Labstack Echo v4: Allow ignoring trace using the response

[rafaeljusto]

Package Name

contrib/labstack/echo.v4

Package Version(s)

1.72.2

Describe the feature you'd like

Add the WithIgnoreResponse option in the Labstack Echo v4 middleware:

// IgnoreResponseFunc determines if tracing will be skipped for a response.
type IgnoreResponseFunc func(c echo.Context) bool

// WithIgnoreResponse sets a function which determines if tracing will be
// skipped for a given response.
func WithIgnoreResponse(ignoreResponseFunc IgnoreResponseFunc) Option {
	return func(cfg *config) {
		cfg.ignoreResponseFunc = ignoreResponseFunc
	}
}

Is your feature request related to a problem?

Yes, I need to ignore traces when a specific endpoint responds with a Service Unavailable (503) status.

Describe alternatives you've considered

The existing WithIgnoreRequest won't contain the response status code since it's checked before the underlying controller is executed. The other useful ones, such as WithStatusCheck and WithErrorCheck, don't have the Echo context to identify the request path and the response status code.

Additional context

No response

[rafaeljusto]

type IgnoreResponseFunc func(c echo.Context) bool

This is the same as IgnoreRequestFunc. I added a new type because we can't rename the existing one for backwards compatibility. I'm ok with also renaming this to IgnoreFunc, and removing the IgnoreRequestFunc on a future v2 release.

[rafaeljusto]

For those looking for a solution, I ended up following @mtoffl01 suggestion and using tracer.WithSamplingRules:

#3363 (comment)

tracer.Start(
  tracer.WithSamplingRules([]tracer.SamplingRule{
    {
      Tags: map[string]*regexp.Regexp{
        ext.HTTPCode: re503,
      },
      Rate: 0.0,
    },
  }),
)