HttpTimeoutPolicy: Fixes aggressive 500ms first-attempt timeout in HttpTimeoutPolicyControlPlaneRetriableHotPath

Raises the first-attempt timeout for HttpTimeoutPolicyControlPlaneRetriableHotPath
from 500ms to 1s, aligning with the precedent set by HttpTimeoutPolicyForThinClient
(#5496) and HttpTimeoutPolicyForPartitionFailover (#5484).

The original 500ms value was too aggressive for .NET 10's HttpConnectionPool
behavior and any environment with moderate network latency, producing spurious
TaskCanceledExceptions that the SDK then retried successfully but at the cost
of wasted work and noisy customer telemetry.

The 5s and 65s tail attempts are preserved to keep the existing retry budget
for genuinely slow control-plane operations.

Fixes #5642

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: NaluTripician

Microsoft.Azure.Cosmos/src/HttpClient/HttpTimeoutPolicyControlPlaneRetriableHotPath.cs

@@ -20,9 +20,14 @@ private HttpTimeoutPolicyControlPlaneRetriableHotPath(bool shouldThrow503OnTimeo
             this.shouldThrow503OnTimeout = shouldThrow503OnTimeout;
         }
 
+        // The first-attempt timeout was raised from 500ms to 1s to align with HttpTimeoutPolicyForThinClient
+        // (see issue #5642). The original 500ms value caused spurious TaskCanceledException retries on
+        // .NET 10 due to changes in HttpConnectionPool behavior and any environment with moderate network
+        // latency. The 5s and 65s tail attempts are preserved to keep the existing retry budget for slow
+        // control-plane operations.
         private readonly IReadOnlyList<(TimeSpan requestTimeout, TimeSpan delayForNextRequest)> TimeoutsAndDelays = new List<(TimeSpan requestTimeout, TimeSpan delayForNextRequest)>()
         {
-            (TimeSpan.FromSeconds(.5), TimeSpan.Zero),
+            (TimeSpan.FromSeconds(1), TimeSpan.Zero),
             (TimeSpan.FromSeconds(5), TimeSpan.FromSeconds(1)),
             (TimeSpan.FromSeconds(65), TimeSpan.Zero),
         };

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/CosmosHttpClientCoreTests.cs

@@ -75,7 +75,7 @@ public async Task RetryTransientIssuesTestAsync()
                 }},
                 {HttpTimeoutPolicyControlPlaneRetriableHotPath.Instance,  new List<TimeSpan>()
                 {
-                    TimeSpan.FromSeconds(1),
+                    TimeSpan.FromSeconds(2),
                     TimeSpan.FromSeconds(6),
                     TimeSpan.FromSeconds(66)
                 }},