[Internal] Per Partition Automatic Failover: Fixes Gateway 503 Cold Start Issue

Microsoft.Azure.Cosmos/src/ClientRetryPolicy.cs

@@ -247,8 +247,7 @@ private async Task<ShouldRetryResult> ShouldRetryInternalAsync(
             }
 
             // Received 503 due to client connect timeout or Gateway
-            if (statusCode == HttpStatusCode.ServiceUnavailable
-                && ClientRetryPolicy.IsRetriableServiceUnavailable(subStatusCode))
+            if (statusCode == HttpStatusCode.ServiceUnavailable)
             {
                 DefaultTrace.TraceWarning("ClientRetryPolicy: ServiceUnavailable. Refresh cache and retry. Failed Location: {0}; ResourceAddress: {1}",
                     this.documentServiceRequest?.RequestContext?.LocationEndpointToRoute?.ToString() ?? string.Empty,
@@ -265,12 +264,6 @@ private async Task<ShouldRetryResult> ShouldRetryInternalAsync(
             return null;
         }
 
-        private static bool IsRetriableServiceUnavailable(SubStatusCodes? subStatusCode)
-        {
-            return subStatusCode == SubStatusCodes.Unknown ||
-                (subStatusCode.HasValue && subStatusCode.Value.IsSDKGeneratedSubStatus());
-        }
-
         private async Task<ShouldRetryResult> ShouldRetryOnEndpointFailureAsync(
             bool isReadRequest,
             bool markBothReadAndWriteAsUnavailable,
@@ -390,7 +383,7 @@ private ShouldRetryResult ShouldRetryOnSessionNotAvailable()
 
         /// <summary>
         /// For a ServiceUnavailable (503.0) we could be having a timeout from Direct/TCP locally or a request to Gateway request with a similar response due to an endpoint not yet available.
-        /// We try and retry the request only if there are other regions available.
+        /// We try and retry the request only if there are other regions available. The retry logic is applicable for single master write accounts as well.
         /// </summary>
         private ShouldRetryResult ShouldRetryOnServiceUnavailable()
         {
@@ -400,13 +393,6 @@ private ShouldRetryResult ShouldRetryOnServiceUnavailable()
                 return ShouldRetryResult.NoRetry();
             }
 
-            if (!this.canUseMultipleWriteLocations
-                    && !this.isReadRequest)
-            {
-                // Write requests on single master cannot be retried, no other regions available
-                return ShouldRetryResult.NoRetry();
-            }
-
             int availablePreferredLocations = this.globalEndpointManager.PreferredLocationCount;
 
             if (availablePreferredLocations <= 1)

Microsoft.Azure.Cosmos/src/Routing/LocationCache.cs

@@ -276,7 +276,7 @@ public Uri ResolveServiceEndpoint(DocumentServiceRequest request)
             }
             else
             {
-                ReadOnlyCollection<Uri> endpoints = request.OperationType.IsWriteOperation() ? this.WriteEndpoints : this.ReadEndpoints;
+                ReadOnlyCollection<Uri> endpoints = this.ReadEndpoints;
                 locationEndpointToRoute = endpoints[locationIndex % endpoints.Count];
             }