http.go

Documentation: github.com/go-kit/kit/tracing/opentracing

     1  package opentracing
     2  
     3  import (
     4  	"context"
     5  	"net"
     6  	"net/http"
     7  	"strconv"
     8  
     9  	opentracing "github.com/opentracing/opentracing-go"
    10  	"github.com/opentracing/opentracing-go/ext"
    11  
    12  	kithttp "github.com/go-kit/kit/transport/http"
    13  	"github.com/go-kit/log"
    14  )
    15  
    16  // ContextToHTTP returns an http RequestFunc that injects an OpenTracing Span
    17  // found in `ctx` into the http headers. If no such Span can be found, the
    18  // RequestFunc is a noop.
    19  func ContextToHTTP(tracer opentracing.Tracer, logger log.Logger) kithttp.RequestFunc {
    20  	return func(ctx context.Context, req *http.Request) context.Context {
    21  		// Try to find a Span in the Context.
    22  		if span := opentracing.SpanFromContext(ctx); span != nil {
    23  			// Add standard OpenTracing tags.
    24  			ext.HTTPMethod.Set(span, req.Method)
    25  			ext.HTTPUrl.Set(span, req.URL.String())
    26  			host, portString, err := net.SplitHostPort(req.URL.Host)
    27  			if err == nil {
    28  				ext.PeerHostname.Set(span, host)
    29  				if port, err := strconv.Atoi(portString); err == nil {
    30  					ext.PeerPort.Set(span, uint16(port))
    31  				}
    32  			} else {
    33  				ext.PeerHostname.Set(span, req.URL.Host)
    34  			}
    35  
    36  			// There's nothing we can do with any errors here.
    37  			if err = tracer.Inject(
    38  				span.Context(),
    39  				opentracing.HTTPHeaders,
    40  				opentracing.HTTPHeadersCarrier(req.Header),
    41  			); err != nil {
    42  				logger.Log("err", err)
    43  			}
    44  		}
    45  		return ctx
    46  	}
    47  }
    48  
    49  // HTTPToContext returns an http RequestFunc that tries to join with an
    50  // OpenTracing trace found in `req` and starts a new Span called
    51  // `operationName` accordingly. If no trace could be found in `req`, the Span
    52  // will be a trace root. The Span is incorporated in the returned Context and
    53  // can be retrieved with opentracing.SpanFromContext(ctx).
    54  func HTTPToContext(tracer opentracing.Tracer, operationName string, logger log.Logger) kithttp.RequestFunc {
    55  	return func(ctx context.Context, req *http.Request) context.Context {
    56  		// Try to join to a trace propagated in `req`.
    57  		var span opentracing.Span
    58  		wireContext, err := tracer.Extract(
    59  			opentracing.HTTPHeaders,
    60  			opentracing.HTTPHeadersCarrier(req.Header),
    61  		)
    62  		if err != nil && err != opentracing.ErrSpanContextNotFound {
    63  			logger.Log("err", err)
    64  		}
    65  
    66  		span = tracer.StartSpan(operationName, ext.RPCServerOption(wireContext))
    67  		ext.HTTPMethod.Set(span, req.Method)
    68  		ext.HTTPUrl.Set(span, req.URL.String())
    69  		return opentracing.ContextWithSpan(ctx, span)
    70  	}
    71  }
    72
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