FC17 Real world example of not reusing JSON contract resolver

In FC13 Reuse contract resolver objects (beehiiv.com), we discussed the importance of reusing JSON contract resolver objects. Today, I found a real-world example of not reusing contract resolver objects.

This is found in Visual Studio 2022 ServiceHub.Host.AnyCPU process. Here is allocation stack:

TryGetArgumentByNameOrIndex is responsible for 42% of total allocations in the process. There are large numbers of allocations coming from MarshalContractResolver.ResolveContract, mostly for reflection calls for creating new contracts.

Here is MarshalContractResolver constructor:

Allocating DefaultContractResolver is the wrong thing to do, unless this is singleton object.

Here is caller source code:

Again, this is the wrong way to do business, unless JsonMessageFormatter is singleton.

A single allocation sample is found:

So this does not look like singleton object.

Now let’s check CPU stacks:

20.9% in ResolveContract. Expensive lawyers are hired to write the same contracts over and over again.

Now let’s check JIT events:

It looks this code path is executed 34 times in 7 second interval. This shows the cost of not reusing JSON contract resolver for real. Once this issue is fixed, the code will be much faster.