cli,storage: add emergency ballast

Add an automatically created, on-by-default emergency ballast file. This
new ballast defaults to the minimum of 1% total disk capacity or 1GiB.
The size of the ballast may be configured via the `--store` flag with a
`ballast-size` field, accepting the same value formats as the `size`
field.

The ballast is automatically created when either available disk space is
at least four times the ballast size, or when available disk space after
creating the ballast is at least 10 GiB. Creation of the ballast happens
either when the engine is opened or during the periodic Capacity
calculations driven by the `kvserver.Store`.

During node start, if available disk space is less than or equal to half
the ballast size, exit immediately with a new Disk Full (10) exit code.

See #66493.

Release note (ops change): Add an automatically created, on by default
emergency ballast file. This new ballast defaults to the minimum of 1%
total disk capacity or 1GiB.  The size of the ballast may be configured
via the `--store` flag with a `ballast-size` field, accepting the same
value formats as the `size` field.

pkg/base/config.go

@@ -522,6 +522,9 @@ type StorageConfig struct {
 	// MaxSize is used for calculating free space and making rebalancing
 	// decisions. Zero indicates that there is no maximum size.
 	MaxSize int64
+	// BallastSize is the amount reserved by a ballast file for manual
+	// out-of-disk recovery.
+	BallastSize int64
 	// Settings instance for cluster-wide knobs.
 	Settings *cluster.Settings
 	// UseFileRegistry is true if the file registry is needed (eg: encryption-at-rest).

