Instrument fs ops only when tracing enabled. (#2542)

* Instrument fs ops only when tracing enabled.

While the calls to tracing APIs are cheap,
we can reduce the performance impact by
conditionally instrumenting code only if tracing is enabled.

cfg/config_util.go

@@ -34,6 +34,11 @@ func IsParallelDownloadsEnabled(mountConfig *Config) bool {
 	return IsFileCacheEnabled(mountConfig) && mountConfig.FileCache.EnableParallelDownloads
 }
 
+// IsTracingEnabled returns true if tracing is enabled.
+func IsTracingEnabled(mountConfig *Config) bool {
+	return mountConfig.Monitoring.ExperimentalTracingMode != ""
+}
+
 // ListCacheTTLSecsToDuration converts TTL in seconds to time.Duration.
 func ListCacheTTLSecsToDuration(secs int64) time.Duration {
 	err := isTTLInSecsValid(secs)

cfg/config_util_test.go

@@ -180,3 +180,26 @@ func TestIsNegativeNumber(t *testing.T) {
 		})
 	}
 }
+
+func TestIsTracingEnabled(t *testing.T) {
+	t.Parallel()
+	var testCases = []struct {
+		testName  string
+		traceMode string
+		expected  bool
+	}{
+		{"empty", "", false},
+		{"not_empty", "gcptrace", true},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.testName, func(t *testing.T) {
+			t.Parallel()
+
+			assert.Equal(t, tc.expected, IsTracingEnabled(&Config{Monitoring: MonitoringConfig{
+				ExperimentalTracingMode: tc.traceMode,
+			}}))
+		})
+	}
+}

internal/fs/server.go

@@ -17,6 +17,7 @@ package fs
 import (
 	"fmt"
 
+	newcfg "github.com/googlecloudplatform/gcsfuse/v2/cfg"
 	"github.com/googlecloudplatform/gcsfuse/v2/internal/fs/wrappers"
 	"github.com/jacobsa/fuse"
 	"github.com/jacobsa/fuse/fuseutil"
@@ -31,6 +32,9 @@ func NewServer(ctx context.Context, cfg *ServerConfig) (fuse.Server, error) {
 	}
 
 	fs = wrappers.WithErrorMapping(fs)
+	if newcfg.IsTracingEnabled(cfg.NewConfig) {
+		fs = wrappers.WithTracing(fs)
+	}
 	fs = wrappers.WithMonitoring(fs)
 	return fuseutil.NewFileSystemServer(fs), nil
 }

internal/fs/wrappers/monitoring.go

@@ -30,9 +30,6 @@ import (
 	"go.opencensus.io/stats"
 	"go.opencensus.io/stats/view"
 	"go.opencensus.io/tag"
-	"go.opentelemetry.io/otel"
-	"go.opentelemetry.io/otel/codes"
-	"go.opentelemetry.io/otel/trace"
 )
 
 const name = "cloud.google.com/gcsfuse"
@@ -318,13 +315,11 @@ func recordOp(ctx context.Context, method string, start time.Time, fsErr error)
 func WithMonitoring(fs fuseutil.FileSystem) fuseutil.FileSystem {
 	return &monitoring{
 		wrapped: fs,
-		tracer:  otel.Tracer(name),
 	}
 }
 
 type monitoring struct {
 	wrapped fuseutil.FileSystem
-	tracer  trace.Tracer
 }
 
 func (fs *monitoring) Destroy() {
@@ -334,17 +329,8 @@ func (fs *monitoring) Destroy() {
 type wrappedCall func(ctx context.Context) error
 
 func (fs *monitoring) invokeWrapped(ctx context.Context, opName string, w wrappedCall) error {
-	// Span's SpanKid is set to trace.SpanKindServer since GCSFuse is like a server for the requests that the Kernel sends.
-	ctx, span := fs.tracer.Start(ctx, opName, trace.WithSpanKind(trace.SpanKindServer))
-	defer span.End()
 	startTime := time.Now()
 	err := w(ctx)
-
-	if err != nil {
-		span.RecordError(err)
-		span.SetStatus(codes.Error, err.Error())
-	}
-
 	recordOp(ctx, opName, startTime, err)
 	return err
 }

