// New returns an AddService backed by an HTTP server living at the remote
// instance. We expect instance to come from a service discovery system, so
// likely of the form "host:port".
func New(instance string, tracer stdopentracing.Tracer, logger log.Logger) (addsvc.Service, error) {
if !strings.HasPrefix(instance, "http") {
instance = "http://" + instance
}
u, err := url.Parse(instance)
if err != nil {
return nil, err
}
// We construct a single ratelimiter middleware, to limit the total outgoing
// QPS from this client to all methods on the remote instance. We also
// construct per-endpoint circuitbreaker middlewares to demonstrate how
// that's done, although they could easily be combined into a single breaker
// for the entire remote instance, too.
limiter := ratelimit.NewTokenBucketLimiter(jujuratelimit.NewBucketWithRate(100, 100))
var sumEndpoint endpoint.Endpoint
{
sumEndpoint = httptransport.NewClient(
"POST",
copyURL(u, "/sum"),
addsvc.EncodeHTTPGenericRequest,
addsvc.DecodeHTTPSumResponse,
httptransport.ClientBefore(opentracing.ToHTTPRequest(tracer, logger)),
).Endpoint()
sumEndpoint = opentracing.TraceClient(tracer, "Sum")(sumEndpoint)
sumEndpoint = limiter(sumEndpoint)
sumEndpoint = circuitbreaker.Gobreaker(gobreaker.NewCircuitBreaker(gobreaker.Settings{
Name: "Sum",
Timeout: 30 * time.Second,
}))(sumEndpoint)
}
var concatEndpoint endpoint.Endpoint
{
concatEndpoint = httptransport.NewClient(
"POST",
copyURL(u, "/concat"),
addsvc.EncodeHTTPGenericRequest,
addsvc.DecodeHTTPConcatResponse,
httptransport.ClientBefore(opentracing.ToHTTPRequest(tracer, logger)),
).Endpoint()
concatEndpoint = opentracing.TraceClient(tracer, "Concat")(concatEndpoint)
concatEndpoint = limiter(concatEndpoint)
sumEndpoint = circuitbreaker.Gobreaker(gobreaker.NewCircuitBreaker(gobreaker.Settings{
Name: "Concat",
Timeout: 30 * time.Second,
}))(sumEndpoint)
}
return addsvc.Endpoints{
SumEndpoint: sumEndpoint,
ConcatEndpoint: concatEndpoint,
}, nil
}
func TestTraceHTTPRequestRoundtrip(t *testing.T) {
logger := log.NewNopLogger()
tracer := mocktracer.New()
// Initialize the ctx with a Span to inject.
beforeSpan := tracer.StartSpan("to_inject").(*mocktracer.MockSpan)
defer beforeSpan.Finish()
beforeSpan.SetBaggageItem("baggage", "check")
beforeCtx := opentracing.ContextWithSpan(context.Background(), beforeSpan)
toHTTPFunc := kitot.ToHTTPRequest(tracer, logger)
req, _ := http.NewRequest("GET", "http://test.biz/url", nil)
// Call the RequestFunc.
afterCtx := toHTTPFunc(beforeCtx, req)
// The Span should not have changed.
afterSpan := opentracing.SpanFromContext(afterCtx)
if beforeSpan != afterSpan {
t.Errorf("Should not swap in a new span")
}
// No spans should have finished yet.
finishedSpans := tracer.FinishedSpans()
if want, have := 0, len(finishedSpans); want != have {
t.Errorf("Want %v span(s), found %v", want, have)
}
// Use FromHTTPRequest to verify that we can join with the trace given a req.
fromHTTPFunc := kitot.FromHTTPRequest(tracer, "joined", logger)
joinCtx := fromHTTPFunc(afterCtx, req)
joinedSpan := opentracing.SpanFromContext(joinCtx).(*mocktracer.MockSpan)
joinedContext := joinedSpan.Context().(mocktracer.MockSpanContext)
beforeContext := beforeSpan.Context().(mocktracer.MockSpanContext)
if joinedContext.SpanID == beforeContext.SpanID {
t.Error("SpanID should have changed", joinedContext.SpanID, beforeContext.SpanID)
}
// Check that the parent/child relationship is as expected for the joined span.
if want, have := beforeContext.SpanID, joinedSpan.ParentID; want != have {
t.Errorf("Want ParentID %q, have %q", want, have)
}
if want, have := "joined", joinedSpan.OperationName; want != have {
t.Errorf("Want %q, have %q", want, have)
}
if want, have := "check", joinedSpan.BaggageItem("baggage"); want != have {
t.Errorf("Want %q, have %q", want, have)
}
}
// MakeConcatEndpointFactory generates a Factory that transforms an http url
// into an Endpoint.
//
// The path of the url is reset to /concat.
func MakeConcatEndpointFactory(tracer opentracing.Tracer, tracingLogger log.Logger) loadbalancer.Factory {
return func(instance string) (endpoint.Endpoint, io.Closer, error) {
concatURL, err := url.Parse(instance)
if err != nil {
return nil, nil, err
}
concatURL.Path = "/concat"
client := httptransport.NewClient(
"GET",
concatURL,
server.EncodeConcatRequest,
server.DecodeConcatResponse,
httptransport.SetClient(nil),
httptransport.SetClientBefore(kitot.ToHTTPRequest(tracer, tracingLogger)),
)
return client.Endpoint(), nil, nil
}
}