pkg/base/store_spec.go

@@ -79,7 +79,7 @@ type floatInterval struct {
 // NewSizeSpec parses the string passed into a --size flag and returns a
 // SizeSpec if it is correctly parsed.
 func NewSizeSpec(
-	value string, bytesRange *intInterval, percentRange *floatInterval,
+	field, value string, bytesRange *intInterval, percentRange *floatInterval,
 ) (SizeSpec, error) {
 	var size SizeSpec
 	if fractionRegex.MatchString(value) {
@@ -93,13 +93,14 @@ func NewSizeSpec(
 		size.Percent, err = strconv.ParseFloat(factorValue, 64)
 		size.Percent *= percentFactor
 		if err != nil {
-			return SizeSpec{}, fmt.Errorf("could not parse store size (%s) %s", value, err)
+			return SizeSpec{}, fmt.Errorf("could not parse %s size (%s) %s", field, value, err)
 		}
 		if percentRange != nil {
 			if (percentRange.min != nil && size.Percent < *percentRange.min) ||
 				(percentRange.max != nil && size.Percent > *percentRange.max) {
 				return SizeSpec{}, fmt.Errorf(
-					"store size (%s) must be between %f%% and %f%%",
+					"%s size (%s) must be between %f%% and %f%%",
+					field,
 					value,
 					*percentRange.min,
 					*percentRange.max,
@@ -110,16 +111,16 @@ func NewSizeSpec(
 		var err error
 		size.InBytes, err = humanizeutil.ParseBytes(value)
 		if err != nil {
-			return SizeSpec{}, fmt.Errorf("could not parse store size (%s) %s", value, err)
+			return SizeSpec{}, fmt.Errorf("could not parse %s size (%s) %s", field, value, err)
 		}
 		if bytesRange != nil {
 			if bytesRange.min != nil && size.InBytes < *bytesRange.min {
-				return SizeSpec{}, fmt.Errorf("store size (%s) must be larger than %s", value,
-					humanizeutil.IBytes(*bytesRange.min))
+				return SizeSpec{}, fmt.Errorf("%s size (%s) must be larger than %s",
+					field, value, humanizeutil.IBytes(*bytesRange.min))
 			}
 			if bytesRange.max != nil && size.InBytes > *bytesRange.max {
-				return SizeSpec{}, fmt.Errorf("store size (%s) must be smaller than %s", value,
-					humanizeutil.IBytes(*bytesRange.max))
+				return SizeSpec{}, fmt.Errorf("%s size (%s) must be smaller than %s",
+					field, value, humanizeutil.IBytes(*bytesRange.max))
 			}
 		}
 	}
@@ -150,7 +151,7 @@ var _ pflag.Value = &SizeSpec{}
 // Set adds a new value to the StoreSpecValue. It is the important part of
 // pflag's value interface.
 func (ss *SizeSpec) Set(value string) error {
-	spec, err := NewSizeSpec(value, nil, nil)
+	spec, err := NewSizeSpec("", value, nil, nil)
 	if err != nil {
 		return err
 	}
@@ -162,10 +163,11 @@ func (ss *SizeSpec) Set(value string) error {
 // StoreSpec contains the details that can be specified in the cli pertaining
 // to the --store flag.
 type StoreSpec struct {
-	Path       string
-	Size       SizeSpec
-	InMemory   bool
-	Attributes roachpb.Attributes
+	Path        string
+	Size        SizeSpec
+	BallastSize *SizeSpec
+	InMemory    bool
+	Attributes  roachpb.Attributes
 	// StickyInMemoryEngineID is a unique identifier associated with a given
 	// store which will remain in memory even after the default Engine close
 	// until it has been explicitly cleaned up by CleanupStickyInMemEngine[s]
@@ -203,6 +205,14 @@ func (ss StoreSpec) String() string {
 	if ss.Size.Percent > 0 {
 		fmt.Fprintf(&buffer, "size=%s%%,", humanize.Ftoa(ss.Size.Percent))
 	}
+	if ss.BallastSize != nil {
+		if ss.BallastSize.InBytes > 0 {
+			fmt.Fprintf(&buffer, "ballast-size=%s,", humanizeutil.IBytes(ss.BallastSize.InBytes))
+		}
+		if ss.BallastSize.Percent > 0 {
+			fmt.Fprintf(&buffer, "ballast-size=%s%%,", humanize.Ftoa(ss.BallastSize.Percent))
+		}
+	}
 	if len(ss.Attributes.Attrs) > 0 {
 		fmt.Fprint(&buffer, "attrs=")
 		for i, attr := range ss.Attributes.Attrs {
@@ -308,13 +318,28 @@ func NewStoreSpec(value string) (StoreSpec, error) {
 			var minPercent float64 = 1
 			var maxPercent float64 = 100
 			ss.Size, err = NewSizeSpec(
+				"store",
 				value,
 				&intInterval{min: &minBytesAllowed},
 				&floatInterval{min: &minPercent, max: &maxPercent},
 			)
 			if err != nil {
 				return StoreSpec{}, err
 			}
+		case "ballast-size":
+			var minBytesAllowed int64
+			var minPercent float64 = 0
+			var maxPercent float64 = 50
+			ballastSize, err := NewSizeSpec(
+				"ballast",
+				value,
+				&intInterval{min: &minBytesAllowed},
+				&floatInterval{min: &minPercent, max: &maxPercent},
+			)
+			if err != nil {
+				return StoreSpec{}, err
+			}
+			ss.BallastSize = &ballastSize
 		case "attrs":
 			// Check to make sure there are no duplicate attributes.
 			attrMap := make(map[string]struct{})
@@ -384,6 +409,9 @@ func NewStoreSpec(value string) (StoreSpec, error) {
 		if ss.Size.Percent == 0 && ss.Size.InBytes == 0 {
 			return StoreSpec{}, fmt.Errorf("size must be specified for an in memory store")
 		}
+		if ss.BallastSize != nil {
+			return StoreSpec{}, fmt.Errorf("ballast-size specified for in memory store")
+		}
 	} else if ss.Path == "" {
 		return StoreSpec{}, fmt.Errorf("no path specified")
 	}
@@ -417,6 +445,14 @@ func (ssl StoreSpecList) String() string {
 // root directory. It must not be changed without a proper migration.
 const AuxiliaryDir = "auxiliary"
 
+// EmergencyBallastFile returns the path (relative to a data directory) used
+// for an emergency ballast file. The returned path must be stable across
+// releases (eg, we cannot change these constants), otherwise we may duplicate
+// ballasts.
+func EmergencyBallastFile(pathJoin func(...string) string, dataDir string) string {
+	return pathJoin(dataDir, AuxiliaryDir, "EMERGENCY_BALLAST")
+}
+
 // PreventedStartupFile is the filename (relative to 'dir') used for files that
 // can block server startup.
 func PreventedStartupFile(dir string) string {

pkg/base/store_spec_test.go

@@ -128,6 +128,13 @@ target_file_size=2097152`
 		{"size=20GiB,path=/mnt/hda1,size=20GiB", "size field was used twice in store definition", StoreSpec{}},
 		{"size=123TB", "no path specified", StoreSpec{}},
 
