idp handle host unknown (#3192)

when host is not known, handle exception so we give back a better error message

src/Microsoft.Health.Dicom.Blob/Features/Storage/BlobFileStore.cs

@@ -558,6 +558,14 @@ private async Task<T> ExecuteAsync<T>(
             _logger.LogError(ex, message: "Access to storage account failed with ErrorCode: {ErrorCode}", ex.ErrorCode);
             throw new DataStoreRequestFailedException(ex, _blobClient.IsExternal);
         }
+        catch (AggregateException ex) when (_blobClient.IsExternal && ex.InnerException is RequestFailedException)
+        {
+            var innerEx = ex.InnerException as RequestFailedException;
+            _logger.LogError(innerEx,
+                    message: "Access to external storage account failed with ErrorCode: {ErrorCode}",
+                    innerEx.ErrorCode);
+            throw new DataStoreRequestFailedException(innerEx, _blobClient.IsExternal);
+        }
         catch (Exception ex)
         {
             _logger.LogError(ex, "Access to storage account failed");

src/Microsoft.Health.Dicom.Core/DicomCoreResource.resx

@@ -667,6 +667,12 @@ For details on valid range queries, please refer to Search Matching section in C
   <data name="ExternalDataStoreOperationFailed" xml:space="preserve">
     <value>Error occurred during an operation on the configured storage account. Use the https://go.microsoft.com/fwlink/?linkid=2251550 to troubleshoot the issue. Received the following error code: {0}</value>
   </data>
+  <data name="ExternalDataStoreHostIsUnknown" xml:space="preserve">
+    <value>Error occurred during an operation on the configured storage account. Use the https://go.microsoft.com/fwlink/?linkid=2251550 to troubleshoot the issue. No such host is known.</value>
+  </data>
+  <data name="ExternalDataStoreOperationFailedUnknownIssue" xml:space="preserve">
+    <value>Error occurred during an operation on the configured storage account. Use the https://go.microsoft.com/fwlink/?linkid=2251550 to troubleshoot the issue.</value>
+  </data>
   <data name="ExternalDataStoreBlobModified" xml:space="preserve">
     <value>Received the following error code from blob storage account: {0}. Can not perform operation '{1}' because the blob '{2}' with eTag '{3}' has been modified or deleted by another process. Use the https://go.microsoft.com/fwlink/?linkid=2251550 to troubleshoot the issue.</value>
   </data>

src/Microsoft.Health.Dicom.Core/Exceptions/DataStoreRequestFailedException.cs

@@ -3,6 +3,7 @@
 // Licensed under the MIT License (MIT). See LICENSE in the repo root for license information.
 // -------------------------------------------------------------------------------------------------
 
+using System;
 using System.Globalization;
 using Azure;
 
@@ -17,10 +18,33 @@ public class DataStoreRequestFailedException : ConditionalExternalException
     public DataStoreRequestFailedException(RequestFailedException ex, bool isExternal = false)
         : base(
             (isExternal ?
-                string.Format(CultureInfo.InvariantCulture, DicomCoreResource.ExternalDataStoreOperationFailed, ex?.ErrorCode)
+                getFormattedExternalStoreMessage(ex)
                 : DicomCoreResource.DataStoreOperationFailed),
             ex,
             isExternal)
     {
     }
+
+    private static string getFormattedExternalStoreMessage(RequestFailedException ex)
+    {
+        return !string.IsNullOrEmpty(ex?.ErrorCode)
+                ? string.Format(
+                    CultureInfo.InvariantCulture,
+                    DicomCoreResource.ExternalDataStoreOperationFailed,
+                    ex?.ErrorCode)
+                : GetFormattedExternalStoreMessageWithoutErrorCode(ex)
+            ;
+    }
+
+    private static string GetFormattedExternalStoreMessageWithoutErrorCode(RequestFailedException ex)
+    {
+        if (ex.Message.Contains("No such host is known", StringComparison.OrdinalIgnoreCase))
+        {
+            return DicomCoreResource.ExternalDataStoreHostIsUnknown;
+        }
+
+        // if we do not have an error code and internal message is not "host not known", we are not familiar with the issue
+        // we can't just give back the exception message as it may contain sensitive information
+        return DicomCoreResource.ExternalDataStoreOperationFailedUnknownIssue;
+    }
 }