redirect by per client's capability

src/commands.def

@@ -1083,6 +1083,28 @@ struct COMMAND_ARG CLIENT_CACHING_Args[] = {
 {MAKE_ARG("mode",ARG_TYPE_ONEOF,-1,NULL,NULL,NULL,CMD_ARG_NONE,2,NULL),.subargs=CLIENT_CACHING_mode_Subargs},
 };
 
+/********** CLIENT CAPA ********************/
+
+#ifndef SKIP_CMD_HISTORY_TABLE
+/* CLIENT CAPA history */
+#define CLIENT_CAPA_History NULL
+#endif
+
+#ifndef SKIP_CMD_TIPS_TABLE
+/* CLIENT CAPA tips */
+#define CLIENT_CAPA_Tips NULL
+#endif
+
+#ifndef SKIP_CMD_KEY_SPECS_TABLE
+/* CLIENT CAPA key specs */
+#define CLIENT_CAPA_Keyspecs NULL
+#endif
+
+/* CLIENT CAPA argument table */
+struct COMMAND_ARG CLIENT_CAPA_Args[] = {
+{MAKE_ARG("capability",ARG_TYPE_STRING,-1,NULL,NULL,NULL,CMD_ARG_NONE,0,NULL)},
+};
+
 /********** CLIENT GETNAME ********************/
 
 #ifndef SKIP_CMD_HISTORY_TABLE
@@ -1543,6 +1565,7 @@ struct COMMAND_ARG CLIENT_UNBLOCK_Args[] = {
 /* CLIENT command table */
 struct COMMAND_STRUCT CLIENT_Subcommands[] = {
 {MAKE_CMD("caching","Instructs the server whether to track the keys in the next request.","O(1)","6.0.0",CMD_DOC_NONE,NULL,NULL,"connection",COMMAND_GROUP_CONNECTION,CLIENT_CACHING_History,0,CLIENT_CACHING_Tips,0,clientCommand,3,CMD_NOSCRIPT|CMD_LOADING|CMD_STALE|CMD_SENTINEL,ACL_CATEGORY_CONNECTION,CLIENT_CACHING_Keyspecs,0,NULL,1),.args=CLIENT_CACHING_Args},
+{MAKE_CMD("capa","A client claims its capability.","O(1)","8.0.0",CMD_DOC_NONE,NULL,NULL,"connection",COMMAND_GROUP_CONNECTION,CLIENT_CAPA_History,0,CLIENT_CAPA_Tips,0,clientCommand,3,CMD_NOSCRIPT|CMD_LOADING|CMD_STALE,ACL_CATEGORY_CONNECTION,CLIENT_CAPA_Keyspecs,0,NULL,1),.args=CLIENT_CAPA_Args},
 {MAKE_CMD("getname","Returns the name of the connection.","O(1)","2.6.9",CMD_DOC_NONE,NULL,NULL,"connection",COMMAND_GROUP_CONNECTION,CLIENT_GETNAME_History,0,CLIENT_GETNAME_Tips,0,clientCommand,2,CMD_NOSCRIPT|CMD_LOADING|CMD_STALE|CMD_SENTINEL,ACL_CATEGORY_CONNECTION,CLIENT_GETNAME_Keyspecs,0,NULL,0)},
 {MAKE_CMD("getredir","Returns the client ID to which the connection's tracking notifications are redirected.","O(1)","6.0.0",CMD_DOC_NONE,NULL,NULL,"connection",COMMAND_GROUP_CONNECTION,CLIENT_GETREDIR_History,0,CLIENT_GETREDIR_Tips,0,clientCommand,2,CMD_NOSCRIPT|CMD_LOADING|CMD_STALE|CMD_SENTINEL,ACL_CATEGORY_CONNECTION,CLIENT_GETREDIR_Keyspecs,0,NULL,0)},
 {MAKE_CMD("help","Returns helpful text about the different subcommands.","O(1)","5.0.0",CMD_DOC_NONE,NULL,NULL,"connection",COMMAND_GROUP_CONNECTION,CLIENT_HELP_History,0,CLIENT_HELP_Tips,0,clientCommand,2,CMD_LOADING|CMD_STALE|CMD_SENTINEL,ACL_CATEGORY_CONNECTION,CLIENT_HELP_Keyspecs,0,NULL,0)},

src/config.c

@@ -3100,7 +3100,6 @@ standardConfig static_configs[] = {
     createBoolConfig("replica-serve-stale-data", "slave-serve-stale-data", MODIFIABLE_CONFIG, server.repl_serve_stale_data, 1, NULL, NULL),
     createBoolConfig("replica-read-only", "slave-read-only", DEBUG_CONFIG | MODIFIABLE_CONFIG, server.repl_slave_ro, 1, NULL, NULL),
     createBoolConfig("replica-ignore-maxmemory", "slave-ignore-maxmemory", MODIFIABLE_CONFIG, server.repl_slave_ignore_maxmemory, 1, NULL, NULL),
-    createBoolConfig("replica-enable-redirect", NULL, MODIFIABLE_CONFIG, server.repl_replica_enable_redirect, 0, NULL, NULL),
     createBoolConfig("jemalloc-bg-thread", NULL, MODIFIABLE_CONFIG, server.jemalloc_bg_thread, 1, NULL, updateJemallocBgThread),
     createBoolConfig("activedefrag", NULL, DEBUG_CONFIG | MODIFIABLE_CONFIG, server.active_defrag_enabled, 0, isValidActiveDefrag, NULL),
     createBoolConfig("syslog-enabled", NULL, IMMUTABLE_CONFIG, server.syslog_enabled, 0, NULL, NULL),

