diff options
Diffstat (limited to 'vendor/github.com/opentracing/opentracing-go/propagation.go')
| -rw-r--r-- | vendor/github.com/opentracing/opentracing-go/propagation.go | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/vendor/github.com/opentracing/opentracing-go/propagation.go b/vendor/github.com/opentracing/opentracing-go/propagation.go new file mode 100644 index 000000000..b0c275eb0 --- /dev/null +++ b/vendor/github.com/opentracing/opentracing-go/propagation.go @@ -0,0 +1,176 @@ +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 HTTPHeadersCarrier 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.Context(), opentracing.HTTPHeaders, carrier) + // + // Or Extract(): + // + // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) + // clientContext, 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) +// 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 + +// Set conforms to the TextMapWriter interface. +func (c HTTPHeadersCarrier) Set(key, val string) { + h := http.Header(c) + h.Set(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 +} |