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Add a span name getter to opencensus endpoint options (#948)
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* Add a span name getter to opencensus endpoint options

* Add GetSpanDetails option

* Split GetSpanDetails function

* Simplify getting the name

* Improve documentation

* Simplify attributes

* Update documentation

* Update tracing/opencensus/endpoint_options.go

Co-authored-by: Peter Bourgon <[email protected]>
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sagikazarmark and peterbourgon authored Feb 17, 2020
1 parent 4f34beb commit cc938d5
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Showing 3 changed files with 69 additions and 3 deletions.
12 changes: 12 additions & 0 deletions tracing/opencensus/endpoint.go
Original file line number Diff line number Diff line change
Expand Up @@ -31,12 +31,24 @@ func TraceEndpoint(name string, options ...EndpointOption) endpoint.Middleware {

return func(next endpoint.Endpoint) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (response interface{}, err error) {
if cfg.GetName != nil {
if newName := cfg.GetName(ctx, name); newName != "" {
name = newName
}
}

ctx, span := trace.StartSpan(ctx, name)
if len(cfg.Attributes) > 0 {
span.AddAttributes(cfg.Attributes...)
}
defer span.End()

if cfg.GetAttributes != nil {
if attrs := cfg.GetAttributes(ctx); len(attrs) > 0 {
span.AddAttributes(attrs...)
}
}

defer func() {
if err != nil {
if lberr, ok := err.(lb.RetryError); ok {
Expand Down
30 changes: 29 additions & 1 deletion tracing/opencensus/endpoint_options.go
Original file line number Diff line number Diff line change
@@ -1,6 +1,10 @@
package opencensus

import "go.opencensus.io/trace"
import (
"context"

"go.opencensus.io/trace"
)

// EndpointOptions holds the options for tracing an endpoint
type EndpointOptions struct {
Expand All @@ -11,6 +15,16 @@ type EndpointOptions struct {
// Attributes holds the default attributes which will be set on span
// creation by our Endpoint middleware.
Attributes []trace.Attribute

// GetName is an optional function that can set the span name based on the existing name
// for the endpoint and information in the context.
//
// If the function is nil, or the returned name is empty, the existing name for the endpoint is used.
GetName func(ctx context.Context, name string) string

// GetAttributes is an optional function that can extract trace attributes
// from the context and add them to the span.
GetAttributes func(ctx context.Context) []trace.Attribute
}

// EndpointOption allows for functional options to our OpenCensus endpoint
Expand Down Expand Up @@ -40,3 +54,17 @@ func WithIgnoreBusinessError(val bool) EndpointOption {
o.IgnoreBusinessError = val
}
}

// WithSpanName extracts additional attributes from the request context.
func WithSpanName(fn func(ctx context.Context, name string) string) EndpointOption {
return func(o *EndpointOptions) {
o.GetName = fn
}
}

// WithSpanAttributes extracts additional attributes from the request context.
func WithSpanAttributes(fn func(ctx context.Context) []trace.Attribute) EndpointOption {
return func(o *EndpointOptions) {
o.GetAttributes = fn
}
}
30 changes: 28 additions & 2 deletions tracing/opencensus/endpoint_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ const (
span3 = "SPAN-3"
span4 = "SPAN-4"
span5 = "SPAN-5"
span6 = "SPAN-6"
)

var (
Expand Down Expand Up @@ -76,13 +77,29 @@ func TestTraceEndpoint(t *testing.T) {
mw = opencensus.TraceEndpoint(span4)
mw(passEndpoint)(ctx, failedResponse{err: err3})

// span4
// span5
mw = opencensus.TraceEndpoint(span5, opencensus.WithIgnoreBusinessError(true))
mw(passEndpoint)(ctx, failedResponse{err: err4})

// span6
span6Attrs := []trace.Attribute{
trace.StringAttribute("string", "value"),
trace.Int64Attribute("int64", 42),
}
mw = opencensus.TraceEndpoint(
"",
opencensus.WithSpanName(func(ctx context.Context, name string) string {
return span6
}),
opencensus.WithSpanAttributes(func(ctx context.Context) []trace.Attribute {
return span6Attrs
}),
)
mw(endpoint.Nop)(ctx, nil)

// check span count
spans := e.Flush()
if want, have := 5, len(spans); want != have {
if want, have := 6, len(spans); want != have {
t.Fatalf("incorrected number of spans, wanted %d, got %d", want, have)
}

Expand Down Expand Up @@ -156,4 +173,13 @@ func TestTraceEndpoint(t *testing.T) {
t.Fatalf("incorrect attribute count, wanted %d, got %d", want, have)
}

// test span 6
span = spans[5]
if want, have := span6, span.Name; want != have {
t.Errorf("incorrect span name, wanted %q, got %q", want, have)
}

if want, have := 2, len(span.Attributes); want != have {
t.Fatalf("incorrect attribute count, wanted %d, got %d", want, have)
}
}

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