src/networking.c

@@ -166,6 +166,7 @@ client *createClient(connection *conn) {
     c->bulklen = -1;
     c->sentlen = 0;
     c->flags = 0;
+    c->capa = 0;
     c->slot = -1;
     c->ctime = c->lastinteraction = server.unixtime;
     c->duration = 0;
@@ -3583,6 +3584,13 @@ NULL
         } else {
             addReplyErrorObject(c,shared.syntaxerr);
         }
+    } else if (!strcasecmp(c->argv[1]->ptr,"capa") && c->argc == 3) {
+        if (!strcasecmp(c->argv[2]->ptr,"redirect")) {
+            c->capa |= CLIENT_CAPA_REDIRECT;
+            addReply(c,shared.ok);
+        } else {
+            addReplyErrorObject(c,shared.syntaxerr);
+        }
     } else {
         addReplySubcommandSyntaxError(c);
     }

src/server.c

@@ -4040,7 +4040,7 @@ int processCommand(client *c) {
     }
 
     if (!server.cluster_enabled &&
-        server.repl_replica_enable_redirect &&
+        c->capa & CLIENT_CAPA_REDIRECT &&
         server.masterhost &&
         !mustObeyClient(c) &&
         (is_write_command ||

src/server.h

@@ -404,6 +404,9 @@ extern int configOOMScoreAdjValuesDefaults[CONFIG_OOM_COUNT];
 #define CLIENT_REPROCESSING_COMMAND (1ULL<<50) /* The client is re-processing the command. */
 #define CLIENT_PREREPL_DONE (1ULL<<51) /* Indicate that pre-replication has been done on the client */
 
+/* Client capabilities */
+#define CLIENT_CAPA_REDIRECT (1<<0)    /* Indicate that the client can handle redirection */
+
 /* Client block type (btype field in client structure)
  * if CLIENT_BLOCKED flag is set. */
 typedef enum blocking_type {
@@ -1164,6 +1167,7 @@ typedef struct {
 typedef struct client {
     uint64_t id;            /* Client incremental unique ID. */
     uint64_t flags;         /* Client flags: CLIENT_* macros. */
+    uint64_t capa;          /* Client capabilities: CLIENT_CAPA* macros. */
     connection *conn;
     int resp;               /* RESP protocol version. Can be 2 or 3. */
     serverDb *db;            /* Pointer to currently SELECTed DB. */
@@ -1917,7 +1921,6 @@ struct valkeyServer {
     int repl_serve_stale_data; /* Serve stale data when link is down? */
     int repl_slave_ro;          /* Slave is read only? */
     int repl_slave_ignore_maxmemory;    /* If true slaves do not evict. */
-    int repl_replica_enable_redirect;   /* If true replica would redirect read&write commands to master. */
     time_t repl_down_since; /* Unix time at which link with master went down */
     int repl_disable_tcp_nodelay;   /* Disable TCP_NODELAY after SYNC? */
     int slave_priority;             /* Reported in INFO and used by Sentinel. */

tests/integration/replica-redirect.tcl

@@ -18,8 +18,8 @@ start_server {tags {needs:repl external:skip}} {
             assert_error {READONLY*} {r set foo bar}
         }
 
-        test {replica redirect read and write command when enable replica-enable-redirect} {
-            r config set replica-enable-redirect yes
+        test {replica redirect read and write command after CLIENT CAPA REDIRECT} {
+            r client capa redirect
             assert_error "REDIRECT $master_host:$master_port" {r set foo bar}
             assert_error "REDIRECT $master_host:$master_port" {r get foo}
         }

valkey.conf

@@ -826,18 +826,6 @@ replica-priority 100
 # replica-announce-ip 5.5.5.5
 # replica-announce-port 1234
 
-# You can configure a replica instance to redirect data access commands
-# to its master or not, excluding commands such as:
-# INFO, AUTH, ROLE, SUBSCRIBE, UNSUBSCRIBE, PUBLISH.
-#
-# When enabled, a replica instance will reply "-MOVED -1 master-ip:port"
-# for data access commands. Normally these are write or read commands, if
-# you want to run read commands while replica-enable-redirect is enabled,
-# use the READONLY command first.
-#
-# This config only takes effect in standalone mode.
-replica-enable-redirect no
-
 ############################### KEYS TRACKING #################################
 
 # The client side caching of values is assisted via server-side support.