Configurable cluster blacklist TTL

src/cluster_legacy.c

@@ -1773,14 +1773,14 @@ void clusterHandleConfigEpochCollision(clusterNode *sender) {
  *
  * The nodes blacklist is just a way to ensure that a given node with a given
  * Node ID is not re-added before some time elapsed (this time is specified
- * in seconds in CLUSTER_BLACKLIST_TTL).
+ * in seconds by the configurable cluster-blacklist-ttl).
  *
  * This is useful when we want to remove a node from the cluster completely:
  * when CLUSTER FORGET is called, it also puts the node into the blacklist so
  * that even if we receive gossip messages from other nodes that still remember
  * about the node we want to remove, we don't re-add it before some time.
  *
- * Currently the CLUSTER_BLACKLIST_TTL is set to 1 minute, this means
+ * The CLUSTER_DEFAULT_BLACKLIST_TTL is set to 1 minute which means
  * that valkey-cli has 60 seconds to send CLUSTER FORGET messages to nodes
  * in the cluster without dealing with the problem of other nodes re-adding
  * back the node to nodes we already sent the FORGET command to.
@@ -1790,9 +1790,6 @@ void clusterHandleConfigEpochCollision(clusterNode *sender) {
  * value.
  * -------------------------------------------------------------------------- */
 
-#define CLUSTER_BLACKLIST_TTL 60 /* 1 minute. */
-
-
 /* Before of the addNode() or Exists() operations we always remove expired
  * entries from the black list. This is an O(N) operation but it is not a
  * problem since add / exists operations are called very infrequently and
@@ -1824,7 +1821,7 @@ void clusterBlacklistAddNode(clusterNode *node) {
         id = sdsdup(id);
     }
     de = dictFind(server.cluster->nodes_black_list, id);
-    dictSetUnsignedIntegerVal(de, time(NULL) + CLUSTER_BLACKLIST_TTL);
+    dictSetUnsignedIntegerVal(de, time(NULL) + server.cluster_blacklist_ttl);
     sdsfree(id);
 }
 

src/cluster_legacy.h

@@ -3,6 +3,8 @@
 
 #define CLUSTER_PORT_INCR 10000 /* Cluster port = baseport + PORT_INCR */
 
+#define CLUSTER_DEFAULT_BLACKLIST_TTL 60 /* 1 minute. */
+
 /* The following defines are amount of time, sometimes expressed as
  * multiplicators of the node timeout value (when ending with MULT). */
 #define CLUSTER_FAIL_REPORT_VALIDITY_MULT 2  /* Fail report validity. */

src/config.c

@@ -30,6 +30,7 @@
 
 #include "server.h"
 #include "cluster.h"
+#include "cluster_legacy.h"
 #include "connection.h"
 #include "bio.h"
 
@@ -3173,6 +3174,7 @@ standardConfig static_configs[] = {
     createULongConfig("active-defrag-max-scan-fields", NULL, MODIFIABLE_CONFIG, 1, LONG_MAX, server.active_defrag_max_scan_fields, 1000, INTEGER_CONFIG, NULL, NULL), /* Default: keys with more than 1000 fields will be processed separately */
     createULongConfig("slowlog-max-len", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, server.slowlog_max_len, 128, INTEGER_CONFIG, NULL, NULL),
     createULongConfig("acllog-max-len", NULL, MODIFIABLE_CONFIG, 0, LONG_MAX, server.acllog_max_len, 128, INTEGER_CONFIG, NULL, NULL),
+    createULongConfig("cluster-blacklist-ttl", NULL, MODIFIABLE_CONFIG, 0, ULONG_MAX, server.cluster_blacklist_ttl, CLUSTER_DEFAULT_BLACKLIST_TTL, INTEGER_CONFIG, NULL, NULL),
 
     /* Long Long configs */
     createLongLongConfig("busy-reply-threshold", "lua-time-limit", MODIFIABLE_CONFIG, 0, LONG_MAX, server.busy_reply_threshold, 5000, INTEGER_CONFIG, NULL, NULL), /* milliseconds */

src/server.h

@@ -2073,6 +2073,8 @@ struct valkeyServer {
     unsigned long long cluster_link_msg_queue_limit_bytes; /* Memory usage limit on individual link msg queue */
     int cluster_drop_packet_filter;                        /* Debug config that allows tactically
                                                             * dropping packets of a specific type */
+    unsigned long cluster_blacklist_ttl;                   /* Duration in seconds that a node is denied re-entry into 
+                                                            * the cluster after it is forgotten with CLUSTER FORGET. */
     /* Debug config that goes along with cluster_drop_packet_filter. When set, the link is closed on packet drop. */
     uint32_t debug_cluster_close_link_on_packet_drop : 1;
     sds cached_cluster_slot_info[CACHE_CONN_TYPE_MAX][4]; /* Align to RESP3 */

valkey.conf

@@ -1771,6 +1771,14 @@ aof-timestamp-enabled no
 #
 # cluster-preferred-endpoint-type ip
 
+# The cluster blacklist is useful when removing a node from the cluster completely. 
+# When CLUSTER FORGET is called for a node, that node is put into the blacklist for
+# some time so that when gossip messages are received from other nodes that still
+# remember it, it is not re-added. This gives time for CLUSTER FORGET to be sent to
+# every node in the cluster. The blacklist TTL is 60 seconds by default.
+#
+# cluster-blacklist-ttl
+
 # In order to setup your cluster make sure to read the documentation
 # available at https://valkey.io web site.