Significance of bool IsReusable in http handler interface

Question

When writing a http handler/module, there is an interface member to implement called - bool IsReusable.

What is the significance of this member? If I set it to false (or

Answer 1

Further to AnthonyWJones's answer, if your HTTP handler returns true for IsReusable then you should ensure that it is fully thread-safe.

There's nothing in the documentation to indicate that reusable handlers can't be reused concurrently, although the current Microsoft implementations only appear to reuse them consecutively. But, at least in theory, a single handler instance could be reused simultaneously by multiple requests, so you shouldn't rely on any data which might be modified by other concurrent threads.