This post has been imported from my previous blog. I did my best to parse XML properly, but it might have some errors.
If you find one, send a Pull Request.
This is a follow up entry to Stateful Service Fabric that introduced all the kinds of statefulness you can out of the box from the Fabric SDK. It’s time to move on with providing a better stateful service. First, we need to define what better means.
The underlying actors’ persistence is based on KeyValueStoreReplica. This class provides a high level API for low level interop interfaces provided by Service Fabric. Yep, you heard it. The runtime of the Fabric is unmanaged and is exposed via COM+ interfaces. Then they are wrapped in a nice .NET classes just to be delivered to you. The question is how nice are these classes? Let’s take a look at the decompiled part of a method.
private void UpdateHelper(TransactionBase transactionBase, string key, byte[] value, long checkSequenceNumber)
{
using (PinCollection pin = new PinCollection())
{
IntPtr key1 = pin.AddBlittable((object) key);
Tuple<uint, IntPtr> nativeBytes = NativeTypes.ToNativeBytes(pin, value);
this.nativeStore.Update(transactionBase.NativeTransactionBase, key1, (int) nativeBytes.Item1, nativeBytes.Item2, checkSequenceNumber);
}
}
As you can see above, when you pass a string key and a byte[] value a lot must be done to execute the update:
value needs to be allocated every time
as there’s no interface accepting Stream or *ArraySegment
key and value are pinned for the time of executing update.
Pinning, is nothing more or less than prohibiting object from being moved by GC. The same effect that you get when using fixed keyword or using GCHandle.Alloc. When handles not that many requests it’s ok to do it. When GC kicks in frequently, this might be a problem.
The interesting part is the nativeStore field that provides the COM+ seam to the Fabric internal interface. This is the interface that is closest to the Fabric surface and that allows to squeeze performance out of it.
You can probably see, when this leads us. Seeing that underneath the .NET wrapper there is a COM+ that has much more low level interface and allows to use raw memory, we can try to access it directly, skipping KeyValueStoreReplica altogether and write a custom implementation that will enable to maximize the performance.