+		// ballast size
+		{"path=/mnt/hda1,ballast-size=671088640", "", StoreSpec{Path: "/mnt/hda1", BallastSize: &SizeSpec{InBytes: 671088640}}},
+		{"path=/mnt/hda1,ballast-size=20GB", "", StoreSpec{Path: "/mnt/hda1", BallastSize: &SizeSpec{InBytes: 20000000000}}},
+		{"path=/mnt/hda1,ballast-size=1%", "", StoreSpec{Path: "/mnt/hda1", BallastSize: &SizeSpec{Percent: 1}}},
+		{"path=/mnt/hda1,ballast-size=100.000%", "ballast size (100.000%) must be between 0.000000% and 50.000000%", StoreSpec{}},
+		{"ballast-size=20GiB,path=/mnt/hda1,ballast-size=20GiB", "ballast-size field was used twice in store definition", StoreSpec{}},
+
 		// type
 		{"type=mem,size=20GiB", "", StoreSpec{Size: SizeSpec{InBytes: 21474836480}, InMemory: true}},
 		{"size=20GiB,type=mem", "", StoreSpec{Size: SizeSpec{InBytes: 21474836480}, InMemory: true}},

pkg/cli/exit/codes.go

@@ -58,6 +58,10 @@ func TimeoutAfterFatalError() Code { return Code{8} }
 // during a logging operation to a network collector.
 func LoggingNetCollectorUnavailable() Code { return Code{9} }
 
+// DiskFull (10) indicates an emergency shutdown in response to a
+// store's full disk.
+func DiskFull() Code { return Code{10} }
+
 // Codes that are specific to client commands follow. It's possible
 // for codes to be reused across separate client or server commands.
 // Command-specific exit codes should be allocated down from 125.

pkg/cli/start.go

@@ -54,6 +54,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/timeutil"
 	"github.com/cockroachdb/cockroach/pkg/util/tracing"
 	"github.com/cockroachdb/errors"
+	"github.com/cockroachdb/pebble/vfs"
 	"github.com/cockroachdb/redact"
 	"github.com/spf13/cobra"
 	"google.golang.org/grpc"
@@ -331,6 +332,16 @@ func runStart(cmd *cobra.Command, args []string, startSingleNode bool) (returnEr
 		}()
 	}
 
+	// Check for stores with full disks and exit with an informative exit
+	// code. This needs to happen early during start, before we perform any
+	// writes to the filesystem including log rotation. We need to guarantee
+	// that the process continues to exit with the Disk Full exit code. A
+	// flapping exit code can affect alerting, including the alerting
+	// performed within CockroachCloud.
+	if err := exitIfDiskFull(serverCfg.Stores.Specs); err != nil {
+		return err
+	}
+
 	// Set up a cancellable context for the entire start command.
 	// The context will be canceled at the end.
 	ctx, cancel := context.WithCancel(context.Background())
@@ -999,6 +1010,37 @@ func maybeWarnMemorySizes(ctx context.Context) {
 	}
 }
 
+func exitIfDiskFull(specs []base.StoreSpec) error {
+	var cause error
+	var ballastPaths []string
+	for _, spec := range specs {
+		isDiskFull, err := storage.IsDiskFull(vfs.Default, spec)
+		if err != nil {
+			return err
+		}
+		if !isDiskFull {
+			continue
+		}
+		ballastPaths = append(ballastPaths, base.EmergencyBallastFile(vfs.Default.PathJoin, spec.Path))
+		cause = errors.CombineErrors(cause, errors.Errorf(`store %s: out of disk space`, spec.Path))
+	}
+	if cause == nil {
+		return nil
+	}
+
+	// TODO(jackson): Link to documentation surrounding the ballast.
+	var err error = &cliError{
+		exitCode: exit.DiskFull(),
+		cause:    cause,
+	}
+	ballastPathsStr := strings.Join(ballastPaths, "\n")
+	err = errors.WithDetailf(err, `Deleting or truncating the ballast file(s) at
+%s
+may reclaim enough space to start. Proceed with caution. Complete
+disk space exhaustion may result in node loss.`, ballastPathsStr)
+	return err
+}
+
 // setupAndInitializeLoggingAndProfiling does what it says on the label.
 // Prior to this however it determines suitable defaults for the
 // logging output directory and the verbosity level of stderr logging.

