Takahiro Suzuki | d7bf820 | 2020-12-17 20:21:59 +0900 | [diff] [blame] | 1 | package opentracing |
| 2 | |
| 3 | import ( |
| 4 | "errors" |
| 5 | "net/http" |
| 6 | ) |
| 7 | |
| 8 | /////////////////////////////////////////////////////////////////////////////// |
| 9 | // CORE PROPAGATION INTERFACES: |
| 10 | /////////////////////////////////////////////////////////////////////////////// |
| 11 | |
| 12 | var ( |
| 13 | // ErrUnsupportedFormat occurs when the `format` passed to Tracer.Inject() or |
| 14 | // Tracer.Extract() is not recognized by the Tracer implementation. |
| 15 | ErrUnsupportedFormat = errors.New("opentracing: Unknown or unsupported Inject/Extract format") |
| 16 | |
| 17 | // ErrSpanContextNotFound occurs when the `carrier` passed to |
| 18 | // Tracer.Extract() is valid and uncorrupted but has insufficient |
| 19 | // information to extract a SpanContext. |
| 20 | ErrSpanContextNotFound = errors.New("opentracing: SpanContext not found in Extract carrier") |
| 21 | |
| 22 | // ErrInvalidSpanContext errors occur when Tracer.Inject() is asked to |
| 23 | // operate on a SpanContext which it is not prepared to handle (for |
| 24 | // example, since it was created by a different tracer implementation). |
| 25 | ErrInvalidSpanContext = errors.New("opentracing: SpanContext type incompatible with tracer") |
| 26 | |
| 27 | // ErrInvalidCarrier errors occur when Tracer.Inject() or Tracer.Extract() |
| 28 | // implementations expect a different type of `carrier` than they are |
| 29 | // given. |
| 30 | ErrInvalidCarrier = errors.New("opentracing: Invalid Inject/Extract carrier") |
| 31 | |
| 32 | // ErrSpanContextCorrupted occurs when the `carrier` passed to |
| 33 | // Tracer.Extract() is of the expected type but is corrupted. |
| 34 | ErrSpanContextCorrupted = errors.New("opentracing: SpanContext data corrupted in Extract carrier") |
| 35 | ) |
| 36 | |
| 37 | /////////////////////////////////////////////////////////////////////////////// |
| 38 | // BUILTIN PROPAGATION FORMATS: |
| 39 | /////////////////////////////////////////////////////////////////////////////// |
| 40 | |
| 41 | // BuiltinFormat is used to demarcate the values within package `opentracing` |
| 42 | // that are intended for use with the Tracer.Inject() and Tracer.Extract() |
| 43 | // methods. |
| 44 | type BuiltinFormat byte |
| 45 | |
| 46 | const ( |
| 47 | // Binary represents SpanContexts as opaque binary data. |
| 48 | // |
| 49 | // For Tracer.Inject(): the carrier must be an `io.Writer`. |
| 50 | // |
| 51 | // For Tracer.Extract(): the carrier must be an `io.Reader`. |
| 52 | Binary BuiltinFormat = iota |
| 53 | |
| 54 | // TextMap represents SpanContexts as key:value string pairs. |
| 55 | // |
| 56 | // Unlike HTTPHeaders, the TextMap format does not restrict the key or |
| 57 | // value character sets in any way. |
| 58 | // |
| 59 | // For Tracer.Inject(): the carrier must be a `TextMapWriter`. |
| 60 | // |
| 61 | // For Tracer.Extract(): the carrier must be a `TextMapReader`. |
| 62 | TextMap |
| 63 | |
| 64 | // HTTPHeaders represents SpanContexts as HTTP header string pairs. |
| 65 | // |
| 66 | // Unlike TextMap, the HTTPHeaders format requires that the keys and values |
| 67 | // be valid as HTTP headers as-is (i.e., character casing may be unstable |
| 68 | // and special characters are disallowed in keys, values should be |
| 69 | // URL-escaped, etc). |
| 70 | // |
| 71 | // For Tracer.Inject(): the carrier must be a `TextMapWriter`. |
| 72 | // |
| 73 | // For Tracer.Extract(): the carrier must be a `TextMapReader`. |
| 74 | // |
| 75 | // See HTTPHeadersCarrier for an implementation of both TextMapWriter |
| 76 | // and TextMapReader that defers to an http.Header instance for storage. |
| 77 | // For example, Inject(): |
| 78 | // |
| 79 | // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) |
| 80 | // err := span.Tracer().Inject( |
| 81 | // span.Context(), opentracing.HTTPHeaders, carrier) |
