Very High Memory Usage in .NET 4.0

I ran into this exact issue. And it is true that app domains are created and not cleaned up. However I wouldn't recommend reverting to legacy. They can be cleaned up by ReleaseSandboxAppDomain().

LocalReport report = new LocalReport();
...
report.ReleaseSandboxAppDomain();

Some other things I also do to clean up:

Unsubscribe to any SubreportProcessing events, Clear Data Sources, Dispose the report.

Our windows service processes several reports a second and there are no leaks.

I'm pretty late to this, but I have a real solution and can explain why!

It turns out that LocalReport here is using .NET Remoting to dynamically create a sub appdomain and run the report in order to avoid a leak internally somewhere. We then notice that, eventually, the report will release all the memory after 10 to 20 minutes. For people with a lot of PDFs being generated, this isn't going to work. However, the key here is that they are using .NET Remoting. One of the key parts to Remoting is something called "Leasing". Leasing means that it will keep that Marshal Object around for a while since Remoting is usually expensive to setup and its probably going to be used more than once. LocalReport RDLC is abusing this.

By default, the leasing time is... 10 minutes! Also, if something makes various calls into it, it adds another 2 minutes to the wait time! Thus, it can randomly be between 10 and 20 minutes depending how the calls line up. Luckily, you can change how long this timeout happens. Unluckily, you can only set this once per app domain... Thus, if you need remoting other than PDF generation, you will probably need to make another service running it so you can change the defaults. To do this, all you need to do is run these 4 lines of code at startup:

    LifetimeServices.LeaseTime = TimeSpan.FromSeconds(5);
    LifetimeServices.LeaseManagerPollTime = TimeSpan.FromSeconds(5);
    LifetimeServices.RenewOnCallTime = TimeSpan.FromSeconds(1);
    LifetimeServices.SponsorshipTimeout = TimeSpan.FromSeconds(5);

You'll see the memory use start to rise and then within a few seconds you should see the memory start coming back down. Took me days with a memory profiler to really track this down and realize what was happening.

You can't wrap ReportViewer in a using statement (Dispose crashes), but you should be able to if you use LocalReport directly. After that disposes, you can call GC.Collect() if you want to be doubly sure you are doing everything you can to free up that memory.

Hope this helps!

Edit

Apparently, you should call GC.Collect(0) after generating a PDF report or else it appears the memory use could still get high for some reason.

Well this was an interesting one.

The root cause turns out to be a change in the behavior of SQL Server Reporting Services' LocalReport class (v2010) when running this on top of .NET 4.0.

Basically, Microsoft altered the behavior of RDLC processing so that each time a report was processed it was done so in a seperate application domain. This was actually done specifically to address a memory leak caused by the inability to unload assemblies from app domains. When the LocalReport class processed an RDLC file, it actually creates an assembly on the fly and loads it into the app domain.

In my case, due to the large volume of report I was processing, this was resulting in very large numbers of System.Runtime.Remoting.ServerIdentity objects being created. This was my tip off to the cause, as I was confused as to why processing an RLDC required remoting.

Of course, to call a method on a class in another app domain, remoting is exactly what you use. In .NET 3.5, this wasn't necessary as, by default, the RDLC-assembly was loaded into the same app domain. In .NET 4.0, however, a new app domain is created by default.

The fix was fairly easy. First I needed to go enable legacy security policy using the following config:

  <runtime>
    <NetFx40_LegacySecurityPolicy enabled="true"/>
  </runtime>

Next, I needed to force the RDLCs to be processed in the same app domain as my service by calling the following:

myLocalReport.ExecuteReportInCurrentAppDomain(AppDomain.CurrentDomain.Evidence);

This resolved the issue.