Add generations command

cmd/litestream/config.go

@@ -1,69 +0,0 @@
-package main
-
-import (
-	"flag"
-	"fmt"
-	"io/ioutil"
-	"os"
-	"os/user"
-	"path/filepath"
-	"strings"
-
-	"gopkg.in/yaml.v2"
-)
-
-// Default settings.
-const (
-	DefaultConfigPath = "~/litestream.yml"
-)
-
-// Config represents a configuration file for the litestream daemon.
-type Config struct {
-	DBs []*DBConfig `yaml:"databases"`
-}
-
-// DefaultConfig returns a new instance of Config with defaults set.
-func DefaultConfig() Config {
-	return Config{}
-}
-
-// ReadConfigFile unmarshals config from filename. Expands path if needed.
-func ReadConfigFile(filename string) (Config, error) {
-	config := DefaultConfig()
-
-	// Expand filename, if necessary.
-	if prefix := "~" + string(os.PathSeparator); strings.HasPrefix(filename, prefix) {
-		u, err := user.Current()
-		if err != nil {
-			return config, err
-		} else if u.HomeDir == "" {
-			return config, fmt.Errorf("home directory unset")
-		}
-		filename = filepath.Join(u.HomeDir, strings.TrimPrefix(filename, prefix))
-	}
-
-	// Read & deserialize configuration.
-	if buf, err := ioutil.ReadFile(filename); os.IsNotExist(err) {
-		return config, fmt.Errorf("config file not found: %s", filename)
-	} else if err != nil {
-		return config, err
-	} else if err := yaml.Unmarshal(buf, &config); err != nil {
-		return config, err
-	}
-	return config, nil
-}
-
-type DBConfig struct {
-	Path     string           `yaml:"path"`
-	Replicas []*ReplicaConfig `yaml:"replicas"`
-}
-
-type ReplicaConfig struct {
-	Type string `yaml:"type"` // "file", "s3"
-	Name string `yaml:"name"` // name of replicator, optional.
-	Path string `yaml:"path"` // used for file replicators
-}
-
-func registerConfigFlag(fs *flag.FlagSet, p *string) {
-	fs.StringVar(p, "config", DefaultConfigPath, "config path")
-}

cmd/litestream/generations.go

@@ -0,0 +1,137 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"text/tabwriter"
+	"time"
+)
+
+type GenerationsCommand struct {
+	ConfigPath string
+	Config     Config
+
+	DBPath string
+}
+
+func NewGenerationsCommand() *GenerationsCommand {
+	return &GenerationsCommand{}
+}
+
+func (c *GenerationsCommand) Run(ctx context.Context, args []string) (err error) {
+	fs := flag.NewFlagSet("litestream-generations", flag.ContinueOnError)
+	registerConfigFlag(fs, &c.ConfigPath)
+	fs.Usage = c.Usage
+	if err := fs.Parse(args); err != nil {
+		return err
+	} else if fs.NArg() > 1 {
+		return fmt.Errorf("too many arguments")
+	}
+
+	// Load configuration.
+	if c.ConfigPath == "" {
+		return errors.New("-config required")
+	}
+	config, err := ReadConfigFile(c.ConfigPath)
+	if err != nil {
+		return err
+	}
+
+	// Determine absolute path for database, if specified.
+	if c.DBPath = fs.Arg(0); c.DBPath != "" {
+		if c.DBPath, err = filepath.Abs(c.DBPath); err != nil {
+			return err
+		}
+	}
+
+	// List each generation.
+	w := tabwriter.NewWriter(os.Stdout, 0, 8, 1, '\t', 0)
+	fmt.Fprintln(w, "db\tname\tgeneration\tlag\tstart\tend")
+	for _, dbConfig := range config.DBs {
+		// Filter database, if specified in the arguments.
+		if c.DBPath != "" && dbConfig.Path != c.DBPath {
+			continue
+		}
+
+		// Instantiate DB from from configuration.
+		db, err := newDBFromConfig(dbConfig)
+		if err != nil {
+			return err
+		}
+
+		// Determine last time database or WAL was updated.
+		updatedAt, err := db.UpdatedAt()
+		if err != nil {
+			return err
+		}
+
+		// Iterate over each replicator in the database.
+		for _, r := range db.Replicators {
+			generations, err := r.Generations()
+			if err != nil {
+				log.Printf("%s: cannot list generations", r.Name(), err)
+				continue
+			}
+
+			// Iterate over each generation for the replicator.
+			for _, generation := range generations {
+				stats, err := r.GenerationStats(generation)
+				if err != nil {
+					log.Printf("%s: cannot find generation stats: %s", r.Name(), err)
+					continue
+				}
+
+				fmt.Fprintf(w, "%s\t%s\t%s\t%s\t%s\t%s\n",
+					db.Path(),
+					r.Name(),
+					generation,
+					truncateDuration(stats.UpdatedAt.Sub(updatedAt)).String(),
+					stats.CreatedAt.Format(time.RFC3339),
+					stats.UpdatedAt.Format(time.RFC3339),
+				)
+			}
+		}
+	}
+	w.Flush()
+
+	return nil
+}
+
+func (c *GenerationsCommand) Usage() {
+	fmt.Printf(`
+The generations command lists all generations across all replicas along with
+stats about their lag behind the primary database and the time range they cover.
+
+Usage:
+
+	litestream generations [arguments] DB
+
+Arguments:
+
+	-config PATH
+	    Specifies the configuration file. Defaults to %s
+
+`[1:],
+		DefaultConfigPath,
+	)
+}
+
+func truncateDuration(d time.Duration) time.Duration {
+	if d > time.Hour {
+		return d.Truncate(time.Hour)
+	} else if d > time.Minute {
+		return d.Truncate(time.Minute)
+	} else if d > time.Second {
+		return d.Truncate(time.Second)
+	} else if d > time.Millisecond {
+		return d.Truncate(time.Millisecond)
+	} else if d > time.Microsecond {
+		return d.Truncate(time.Microsecond)
+	}
+	return d
+}

