Do not send tracers when running second iteration of cluster nodes di… (#2525)

Sending tracers is not necessary because we just connected to the nodes a few seconds ago. It causes problems because sent tracers do not have enough time to respond.

Author: Matiszak

docs/ReleaseNotes.md

@@ -18,6 +18,7 @@ Current package versions:
 
 - Change: Target net6.0 instead of net5.0, since net5.0 is end of life. ([#2497 by eerhardt](https://github.com/StackExchange/StackExchange.Redis/pull/2497))
 - Fix: Fix nullability annotation of IConnectionMultiplexer.RegisterProfiler ([#2494 by eerhardt](https://github.com/StackExchange/StackExchange.Redis/pull/2494))
+- Fix [#2520](https://github.com/StackExchange/StackExchange.Redis/issues/2520): Improve cluster connections in down scenarios by not re-pinging successful nodes ([#2525 by Matiszak](https://github.com/StackExchange/StackExchange.Redis/pull/2525))
 - Add: `Timer.ActiveCount` under `POOL` in timeout messages on .NET 6+ to help diagnose timer overload affecting timeout evaluations ([#2500 by NickCraver](https://github.com/StackExchange/StackExchange.Redis/pull/2500))
 - Add: `LibraryName` configuration option; allows the library name to be controlled at the individual options level (in addition to the existing controls in `DefaultOptionsProvider`) ([#2502 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2502))
 - Add: `DefaultOptionsProvider.GetProvider` allows lookup of provider by endpoint ([#2502 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2502))

src/StackExchange.Redis/ConnectionMultiplexer.cs

@@ -1487,8 +1487,9 @@ internal async Task<bool> ReconfigureAsync(bool first, bool reconfigureAll, ILog
                             servers[i] = server;
 
                             // This awaits either the endpoint's initial connection, or a tracer if we're already connected
-                            // (which is the reconfigure case)
-                            available[i] = server.OnConnectedAsync(log, sendTracerIfConnected: true, autoConfigureIfConnected: reconfigureAll);
+                            // (which is the reconfigure case, except second iteration which is only for newly discovered cluster members).
+                            var isFirstIteration = iter == 0;
+                            available[i] = server.OnConnectedAsync(log, sendTracerIfConnected: isFirstIteration, autoConfigureIfConnected: reconfigureAll);
                         }
 
                         watch ??= ValueStopwatch.StartNew();