pkg/cli/start_test.go

@@ -104,6 +104,13 @@ func TestStartArgChecking(t *testing.T) {
 		{[]string{`--store=size=-1231MB`}, `store size \(-1231MB\) must be larger than`},
 		{[]string{`--store=size=1231B`}, `store size \(1231B\) must be larger than`},
 		{[]string{`--store=size=1231BLA`}, `unhandled size name: bla`},
+		{[]string{`--store=ballast-size=60.0`}, `ballast size \(60.0\) must be between 0.000000% and 50.000000%`},
+		{[]string{`--store=ballast-size=1231BLA`}, `unhandled size name: bla`},
+		{[]string{`--store=ballast-size=0.5%,path=.`}, ``},
+		{[]string{`--store=ballast-size=.5,path=.`}, ``},
+		{[]string{`--store=ballast-size=50.%,path=.`}, ``},
+		{[]string{`--store=ballast-size=50%,path=.`}, ``},
+		{[]string{`--store=ballast-size=2GiB,path=.`}, ``},
 		{[]string{`--store=attrs=bli:bli`}, `duplicate attribute`},
 		{[]string{`--store=type=bli`}, `bli is not a valid store type`},
 		{[]string{`--store=bla=bli`}, `bla is not a valid store field`},

pkg/server/config.go

@@ -514,11 +514,14 @@ func (cfg *Config) CreateEngines(ctx context.Context) (Engines, error) {
 				engines = append(engines, storage.NewInMem(ctx, spec.Attributes, cfg.CacheSize, sizeInBytes, cfg.Settings))
 			}
 		} else {
+			if err := vfs.Default.MkdirAll(spec.Path, 0755); err != nil {
+				return Engines{}, errors.Wrap(err, "creating store directory")
+			}
+			du, err := vfs.Default.GetDiskUsage(spec.Path)
+			if err != nil {
+				return Engines{}, errors.Wrap(err, "retrieving disk usage")
+			}
 			if spec.Size.Percent > 0 {
-				du, err := vfs.Default.GetDiskUsage(spec.Path)
-				if err != nil {
-					return Engines{}, err
-				}
 				sizeInBytes = int64(float64(du.TotalBytes) * spec.Size.Percent / 100)
 			}
 			if sizeInBytes != 0 && !skipSizeCheck && sizeInBytes < base.MinimumStoreSize {
@@ -532,6 +535,7 @@ func (cfg *Config) CreateEngines(ctx context.Context) (Engines, error) {
 			storageConfig := base.StorageConfig{
 				Attrs:             spec.Attributes,
 				Dir:               spec.Path,
+				BallastSize:       storage.BallastSizeBytes(spec, du),
 				MaxSize:           sizeInBytes,
 				Settings:          cfg.Settings,
 				UseFileRegistry:   spec.UseFileRegistry,

pkg/storage/BUILD.bazel

@@ -5,6 +5,7 @@ go_library(
     srcs = [
         "array_32bit.go",
         "array_64bit.go",
+        "ballast.go",
         "batch.go",
         "disk_map.go",
         "doc.go",
@@ -73,6 +74,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/base",
+        "//pkg/cli/exit",
         "//pkg/clusterversion",
         "//pkg/keys",
         "//pkg/kv/kvserver/concurrency/lock",
@@ -94,6 +96,7 @@ go_library(
         "//pkg/util/protoutil",
         "//pkg/util/stop",
         "//pkg/util/syncutil",
+        "//pkg/util/sysutil",
         "//pkg/util/timeutil",
         "//pkg/util/uuid",
         "@com_github_cockroachdb_errors//:errors",
@@ -113,6 +116,7 @@ go_test(
     name = "storage_test",
     size = "medium",
     srcs = [
+        "ballast_test.go",
         "batch_test.go",
         "bench_pebble_test.go",
         "bench_test.go",
@@ -164,6 +168,7 @@ go_test(
         "//pkg/util/randutil",
         "//pkg/util/shuffle",
         "//pkg/util/stop",
+        "//pkg/util/sysutil",
         "//pkg/util/timeutil",
         "//pkg/util/uint128",
         "//pkg/util/uuid",