// TextMapCarrier allows the use of regular map[string]string
// as both TextMapWriter and TextMapReader.
type TextMapCarrier map[string]string
// HTTPHeadersCarrier satisfies both TextMapWriter and TextMapReader.
//
// Example usage for server side:
//
// carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
// clientContext, err := tracer.Extract(opentracing.HTTPHeaders, carrier)
//
// Example usage for client side:
//
// carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
// err := tracer.Inject(
// span.Context(),
// opentracing.HTTPHeaders,
// carrier)
//
type HTTPHeadersCarrier http.Header
// TextMapWriter is the Inject() carrier for the TextMap builtin format. With
// it, the caller can encode a SpanContext for propagation as entries in a map
// of unicode strings.
type TextMapWriter interface {
// Set a key:value pair to the carrier. Multiple calls to Set() for the
// same key leads to undefined behavior.
//
// NOTE: The backing store for the TextMapWriter may contain data unrelated
// to SpanContext. As such, Inject() and Extract() implementations that
// call the TextMapWriter and TextMapReader interfaces must agree on a
// prefix or other convention to distinguish their own key:value pairs.
Set(key, val string)
}
// TextMapReader is the Extract() carrier for the TextMap builtin format. With it,
// the caller can decode a propagated SpanContext as entries in a map of
// unicode strings.
type TextMapReader interface {
// ForeachKey returns TextMap contents via repeated calls to the `handler`
// function. If any call to `handler` returns a non-nil error, ForeachKey
// terminates and returns that error.
//
// NOTE: The backing store for the TextMapReader may contain data unrelated
// to SpanContext. As such, Inject() and Extract() implementations that
// call the TextMapWriter and TextMapReader interfaces must agree on a
// prefix or other convention to distinguish their own key:value pairs.
//
// The "foreach" callback pattern reduces unnecessary copying in some cases
// and also allows implementations to hold locks while the map is read.
ForeachKey(handler func(key, val string) error) error
}
我们接下来来实现一下两个接口，采用一个自定义的carrier。
// MDCarrier custome carrier
type MDCarrier struct {
metadata.MD
}
// ForeachKey conforms to the TextMapReader interface.
// 这里必须要实现这个 TextMapReader 这个接口
// TextMapReader is the Extract() carrier for the TextMap builtin format. With it,
// the caller can decode a propagated SpanContext as entries in a map of
// unicode strings.
//type TextMapReader interface {
// // ForeachKey returns TextMap contents via repeated calls to the `handler`
// // function. If any call to `handler` returns a non-nil error, ForeachKey
// // terminates and returns that error.
// //
// // NOTE: The backing store for the TextMapReader may contain data unrelated
// // to SpanContext. As such, Inject() and Extract() implementations that
// // call the TextMapWriter and TextMapReader interfaces must agree on a
// // prefix or other convention to distinguish their own key:value pairs.
// //
// // The "foreach" callback pattern reduces unnecessary copying in some cases
// // and also allows implementations to hold locks while the map is read.
// ForeachKey(handler func(key, val string) error) error
//}
func (m MDCarrier) ForeachKey(handler func(key, val string) error) error {
for k, strs := range m.MD {
for _, v := range strs {
if err := handler(k, v); err != nil {
return err
}
}
}
return nil
}
// Set implements Set() of opentracing.TextMapWriter
// 这里也必须要实现
// TextMapWriter is the Inject() carrier for the TextMap builtin format. With
// it, the caller can encode a SpanContext for propagation as entries in a map
// of unicode strings.
//type TextMapWriter interface {
// // Set a key:value pair to the carrier. Multiple calls to Set() for the
// // same key leads to undefined behavior.
// //
// // NOTE: The backing store for the TextMapWriter may contain data unrelated
// // to SpanContext. As such, Inject() and Extract() implementations that
// // call the TextMapWriter and TextMapReader interfaces must agree on a
// // prefix or other convention to distinguish their own key:value pairs.
// Set(key, val string)
//}
func (m MDCarrier) Set(key, val string) {
m.MD[key] = append(m.MD[key], val)
}
创建 GlobalTracer
// NewJaegerTracer NewJaegerTracer for current service
func NewJaegerTracer(serviceName string, jagentHost string) (tracer opentracing.Tracer, closer io.Closer, err error) {
cfg := jaegercfg.Configuration{
ServiceName: serviceName,
Sampler: &jaegercfg.SamplerConfig{
Type: jaeger.SamplerTypeConst,
Param: 1,
},
Reporter: &jaegercfg.ReporterConfig{
LogSpans: true,
BufferFlushInterval: 1 * time.Second,
LocalAgentHostPort: jagentHost,
},
}
// Example logger and metrics factory. Use github.com/uber/jaeger-client-go/log
// and github.com/uber/jaeger-lib/metrics respectively to bind to real logging and metrics
// frameworks.
jLogger := jaegerlog.StdLogger
jMetricsFactory := metrics.NullFactory
// Initialize tracer with a logger and a metrics factory
tracer, closer, err = cfg.NewTracer(
jaegercfg.Logger(jLogger),
jaegercfg.Metrics(jMetricsFactory))
opentracing.SetGlobalTracer(tracer)
if err != nil {
grpclog.Errorf("Could not initialize jaeger tracer: %s", err.Error())
return
}
return
}
