Source: tracez.go in package go.opencensus.io/zpages

Copyright 2017, 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.


package zpages

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"text/tabwriter"
	"time"

	"go.opencensus.io/internal"
	"go.opencensus.io/trace"
)

spanNameQueryField is the header for span name.

spanTypeQueryField is the header for type (running = 0, latency = 1, error = 2) to display.

spanSubtypeQueryField is the header for sub-type: * for latency based samples [0, 8] representing the latency buckets, where 0 is the first one; * for error based samples, 0 means all, otherwise the error code;

maxTraceMessageLength is the maximum length of a message in tracez output.

	maxTraceMessageLength = 1024
)

var (
	defaultLatencies = [...]time.Duration{
		10 * time.Microsecond,
		100 * time.Microsecond,
		time.Millisecond,
		10 * time.Millisecond,
		100 * time.Millisecond,
		time.Second,
		10 * time.Second,
		100 * time.Second,
	}
	canonicalCodes = [...]string{
		"OK",
		"CANCELLED",
		"UNKNOWN",
		"INVALID_ARGUMENT",
		"DEADLINE_EXCEEDED",
		"NOT_FOUND",
		"ALREADY_EXISTS",
		"PERMISSION_DENIED",
		"RESOURCE_EXHAUSTED",
		"FAILED_PRECONDITION",
		"ABORTED",
		"OUT_OF_RANGE",
		"UNIMPLEMENTED",
		"INTERNAL",
		"UNAVAILABLE",
		"DATA_LOSS",
		"UNAUTHENTICATED",
	}
)

func canonicalCodeString(code int32) string {
	if code < 0 || int(code) >= len(canonicalCodes) {
		return "error code " + strconv.FormatInt(int64(code), 10)
	}
	return canonicalCodes[code]
}

func tracezHandler(w http.ResponseWriter, r *http.Request) {
	r.ParseForm()
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	name := r.Form.Get(spanNameQueryField)
	t, _ := strconv.Atoi(r.Form.Get(spanTypeQueryField))
	st, _ := strconv.Atoi(r.Form.Get(spanSubtypeQueryField))
	WriteHTMLTracezPage(w, name, t, st)
}

WriteHTMLTracezPage writes an HTML document to w containing locally-sampled trace spans.

func WriteHTMLTracezPage(w io.Writer, spanName string, spanType, spanSubtype int) {
	if err := headerTemplate.Execute(w, headerData{Title: "Trace Spans"}); err != nil {
		log.Printf("zpages: executing template: %v", err)
	}
	WriteHTMLTracezSummary(w)
	WriteHTMLTracezSpans(w, spanName, spanType, spanSubtype)
	if err := footerTemplate.Execute(w, nil); err != nil {
		log.Printf("zpages: executing template: %v", err)
	}
}

WriteHTMLTracezSummary writes HTML to w containing a summary of locally-sampled trace spans. It includes neither a header nor footer, so you can embed this data in other pages.

func WriteHTMLTracezSummary(w io.Writer) {
	if err := summaryTableTemplate.Execute(w, getSummaryPageData()); err != nil {
		log.Printf("zpages: executing template: %v", err)
	}
}

WriteHTMLTracezSpans writes HTML to w containing locally-sampled trace spans. It includes neither a header nor footer, so you can embed this data in other pages.

func WriteHTMLTracezSpans(w io.Writer, spanName string, spanType, spanSubtype int) {
	if spanName == "" {
		return
	}
	if err := tracesTableTemplate.Execute(w, traceDataFromSpans(spanName, traceSpans(spanName, spanType, spanSubtype))); err != nil {
		log.Printf("zpages: executing template: %v", err)
	}
}

WriteTextTracezSpans writes formatted text to w containing locally-sampled trace spans.

func WriteTextTracezSpans(w io.Writer, spanName string, spanType, spanSubtype int) {
	spans := traceSpans(spanName, spanType, spanSubtype)
	data := traceDataFromSpans(spanName, spans)
	writeTextTraces(w, data)
}

WriteTextTracezSummary writes formatted text to w containing a summary of locally-sampled trace spans.

func WriteTextTracezSummary(w io.Writer) {
	w.Write([]byte("Locally sampled spans summary\n\n"))

	data := getSummaryPageData()
	if len(data.Rows) == 0 {
		return
	}

	tw := tabwriter.NewWriter(w, 8, 8, 1, ' ', 0)

	for i, s := range data.Header {
		if i != 0 {
			tw.Write([]byte("\t"))
		}
		tw.Write([]byte(s))
	}
	tw.Write([]byte("\n"))

	put := func(x int) {
		if x == 0 {
			tw.Write([]byte(".\t"))
			return
		}
		fmt.Fprintf(tw, "%d\t", x)
	}
	for _, r := range data.Rows {
		tw.Write([]byte(r.Name))
		tw.Write([]byte("\t"))
		put(r.Active)
		for _, l := range r.Latency {
			put(l)
		}
		put(r.Errors)
		tw.Write([]byte("\n"))
	}
	tw.Flush()
}

traceData contains data for the trace data template.

