Revert "Remove fs-error label"

This reverts commit 848d75a.

internal/fs/wrappers/monitoring.go

@@ -62,7 +62,7 @@ func init() {
 			Measure:     opsErrorCount,
 			Description: "The cumulative number of errors generated by file system operations",
 			Aggregation: view.Sum(),
-			TagKeys:     []tag.Key{tags.FSOp, tags.FSErrCategory},
+			TagKeys:     []tag.Key{tags.FSOp, tags.FSError, tags.FSErrCategory},
 		},
 		&view.View{
 			Name:        "fs/ops_latency",
@@ -75,17 +75,24 @@ func init() {
 	}
 }
 
-// categorize maps an error to an error-category.
-// This helps reduce the cardinality of the labels to less than 30.
-// This lower number of errors allows the various errors to get piped to Cloud metrics without getting dropped.
-func categorize(err error) string {
+// errStrAndCategory maps an error to an error string and an error category.
+// Uncommon errors are bucketed into categories to reduce the cardinality of the
+// error so that the metric is not rejected by Cloud Monarch.
+func errStrAndCategory(err error) (str string, category string) {
 	if err == nil {
-		return ""
+		return "", ""
 	}
 	var errno syscall.Errno
 	if !errors.As(err, &errno) {
 		errno = DefaultFSError
 	}
+	return errno.Error(), errCategory(errno)
+}
+
+// errCategory maps an error to an error-category.
+// This helps reduce the cardinality of the labels to less than 30.
+// This lower number of errors allows the various errors to get piped to Cloud metrics without getting dropped.
+func errCategory(errno syscall.Errno) string {
 	switch errno {
 	case syscall.ELNRNG,
 		syscall.ENODEV,
@@ -254,6 +261,7 @@ func categorize(err error) string {
 
 // Records file system operation count, failed operation count and the operation latency.
 func recordOp(ctx context.Context, method string, start time.Time, fsErr error) {
+
 	// Recording opCount.
 	if err := stats.RecordWithTags(
 		ctx,
@@ -268,11 +276,12 @@ func recordOp(ctx context.Context, method string, start time.Time, fsErr error)
 
 	// Recording opErrorCount.
 	if fsErr != nil {
-		errCategory := categorize(fsErr)
+		errStr, errCategory := errStrAndCategory(fsErr)
 		if err := stats.RecordWithTags(
 			ctx,
 			[]tag.Mutator{
 				tag.Upsert(tags.FSOp, method),
+				tag.Upsert(tags.FSError, errStr),
 				tag.Upsert(tags.FSErrCategory, errCategory),
 			},
 			opsErrorCount.M(1),

internal/fs/wrappers/monitoring_test.go

@@ -33,66 +33,82 @@ func TestFsErrStrAndCategory(t *testing.T) {
 	t.Parallel()
 	tests := []struct {
 		fsErr            error
+		expectedStr      string
 		expectedCategory string
 	}{
 		{
 			fsErr:            fmt.Errorf("some random error"),
+			expectedStr:      "input/output error",
 			expectedCategory: "input/output error",
 		},
 		{
 			fsErr:            syscall.ENOTEMPTY,
+			expectedStr:      "directory not empty",
 			expectedCategory: "directory not empty",
 		},
 		{
 			fsErr:            syscall.EEXIST,
+			expectedStr:      "file exists",
 			expectedCategory: "file exists",
 		},
 		{
 			fsErr:            syscall.EINVAL,
+			expectedStr:      "invalid argument",
 			expectedCategory: "invalid argument",
 		},
 		{
 			fsErr:            syscall.EINTR,
+			expectedStr:      "interrupted system call",
 			expectedCategory: "interrupt errors",
 		},
 		{
 			fsErr:            syscall.ENOSYS,
+			expectedStr:      "function not implemented",
 			expectedCategory: "function not implemented",
 		},
 		{
 			fsErr:            syscall.ENOSPC,
+			expectedStr:      "no space left on device",
 			expectedCategory: "process/resource management errors",
 		},
 		{
 			fsErr:            syscall.E2BIG,
+			expectedStr:      "argument list too long",
 			expectedCategory: "invalid operation",
 		},
 		{
 			fsErr:            syscall.EHOSTDOWN,
+			expectedStr:      "host is down",
 			expectedCategory: "network errors",
 		},
 		{
 			fsErr:            syscall.ENODATA,
+			expectedStr:      "no data available",
 			expectedCategory: "miscellaneous errors",
 		},
 		{
 			fsErr:            syscall.ENODEV,
+			expectedStr:      "no such device",
 			expectedCategory: "device errors",
 		},
 		{
 			fsErr:            syscall.EISDIR,
+			expectedStr:      "is a directory",
 			expectedCategory: "file/directory errors",
 		},
 		{
 			fsErr:            syscall.ENOSYS,
+			expectedStr:      "function not implemented",
 			expectedCategory: "function not implemented",
 		},
 		{
 			fsErr:            syscall.ENFILE,
+			expectedStr:      "too many open files in system",
 			expectedCategory: "too many open files",
 		},
 		{
 			fsErr:            syscall.EPERM,
+			expectedStr:      "operation not permitted",
 			expectedCategory: "permission errors",
 		},
 	}
@@ -101,7 +117,10 @@ func TestFsErrStrAndCategory(t *testing.T) {
 		t.Run(fmt.Sprintf("fsErrStrAndCategor_case_%d", idx), func(t *testing.T) {
 			t.Parallel()
 
-			assert.Equal(t, tc.expectedCategory, categorize(tc.fsErr))
+			actualErrStr, actualErrGrp := errStrAndCategory(tc.fsErr)
+
+			assert.Equal(t, tc.expectedStr, actualErrStr)
+			assert.Equal(t, tc.expectedCategory, actualErrGrp)
 		})
 	}
 }

internal/monitor/tags/tags.go

@@ -29,6 +29,9 @@ var (
 	// FSOp annotates the file system op processed.
 	FSOp = tag.MustNewKey("fs_op")
 
+	// FSError annotates the file system failed operations with the error type
+	FSError = tag.MustNewKey("fs_error")
+
 	// FSErrCategory reduces the cardinality of FSError by grouping errors together.
 	FSErrCategory = tag.MustNewKey("fs_error_category")