                else map
+                  (d: "${toString (builtins.elemAt d 0)} ${toString (builtins.elemAt d 1)}")
+                  config.save;
               dbfilename = "dump.rdb";
               dir = "/var/lib/${redisName name}";
               appendOnly = config.appendOnly;