runtime/trace, internal/trace: script to collect canned traces

This adds support to the runtime/trace test for saving traces
collected by its tests to disk and a script in internal/trace that
uses this to collect canned traces for the trace test suite. This can
be used to add to the test suite when we introduce a new trace format
version.

Change-Id: Id9ac1ff312235bf02f982fdfff8a827f54035758
Reviewed-on: https://go-review.googlesource.com/32290
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

src/internal/trace/mkcanned.bash

+#!/usr/bin/env bash
+# Copyright 2016 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# mkcanned.bash creates canned traces for the trace test suite using
+# the current Go version.
+
+set -e
+
+if [ $# != 1 ]; then
+    echo "usage: $0 <label>" >&2
+    exit 1
+fi
+
+go test -run ClientServerParallel4 -trace "testdata/http_$1_good" net/http
+go test -run 'TraceStress$|TraceStressStartStop$' runtime/trace -savetraces
+mv ../../runtime/trace/TestTraceStress.trace "testdata/stress_$1_good"
+mv ../../runtime/trace/TestTraceStressStartStop.trace "testdata/stress_start_stop_$1_good"

src/internal/trace/parser.go

@@ -128,6 +128,8 @@ func readTrace(r io.Reader) (ver int, events []rawEvent, strings map[uint64]stri
 	}
 	switch ver {
 	case 1005, 1007, 1008:
+		// Note: When adding a new version, add canned traces
+		// from the old version to the test suite using mkcanned.bash.
 		break
 	default:
 		err = fmt.Errorf("unsupported trace file version %v.%v (update Go toolchain) %v", ver/1000, ver%1000, ver)

src/runtime/trace/trace_test.go

@@ -6,8 +6,10 @@ package trace_test
 
 import (
 	"bytes"
+	"flag"
 	"internal/trace"
 	"io"
+	"io/ioutil"
 	"net"
 	"os"
 	"runtime"
@@ -17,6 +19,10 @@ import (
 	"time"
 )
 
+var (
+	saveTraces = flag.Bool("savetraces", false, "save traces collected by tests")
+)
+
 func TestTraceStartStop(t *testing.T) {
 	buf := new(bytes.Buffer)
 	if err := Start(buf); err != nil {
@@ -31,6 +37,7 @@ func TestTraceStartStop(t *testing.T) {
 	if size != buf.Len() {
 		t.Fatalf("trace writes after stop: %v -> %v", size, buf.Len())
 	}
+	saveTrace(t, buf, "TestTraceStartStop")
 }
 
 func TestTraceDoubleStart(t *testing.T) {
@@ -52,6 +59,7 @@ func TestTrace(t *testing.T) {
 		t.Fatalf("failed to start tracing: %v", err)
 	}
 	Stop()
+	saveTrace(t, buf, "TestTrace")
 	_, err := trace.Parse(buf, "")
 	if err == trace.ErrTimeOrder {
 		t.Skipf("skipping trace: %v", err)
@@ -233,6 +241,7 @@ func TestTraceStress(t *testing.T) {
 	runtime.GOMAXPROCS(procs)
 
 	Stop()
+	saveTrace(t, buf, "TestTraceStress")
 	trace := buf.Bytes()
 	parseTrace(t, buf)
 	testBrokenTimestamps(t, trace)
@@ -376,6 +385,7 @@ func TestTraceStressStartStop(t *testing.T) {
 		}
 		time.Sleep(time.Millisecond)
 		Stop()
+		saveTrace(t, buf, "TestTraceStressStartStop")
 		trace := buf.Bytes()
 		parseTrace(t, buf)
 		testBrokenTimestamps(t, trace)
@@ -436,6 +446,7 @@ func TestTraceFutileWakeup(t *testing.T) {
 	done.Wait()
 
 	Stop()
+	saveTrace(t, buf, "TestTraceFutileWakeup")
 	events, _ := parseTrace(t, buf)
 	// Check that (1) trace does not contain EvFutileWakeup events and
 	// (2) there are no consecutive EvGoBlock/EvGCStart/EvGoBlock events
@@ -464,3 +475,12 @@ func TestTraceFutileWakeup(t *testing.T) {
 		}
 	}
 }
+
+func saveTrace(t *testing.T, buf *bytes.Buffer, name string) {
+	if !*saveTraces {
+		return
+	}
+	if err := ioutil.WriteFile(name+".trace", buf.Bytes(), 0600); err != nil {
+		t.Errorf("failed to write trace file: %s", err)
+	}
+}