This document contains answers to questions frequently asked by users. Just because something is listed here doesn't mean it's beyond question, so feel free to open an issue if you want to change or improve any of these things, but this should provide useful information about how things are and why they are that way.
This repository currently takes an idiosyncratic approach to using Go modules. You may notice that the go.mod file does not list all dependencies of the project, but instead just lists the ones that the core logic depends on (ddtrace/..., profiler/... and a couple other packages).
As a user of the dd-trace-go module, this should be transparent and, if anything, make life easier for you. For those wanting to contribute, this can be confusing and annoying.
The primary reason that we do this is for compatibility. dd-trace-go contains many contrib packages for many many libraries, all of which are optional features. If we included all of the dd-trace-go dependencies in the go.mod file, users' projects would transitively include dependencies for multiple web frameworks, grpc, sql libraries, redis, and lots of other stuff. That's bothersome enough, but worse is that users may end up having versions of libraries forcibly updated, even when they're not using integrations for those libraries. If a user wanted to include dd-trace-go to trace their web router but was using an old version of go-redis or somesuch, they would be forced to update, even if they don't want to trace go-redis and dd-trace-go doesn't actually need it. The more integrations we include in dd-trace-go, the more likely this situation becomes when we add all dependencies into the go.mod file.
Another reason is that we can't. Due to some of the projects we integrate with breaking semantic versioning, it's not possible for us to include all the required dependencies and versions, since we need to depend on multiple, incompatible minor versions of some packages, namely google.golang.org/grpc (See: grpc/grpc-go#3726)
The way forward is through submodules, allowing us to have multiple dependency sets inside dd-trace-go and only including what's actually necessary in a user's application. Unfortunately, a prerequisite for this is to get away from gopkg.in, which does not support submodules.
Note also that the Contribution Guidelines contain information on working with this setup.
Integrations that are considered clients (http clients, grpc clients, sql clients) do not use the globally-configured service name. This is by design and is a product-level decision that spans across all the languages' tracers. This is likely to segregate the time spent actually doing the work of the service from the time waiting for another service (i.e. waiting on a web server to return a response).
While there are good arguments to be made that client integrations should take the same service name as everything else in the service, that's not how the library is intended to function today. As a work-around, most integrations have a WithServiceName Option that will allow you to override the default. If the integration you are using cannot be configured the way you want, please open an issue to discuss adding as option.
This is primarily for 2 reasons:
- Cost - often a traced client will speak to a traced server. If both are measured, there is duplication of measurement here, and duplication of cost for no benefit. By measuring only the server, we get analytics without duplication.
- Name conflicts - Today, metrics are calculated based on a key of the span's service name and operation name. This can cause clashes when a client and server both use the same operation name.
For example, net/http server tracing:
span, ctx := tracer.StartSpanFromContext(cfg.Request.Context(), "http.request", opts...)
and net/http client tracing:
span, ctx := tracer.StartSpanFromContext(req.Context(), "http.request", opts...)
This is something that users ask for from time to time, and there is work internally to resolve this. Please follow #1006 to track the progress.