memberlist: Log fast-join failures at info instead of debug (#585)

Not being able to fast-join via contacting a node is suspicious and might
indicate a problem. Logging at info makes this easier to troubleshoot.

Signed-off-by: Nick Pillitteri <nick.pillitteri@grafana.com>

CHANGELOG.md

@@ -81,6 +81,7 @@
 * [CHANGE] Cache: Remove superfluous `cache.RemoteCacheClient` interface and unify all caches using the `cache.Cache` interface. #520
 * [CHANGE] Updated the minimum required Go version to 1.21. #540
 * [CHANGE] memberlist: Metric `memberlist_client_messages_in_broadcast_queue` is now split into `queue="local"` and `queue="gossip"` values. #539
+* [CHANGE] memberlist: Failure to fast-join a cluster via contacting a node is now logged at `info` instead of `debug`. #585 
 * [CHANGE] `Service.AddListener` and `Manager.AddListener` now return function for stopping the listener. #564
 * [FEATURE] Cache: Add support for configuring a Redis cache backend. #268 #271 #276
 * [FEATURE] Add support for waiting on the rate limiter using the new `WaitN` method. #279

kv/memberlist/memberlist_client.go

@@ -552,7 +552,7 @@ func (m *KV) fastJoinMembersOnStartup(ctx context.Context) {
 	for toJoin > 0 && len(nodes) > 0 && ctx.Err() == nil {
 		reached, err := m.memberlist.Join(nodes[0:1]) // Try to join single node only.
 		if err != nil {
-			level.Debug(m.logger).Log("msg", "fast-joining node failed", "node", nodes[0], "err", err)
+			level.Info(m.logger).Log("msg", "fast-joining node failed", "node", nodes[0], "err", err)
 		}
 
 		totalJoined += reached