Moved logic for creating a blob to the data provider.

It's data provider responsibility to create a blob.

Author: ob1dev

src/Sitecore.Azure.Diagnostics/Appenders/AzureBlobStorageAppender.cs

@@ -106,25 +106,9 @@ protected override void Append(LoggingEvent loggingEvent)
       var blob = this.Blob as CloudAppendBlob;
       string message = this.RenderLoggingEvent(loggingEvent);
 
-      CreateBlobIfNotExists(blob);
       blob.AppendText(message);
     }    
 
-    /// <summary>
-    /// Creates a new blob for the specified <see cref="CloudAppendBlob" /> if it does not already exist.
-    /// </summary>
-    /// <param name="blob">The <see cref="CloudAppendBlob" />.</param>
-    /// <param name="accessCondition">The access condition.</param>
-    /// <param name="blobRequestOptions">The blob request options.</param>
-    /// <param name="operationContext">The operation context.</param>
-    protected static void CreateBlobIfNotExists(CloudAppendBlob blob, AccessCondition accessCondition = null, BlobRequestOptions blobRequestOptions = null, OperationContext operationContext = null)
-    {
-        if (!blob.Exists(blobRequestOptions, operationContext))
-        {
-            blob.CreateOrReplace(accessCondition, blobRequestOptions, operationContext);
-        }
-    }
-
     /// <summary>
     /// Gets the new cloud blob for diagnostic messages.
     /// </summary>

src/Sitecore.Azure.Diagnostics/Storage/AzureBlobStorageProvider.cs

@@ -254,10 +254,16 @@ public virtual ICloudBlob CreateBlob(string blobName)
       // Build blob name for a Role Environment using the following format: {DeploymentId}/{RoleInstanceId}/{BlobName}.
       blobName = string.IsNullOrEmpty(webRoleRelativeAddress) ? blobName : string.Format("{0}/{1}", webRoleRelativeAddress, blobName);
 
-      ICloudBlob blob = this.CloudBlobContainer.Exists() ?
+      var blob = this.CloudBlobContainer.Exists() ?
         this.CloudBlobContainer.GetAppendBlobReference(blobName) :
         this.GetContainer(this.ContainerName).GetAppendBlobReference(blobName);
 
+      if (!blob.Exists())
+      {
+        // Create an empty append blob or throw an exception if the blob exists.
+        blob.CreateOrReplace(AccessCondition.GenerateIfNotExistsCondition());
+      }
+
       return blob;
     }