add initial version of W3C tracestate #887
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| // Copyright 2018, OpenCensus Authors | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
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| package trace | ||
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| import ( | ||
| "fmt" | ||
| "regexp" | ||
| ) | ||
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| const ( | ||
| keyWithoutVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,255}` | ||
| keyWithVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}` | ||
| keyFormat = `(` + keyWithoutVendorFormat + `)|(` + keyWithVendorFormat + `)` | ||
| valueFormat = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]` | ||
| ) | ||
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| var keyValidationRegExp = regexp.MustCompile(`^(` + keyFormat + `)$`) | ||
| var valueValidationRegExp = regexp.MustCompile(`^(` + valueFormat + `)$`) | ||
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| type TracestateEntry struct { | ||
| key string | ||
| value string | ||
| } | ||
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| func (ts *TracestateEntry) IsValid() bool { | ||
| return keyValidationRegExp.MatchString(ts.key) && | ||
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There was a problem hiding this comment. Is an empty key valid? Is an empty value? It seems from the pattern that it is. Should it be? Ideally we would have a test for this. |
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| valueValidationRegExp.MatchString(ts.value) | ||
| } | ||
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| // Tracestate is a tracing-system specific context in a list of key-value pairs. | ||
| // Tracestate allows different vendors propagate additional information and | ||
| // inter-operate with their legacy Id formats. | ||
| type Tracestate struct { | ||
| entries []TracestateEntry | ||
| } | ||
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| func (ts *Tracestate) IsValid() bool { | ||
| if len(ts.entries) == 0 || len(ts.entries) > 32 { | ||
| return false | ||
| } | ||
| for _, entry := range ts.entries { | ||
| if !entry.IsValid() { | ||
| return false | ||
| } | ||
| } | ||
| return true | ||
| } | ||
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| func (ts *Tracestate) Fork() *Tracestate { | ||
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There was a problem hiding this comment. I think we should remove this method as well. It only makes sense if Tracestate is mutable. |
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| retval := Tracestate{entries: ts.entries} | ||
| return &retval | ||
| } | ||
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| func (ts *Tracestate) Get(key string) string { | ||
| for _, entry := range ts.entries { | ||
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There was a problem hiding this comment. To make the zero value of There was a problem hiding this comment. Should this method distinguish between an empty string value and the absence of a key? If so, perhaps it should return There was a problem hiding this comment. Empty string means the key doesn't exist, as the W3C spec wouldn't allow empty string as the value. |
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| if entry.key == key { | ||
| return entry.value | ||
| } | ||
| } | ||
| return "" | ||
| } | ||
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| /* | ||
| TODO: we're making Tracestate immutable for now, ramonza and reyang to figure | ||
| out how to change it. | ||
| https://github.com/census-instrumentation/opencensus-go/pull/887 | ||
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| func (ts *Tracestate) Remove(key string) string { | ||
| return ts.Set(key, "") | ||
| } | ||
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| func (ts *Tracestate) Set(key string, value string) string { | ||
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There was a problem hiding this comment. I don't think we should make any part of SpanContext mutable. Can we make Tracestate immutable for now? I think we can figure out how to make it possible to change the Tracestate in a subsequent PR - I think the focus of this initial work should just be on correct propagation. There was a problem hiding this comment. Sure, we can take the step-by-step approach. To provide more context, census-instrumentation/opencensus-specs#70 (comment) and census-instrumentation/opencensus-specs#131. Also adding @wu-sheng for awareness. There was a problem hiding this comment. @Ramonza, I've commented out the Tracestate.Remove and Tracestate.Set for now. Regarding SpanContext, I'm putting a pointer to Tracestate rather than a hardy copy for Tracestate as we would want to have COW (copy-on-write) Tracestate in the future for performance, taking a hard copy is too expensive. There was a problem hiding this comment. Would you mind removing them entirely for now? We in general never keep around commented code. There was a problem hiding this comment. Sure, I'll remove it. |
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| retval := "" | ||
| newEntry := TracestateEntry{key: key, value: value} | ||
| if !newEntry.IsValid() && value != "" { | ||
| return retval | ||
| } | ||
| for index, entry := range ts.entries { | ||
| if entry.key == key { | ||
| ts.entries = append(ts.entries[:index], ts.entries[index+1:]...) | ||
| retval = entry.value | ||
| break | ||
| } | ||
| } | ||
| if value != "" { | ||
| ts.entries = append([]TracestateEntry{newEntry}, ts.entries...) | ||
| } | ||
| return retval | ||
| } | ||
| */ | ||
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| func (ts *Tracestate) String() string { | ||
| return fmt.Sprintf("tracestate%s", ts.entries) | ||
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There was a problem hiding this comment. I don't think this will be a useful output for String() - I would recommend just removing the method There was a problem hiding this comment. Alternatively, I think it would be reasonable for There was a problem hiding this comment. Please refer to census-instrumentation/opencensus-python#238 (comment) where we agreed to separate the in-process representation and the actual HTTP header format. |
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| } | ||
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The zero value of
*Tracestate(nil) should be a valid empty Tracestate in the spirit of making the zero value useful. So it should not be necessary to set it here.