Print an empty primary log when primary lost its last slot (valkey-io#1064)

The one in CLUSTER SETSLOT help us keep track of state better,
of course it also can make the test case happy.

The one in gossip process fixes a problem that a replica can
print a log saying it is an empty primary.

Signed-off-by: Binbin <[email protected]>
Co-authored-by: Ping Xie <[email protected]>
Signed-off-by: naglera <[email protected]>

Author: 2 people

src/cluster_legacy.c

@@ -2670,7 +2670,7 @@ void clusterUpdateSlotsConfigWith(clusterNode *sender, uint64_t senderConfigEpoc
              * If the sender and myself are in the same shard, try psync. */
             clusterSetPrimary(sender, !are_in_same_shard, !are_in_same_shard);
             clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_UPDATE_STATE | CLUSTER_TODO_FSYNC_CONFIG);
-        } else if ((sender_slots >= migrated_our_slots) && !are_in_same_shard) {
+        } else if (nodeIsPrimary(myself) && (sender_slots >= migrated_our_slots) && !are_in_same_shard) {
             /* When all our slots are lost to the sender and the sender belongs to
              * a different shard, this is likely due to a client triggered slot
              * migration. Don't reconfigure this node to migrate to the new shard
@@ -6422,11 +6422,12 @@ void clusterCommandSetSlot(client *c) {
         int slot_was_mine = server.cluster->slots[slot] == my_primary;
         clusterDelSlot(slot);
         clusterAddSlot(n, slot);
+        int shard_is_empty = my_primary->numslots == 0;
 
         /* If replica migration is allowed, check if the primary of this shard
          * loses its last slot and the shard becomes empty. In this case, we
          * should turn into a replica of the new primary. */
-        if (server.cluster_allow_replica_migration && slot_was_mine && my_primary->numslots == 0) {
+        if (server.cluster_allow_replica_migration && slot_was_mine && shard_is_empty) {
             serverAssert(n != my_primary);
             serverLog(LL_NOTICE,
                       "Lost my last slot during slot migration. Reconfiguring myself "
@@ -6442,6 +6443,16 @@ void clusterCommandSetSlot(client *c) {
             clusterDoBeforeSleep(CLUSTER_TODO_SAVE_CONFIG | CLUSTER_TODO_UPDATE_STATE | CLUSTER_TODO_FSYNC_CONFIG);
         }
 
+        /* If replica migration is not allowed, check if the primary of this shard
+         * loses its last slot and the shard becomes empty. In this case, we will
+         * print the exact same log as during the gossip process. */
+        if (!server.cluster_allow_replica_migration && nodeIsPrimary(myself) && slot_was_mine && shard_is_empty) {
+            serverAssert(n != my_primary);
+            serverLog(LL_NOTICE,
+                      "My last slot was migrated to node %.40s (%s) in shard %.40s. I am now an empty primary.",
+                      n->name, n->human_nodename, n->shard_id);
+        }
+
         /* If this node or this node's primary was importing this slot,
          * assigning the slot to itself also clears the importing status. */
         if ((n == myself || n == myself->replicaof) && server.cluster->importing_slots_from[slot]) {

tests/unit/cluster/replica-migration.tcl

@@ -372,7 +372,7 @@ proc test_cluster_setslot {type} {
             fail "valkey-cli --cluster rebalance returns non-zero exit code, output below:\n$result"
         }
 
-        # Wait for R 3 to report that it is an empty replica (cluster-allow-replica-migration no)
+        # Wait for R 3 to report that it is an empty primary (cluster-allow-replica-migration no)
         wait_for_log_messages -3 {"*I am now an empty primary*"} 0 1000 50
 
         if {$type == "setslot"} {