internal/fs/wrappers/tracing.go

@@ -0,0 +1,172 @@
+// Copyright 2024 Google LLC
+//
+// 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 wrappers
+
+import (
+	"context"
+
+	"github.com/jacobsa/fuse/fuseops"
+	"github.com/jacobsa/fuse/fuseutil"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
+)
+
+type tracing struct {
+	wrapped fuseutil.FileSystem
+	tracer  trace.Tracer
+}
+
+// WithTracing wraps a FileSystem and creates a root trace.
+func WithTracing(wrapped fuseutil.FileSystem) fuseutil.FileSystem {
+	return &tracing{
+		wrapped: wrapped,
+		tracer:  otel.Tracer(name),
+	}
+}
+
+func (fs *tracing) Destroy() {
+	fs.wrapped.Destroy()
+}
+
+func (fs *tracing) invokeWrapped(ctx context.Context, opName string, w wrappedCall) error {
+	// Span's SpanKind is set to trace.SpanKindServer since GCSFuse is like a server for the requests that the Kernel sends.
+	ctx, span := fs.tracer.Start(ctx, opName, trace.WithSpanKind(trace.SpanKindServer))
+	defer span.End()
+	err := w(ctx)
+
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+	}
+
+	return err
+}
+
+func (fs *tracing) StatFS(ctx context.Context, op *fuseops.StatFSOp) error {
+	return fs.invokeWrapped(ctx, "StatFS", func(ctx context.Context) error { return fs.wrapped.StatFS(ctx, op) })
+}
+
+func (fs *tracing) LookUpInode(ctx context.Context, op *fuseops.LookUpInodeOp) error {
+	return fs.invokeWrapped(ctx, "LookUpInode", func(ctx context.Context) error { return fs.wrapped.LookUpInode(ctx, op) })
+}
+
+func (fs *tracing) GetInodeAttributes(ctx context.Context, op *fuseops.GetInodeAttributesOp) error {
+	return fs.invokeWrapped(ctx, "GetInodeAttributes", func(ctx context.Context) error { return fs.wrapped.GetInodeAttributes(ctx, op) })
+}
+
+func (fs *tracing) SetInodeAttributes(ctx context.Context, op *fuseops.SetInodeAttributesOp) error {
+	return fs.invokeWrapped(ctx, "SetInodeAttributes", func(ctx context.Context) error { return fs.wrapped.SetInodeAttributes(ctx, op) })
+}
+
+func (fs *tracing) ForgetInode(ctx context.Context, op *fuseops.ForgetInodeOp) error {
+	return fs.invokeWrapped(ctx, "ForgetInode", func(ctx context.Context) error { return fs.wrapped.ForgetInode(ctx, op) })
+}
+
+func (fs *tracing) BatchForget(ctx context.Context, op *fuseops.BatchForgetOp) error {
+	return fs.invokeWrapped(ctx, "BatchForget", func(ctx context.Context) error { return fs.wrapped.BatchForget(ctx, op) })
+}
+
+func (fs *tracing) MkDir(ctx context.Context, op *fuseops.MkDirOp) error {
+	return fs.invokeWrapped(ctx, "MkDir", func(ctx context.Context) error { return fs.wrapped.MkDir(ctx, op) })
+}
+
+func (fs *tracing) MkNode(ctx context.Context, op *fuseops.MkNodeOp) error {
+	return fs.invokeWrapped(ctx, "MkNode", func(ctx context.Context) error { return fs.wrapped.MkNode(ctx, op) })
+}
+
+func (fs *tracing) CreateFile(ctx context.Context, op *fuseops.CreateFileOp) error {
+	return fs.invokeWrapped(ctx, "CreateFile", func(ctx context.Context) error { return fs.wrapped.CreateFile(ctx, op) })
+}
+
+func (fs *tracing) CreateLink(ctx context.Context, op *fuseops.CreateLinkOp) error {
+	return fs.invokeWrapped(ctx, "CreateLink", func(ctx context.Context) error { return fs.wrapped.CreateLink(ctx, op) })
+}
+
+func (fs *tracing) CreateSymlink(ctx context.Context, op *fuseops.CreateSymlinkOp) error {
+	return fs.invokeWrapped(ctx, "CreateSymlink", func(ctx context.Context) error { return fs.wrapped.CreateSymlink(ctx, op) })
+}
+
+func (fs *tracing) Rename(ctx context.Context, op *fuseops.RenameOp) error {
+	return fs.invokeWrapped(ctx, "Rename", func(ctx context.Context) error { return fs.wrapped.Rename(ctx, op) })
+}
+
+func (fs *tracing) RmDir(ctx context.Context, op *fuseops.RmDirOp) error {
