Add a private flag to throw clobbered error messages (#2710)

* Add a private flag to throw clobbered error messages in case of write failures.

* added config validation test

* Updated flag name and usage

cfg/config.go

@@ -108,6 +108,8 @@ type FileSystemConfig struct {
 
 	KernelListCacheTtlSecs int64 `yaml:"kernel-list-cache-ttl-secs"`
 
+	PreconditionErrors bool `yaml:"precondition-errors"`
+
 	RenameDirLimit int64 `yaml:"rename-dir-limit"`
 
 	TempDir ResolvedPath `yaml:"temp-dir"`
@@ -459,6 +461,12 @@ func BuildFlagSet(flagSet *pflag.FlagSet) error {
 
 	flagSet.StringP("only-dir", "", "", "Mount only a specific directory within the bucket. See docs/mounting for more information")
 
+	flagSet.BoolP("precondition-errors", "", true, "Throw Stale NFS file handle error in case the object being synced or read  from is modified by some other concurrent process. This helps prevent  silent data loss or data corruption.")
+
+	if err := flagSet.MarkHidden("precondition-errors"); err != nil {
+		return err
+	}
+
 	flagSet.IntP("prometheus-port", "", 0, "Expose Prometheus metrics endpoint on this port and a path of /metrics.")
 
 	if err := flagSet.MarkHidden("prometheus-port"); err != nil {
@@ -523,7 +531,7 @@ func BuildFlagSet(flagSet *pflag.FlagSet) error {
 		return err
 	}
 
-	flagSet.StringP("temp-dir", "", "", "Path to the temporary directory where writes are staged prior to upload to Cloud Storage. (default: system default, likely /tmp)\"")
+	flagSet.StringP("temp-dir", "", "", "Path to the temporary directory where writes are staged prior to upload to Cloud Storage. (default: system default, likely /tmp)")
 
 	flagSet.StringP("token-url", "", "", "A url for getting an access token when the key-file is absent.")
 
@@ -796,6 +804,10 @@ func BindFlags(v *viper.Viper, flagSet *pflag.FlagSet) error {
 		return err
 	}
 
+	if err := v.BindPFlag("file-system.precondition-errors", flagSet.Lookup("precondition-errors")); err != nil {
+		return err
+	}
+
 	if err := v.BindPFlag("metrics.prometheus-port", flagSet.Lookup("prometheus-port")); err != nil {
 		return err
 	}

cfg/params.yaml

@@ -194,6 +194,16 @@
     will throw error.
   default: "0"
 
+- config-path: "file-system.precondition-errors"
+  flag-name: "precondition-errors"
+  type: "bool"
+  usage: >-
+    Throw Stale NFS file handle error in case the object being synced or read 
+    from is modified by some other concurrent process. This helps prevent 
+    silent data loss or data corruption.
+  hide-flag: true
+  default: true
+
 - config-path: "file-system.rename-dir-limit"
   flag-name: "rename-dir-limit"
   type: "int"
@@ -205,7 +215,7 @@
   type: "resolvedPath"
   usage: >-
     Path to the temporary directory where writes are staged prior to upload to
-    Cloud Storage. (default: system default, likely /tmp)"
+    Cloud Storage. (default: system default, likely /tmp)
   default: ""
 
 - config-path: "file-system.uid"

cmd/config_validation_test.go

@@ -514,6 +514,7 @@ func TestValidateConfigFile_FileSystemConfigSuccessful(t *testing.T) {
 					KernelListCacheTtlSecs: 0,
 					RenameDirLimit:         0,
 					TempDir:                "",
+					PreconditionErrors:     true,
 					Uid:                    -1,
 					HandleSigterm:          true,
 				},
@@ -533,6 +534,7 @@ func TestValidateConfigFile_FileSystemConfigSuccessful(t *testing.T) {
 					KernelListCacheTtlSecs: 0,
 					RenameDirLimit:         0,
 					TempDir:                "",
+					PreconditionErrors:     true,
 					Uid:                    -1,
 					HandleSigterm:          true,
 				},
@@ -552,6 +554,7 @@ func TestValidateConfigFile_FileSystemConfigSuccessful(t *testing.T) {
 					KernelListCacheTtlSecs: 300,
 					RenameDirLimit:         10,
 					TempDir:                cfg.ResolvedPath(path.Join(hd, "temp")),
+					PreconditionErrors:     false,
 					Uid:                    8,
 					HandleSigterm:          true,
 				},

cmd/root_test.go

@@ -641,7 +641,7 @@ func TestArgsParsing_FileSystemFlags(t *testing.T) {
 	}{
 		{
 			name: "normal",
-			args: []string{"gcsfuse", "--dir-mode=0777", "--disable-parallel-dirops", "--file-mode=0666", "--o", "ro", "--gid=7", "--ignore-interrupts=false", "--kernel-list-cache-ttl-secs=300", "--rename-dir-limit=10", "--temp-dir=~/temp", "--uid=8", "abc", "pqr"},
+			args: []string{"gcsfuse", "--dir-mode=0777", "--disable-parallel-dirops", "--file-mode=0666", "--o", "ro", "--gid=7", "--ignore-interrupts=false", "--kernel-list-cache-ttl-secs=300", "--rename-dir-limit=10", "--temp-dir=~/temp", "--uid=8", "--precondition-errors=false", "abc", "pqr"},
 			expectedConfig: &cfg.Config{
 				FileSystem: cfg.FileSystemConfig{
 					DirMode:                0777,
@@ -653,6 +653,7 @@ func TestArgsParsing_FileSystemFlags(t *testing.T) {
 					KernelListCacheTtlSecs: 300,
 					RenameDirLimit:         10,
 					TempDir:                cfg.ResolvedPath(path.Join(hd, "temp")),
+					PreconditionErrors:     false,
 					Uid:                    8,
 					HandleSigterm:          true,
 				},
@@ -672,6 +673,7 @@ func TestArgsParsing_FileSystemFlags(t *testing.T) {
 					KernelListCacheTtlSecs: 0,
 					RenameDirLimit:         0,
 					TempDir:                "",
+					PreconditionErrors:     true,
 					Uid:                    -1,
 					HandleSigterm:          true,
 				},
@@ -691,6 +693,7 @@ func TestArgsParsing_FileSystemFlags(t *testing.T) {
 					KernelListCacheTtlSecs: 0,
 					RenameDirLimit:         0,
 					TempDir:                "",
+					PreconditionErrors:     true,
 					Uid:                    -1,
 					HandleSigterm:          true,
 				},

cmd/testdata/valid_config.yaml

@@ -51,6 +51,7 @@ file-system:
   kernel-list-cache-ttl-secs: 300
   rename-dir-limit: 10
   temp-dir: ~/temp
+  precondition-errors: false
 list:
   enable-empty-managed-folders: true
 enable-hns: false