Appdomain memory issue

Question

I have created a small windows service that runs plugins.

Each plugin is a dll that gets loaded into its own seperate AppDomain using CreateInstanceAndUnwrap method and I keep a reference to the AppDomain.

Once the plugin completes, I shut down the AppDomain that is created for that plugin. I'm using shadow copy to allow updates to the plugins while they are running in the framework.

It has run for 6 months perfectly untill last week when I decided to put the core functionality of the framework into a seperate dll also and execute that dll in a seperate AppDomain.

The way it works right now is:

Windows service comes up.
The core dll is loaded and executed using CreateInstanceAndUnwrap which in turn is responsible for running the plugins in their own seperate AppDomain

I have couple of different locations for assemblies:

Bin Folder (Bin of the windows service holds only dlls used by the service)
Core DLLs Folder (Core dlls get dropped in here)
References Folder (any references get dropped in here)
Plugins Folder (plugins get dropped in here)

I resolve any unfound dlls by hooking up to each the OnAssemblyResolve event on the AppDomain. This allows dlls to be loaded from over the network.

Now the problem is the windows service ran for one day and the memory went as high as 1.5G. I created a dump of the memory and seems like loaded modules are only 100MB of the whole 1.5G so I dont know where all this memory is going to.

Using debugging I saw an alert for heap fragmentation but I have no idea where I should start to diagnose the issue. Usually when the framework runs for a day it consumed something like 100M.

Also this is not related to the plugins either; when I rolled back my changes to the framework the memroy usage became normal as before. When I create the AppDomain for plugins, I switch the basePath and the bin path of the AppDomain to CORE and References folders that have most of the dlls in there in hope that the assembly resolve gets called less often.

I looked at fusion logs and also read a little bit more about load contexts like default, from, and none but im not sure if thats the right path to take.

Any ideas?

Is it possible to post some code to give us some more information? — Bryan Crosby, Oct 28 '11 at 22:07
Why are you not using the classes in the [`System.AddIn` namespace](http://msdn.microsoft.com/en-us/library/gg145020.aspx)? There's absolutely *no* reason to write this kind of code yourself. — casperOne, Oct 28 '11 at 23:31
Its already late and the project is very coupled with appdomains instead of the system.addins... so no choice right now. — James, Oct 31 '11 at 16:52
Bryan,I'm not really sure which part of the code i should post on here? — James, Oct 31 '11 at 16:53

score 0 · Answer 1 · edited May 23 '17 at 11:47

You should try downloading SciNet memory profiler. I did use that tool to diagnose problems with services and it really does help to figure out where the issue is. There is a free evaluation version available.

If you cannot or do not want to install it, you can try to split your plugins in 2 halfs and see if they have the same memory behavior. You can also try with no plugins at all.

Also, Garbage collecting object across App domains seems to be tricky. You might want to investigate.

Appdomain memory issue

1 Answers1