Semantic Logging Custom sink logs multiple times Event entry

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Practices.EnterpriseLibrary.SemanticLogging;
using Microsoft.Practices.EnterpriseLibrary.SemanticLogging.Formatters;
using Microsoft.WindowsAzure;
using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Blob;
using System.Globalization;
using System.IO;
using Microsoft.Practices.EnterpriseLibrary.TransientFaultHandling;
using Microsoft.WindowsAzure.Storage.RetryPolicies;
namespace SemanticLogging.CustomSink
public class AzureBlobSink : IObserver<EventEntry>
private readonly IEventTextFormatter _formatter;
private string ConnectionString { get; set; }
private string ContainerName { get; set; }
private string BlobName { get; set; }
public AzureBlobSink() : base()
System.Net.WebRequest.DefaultWebProxy.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
public AzureBlobSink(string connectionString, string containerName, string blobname) : base()
this.ConnectionString = connectionString;
this.ContainerName = containerName;
this.BlobName = blobname;
_formatter = new EventTextFormatter();
public void OnCompleted()
//throw new NotImplementedException();
public void OnError(Exception error)
//throw new NotImplementedException();
SemanticLoggingEventSource.Log.CustomSinkUnhandledFault("Exception: " + error.Message + Environment.NewLine + "Stack trace:" + error.StackTrace + Environment.NewLine + "Inner Exception" + error.InnerException + Environment.NewLine);
public void OnNext(EventEntry value)
if (value != null)
using (var writer = new StringWriter())
_formatter.WriteEvent(value, writer);
Postdata(Convert.ToString(writer), BlobName);
/// <summary>
/// create container and upsert block blob content
/// </summary>
/// <param name="content"></param>
private void Postdata(string content, string blobname)
List<string> blockIds = new List<string>();
var bytesToUpload = Encoding.UTF8.GetBytes(content);
//to set default proxy
System.Net.WebRequest.DefaultWebProxy.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
try
using (MemoryStream stream = new MemoryStream(Encoding.UTF8.GetBytes(content),false))
CloudStorageAccount account = CloudStorageAccount.Parse(ConnectionString);
CloudBlobClient blobClient = account.CreateCloudBlobClient();
//linear Retry Policy create a blob container 10 times. The backoff duration is 2 seconds
IRetryPolicy linearRetryPolicy = new LinearRetry(TimeSpan.FromSeconds(2), 10);
//exponential Retry Policy which retries the code to create a blob container 10 times.
IRetryPolicy exponentialRetryPolicy = new ExponentialRetry(TimeSpan.FromSeconds(2), 10);
blobClient.RetryPolicy = linearRetryPolicy;
CloudBlobContainer container = blobClient.GetContainerReference(ContainerName);
container.CreateIfNotExists();
CloudBlockBlob blob = container.GetBlockBlobReference(blobname + System.DateTime.UtcNow.ToString("MMddyyyy") + ".log");
//stream.Seek(0, SeekOrigin.Begin);
if (!blob.Exists())
using (var insertempty = new MemoryStream(Encoding.UTF8.GetBytes("")))
blob.UploadFromStream(insertempty);
blockIds.AddRange(blob.DownloadBlockList(BlockListingFilter.Committed).Select(b => b.Name));
var newId = Convert.ToBase64String(Encoding.UTF8.GetBytes(blockIds.Count.ToString(CultureInfo.InvariantCulture).PadLeft(64, '0')), Base64FormattingOptions.None);
//var newId = Convert.ToBase64String(Encoding.Default.GetBytes(blockIds.Count.ToString()));
blob.PutBlock(newId, new MemoryStream(bytesToUpload), null);
blockIds.Add(newId);
blob.PutBlockList(blockIds);
catch (Exception ex)
SemanticLoggingEventSource.Log.CustomSinkUnhandledFault("Exception: " + ex.Message + Environment.NewLine + "Stack trace:" + ex.StackTrace + Environment.NewLine + "Inner Exception" + ex.InnerException + Environment.NewLine);
I have created custom sink for logging into azure blob.
The code below were giving issue. 
when i execute this method,
First time it write log one time in to blob 
second time it write log two time. 
n-th time it writes n entry to blob. 
Actually, the below code executed n time.
public void OnNext(EventEntry value)
if (value != null)
using (var writer = new StringWriter())
_formatter.WriteEvent(value, writer);
Postdata(Convert.ToString(writer), BlobName);
Help me!
Thanks, SaravanaBharathi.A

Answer 1

Hi Saravanabharathi,
Thank you for posting in here.
We are looking into this and will get back to you at earliest. Your patience is greatly appreciated.
Regards,
Manu Rekhar