A colleague contacted me with a specific error she got. The strange thing was that the error never appeared during local development but only after deploying the application to our Development environment.
Let's first have a look at the error message:
The error happens during the bootstrapping of the application. For me it was immediately clear what the problem was but if you don’t spot the root cause, no worries. I’ll show you the related code, maybe that helps.
First here is the specific Serilog enricher:
And here is the bootstrapping code:
The problem occurs when we resolve the ILogger singleton instance. When we do this a transient enricher is used that injects a scoped IUserFactory. As there is no scope available at that moment, this leads to the error above.
To fix it, we have to change the lifetime of our IUserFactory to transient:
>Than the question remains:
Why this error doesn’t happen during local development?
The answer is Scope Validation:
When the app runs in the Development environment and calls CreateDefaultBuilder to build the host, the default service provider performs checks to verify that:
- Scoped services aren't resolved from the root service provider.
- Scoped services aren't injected into singletons.
Locally we are using a ‘Local’ environment so these checks are not executed. When deploying to ‘Development’ the environment name is switched and the validation checks does occur.