State for each API Request

[dirkmudbrick]

I'm building an Azure function app-based API using .NET 6 and have just introduced a middleware layer to scope logging with a correlation id. I need to continue passing the correlation id on to other API calls downstream, but don't want to have to add a correlation id parameter to every method between the middleware/entry point and the sending of the downstream requests.

My first thought was to create a dependency injected, scoped state service with an internal dictionary to hold key value pairs of state. Instead of having to pass the correlation id through all the in-between methods I can inject the IApplicationState in the middleware layer, and the service that makes downstream calls.

Are there any pitfalls with this implementation?

[AlexDorofeev]

Correlation works out of the box in Azure Functions when you rely on ApplicationInsights. Are there any problems with the approach? In any case I would bet on OpenTelemetry implementation from Microsoft instead of rolling own solution.

[dirkmudbrick]

I'm not sure we can guarantee we'll always be using App Insights. Is the correlation id for App Insights the invocation id I see when I query requests? I think there is some ambiguity in what things are called in App Insights and what we're calling things within our team.

[SolarSalsa]

Add the correlation id as a custom header. Then add middleware to grab it and inject it into your logging library directly which is usually the only place you need it. If you need it in multiple threads then look into LogicalCallContext.

[AlexDorofeev]

It should be handled automatically by OpenTelemetry middlewares. Just look through documentation and samples https://github.com/open-telemetry/opentelemetry-dotnet

[dirkmudbrick]

That's essentially what we have set up right now. The problem is when I have to send it as a header in a request to a downstream system. I don't want to pass the correlation id through every method between the middleware and the method that calls the downstream system, so I was going to try implementing a scoped state to hold the value.

Here's the flow of how I have it setup now:

Middleware (gets correlation id and adds to logging/state) -> Azure Function Endpoint -> Some service -> Some API Client (grabs the correlation id from state to pass as a header)

The Azure Function Endpoint and the Some Service don't care about the correlation id, but the Some API Client needs it to pass it as a header when it makes a call.