SQL CLR function stops working sometime after processing 10,000 web requests....

Question

The CLR functon below works fine up to around 12,000 requests and then stops working. Am I missing something? If I remove then redeploy the function it again will work for another 12,000 requests. I don't see a memory leak but then my C# skills are rusty. Thanks!-----------------------------------------------------------------------------------------------
-- Web Request CLR functions.
USE MyDb
GO
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[GetWebRequest]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[GetWebRequest]
GO
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[PostWebRequest]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[PostWebRequest]
GO
BEGIN TRY
DROP ASSEMBLY [SqlClrLibrary]
END TRY
BEGIN CATCH
SELECT 'SqlClrLibrary not found.... creating'
END CATCH
CREATE ASSEMBLY [SqlClrLibrary]
FROM 'c:\\SqlClrLibrary.dll'
WITH PERMISSION_SET=UNSAFE;
GO
-- PostWebRequest
USE MyDb
GO
/****** Object: UserDefinedFunction [dbo].[PostWebRequest] Script Date: 07/18/2014 12:03:32 ******/
CREATE FUNCTION [dbo].[PostWebRequest](@uri [nvarchar](256), @postdata [nvarchar](max), @UserAgent [nvarchar](256), @ContentType [nvarchar](256))
RETURNS [nvarchar](max) WITH EXECUTE AS CALLER
AS
EXTERNAL NAME [SqlClrLibrary].[SqlClrLibrary.Functions].[POST]
GO
// Below is the CLR code....
using System;
using System.IO;
using System.Net;
using System.Text;
using Microsoft.SqlServer.Server;
namespace SqlClrLibrary
/// <summary>
/// CLR Functions.
/// </summary>
    public static class Functions
/// <summary>
/// Send an Http Post request and return a scrubbed result.
/// NOTE: The response is always set to lowercase... This is due to performance issues related to sql injection scrubbing.
/// See SqlInjectionScubber.Scrub.
/// </summary>
/// <param name="Uri">Web address for the POST request.</param>
/// <param name="PostData">Payload name value pairs for request parameters.</param>
/// <param name="UserAgent">Http user agent sending this request.</param>
/// <param name="ContentType">Mime type.</param>
/// <returns></returns>
[Microsoft.SqlServer.Server.SqlFunction(DataAccess = DataAccessKind.Read)]
public static string POST(string Uri, string PostData, string UserAgent, string ContentType)
var postByteArray = Encoding.UTF8.GetBytes(Convert.ToString(PostData));
// Set up the request
var req = WebRequest.Create(Uri);
req.Method = "POST";
req.ContentType = ContentType;
((HttpWebRequest)req).UserAgent = UserAgent;
// Submit the POST data
var dataStream = req.GetRequestStream();
dataStream.Write(postByteArray, 0, postByteArray.Length);
dataStream.Close();
// Collect the response, put it in the string variable "document"
var resp = req.GetResponse();
dataStream = resp.GetResponseStream();
if (dataStream != null)
var rdr = new StreamReader(dataStream);
var document = rdr.ReadToEnd();
// Close up and return
rdr.Close();
dataStream.Close();
resp.Close();
// Scrub the result.
return document;
return String.Empty;
Scott Mitchell

Answer 1

Hi Scott,
There's not enough information there to troubleshoot the problem. Try looking in the forum for similar problem postings (there have been a few, IIRC). First thing to try would be issuing the same number of requests in a batch program, to isolate the behavior
to "code is running in SQLCLR". That would also help you isolate memory leaks, if any. Also:
Need version of SQL Server (version, service pack, and cumulative updates, is it 32 or 64 bit version). It matters.
Define "stops working". Does it produce an error message or appear to hang or something else? Does it bring down the appdomain (there's messages for that in SQL Server log). And does "redeploy" mean just DROP/CREATE assembly? Or bounce
SQL Server, or something else?
And since it's a web service you're calling... if you trace to network traffic, is the message actually sent? Is the message received at the service? Does the service return a response? And does the SQL function process the response? Is it "your"
service or an "outside" service (perhaps there's a limit on number of requests or number of requests in a certain time period. Is it exactly 12000 requests or about 12000, and how many requests per minute? Isolate where in the intersystem communication
it fails.
It could be a memory shortage or fragmentation problem. SQLCLR memory handling differs in SQL Server 2012 vs. other releases and also differs in 32 vs. 64 bit SQL Server. You can look at memory consumed by SQLCLR (sys.dm_os_memory_objects where
type like '%CLR%'). You can look at perfmon counter(s) for SQL Server or .NET perfmon counters for the SQL Server process to track CLR garbage collections (which does work differently in SQLCLR). You can look at sys.dm_os_wait_stats if it's hanging. And in
SQL Server log for SQL Server errors.  SQLCLR can fragment memory in older versions so that there's not a big enough fragment left to allocate. If it's pre-2012 read up on "mem-to-leave or mem-to-reserve" (two different terms for the same
thing).
Hope this helps, Bob