spans

type Factory interface {

	// GetProjectID() returns the GCP Project ID (which is not the Project
	// Number) for which spans will be registered.
	//
	GetProjectID() string

	// GetTraceID() returns "" if the Factory is empty.  Otherwise it returns
	// the trace ID of the contained span (which will not be "" nor a
	// hexadecimal representation of 0).
	//
	GetTraceID() string

	// GetSpanID() returns 0 if the Factory is empty.  Otherwise it returns
	// the span ID of the contained span (which will not be 0).
	//
	GetSpanID() uint64

	// GetStart() returns the time at which the span began.  Returns a zero
	// time if the Factory is empty or the contained span was Import()ed.
	//
	GetStart() time.Time

	// GetDuration() returns a negative duration if the factory is empty or
	// if the span has not been Finish()ed yet.  Otherwise, it returns the
	// span's duration.
	//
	GetDuration() time.Duration

	// GetTracePath() returns "" if the Factory is empty.  Otherwise it
	// returns the trace's resource sub-path which will be in the form
	// "projects/{projectID}/traces/{traceID}".
	//
	GetTracePath() string

	// GetSpanPath() returns "" if the Factory is empty.  Otherwise it
	// returns the span's resource sub-path which will be in the form
	// "traces/{traceID}/spans/{spanID}" where both IDs are in hexadecimal.
	//
	GetSpanPath() string

	// GetCloudContext() returns "" if the Factory is empty.  Otherwise it
	// returns a value appropriate for the "X-Cloud-Trace-Context:" header
	// which will be in the form "{traceID}/{spanID}" where spanID is in
	// base 10.
	//
	GetCloudContext() string

	// Import() returns a new Factory containing a span created somewhere
	// else.  If the traceID or spanID is invalid, then a 'nil' Factory and
	// an error are returned.  The usual reason to do this is so that you can
	// then call NewSubSpan().
	//
	Import(traceID string, spanID uint64) (Factory, error)

	// ImportFromHeaders() returns a new Factory containing a span created
	// somewhere else based on the "X-Cloud-Trace-Context:" header.  If the
	// header does not contain a valid CloudContext value, then a valid but
	// empty Factory is returned.
	//
	ImportFromHeaders(headers http.Header) Factory

	// SetHeader() sets the "X-Cloud-Trace-Context:" header if the Factory
	// is not empty.  Always returns the calling Factory so that further
	// method calls can be chained.
	//
	SetHeader(headers http.Header) Factory

	// NewTrace() returns a new Factory holding a new span, part of a new
	// trace.  Any span held in the invoking Factory is ignored.
	//
	NewTrace() Factory

	// NewSubSpan() returns a new Factory holding a new span that is a
	// sub-span of the span contained in the invoking Factory.  If the
	// invoking Factory was empty, then a failure with a stack trace is
	// logged and a 'nil' Factory is returned.
	//
	NewSubSpan() Factory

	// NewSpan() returns a new Factory holding a new span.  It does
	// NewTrace() if the Factory was empty and NewSubSpan() otherwise.
	//
	NewSpan() Factory

	// Sets the span kind to "SERVER".  Does nothing except log a failure
	// with a stack trace if the Factory is empty.  Always returns the calling
	// Factory so further method calls can be chained.
	//
	SetIsServer() Factory

	// Sets the span kind to "CLIENT".  Does nothing except log a failure
	// with a stack trace if the Factory is empty.  Always returns the
	// calling Factory so further method calls can be chained.
	//
	SetIsClient() Factory

	// Sets the span kind to "PRODUCER" (the term used for a process that
	// asynchronously publishes data like with pub/sub).  Does nothing
	// except log a failure with a stack trace if the Factory is empty.
	// Always returns the calling Factory so further method calls can be
	// chained.
	//
	SetIsPublisher() Factory

	// Sets the span kind to "CONSUMER" (the term used for a process that
	// asynchronously receives data like a pub/sub subscriber).  Does nothing
	// except log a failure with a stack trace if the Factory is empty.
	// Always returns the calling Factory so further method calls can be
	// chained.
	//
	SetIsSubscriber() Factory

	// SetDisplayName() sets the display name on the contained span.  Does
	// nothing except log a failure with a stack trace if the Factory is
	// empty.  Always returns the calling Factory so further method calls
	// can be chained.
	//
	SetDisplayName(desc string) Factory

	// AddAttribute() adds an attribute key/value pair to the contained span.
	// Does nothing except log a failure with a stack trace if the Factory is
	// empty (even returning a 'nil' error).
	//
	// 'val' can be a 'string', an 'int' or 'int64', or a 'bool'.  If 'key'
	// is empty or 'val' is not one of the listed types, then an error is
	// returned and the attribute is not added.
	//
	AddAttribute(key string, val interface{}) error

	// AddPairs() takes a list of attribute key/value pairs.  For each pair,
	// AddAttribute() is called and any returned error is logged (including
	// a reference to the line of code that called AddPairs).  Always returns
	// the calling Factory so further method calls can be chained.
	//
	AddPairs(pairs ...interface{}) Factory

	// SetStatusCode() sets the status code on the contained span.
	// 'code' is expected to be a value from
	// google.golang.org/genproto/googleapis/rpc/code but this is not
	// verified.  HTTP status codes are also understood by the library.
	// Does nothing except log a failure with a stack trace if the Factory
	// is empty.  Always returns the calling span so further method calls
	// can be chained.
	//
	SetStatusCode(code int64) Factory

	// SetStatusMessage() sets the status message string on the contained
	// span.  By convention, only a failure should set a status message.
	// Does nothing except log a failure with a stack trace if the Factory
	// is empty.  Always returns the calling Factory so further method calls
	// can be chained.
	//
	SetStatusMessage(msg string) Factory

	// Finish() notifies the Factory that the contained span is finished.
	// The Factory will be empty afterward.  The Factory will arrange for the
	// span to be registered.
	//
	// The returned value is the duration of the span's life.  If the Factory
	// was already empty or the contained span was from Import(), then a
	// failure with a stack trace is logged and a 0 duration is returned.
	//
	Finish() time.Duration
}

type ROSpan struct {
	// contains filtered or unexported fields
}