telemetry: fix automated crash reporting using telemetry.Start

Following CL 592017, the child process started by telemetry.Start no
longer opens the counter file, causing crash reports to be dropped on
the floor. Fix this, with a test.

Fixes golang/go#69681

Change-Id: I423533d5b1e2369f13880cecd9137cd7c9239240
Reviewed-on: https://go-review.googlesource.com/c/telemetry/+/616396
Reviewed-by: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Robert Findley <[email protected]>

start.go

@@ -271,6 +271,9 @@ func child(config Config) {
 	uploadStartTime := config.UploadStartTime
 	uploadURL := config.UploadURL
 
+	// The crashmonitor and/or upload process may themselves record counters.
+	counter.Open()
+
 	// Start crashmonitoring and uploading depending on what's requested
 	// and wait for the longer running child to complete before exiting:
 	// if we collected a crash before the upload finished, wait for the

start_test.go

@@ -21,6 +21,7 @@ import (
 	"golang.org/x/telemetry/counter/countertest"
 	"golang.org/x/telemetry/internal/configtest"
 	ic "golang.org/x/telemetry/internal/counter"
+	"golang.org/x/telemetry/internal/crashmonitor"
 	"golang.org/x/telemetry/internal/regtest"
 	it "golang.org/x/telemetry/internal/telemetry"
 	"golang.org/x/telemetry/internal/testenv"
@@ -48,7 +49,6 @@ func TestMain(m *testing.M) {
 // runProg runs the given program.
 // See the switch statement below.
 func runProg(prog string) int {
-
 	mustGetEnv := func(envvar string) string {
 		v := os.Getenv(envvar)
 		if v == "" {
@@ -65,56 +65,80 @@ func runProg(prog string) int {
 
 	// Set global state.
 	ic.CounterTime = func() time.Time { return asof } // must be done before Open
-	countertest.Open(mustGetEnv(telemetryDirEnv))
+
+	telemetryDir := mustGetEnv(telemetryDirEnv)
 
 	switch prog {
 	case "setmode":
+		countertest.Open(telemetryDir)
 		// Use the modified time above for the asof time.
 		if err := it.Default.SetModeAsOf("on", asof); err != nil {
 			log.Fatalf("setting mode: %v", err)
 		}
 	case "inc":
+		countertest.Open(telemetryDir)
 		// (CounterTime is already set above)
 		counter.Inc("teststart/counter")
 
-	case "start":
+	case "crash":
+		telemetry.Start(telemetry.Config{
+			// Do not call Open, to assert that Start does it (golang/go#69681).
+			TelemetryDir:  telemetryDir,
+			ReportCrashes: true,
+		})
+		// Note: don't await the result of start: the child process won't complete
+		// until the crash occurs.
+		panic("crash!")
+
+	case "upload":
 		res := telemetry.Start(telemetry.Config{
-			// No need to set TelemetryDir since the Default dir is already set by countertest.Open.
+			TelemetryDir:    telemetryDir,
 			Upload:          true,
 			UploadURL:       mustGetEnv(uploadURLEnv),
 			UploadStartTime: asof,
 		})
 		res.Wait()
+
 	default:
 		log.Fatalf("unknown program %q", prog)
 	}
 	return 0
 }
 
-func execProg(t *testing.T, telemetryDir, prog string, asof time.Time, env ...string) {
+func execProg(t *testing.T, telemetryDir, prog string, asof time.Time, expectFailure bool, env ...string) {
 	// Run the runStart function below, via a fork+exec trick.
 	exe, err := os.Executable()
 	if err != nil {
 		t.Error(err)
 		return
 	}
 	cmd := exec.Command(exe, "** TestStart **") // this unused arg is just for ps(1)
-	cmd.Stderr = os.Stderr
+	if !expectFailure {
+		cmd.Stderr = os.Stderr
+	}
 	cmd.Env = os.Environ()
 	cmd.Env = append(cmd.Env, asofEnv+"="+asof.Format(it.DateOnly))
 	cmd.Env = append(cmd.Env, telemetryDirEnv+"="+telemetryDir)
 	cmd.Env = append(cmd.Env, runStartEnv+"="+prog) // see TestMain
 	cmd.Env = append(cmd.Env, env...)
 	out, err := cmd.Output()
-	if err != nil {
-		t.Errorf("program failed unexpectedly (%v)\n%s", err, out)
+	if expectFailure {
+		if err == nil {
+			t.Errorf("program succeeded unexpectedly:\n%s", out)
+		}
+	} else if err != nil {
+		t.Errorf("program failed unexpectedly (%v):\n%s", err, out)
 	}
 }
 
 func TestStart(t *testing.T) {
 	testenv.SkipIfUnsupportedPlatform(t)
 	testenv.MustHaveExec(t)
 
