Decouple github.com/Comcast/webpa-common/tracing

[schmidtw]

wrpendpoint/requestResponse.go
wrpendpoint/requestResponse_test.go
wrphttp/mocks_test.go

The wrp-go package shouldn't depend on the tracing solution from webpa-common.

[denopink]

@johnabass would we replace this dependence with candlelight?

[denopink]

looks like we're leverage the following from webpa-common/tracing

wrp-go/wrpendpoint/requestResponse.go

Lines 193 to 217 in 5acbd90

	type Response interface {
	Note
	tracing.Mergeable
	}
	// response is the internal Response implementation
	type response struct {
	note
	spans []tracing.Span
	}
	func (r *response) Spans() []tracing.Span {
	return r.spans
	}
	func (r *response) WithSpans(spans ...tracing.Span) interface{} {
	if len(spans) > 0 {
	return &response{
	note: r.note,
	spans: spans,
	}
	}
	return r
	}

wrp-go/wrpendpoint/requestResponse_test.go

Lines 307 to 313 in 3719b16

	func testResponseSpans(t *testing.T, message wrp.Message) {
	var (
	require = require.New(t)
	assert = assert.New(t)
	spanner = tracing.NewSpanner()
	original = WrapAsResponse(&message)
	)

// NewSpanner constructs a new Spanner with the given options.  By default, a Spanner
// will use time.Now() to get the current time and time.Since() to compute durations.
func NewSpanner(o ...SpannerOption) Spanner {
	sp := &spanner{
		now:   time.Now,
		since: time.Since,
	}

	for _, option := range o {
		option(sp)
	}

	return sp
}

// Mergeable represents a Spanned which can be merged with other spans
type Mergeable interface {
	Spanned

	// WithSpans returns an instance of this object with the new Spans, possibly
	// merged into those returned by Spans.  This method should generally return
	// a shallow copy of itself with the new spans, to preserve immutability.
	WithSpans(...Span) interface{}
}

// Span represents the result of some arbitrary section of code.  Clients create Span objects
// via a Spanner.  A Span is immutable once it has been created via a Spanner closure.
type Span interface {
	// Name is the name of the operation
	Name() string

	// Start is the time at which the operation started
	Start() time.Time

	// Duration is how long the operation took.  This value is computed once, when the
	// closure from Spanner.Start is called.
	Duration() time.Duration

	// Error is any error that occurred.  This will be the error passed to the closure
	// returned from Spanner.Start.  This error can be nil.
	Error() error
}

[denopink]

assigning @renaz6 so she can let us know when candlelight is at a better state