type traceData struct {
	Name string
	Num  int
	Rows []traceRow
}

type traceRow struct {
	Fields [3]string
	trace.SpanContext
	ParentSpanID trace.SpanID
}

type events []interface{}

func (e events) Len() int { return len(e) }
func (e events) Less(i, j int) bool {
	var ti time.Time
	switch x := e[i].(type) {
	case *trace.Annotation:
		ti = x.Time
	case *trace.MessageEvent:
		ti = x.Time
	}
	switch x := e[j].(type) {
	case *trace.Annotation:
		return ti.Before(x.Time)
	case *trace.MessageEvent:
		return ti.Before(x.Time)
	}
	return false
}

func (e events) Swap(i, j int) { e[i], e[j] = e[j], e[i] }

func traceRows(s *trace.SpanData) []traceRow {
	start := s.StartTime

	lasty, lastm, lastd := start.Date()
	wholeTime := func(t time.Time) string {
		return t.Format("2006/01/02-15:04:05") + fmt.Sprintf(".%06d", t.Nanosecond()/1000)
	}
	formatTime := func(t time.Time) string {
		y, m, d := t.Date()
		if y == lasty && m == lastm && d == lastd {
			return t.Format("           15:04:05") + fmt.Sprintf(".%06d", t.Nanosecond()/1000)
		}
		lasty, lastm, lastd = y, m, d
		return wholeTime(t)
	}

	lastTime := start
	formatElapsed := func(t time.Time) string {
		d := t.Sub(lastTime)
		lastTime = t

There are five cases for duration printing: -1234567890s -1234.123456 .123456 12345.123456 12345678901s

		switch {
		case u < -9999999999:
			return fmt.Sprintf("%11ds", u/1e6)
		case u < 0:
			sec := u / 1e6
			u -= sec * 1e6
			return fmt.Sprintf("%5d.%06d", sec, -u)
		case u < 1e6:
			return fmt.Sprintf("     .%6d", u)
		case u <= 99999999999:
			sec := u / 1e6
			u -= sec * 1e6
			return fmt.Sprintf("%5d.%06d", sec, u)
		default:
			return fmt.Sprintf("%11ds", u/1e6)
		}
	}

	firstRow := traceRow{Fields: [3]string{wholeTime(start), "", ""}, SpanContext: s.SpanContext, ParentSpanID: s.ParentSpanID}
	if s.EndTime.IsZero() {
		firstRow.Fields[1] = "            "
	} else {
		firstRow.Fields[1] = formatElapsed(s.EndTime)
		lastTime = start
	}
	out := []traceRow{firstRow}

	formatAttributes := func(a map[string]interface{}) string {
		if len(a) == 0 {
			return ""
		}
		var keys []string
		for key := range a {
			keys = append(keys, key)
		}
		sort.Strings(keys)
		var s []string
		for _, key := range keys {
			val := a[key]
			switch val.(type) {
			case string:
				s = append(s, fmt.Sprintf("%s=%q", key, val))
			default:
				s = append(s, fmt.Sprintf("%s=%v", key, val))
			}
		}
		return "Attributes:{" + strings.Join(s, ", ") + "}"
	}

	if s.Status != (trace.Status{}) {
		msg := fmt.Sprintf("Status{canonicalCode=%s, description=%q}",
			canonicalCodeString(s.Status.Code), s.Status.Message)
		out = append(out, traceRow{Fields: [3]string{"", "", msg}})
	}

	if len(s.Attributes) != 0 {
		out = append(out, traceRow{Fields: [3]string{"", "", formatAttributes(s.Attributes)}})
	}

