auto: enable mutex, blocking profiles by default

This enables the mutex and blocking profiles and adds an escape hatch to
disable or tune them for now.

Signed-off-by: Hank Donnay <hdonnay@redhat.com>

initialize/auto/auto.go

@@ -13,6 +13,7 @@ var msgs = []func(context.Context){}
 func init() {
 	CPU()
 	Memory()
+	Profiling()
 }
 
 // PrintLogs uses zlog to report any messages queued up from the runs of

initialize/auto/profiling.go

@@ -0,0 +1,57 @@
+package auto
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/quay/zlog"
+)
+
+// Profiling enables block and mutex profiling.
+//
+// This function uses the magic environment variable "CLAIRDEBUG" to control the
+// values used. This escape hatch will go away in the future.
+func Profiling() {
+	// Catch contention at a granularity of 1 microsecond.
+	blockCur := 1000
+	// Catch 1/10 mutex contention events.
+	mutexCur := 10
+	fromEnv := false
+	if s, ok := os.LookupEnv(`CLAIRDEBUG`); ok {
+		var err error
+		for _, kv := range strings.Split(s, ",") {
+			k, v, ok := strings.Cut(kv, "=")
+			if !ok {
+				continue
+			}
+			switch k {
+			case "blockprofile":
+				fromEnv = true
+				blockCur, err = strconv.Atoi(v)
+			case "mutexprofile":
+				fromEnv = true
+				mutexCur, err = strconv.Atoi(v)
+			default:
+			}
+			if err != nil {
+				panic(err)
+			}
+		}
+	}
+
+	runtime.SetBlockProfileRate(blockCur)
+	mutexPrev := runtime.SetMutexProfileFraction(mutexCur)
+	msgs = append(msgs, func(ctx context.Context) {
+		zlog.Info(ctx).
+			Bool("from_env", fromEnv).
+			Dur("block_rate", time.Duration(blockCur)*time.Nanosecond).
+			Str("prev_mutex_frac", fmt.Sprintf("1/%d", mutexPrev)).
+			Str("cur_mutex_frac", fmt.Sprintf("1/%d", mutexCur)).
+			Msg("profiling rates configured")
+	})
+}