Fix #2679: connect/config: only access task.Result if we know it completed (#2680)

* connect/config: only access task.Result if we know it completed

* cite PR

* typo

Author: mgravell

docs/ReleaseNotes.md

@@ -8,6 +8,7 @@ Current package versions:
 
 ## Unreleased
 
+- Fix [#2679](https://github.com/StackExchange/StackExchange.Redis/issues/2679) - blocking call in long-running connects ([#2680 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2680))
 - Support async cancellation of `SCAN` enumeration ([#2911 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2911)) 
 - Add `XTRIM MINID` support ([#2842 by kijanawoodard](https://github.com/StackExchange/StackExchange.Redis/pull/2842))
 - Add new CE 8.2 stream support - `XDELEX`, `XACKDEL`, `{XADD|XTRIM} [KEEPREF|DELREF|ACKED]` ([#2912 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2912))

src/StackExchange.Redis/ConnectionMultiplexer.cs

@@ -681,8 +681,17 @@ private static ConnectionMultiplexer ConnectImpl(ConfigurationOptions configurat
                 // note that task has timeouts internally, so it might take *just over* the regular timeout
                 var task = muxer.ReconfigureAsync(first: true, reconfigureAll: false, log, null, "connect");
 
-                if (!task.Wait(muxer.SyncConnectTimeout(true)))
+                if (task.Wait(muxer.SyncConnectTimeout(true)))
                 {
+                    // completed promptly - we can check the outcome; hard failures
+                    // (such as password problems) should be reported promptly - it
+                    // won't magically start working
+                    if (!task.Result) throw ExceptionFactory.UnableToConnect(muxer, muxer.failureMessage);
+                }
+                else
+                {
+                    // incomplete - most likely slow initial connection; optionally
+                    // allow a soft failure mode
                     task.ObserveErrors();
                     if (muxer.RawConfig.AbortOnConnectFail)
                     {
@@ -696,7 +705,6 @@ private static ConnectionMultiplexer ConnectImpl(ConfigurationOptions configurat
                     }
                 }
 
-                if (!task.Result) throw ExceptionFactory.UnableToConnect(muxer, muxer.failureMessage);
                 killMe = null;
                 Interlocked.Increment(ref muxer._connectCompletedCount);