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package opentracing
import (
"errors"
"net/http"
)
///////////////////////////////////////////////////////////////////////////////
// CORE PROPAGATION INTERFACES:
///////////////////////////////////////////////////////////////////////////////
var (
// ErrUnsupportedFormat occurs when the `format` passed to Tracer.Inject() or
// Tracer.Extract() is not recognized by the Tracer implementation.
ErrUnsupportedFormat = errors.New("opentracing: Unknown or unsupported Inject/Extract format")
// ErrSpanContextNotFound occurs when the `carrier` passed to
// Tracer.Extract() is valid and uncorrupted but has insufficient
// information to extract a SpanContext.
ErrSpanContextNotFound = errors.New("opentracing: SpanContext not found in Extract carrier")
// ErrInvalidSpanContext errors occur when Tracer.Inject() is asked to
// operate on a SpanContext which it is not prepared to handle (for
// example, since it was created by a different tracer implementation).
ErrInvalidSpanContext = errors.New("opentracing: SpanContext type incompatible with tracer")
// ErrInvalidCarrier errors occur when Tracer.Inject() or Tracer.Extract()
// implementations expect a different type of `carrier` than they are
// given.
ErrInvalidCarrier = errors.New("opentracing: Invalid Inject/Extract carrier")
// ErrSpanContextCorrupted occurs when the `carrier` passed to
// Tracer.Extract() is of the expected type but is corrupted.
ErrSpanContextCorrupted = errors.New("opentracing: SpanContext data corrupted in Extract carrier")
)
///////////////////////////////////////////////////////////////////////////////
// BUILTIN PROPAGATION FORMATS:
///////////////////////////////////////////////////////////////////////////////
// BuiltinFormat is used to demarcate the values within package `opentracing`
// that are intended for use with the Tracer.Inject() and Tracer.Extract()
// methods.
type BuiltinFormat byte
const (
// Binary represents SpanContexts as opaque binary data.
//
// For Tracer.Inject(): the carrier must be an `io.Writer`.
//
// For Tracer.Extract(): the carrier must be an `io.Reader`.
Binary BuiltinFormat = iota
// TextMap represents SpanContexts as key:value string pairs.
//
// Unlike HTTPHeaders, the TextMap format does not restrict the key or
// value character sets in any way.
//
// For Tracer.Inject(): the carrier must be a `TextMapWriter`.
//
// For Tracer.Extract(): the carrier must be a `TextMapReader`.
TextMap
// HTTPHeaders represents SpanContexts as HTTP header string pairs.
//
// Unlike TextMap, the HTTPHeaders format requires that the keys and values
// be valid as HTTP headers as-is (i.e., character casing may be unstable
// and special characters are disallowed in keys, values should be
// URL-escaped, etc).
//
// For Tracer.Inject(): the carrier must be a `TextMapWriter`.
//
// For Tracer.Extract(): the carrier must be a `TextMapReader`.
//
// See HTTPHeaderCarrier for an implementation of both TextMapWriter
// and TextMapReader that defers to an http.Header instance for storage.
// For example, Inject():
//
// carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
// err := span.Tracer().Inject(
// span, opentracing.HTTPHeaders, carrier)
//
// Or Extract():
//
// carrier := opentracing.HTTPHeadersCarrier(httpReq.Header)
// span, err := tracer.Extract(
// opentracing.HTTPHeaders, carrier)
//
HTTPHeaders
)
// 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
}
// TextMapCarrier allows the use of regular map[string]string
// as both TextMapWriter and TextMapReader.
type TextMapCarrier map[string]string
// ForeachKey conforms to the TextMapReader interface.
func (c TextMapCarrier) ForeachKey(handler func(key, val string) error) error {
for k, v := range c {
if err := handler(k, v); err != nil {
return err
}
}
return nil
}
// Set implements Set() of opentracing.TextMapWriter
func (c TextMapCarrier) Set(key, val string) {
c[key] = val
}
// HTTPHeadersCarrier satisfies both TextMapWriter and TextMapReader.
//
// Example usage for server side:
//
// carrier := opentracing.HttpHeadersCarrier(httpReq.Header)
// spanContext, 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
// Set conforms to the TextMapWriter interface.
func (c HTTPHeadersCarrier) Set(key, val string) {
h := http.Header(c)
h.Add(key, val)
}
// ForeachKey conforms to the TextMapReader interface.
func (c HTTPHeadersCarrier) ForeachKey(handler func(key, val string) error) error {
for k, vals := range c {
for _, v := range vals {
if err := handler(k, v); err != nil {
return err
}
}
}
return nil
}