How to set Sentry Config in asp.net core IMiddleware

[anwarjaved]

I want to use same code on multiple domain and want to set different dsn according to domain, so I need to configure sentry dsn for it, is setting SENTRY_DSN and SENTRY_ENVIRONMENT will work for me if I set it in middleware

[mattjohnsonpint]

Hi @anwarjaved, thanks for your question. We don't allow the DSN to be changed while an application is running. It is expected that a single instance of the Sentry SDK will be used, and the same DSN will be used the entire time.

In an ASP.NET Core application, you can set the DSN in your appsettings.json file. Just like any other setting you may have in that file, it can be configured per environment you might deploy to (production, staging, development, etc.), but not per domain.

[mattjohnsonpint]

No, you should not do that.

You should call UseSentry in the host builder. It adds our own middleware, which initializes once for the entire application. This is the only usage we support or recommend for aspnet core.

If you tried to initialize Sentry in your own middleware per request, the overhead would be horrible and you would likely have one request stepping on another.

[anwarjaved]

Can we use SENTRY_DSN environment variable here?

[mattjohnsonpint]

You can use the SENTRY_DSN environment variable, yes. However, it's just another way to pass the DSN to the application and is read once at startup. You can't change it on the fly to switch DSNs. I appreciate the out of the box thinking though.

Just to be perfectly clear - We do not support using multiple DSN in the same process. This was a fundamental design decision, and we believe it is the correct one.

[anwarjaved]

@mattjohnsonpint ok got it
but can we pass custom tags according to the domain? is that possible or we still have limitations there too.

[mattjohnsonpint]

Absolutely - you can set tags any way you like. They are set on the current scope, so they can contain information that's per-request without any issues. Example here:
https://docs.sentry.io/platforms/dotnet/guides/aspnetcore/enriching-events/tags/

Keep in mind that if you're just setting a tag that contains the domain name itself - that may be redundant, since we already send the URL including the host. It's up to you though, perhaps a tag is more meaningful for your situation.

[mattjohnsonpint]

@anwarjaved - Turns out I was wrong about this in my previous replies. We do have a way to support multiple DSNs in the same application. There's an example app that does that here:
https://github.com/getsentry/sentry-dotnet/blob/main/samples/Sentry.Samples.Console.Customized/Program.cs

Basically, you need a separate SentryClient instance per DSN, then you can apply that client to a particular scope using SentrySdk.BindClient.

In your case, you'd have to pre-create and fill a Dictionary<string, ISentryClient> to map the domain name to the client instance, then configure scope during the request (or in a custom middleware) to pick the appropriate client and bind to it on that scope.

I haven't tested this myself, but in theory it should work. Please let us know if you try and how it goes. Thanks!

[mattjohnsonpint]

BTW, I suggest you make your dictionary case-insenstive.

var sentryClients = new Dictionary<string, ISentryClient>(StringComparer.OrdinalIgnoreCase);

[anwarjaved]

@mattjohnsonpint Thank you, Let me try and get back to you if I need further help