how t0 add a trace for service call chain

[mengxiangyue]

What are you trying to achieve?

If I want to add a trace for our service call chain, do you have some suggestions for below example?

I have AProvider/AClient/BProvider/BClient, the call chain is AClient call AProvider methodA, In AProvider methodA I need to create a new BClient and call BProvider methodB. When I use AClient call AProvider I add callOptions like below

var options = greeter.defaultCallOptions
options.requestIDHeader = "x-trace-id"
options.requestIDProvider = .userDefined("mxy-trace-id")

And in AProvider methodA I also can get the x-trace-id, And I also can create a options then pass to BClient for thist trace.

Even I can use this method to archive my goal, but I think it will generate so much same code. what suggestions do you have? thanks.

[glbrntt]

Tracing is in a slightly awkward space at the moment. There is a Swift package for distributed tracing (https://github.com/apple/swift-distributed-tracing) intended to make this easier. However, it does not have a stable API (so we can't adopt it) and it's likely to be impacted by new language features (see also https://github.com/apple/swift-distributed-tracing#important-note-on-adoption).

At the moment I think your best option is doing what you're doing now but with a set of helpers to reduce the toil of extracting and forwarding trace headers.

[mengxiangyue]

@glbrntt thanks your answer patiently, can I think as if the swift-distributed-tracing api is stable, will adapt it?

[glbrntt]

We would like to but it depends somewhat on the API and supported Swift versions. It may be something that happens more naturally as a v2.0 of grpc-swift.