Check for locked database when writing to perfetto db. (#426)

Previously we would see an infrequent error message saying the
database was locked. This was due to a missing isLocked check on the
path that attempts to assign a replica number to the current
weavelet. Fixed by retrying on a locking error.

Also improved a corresponding error message.

Added a benchmark for calling component methods when tracing is turned
on. (This benchmark is what would trigger the preceding issue.)

.gitignore

@@ -5,3 +5,6 @@ examples/factors/factors
 examples/onlineboutique/onlineboutique
 examples/hello/hello
 website/public/
+
+# Binaries produced by [go test] when passed -c or a profiling option.
+*.test

runtime/perfetto/db.go

@@ -169,7 +169,10 @@ func (d *DB) storeEncoded(ctx context.Context, app, version string, encoded []by
 		VALUES (?,?,?);
 	`
 	_, err := d.execDB(ctx, stmt, app, version, string(encoded))
-	return err
+	if err != nil {
+		return fmt.Errorf("write trace to %s: %w", d.fname, err)
+	}
+	return nil
 }
 
 func (d *DB) encodeSpans(ctx context.Context, app, version string, spans []sdktrace.ReadOnlySpan) ([]byte, error) {
@@ -316,12 +319,18 @@ func (d *DB) getReplicaNumber(ctx context.Context, app, version, weaveletId stri
 		return replicaNum, nil
 	}
 
-	// Get the replica number from the database.
-	replicaNum, err := d.getReplicaNumberUncached(ctx, app, version, weaveletId)
-	if err == nil {
-		d.replicaNumCache.Add(cacheKey, replicaNum)
+	for r := retry.Begin(); r.Continue(ctx); {
+		// Get the replica number from the database.
+		replicaNum, err := d.getReplicaNumberUncached(ctx, app, version, weaveletId)
+		if isLocked(err) {
+			continue
+		}
+		if err == nil {
+			d.replicaNumCache.Add(cacheKey, replicaNum)
+		}
+		return replicaNum, err
 	}
-	return replicaNum, err
+	return -1, ctx.Err()
 }
 
 func (d *DB) getReplicaNumberUncached(ctx context.Context, app, version, weaveletId string) (int, error) {

weavertest/internal/simple/simple_test.go

@@ -26,6 +26,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/ServiceWeaver/weaver/internal/traceio"
 	"github.com/ServiceWeaver/weaver/weavertest"
 	"github.com/ServiceWeaver/weaver/weavertest/internal/simple"
 	"github.com/google/uuid"
@@ -187,12 +188,36 @@ func TestRoutedCall(t *testing.T) {
 func BenchmarkCall(b *testing.B) {
 	for _, runner := range weavertest.AllRunners() {
 		runner.Bench(b, func(b *testing.B, dst simple.Destination) {
+			ctx := context.Background()
 			for i := 0; i < b.N; i++ {
-				_, err := dst.Getpid(context.Background())
+				_, err := dst.Getpid(ctx)
 				if err != nil {
 					b.Fatal(err)
 				}
 			}
 		})
 	}
 }
+
+func BenchmarkTracedCall(b *testing.B) {
+	weavertest.Local.Bench(b, func(b *testing.B, dst simple.Destination) {
+		ctx, span := traceio.TestTracer().Start(context.Background(), "foo")
+
+		// Make a new span every 100 calls.
+		const k = 100
+		for i := 0; i < b.N; {
+			batch := b.N - i
+			if batch > k {
+				batch = k // Bound trace length
+			}
+			i += batch
+			for j := 0; j < batch; j++ {
+				_, err := dst.Getpid(ctx)
+				if err != nil {
+					b.Fatal(err)
+				}
+			}
+			span.End()
+		}
+	})
+}