+	if !crashmonitor.Supported() {
+		t.Skip("crashmonitor not supported")
+	}
+
 	// This test sets up a telemetry environment, and then runs a test program
 	// that increments a counter, and uploads via telemetry.Start.
 
@@ -127,21 +151,26 @@ func TestStart(t *testing.T) {
 		if err != nil {
 			t.Errorf("error reading body: %v", err)
 		} else {
-			if body := string(body); !strings.Contains(body, "teststart/counter") {
+			body := string(body)
+			if !strings.Contains(body, "teststart/counter") {
 				t.Errorf("upload does not contain \"teststart/counter\":\n%s", body)
 			}
+			if !strings.Contains(body, "crash/crash") {
+				t.Errorf("upload does not contain \"crash/crash\":\n%s", body)
+			}
 		}
 	}))
 	uploadEnv := []string{uploadURLEnv + "=" + server.URL}
 
-	uc := regtest.CreateTestUploadConfig(t, []string{"teststart/counter"}, nil)
+	uc := regtest.CreateTestUploadConfig(t, []string{"teststart/counter"}, []string{"crash/crash"})
 	uploadEnv = append(uploadEnv, configtest.LocalProxyEnv(t, uc, "v1.2.3")...)
 
 	// Script programs.
 	now := time.Now()
-	execProg(t, telemetryDir, "setmode", now.Add(-30*24*time.Hour)) // back-date telemetry acceptance
-	execProg(t, telemetryDir, "inc", now.Add(-8*24*time.Hour))      // increment the counter
-	execProg(t, telemetryDir, "start", now, uploadEnv...)           // run start
+	execProg(t, telemetryDir, "setmode", now.Add(-30*24*time.Hour), false) // back-date telemetry acceptance
+	execProg(t, telemetryDir, "inc", now.Add(-8*24*time.Hour), false)      // increment the counter
+	execProg(t, telemetryDir, "crash", now.Add(-8*24*time.Hour), true)     // run start
+	execProg(t, telemetryDir, "upload", now, false, uploadEnv...)          // run start
 
 	if !uploaded {
 		t.Fatalf("no upload occurred on %v", os.Getpid())
@@ -171,12 +200,12 @@ func TestConcurrentStart(t *testing.T) {
 	uploadEnv = append(uploadEnv, configtest.LocalProxyEnv(t, uc, "v1.2.3")...)
 
 	now := time.Now()
-	execProg(t, telemetryDir, "setmode", now.Add(-365*24*time.Hour)) // back-date telemetry acceptance
-	execProg(t, telemetryDir, "inc", now.Add(-8*24*time.Hour))       // increment the counter
+	execProg(t, telemetryDir, "setmode", now.Add(-365*24*time.Hour), false) // back-date telemetry acceptance
+	execProg(t, telemetryDir, "inc", now.Add(-8*24*time.Hour), false)       // increment the counter
 
 	// Populate three weeks of counters to upload.
 	for i := -28; i < -7; i++ { // Populate three weeks of counters to upload.
-		execProg(t, telemetryDir, "inc", now.Add(time.Duration(i)*24*time.Hour))
+		execProg(t, telemetryDir, "inc", now.Add(time.Duration(i)*24*time.Hour), false)
 	}
 
 	// Run start concurrently.
@@ -185,7 +214,7 @@ func TestConcurrentStart(t *testing.T) {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
-			execProg(t, telemetryDir, "start", now, uploadEnv...)
+			execProg(t, telemetryDir, "upload", now, false, uploadEnv...)
 		}()
 	}
 	wg.Wait()