Fix stream consumption bug in GatewayStoreClient.CreateDocumentClientExceptionAsync

Co-authored-by: kirankumarkolli <6880899+kirankumarkolli@users.noreply.github.com>

Author: Copilot

Microsoft.Azure.Cosmos/src/GatewayStoreClient.cs

@@ -168,31 +168,37 @@ internal static async Task<DocumentClientException> CreateDocumentClientExceptio
             }
 
             // If service rejects the initial payload like header is to large it will return an HTML error instead of JSON.
+            string contentString = null;
             if (string.Equals(responseMessage.Content?.Headers?.ContentType?.MediaType, "application/json", StringComparison.OrdinalIgnoreCase) &&
                 responseMessage.Content?.Headers.ContentLength > 0)
             {
                 try
                 {
-                    Stream contentAsStream = await responseMessage.Content.ReadAsStreamAsync();
-                    Error error = JsonSerializable.LoadFrom<Error>(stream: contentAsStream);
-
-                    return new DocumentClientException(
-                        errorResource: error,
-                        responseHeaders: responseMessage.Headers,
-                        statusCode: responseMessage.StatusCode)
+                    // Buffer the content once to avoid "stream already consumed" issue
+                    contentString = await responseMessage.Content.ReadAsStringAsync();
+                    using (MemoryStream contentStream = new MemoryStream(Encoding.UTF8.GetBytes(contentString)))
                     {
-                        StatusDescription = responseMessage.ReasonPhrase,
-                        ResourceAddress = resourceIdOrFullName,
-                        RequestStatistics = requestStatistics
-                    };
+                        Error error = JsonSerializable.LoadFrom<Error>(stream: contentStream);
+
+                        return new DocumentClientException(
+                            errorResource: error,
+                            responseHeaders: responseMessage.Headers,
+                            statusCode: responseMessage.StatusCode)
+                        {
+                            StatusDescription = responseMessage.ReasonPhrase,
+                            ResourceAddress = resourceIdOrFullName,
+                            RequestStatistics = requestStatistics
+                        };
+                    }
                 }
                 catch
                 {
                 }
             }
 
             StringBuilder contextBuilder = new StringBuilder();
-            contextBuilder.AppendLine(await responseMessage.Content.ReadAsStringAsync());
+            // Reuse the already buffered content if available, otherwise read it now
+            contextBuilder.AppendLine(contentString ?? await responseMessage.Content.ReadAsStringAsync());
 
             HttpRequestMessage requestMessage = responseMessage.RequestMessage;
 

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

@@ -246,6 +246,37 @@ public async Task TestCreateDocumentClientExceptionWhenMediaTypeIsApplicationJso
             Assert.IsNotNull(value: documentClientException.Error.Message);
         }
 
+        /// <summary>
+        /// Test to verify the fix for the stream consumption issue when JSON deserialization fails.
+        /// This reproduces the scenario where a 403 response has application/json content type 
+        /// but invalid JSON content, which would previously cause "stream already consumed" exception.
+        /// </summary>
+        [TestMethod]
+        [Owner("copilot")]
+        public async Task TestStreamConsumptionBugFixWhenJsonDeserializationFails()
+        {
+            // Create invalid JSON content that will fail deserialization but has application/json content type
+            string invalidJson = "{ \"error\": invalid json content that will fail parsing }";
+            
+            HttpResponseMessage responseMessage = new HttpResponseMessage(HttpStatusCode.Forbidden)
+            {
+                RequestMessage = new HttpRequestMessage(HttpMethod.Get, "https://test.com/dbs/db1/colls/coll1/docs/doc1"),
+                Content = new StringContent(invalidJson, Encoding.UTF8, "application/json")
+            };
+
+            IClientSideRequestStatistics requestStatistics = GatewayStoreClientTests.CreateClientSideRequestStatistics();
+
+            // This should NOT throw an InvalidOperationException about stream being consumed
+            DocumentClientException exception = await GatewayStoreClient.CreateDocumentClientExceptionAsync(
+                responseMessage: responseMessage,
+                requestStatistics: requestStatistics);
+
+            // Verify the exception was created successfully with fallback logic
+            Assert.IsNotNull(exception);
+            Assert.AreEqual(HttpStatusCode.Forbidden, exception.StatusCode);
+            Assert.IsTrue(exception.Message.Contains(invalidJson), "Exception message should contain the original invalid JSON content");
+        }
+
         private static IClientSideRequestStatistics CreateClientSideRequestStatistics()
         {
             return new ClientSideRequestStatisticsTraceDatum(