AssemblyScanning exclusion list slows down the endpoint startup

[danielmarbach]

Describe the bug

Description

When excluding a larger set of assemblies the assembly scanner scanning algorithm efforts to try to check the assemblies excluded exponentially grows which leads to significantly longer than necessary endpoint creation times.

Expected behavior

While it is expected that the longer the exclusion list is the more time might be required to check the scanned assemblies against the exclusion list it is still surprising to see an exponential growth in exclusion checks.

Actual behavior

Then endpoint creation time is significantly slower than expected.

Versions

All supported versions of NServiceBus

Steps to reproduce

Create an endpoint with a few assemblies to scan and observe relatively fast assembly scanning and thus endpoint creation time.

Add a larger exclusion list with assembly names that do not necessarily match the scanned assemblies and observe how the assembly scanning and thus endpoint creation time get orders of magnitude longer.

var scanner = endpointConfiguration.AssemblyScanner();
scanner.ExcludeAssemblies("MyAssembly1.dll", ...,"MyAssembly70.dll");

Relevant log output

No response

Additional Information

Workarounds

Possible solutions

Additional information

Backported to

• Release 8.1
• Release 8.0
• Release 7.8