Introduce new configuration for limiting replica's local replication buffer during dual-channel replication sync

src/config.c

@@ -3243,6 +3243,7 @@ standardConfig static_configs[] = {
     createSizeTConfig("hll-sparse-max-bytes", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, server.hll_sparse_max_bytes, 3000, MEMORY_CONFIG, NULL, NULL),
     createSizeTConfig("tracking-table-max-keys", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, server.tracking_table_max_keys, 1000000, INTEGER_CONFIG, NULL, NULL), /* Default: 1 million keys max. */
     createSizeTConfig("client-query-buffer-limit", NULL, DEBUG_CONFIG | MODIFIABLE_CONFIG, 1024 * 1024, LONG_MAX, server.client_max_querybuf_len, 1024 * 1024 * 1024, MEMORY_CONFIG, NULL, NULL), /* Default: 1GB max query buffer. */
+    createSizeTConfig("replicas-dual-channel-buffer-limit", NULL, DEBUG_CONFIG | MODIFIABLE_CONFIG, 0, LONG_MAX, server.pending_repl_data.limit_bytes, 1024 * 1024 * 1024, MEMORY_CONFIG, NULL, NULL), /* Default: 1GB max query buffer. */
     createSSizeTConfig("maxmemory-clients", NULL, MODIFIABLE_CONFIG, -100, SSIZE_MAX, server.maxmemory_clients, 0, MEMORY_CONFIG | PERCENT_CONFIG, NULL, applyClientMaxMemoryUsage),
 
     /* Other configs */

src/replication.c

@@ -2797,7 +2797,7 @@ void bufferReplData(connection *conn) {
             remaining_bytes = readIntoReplDataBlock(conn, tail, remaining_bytes);
         }
         if (readlen && remaining_bytes == 0) {
-            if (server.pending_repl_data.len > server.client_obuf_limits[CLIENT_TYPE_REPLICA].hard_limit_bytes) {
+            if (server.pending_repl_data.len > server.pending_repl_data.limit_bytes) {
                 serverLog(LL_NOTICE, "Replication buffer limit reached, stopping buffering.");
                 /* Stop accumulating primary commands. */
                 connSetReadHandler(conn, NULL);

src/server.h

@@ -1118,6 +1118,7 @@ typedef struct replDataBuf {
     list *blocks; /* List of replDataBufBlock */
     size_t len;   /* Number of bytes stored in all blocks */
     size_t peak;
+    size_t limit_bytes; /* Configurable buffer limit */
 } replDataBuf;
 
 typedef struct {

tests/integration/dual-channel-replication.tcl

@@ -328,7 +328,7 @@ start_server {tags {"dual-channel-replication external:skip"}} {
                 # We expect that the next full sync will take 100 seconds (10k*10000)ms
                 # It will give us enough time to fill the replica buffer.
                 $replica1 config set dual-channel-replication-enabled yes
-                $replica1 config set client-output-buffer-limit "replica 16383 16383 0"
+                $replica1 config set replicas-dual-channel-buffer-limit "16383"
 
                 $replica1 replicaof $primary_host $primary_port
                 # Wait for replica to establish psync using main channel
@@ -356,7 +356,7 @@ start_server {tags {"dual-channel-replication external:skip"}} {
             }
 
             $replica1 replicaof no one
-            $replica1 config set client-output-buffer-limit "replica 256mb 256mb 0"; # remove repl buffer limitation
+            $replica1 config set replicas-dual-channel-buffer-limit [expr {1024 * 1024 * 1024}]; # remove repl buffer limitation
             $primary config set rdb-key-save-delay 0
 
             wait_for_condition 500 1000 {

valkey.conf

@@ -689,6 +689,13 @@ repl-diskless-load disabled
 # server, which is typically handling more critical operations.
 dual-channel-replication-enabled no
 
+# This configuration option sets the maximum size of the local replication
+# buffer on the replica during dual-channel-replication syncronization.
+# The local replication buffer is used to store data received from the primary
+# during the sync, before it is written to the replica's database.
+#
+# replicas-dual-channel-buffer-limit <bytes>
+
 # Master send PINGs to its replicas in a predefined interval. It's possible to
 # change this interval with the repl_ping_replica_period option. The default
 # value is 10 seconds.