+	return fs.invokeWrapped(ctx, "RmDir", func(ctx context.Context) error { return fs.wrapped.RmDir(ctx, op) })
+}
+
+func (fs *tracing) Unlink(ctx context.Context, op *fuseops.UnlinkOp) error {
+	return fs.invokeWrapped(ctx, "Unlink", func(ctx context.Context) error { return fs.wrapped.Unlink(ctx, op) })
+}
+
+func (fs *tracing) OpenDir(ctx context.Context, op *fuseops.OpenDirOp) error {
+	return fs.invokeWrapped(ctx, "OpenDir", func(ctx context.Context) error { return fs.wrapped.OpenDir(ctx, op) })
+}
+
+func (fs *tracing) ReadDir(ctx context.Context, op *fuseops.ReadDirOp) error {
+	return fs.invokeWrapped(ctx, "ReadDir", func(ctx context.Context) error { return fs.wrapped.ReadDir(ctx, op) })
+}
+
+func (fs *tracing) ReleaseDirHandle(ctx context.Context, op *fuseops.ReleaseDirHandleOp) error {
+	return fs.invokeWrapped(ctx, "ReleaseDirHandle", func(ctx context.Context) error { return fs.wrapped.ReleaseDirHandle(ctx, op) })
+}
+
+func (fs *tracing) OpenFile(ctx context.Context, op *fuseops.OpenFileOp) error {
+	return fs.invokeWrapped(ctx, "OpenFile", func(ctx context.Context) error { return fs.wrapped.OpenFile(ctx, op) })
+}
+
+func (fs *tracing) ReadFile(ctx context.Context, op *fuseops.ReadFileOp) error {
+	return fs.invokeWrapped(ctx, "ReadFile", func(ctx context.Context) error { return fs.wrapped.ReadFile(ctx, op) })
+}
+
+func (fs *tracing) WriteFile(ctx context.Context, op *fuseops.WriteFileOp) error {
+	return fs.invokeWrapped(ctx, "WriteFile", func(ctx context.Context) error { return fs.wrapped.WriteFile(ctx, op) })
+}
+
+func (fs *tracing) SyncFile(ctx context.Context, op *fuseops.SyncFileOp) error {
+	return fs.invokeWrapped(ctx, "SyncFile", func(ctx context.Context) error { return fs.wrapped.SyncFile(ctx, op) })
+}
+
+func (fs *tracing) FlushFile(ctx context.Context, op *fuseops.FlushFileOp) error {
+	return fs.invokeWrapped(ctx, "FlushFile", func(ctx context.Context) error { return fs.wrapped.FlushFile(ctx, op) })
+}
+
+func (fs *tracing) ReleaseFileHandle(ctx context.Context, op *fuseops.ReleaseFileHandleOp) error {
+	return fs.invokeWrapped(ctx, "ReleaseFileHandle", func(ctx context.Context) error { return fs.wrapped.ReleaseFileHandle(ctx, op) })
+}
+
+func (fs *tracing) ReadSymlink(ctx context.Context, op *fuseops.ReadSymlinkOp) error {
+	return fs.invokeWrapped(ctx, "ReadSymlink", func(ctx context.Context) error { return fs.wrapped.ReadSymlink(ctx, op) })
+}
+
+func (fs *tracing) RemoveXattr(ctx context.Context, op *fuseops.RemoveXattrOp) error {
+	return fs.invokeWrapped(ctx, "RemoveXattr", func(ctx context.Context) error { return fs.wrapped.RemoveXattr(ctx, op) })
+}
+
+func (fs *tracing) GetXattr(ctx context.Context, op *fuseops.GetXattrOp) error {
+	return fs.invokeWrapped(ctx, "GetXattr", func(ctx context.Context) error { return fs.wrapped.GetXattr(ctx, op) })
+}
+
+func (fs *tracing) ListXattr(ctx context.Context, op *fuseops.ListXattrOp) error {
+	return fs.invokeWrapped(ctx, "ListXattr", func(ctx context.Context) error { return fs.wrapped.ListXattr(ctx, op) })
+}
+
+func (fs *tracing) SetXattr(ctx context.Context, op *fuseops.SetXattrOp) error {
+	return fs.invokeWrapped(ctx, "SetXattr", func(ctx context.Context) error { return fs.wrapped.SetXattr(ctx, op) })
+}
+
+func (fs *tracing) Fallocate(ctx context.Context, op *fuseops.FallocateOp) error {
+	return fs.invokeWrapped(ctx, "Fallocate", func(ctx context.Context) error { return fs.wrapped.Fallocate(ctx, op) })
+}

internal/fs/wrappers/tracing_test.go

@@ -162,7 +162,7 @@ func TestSpanCreation(t *testing.T) {
 	t.Cleanup(func() {
 		ex.Reset()
 	})
-	m := monitoring{
+	m := tracing{
 		wrapped: dummyFS{},
 		tracer:  otel.Tracer("test"),
 	}