Tracking Down a .NET Windows Service Memory Leak

Question

Before installing my windows service in production, I was looking for reliable tests that I can perform to make sure my code doesn't contain memory leaks. However, All what I can find on the net was using task manager to look at used memory or some paid memory profiler tools.

From my understanding, looking at the task manager is not really helpful and cannot confirm the memory leakage (in case, there is).

1. How to confirm whether there is a memory leak or not?

2. Is there any free tools to find the source of memory leaks?

Note: I'm using .Net Framework 4.6 and Visual Studio 2015 Community

Answer 1

Well you can use task manager. GC apps can leak memory, and it will show there.

But...

Free tool - ".Net CLR profiler"

There is a free tool, and it's from Microsoft, and it's awesome. This is a must-use for all programs that leak references. Search MS' site.

Leaking references means you forget to set object references to null, or they never leave scope, and this is almost as likely to occur in Garbage collected languages as not - lists building up and not clearing, event handlers pointing to delegates, etc.

It's the GC equivalent of memory leaks and has the same result. This program tells you what references are taking up tons of memory - and you will know if it's supposed to be that way or not, and if not, you can go find them and fix the problem!

It even has a cool visualization of what objects allocate what memory (so you can track down mistakes). I believe there are youtubes of this if you need an explanation.

Wikipedia page with download links...

NOTE: You will likely have to run your app not as a service to use this. It starts first and then runs your app. You can do this with TopShelf or by just putting the guts in a dll that runs from an EXE that implments the service integrations (service host pattern).

Answer 2

Although managed code implies no direct memory management, you still have to manage your instances. Those instances 'claim' memory. And it is all about the usage of these instances, keeping them alive when you don't expect them to be.

Just one of many examples: wrong usage of disposable classes can result in a lot of instances claiming memory. For a windows service, a slow but steady increase of instances can eventually result in to much memory usage.

Yes, there is a tool to analyze memory leaks. It just isn't free. However you might be able to identify your problem within the 7 day trial.

I would suggest to take a loot at the .NET Memory Profiler.

It is great to analyze memory leaks during development. It uses the concept of snapshots to compare new instances, disposed instances etc. This is a great help to understand how your service uses its memory. You can then dig deeper into why new instances get created or are kept alive.

Yes, you can test to confirm whether memory leaks are introduced. However, just out-of-the box this will not be very useful. This is because no one can anticipate what will happen during runtime. The tool can analyze your app for common issues, but this is not guaranteed.

However, you can use this tool to integrate memory consumption into your unit test framework like NUnit or MSTest.