| 82 | // |
| 83 | // Or Extract(): |
| 84 | // |
| 85 | // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) |
| 86 | // clientContext, err := tracer.Extract( |
| 87 | // opentracing.HTTPHeaders, carrier) |
| 88 | // |
| 89 | HTTPHeaders |
| 90 | ) |
| 91 | |
| 92 | // TextMapWriter is the Inject() carrier for the TextMap builtin format. With |
| 93 | // it, the caller can encode a SpanContext for propagation as entries in a map |
| 94 | // of unicode strings. |
| 95 | type TextMapWriter interface { |
| 96 | // Set a key:value pair to the carrier. Multiple calls to Set() for the |
| 97 | // same key leads to undefined behavior. |
| 98 | // |
| 99 | // NOTE: The backing store for the TextMapWriter may contain data unrelated |
| 100 | // to SpanContext. As such, Inject() and Extract() implementations that |
| 101 | // call the TextMapWriter and TextMapReader interfaces must agree on a |
| 102 | // prefix or other convention to distinguish their own key:value pairs. |
| 103 | Set(key, val string) |
| 104 | } |
| 105 | |
| 106 | // TextMapReader is the Extract() carrier for the TextMap builtin format. With it, |
| 107 | // the caller can decode a propagated SpanContext as entries in a map of |
| 108 | // unicode strings. |
| 109 | type TextMapReader interface { |
| 110 | // ForeachKey returns TextMap contents via repeated calls to the `handler` |
| 111 | // function. If any call to `handler` returns a non-nil error, ForeachKey |
| 112 | // terminates and returns that error. |
| 113 | // |
| 114 | // NOTE: The backing store for the TextMapReader may contain data unrelated |
| 115 | // to SpanContext. As such, Inject() and Extract() implementations that |
| 116 | // call the TextMapWriter and TextMapReader interfaces must agree on a |
| 117 | // prefix or other convention to distinguish their own key:value pairs. |
| 118 | // |
| 119 | // The "foreach" callback pattern reduces unnecessary copying in some cases |
| 120 | // and also allows implementations to hold locks while the map is read. |
| 121 | ForeachKey(handler func(key, val string) error) error |
| 122 | } |
| 123 | |
| 124 | // TextMapCarrier allows the use of regular map[string]string |
| 125 | // as both TextMapWriter and TextMapReader. |
| 126 | type TextMapCarrier map[string]string |
| 127 | |
| 128 | // ForeachKey conforms to the TextMapReader interface. |
| 129 | func (c TextMapCarrier) ForeachKey(handler func(key, val string) error) error { |
| 130 | for k, v := range c { |
| 131 | if err := handler(k, v); err != nil { |
| 132 | return err |
| 133 | } |
| 134 | } |
| 135 | return nil |
| 136 | } |
| 137 | |
| 138 | // Set implements Set() of opentracing.TextMapWriter |
| 139 | func (c TextMapCarrier) Set(key, val string) { |
| 140 | c[key] = val |
| 141 | } |
| 142 | |
| 143 | // HTTPHeadersCarrier satisfies both TextMapWriter and TextMapReader. |
| 144 | // |
| 145 | // Example usage for server side: |
| 146 | // |
| 147 | // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) |
| 148 | // clientContext, err := tracer.Extract(opentracing.HTTPHeaders, carrier) |
| 149 | // |
| 150 | // Example usage for client side: |
| 151 | // |
| 152 | // carrier := opentracing.HTTPHeadersCarrier(httpReq.Header) |
| 153 | // err := tracer.Inject( |
| 154 | // span.Context(), |
| 155 | // opentracing.HTTPHeaders, |
| 156 | // carrier) |
| 157 | // |
| 158 | type HTTPHeadersCarrier http.Header |
| 159 | |
| 160 | // Set conforms to the TextMapWriter interface. |
| 161 | func (c HTTPHeadersCarrier) Set(key, val string) { |
| 162 | h := http.Header(c) |
| 163 | h.Set(key, val) |
| 164 | } |
| 165 | |
| 166 | // ForeachKey conforms to the TextMapReader interface. |
| 167 | func (c HTTPHeadersCarrier) ForeachKey(handler func(key, val string) error) error { |
| 168 | for k, vals := range c { |
| 169 | for _, v := range vals { |
| 170 | if err := handler(k, v); err != nil { |
| 171 | return err |
| 172 | } |
| 173 | } |
| 174 | } |
| 175 | return nil |
| 176 | } |