package loggabletracer import ( "bytes" "fmt" "runtime" "strconv" "sync" ) const debugGoroutineIDTag = "_initial_goroutine" type errAssertionFailed struct { span *spanImpl msg string } // Error implements the error interface. func (err *errAssertionFailed) Error() string { return fmt.Sprintf("%s:\n%+v", err.msg, err.span) } func (s *spanImpl) Lock() { s.Mutex.Lock() s.maybeAssertSanityLocked() } func (s *spanImpl) maybeAssertSanityLocked() { if s.tracer == nil { s.Mutex.Unlock() panic(&errAssertionFailed{span: s, msg: "span used after call to Finish()"}) } if s.tracer.options.DebugAssertSingleGoroutine { startID := curGoroutineID() curID, ok := s.raw.Tags[debugGoroutineIDTag].(uint64) if !ok { // This is likely invoked in the context of the SetTag which sets // debugGoroutineTag. return } if startID != curID { s.Mutex.Unlock() panic(&errAssertionFailed{ span: s, msg: fmt.Sprintf("span started on goroutine %d, but now running on %d", startID, curID), }) } } } var goroutineSpace = []byte("goroutine ") var littleBuf = sync.Pool{ New: func() interface{} { buf := make([]byte, 64) return &buf }, } // Credit to @bradfitz: // https://github.com/golang/net/blob/master/http2/gotrack.go#L51 func curGoroutineID() uint64 { bp := littleBuf.Get().(*[]byte) defer littleBuf.Put(bp) b := *bp b = b[:runtime.Stack(b, false)] // Parse the 4707 out of "goroutine 4707 [" b = bytes.TrimPrefix(b, goroutineSpace) i := bytes.IndexByte(b, ' ') if i < 0 { panic(fmt.Sprintf("No space found in %q", b)) } b = b[:i] n, err := strconv.ParseUint(string(b), 10, 64) if err != nil { panic(fmt.Sprintf("Failed to parse goroutine ID out of %q: %v", b, err)) } return n }