Unmanaged memory leak in HttpResponse

I am developing a http handler running under IIS for streaming data from a server down to its clients. This works just fine. Until I open an oracle database connection before I stream the data. After I have opened the connection (and closed it again properly) all the data I am streaming will leak on the server, causing it to consume huge amounts of memory.

The .NET Memory profiler reports the following stack trace for the leaking memory allocations:

HeapAlloc()

[Managed to unmanaged transition]

UnsafeNativeMethods.BufferPoolGetBuffer(IntPtr)

HttpResponseUnmanagedBufferElement..ctor()

HttpWriter.CreateNewMemoryBufferElement()

HttpWriter.BufferData(byte[], int, int, bool)

HttpWriter.WriteFromStream(byte[], int, int)

HttpResponseStream.Write(byte[], int, int)

LeakingHttpHandler.ProcessRequest(HttpContext)

HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()

HttpApplication.ExecuteStep(HttpApplication.IExecutionStep, bool&)

HttpApplication.ResumeSteps(Exception)

HttpApplication.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext, AsyncCallback, object)

HttpRuntime.ProcessRequestInternal(HttpWorkerRequest)

HttpRuntime.ProcessRequestNow(HttpWorkerRequest)

HttpRuntime.ProcessRequestNoDemand(HttpWorkerRequest)

ISAPIRuntime.ProcessRequest(IntPtr, int)

[Unmanaged to managed transition]

Can anyone figure out how opening an oracle connection affects the unmanaged memory buffer pool in System.Web?

I am running Windows Server 2003, IIS 6, .NET 2.0 and have tried both ODP.NET 10.2.0.1.0 and 10.2.0.2.20.

This is an example of a leaking http handler:

using System;
using System.Web;
using Oracle.DataAccess.Client;

namespace MemoryLeak {
class LeakingHttpHandler : IHttpHandler {

public bool IsReusable { get { return true; } }

public void ProcessRequest(HttpContext context) {
using (OracleConnection conn = new OracleConnection("...")) {
conn.Open();
}

context.Response.Buffer = false;
for (int i = 0; i < 100; i++) {
byte[] buffer = new byte[65536];
context.Response.OutputStream.Write(buffer, 0, buffer.Length);
}
context.Response.End();
}
}
}

The http handler is set up with the following Web.config file:

<configuration>
<system.web>
<httpRuntime executionTimeout="1800" />
<httpHandlers>
<add verb="*" path="*.rem" type="MemoryLeak.LeakingHttpHandler, MemoryLeak" />
</httpHandlers>
</system.web>
</configuration>

After creating a virtual directory in IIS (called MemoryLeak) I just have to enter the correct url in Internet Explorer (http://localhost/memoryleak/foo.rem) a few times to make the memory consumption of w3wp.exe go sky high.

If I remove conn.Open() from the code, the memory leak disappears.

If I set context.Response.Buffer = true (which I do not want to do), the memory leak disappears.

If I start a new thread, open the oracle connection in that new thread, and join with the thread, the memory leak disappears.

If I connect to a MSSQL database instead of Oracle, or connect to Oracle using the Microsoft provider in System.Data instead of ODP.NET, the memory leak disappears.

[7829 byte] By [hmanner] at [2007-12-25]

Question about 'Unmanaged memory leak in HttpResponse', No.787677,Posted by hmanner

Unmanaged memory leak in HttpResponse

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