nixos/httpd: add logging related options (#332935)

nixos/modules/services/web-servers/apache-httpd/default.nix

@@ -110,25 +110,20 @@ let
   }
   ++ cfg.extraModules;
 
-  loggingConf = (
-    if cfg.logFormat != "none" then
-      ''
-        ErrorLog ${cfg.logDir}/error.log
+  loggingConf = ''
+    ErrorLog ${if cfg.logFormat != "none" then "${cfg.logDir}/error.log" else "/dev/null"}
+    ${optionalString (cfg.logLevel != null) "LogLevel ${cfg.logLevel}"}
 
-        LogLevel notice
+    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
+    LogFormat "%h %l %u %t \"%r\" %>s %b" common
+    LogFormat "%{Referer}i -> %U" referer
+    LogFormat "%{User-agent}i" agent
+    ${optionalString (
+      cfg.logFormat == "custom"
+    ) "LogFormat ${lib.strings.escapeNixString cfg.customLogFormat} custom"}
 
-        LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
-        LogFormat "%h %l %u %t \"%r\" %>s %b" common
-        LogFormat "%{Referer}i -> %U" referer
-        LogFormat "%{User-agent}i" agent
-
-        CustomLog ${cfg.logDir}/access.log ${cfg.logFormat}
-      ''
-    else
-      ''
-        ErrorLog /dev/null
-      ''
-  );
+    CustomLog ${cfg.logDir}/access.log ${cfg.logFormat}
+  '';
 
   browserHacks = ''
     <IfModule mod_setenvif.c>
@@ -582,12 +577,67 @@ in
       };
 
       logFormat = mkOption {
-        type = types.str;
+        type = types.enum [
+          "combined"
+          "common"
+          "referer"
+          "agent"
+          "custom"
+          "none"
+        ];
         default = "common";
-        example = "combined";
+        example = "custom";
         description = ''
-          Log format for log files. Possible values are: combined, common, referer, agent, none.
-          See <https://httpd.apache.org/docs/2.4/logs.html> for more details.
+          Selects the access log format written to log files.
+
+          The values `combined`, `common`, `referer`, and `agent` correspond to predefined Apache HTTPD log formats.
+          Setting the value to `custom` enables the use of a user-defined format string specified via `customLogFormat`.
+          The value `none` disables access logging entirely.
+
+          Further details on Apache log formats are available at <https://httpd.apache.org/docs/2.4/logs.html>.
+        '';
+      };
+
+      customLogFormat = mkOption {
+        type = types.str;
+        default = null;
+        example = ''%{X-Forwarded-For}i %l %u %t \"%r\" %>s %b'';
+        description = ''
+          Defines a custom Apache HTTPD access log format string.
+
+          This option is only consulted when `logFormat` is set to `custom`.
+          The value must be a valid Apache `LogFormat` specification and will be registered under the symbolic name `custom`.
+
+          See <https://httpd.apache.org/docs/2.4/logs.html#formats> for the formal definition of log format directives.
+        '';
+      };
+
+      logLevel = mkOption {
+        type =
+          with types;
+          nullOr (enum [
+            "emerg"
+            "alert"
+            "crit"
+            "error"
+            "warn"
+            "notice"
+            "info"
+            "debug"
+            "trace1"
+            "trace2"
+            "trace3"
+            "trace4"
+            "trace5"
+            "trace6"
+            "trace7"
+            "trace8"
+          ]);
+        default = "notice";
+        example = "crit";
+        description = ''
+          Controls the verbosity of the ErrorLog.
+          See <https://httpd.apache.org/docs/2.4/mod/core.html#loglevel> for more details.
         '';
       };