	var es events
	for i := range s.Annotations {
		es = append(es, &s.Annotations[i])
	}
	for i := range s.MessageEvents {
		es = append(es, &s.MessageEvents[i])
	}
	sort.Sort(es)
	for _, e := range es {
		switch e := e.(type) {
		case *trace.Annotation:
			msg := e.Message
			if len(e.Attributes) != 0 {
				msg = msg + "  " + formatAttributes(e.Attributes)
			}
			row := traceRow{Fields: [3]string{
				formatTime(e.Time),
				formatElapsed(e.Time),
				msg,
			}}
			out = append(out, row)
		case *trace.MessageEvent:
			row := traceRow{Fields: [3]string{formatTime(e.Time), formatElapsed(e.Time)}}
			switch e.EventType {
			case trace.MessageEventTypeSent:
				row.Fields[2] = fmt.Sprintf("sent message [%d bytes, %d compressed bytes]", e.UncompressedByteSize, e.CompressedByteSize)
			case trace.MessageEventTypeRecv:
				row.Fields[2] = fmt.Sprintf("received message [%d bytes, %d compressed bytes]", e.UncompressedByteSize, e.CompressedByteSize)
			}
			out = append(out, row)
		}
	}
	for i := range out {
		if len(out[i].Fields[2]) > maxTraceMessageLength {
			out[i].Fields[2] = out[i].Fields[2][:maxTraceMessageLength]
		}
	}
	return out
}

func traceSpans(spanName string, spanType, spanSubtype int) []*trace.SpanData {
	internalTrace := internal.Trace.(interface {
		ReportActiveSpans(name string) []*trace.SpanData
		ReportSpansByError(name string, code int32) []*trace.SpanData
		ReportSpansByLatency(name string, minLatency, maxLatency time.Duration) []*trace.SpanData
	})
	var spans []*trace.SpanData
	switch spanType {
	case 0: // active
		spans = internalTrace.ReportActiveSpans(spanName)
	case 1: // latency
		var min, max time.Duration
		n := len(defaultLatencies)
		if spanSubtype == 0 {
			max = defaultLatencies[0]
		} else if spanSubtype == n {
			min, max = defaultLatencies[spanSubtype-1], (1<<63)-1
		} else if 0 < spanSubtype && spanSubtype < n {
			min, max = defaultLatencies[spanSubtype-1], defaultLatencies[spanSubtype]
		}
		spans = internalTrace.ReportSpansByLatency(spanName, min, max)
	case 2: // error
		spans = internalTrace.ReportSpansByError(spanName, 0)
	}
	return spans
}

func traceDataFromSpans(name string, spans []*trace.SpanData) traceData {
	data := traceData{
		Name: name,
		Num:  len(spans),
	}
	for _, s := range spans {
		data.Rows = append(data.Rows, traceRows(s)...)
	}
	return data
}

func writeTextTraces(w io.Writer, data traceData) {
	tw := tabwriter.NewWriter(w, 1, 8, 1, ' ', 0)
	fmt.Fprint(tw, "When\tElapsed(s)\tType\n")
	for _, r := range data.Rows {
		tw.Write([]byte(r.Fields[0]))
		tw.Write([]byte("\t"))
		tw.Write([]byte(r.Fields[1]))
		tw.Write([]byte("\t"))
		tw.Write([]byte(r.Fields[2]))
		if sc := r.SpanContext; sc != (trace.SpanContext{}) {
			fmt.Fprintf(tw, "trace_id: %s span_id: %s", sc.TraceID, sc.SpanID)
			if r.ParentSpanID != (trace.SpanID{}) {
				fmt.Fprintf(tw, " parent_span_id: %s", r.ParentSpanID)
			}
		}
		tw.Write([]byte("\n"))
	}
	tw.Flush()
}

type summaryPageData struct {
	Header             []string
	LatencyBucketNames []string
	Links              bool
	TracesEndpoint     string
	Rows               []summaryPageRow
}

type summaryPageRow struct {
	Name    string
	Active  int
	Latency []int
	Errors  int
}

func getSummaryPageData() summaryPageData {
	data := summaryPageData{
		Links:          true,
		TracesEndpoint: "tracez",
	}
	internalTrace := internal.Trace.(interface {
		ReportSpansPerMethod() map[string]internal.PerMethodSummary
	})
	for name, s := range internalTrace.ReportSpansPerMethod() {
		if len(data.Header) == 0 {
			data.Header = []string{"Name", "Active"}
			for _, b := range s.LatencyBuckets {
				l := b.MinLatency
				s := fmt.Sprintf(">%v", l)
				if l == 100*time.Second {
					s = ">100s"
				}
				data.Header = append(data.Header, s)
				data.LatencyBucketNames = append(data.LatencyBucketNames, s)
			}
			data.Header = append(data.Header, "Errors")
		}
		row := summaryPageRow{Name: name, Active: s.Active}
		for _, l := range s.LatencyBuckets {
			row.Latency = append(row.Latency, l.Size)
		}
		for _, e := range s.ErrorBuckets {
			row.Errors += e.Size
		}
		data.Rows = append(data.Rows, row)
	}
	sort.Slice(data.Rows, func(i, j int) bool {
		return data.Rows[i].Name < data.Rows[j].Name
	})
	return data