Added support for remapping the cluster's keyspace on a failover

barshaul · michael-grunder · commit b1a52688e16d · 2021-11-09T13:26:08.000-08:00
diff --git a/cluster_library.c b/cluster_library.c
@@ -683,7 +683,7 @@ static int cluster_map_slots(redisCluster *c, clusterReply *r) {
     clusterReply *r2, *r3;
     unsigned short port;
     char *host, key[1024];
-
+    zend_hash_clean(c->nodes);
     for (i = 0; i < r->elements; i++) {
         // Inner response
         r2 = r->element[i];
@@ -1396,7 +1396,7 @@ static void cluster_update_slot(redisCluster *c) {
     /* Do we already have the new slot mapped */
     if (c->master[c->redir_slot]) {
         /* No need to do anything if it's the same node */
-        if (!CLUSTER_REDIR_CMP(c)) {
+        if (!CLUSTER_REDIR_CMP(c, SLOT_SOCK(c,c->redir_slot))) {
             return;
         }
 
@@ -1407,6 +1407,22 @@ static void cluster_update_slot(redisCluster *c) {
             /* Just point to this slot */
             c->master[c->redir_slot] = node;
         } else {
+            /* If the redirected node is a replica of the previous slot owner, a failover has taken place.
+            We must then remap the cluster's keyspace in order to update the cluster's topology. */
+            redisClusterNode *prev_master = SLOT(c,c->redir_slot);
+            redisClusterNode *slave;
+            ZEND_HASH_FOREACH_PTR(prev_master->slaves, slave) {
+                if (slave == NULL) {
+                    continue;
+                }
+                if (!CLUSTER_REDIR_CMP(c, slave->sock)) {
+                    // Detected a failover, the redirected node was a replica 
+                    // Remap the cluster's keyspace
+                    cluster_map_keyspace(c);
+                    return;
+                }
+            } ZEND_HASH_FOREACH_END();
+
             /* Create our node */
             node = cluster_node_create(c, c->redir_host, c->redir_host_len,
                 c->redir_port, c->redir_slot, 0);
diff --git a/cluster_library.h b/cluster_library.h
@@ -45,11 +45,11 @@
 #define CMD_SOCK(c) (c->cmd_sock)
 #define CMD_STREAM(c) (c->cmd_sock->stream)
 
-/* Compare redirection slot information with what we have */
-#define CLUSTER_REDIR_CMP(c) \
-    (SLOT_SOCK(c,c->redir_slot)->port != c->redir_port || \
-    ZSTR_LEN(SLOT_SOCK(c,c->redir_slot)->host) != c->redir_host_len || \
-    memcmp(ZSTR_VAL(SLOT_SOCK(c,c->redir_slot)->host),c->redir_host,c->redir_host_len))
+/* Compare redirection slot information with the passed node */
+#define CLUSTER_REDIR_CMP(c, sock) \
+    (sock->port != c->redir_port || \
+    ZSTR_LEN(sock->host) != c->redir_host_len || \
+    memcmp(ZSTR_VAL(sock->host),c->redir_host,c->redir_host_len))
 
 /* Clear out our "last error" */
 #define CLUSTER_CLEAR_ERROR(c) do { \