cmd/litestream/main.go

@@ -4,9 +4,15 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io/ioutil"
 	"log"
 	"os"
+	"os/user"
+	"path/filepath"
 	"strings"
+
+	"github.com/benbjohnson/litestream"
+	"gopkg.in/yaml.v2"
 )
 
 // Build information.
@@ -14,6 +20,9 @@ var (
 	Version = "(development build)"
 )
 
+// DefaultConfigPath is the default configuration path.
+const DefaultConfigPath = "/etc/litestream.yml"
+
 func main() {
 	log.SetFlags(0)
 
@@ -39,6 +48,8 @@ func (m *Main) Run(ctx context.Context, args []string) (err error) {
 	}
 
 	switch cmd {
+	case "generations":
+		return (&GenerationsCommand{}).Run(ctx, args)
 	case "replicate":
 		return (&ReplicateCommand{}).Run(ctx, args)
 	case "version":
@@ -66,3 +77,89 @@ The commands are:
 	version     prints the version
 `[1:])
 }
+
+// Config represents a configuration file for the litestream daemon.
+type Config struct {
+	DBs []*DBConfig `yaml:"databases"`
+}
+
+// DefaultConfig returns a new instance of Config with defaults set.
+func DefaultConfig() Config {
+	return Config{}
+}
+
+// ReadConfigFile unmarshals config from filename. Expands path if needed.
+func ReadConfigFile(filename string) (Config, error) {
+	config := DefaultConfig()
+
+	// Expand filename, if necessary.
+	if prefix := "~" + string(os.PathSeparator); strings.HasPrefix(filename, prefix) {
+		u, err := user.Current()
+		if err != nil {
+			return config, err
+		} else if u.HomeDir == "" {
+			return config, fmt.Errorf("home directory unset")
+		}
+		filename = filepath.Join(u.HomeDir, strings.TrimPrefix(filename, prefix))
+	}
+
+	// Read & deserialize configuration.
+	if buf, err := ioutil.ReadFile(filename); os.IsNotExist(err) {
+		return config, fmt.Errorf("config file not found: %s", filename)
+	} else if err != nil {
+		return config, err
+	} else if err := yaml.Unmarshal(buf, &config); err != nil {
+		return config, err
+	}
+	return config, nil
+}
+
+type DBConfig struct {
+	Path     string           `yaml:"path"`
+	Replicas []*ReplicaConfig `yaml:"replicas"`
+}
+
+type ReplicaConfig struct {
+	Type string `yaml:"type"` // "file", "s3"
+	Name string `yaml:"name"` // name of replicator, optional.
+	Path string `yaml:"path"` // used for file replicators
+}
+
+func registerConfigFlag(fs *flag.FlagSet, p *string) {
+	fs.StringVar(p, "config", DefaultConfigPath, "config path")
+}
+
+// newDBFromConfig instantiates a DB based on a configuration.
+func newDBFromConfig(config *DBConfig) (*litestream.DB, error) {
+	// Initialize database with given path.
+	db := litestream.NewDB(config.Path)
+
+	// Instantiate and attach replicators.
+	for _, rconfig := range config.Replicas {
+		r, err := newReplicatorFromConfig(db, rconfig)
+		if err != nil {
+			return nil, err
+		}
+		db.Replicators = append(db.Replicators, r)
+	}
+
+	return db, nil
+}
+
+// newReplicatorFromConfig instantiates a replicator for a DB based on a config.
+func newReplicatorFromConfig(db *litestream.DB, config *ReplicaConfig) (litestream.Replicator, error) {
+	switch config.Type {
+	case "", "file":
+		return newFileReplicatorFromConfig(db, config)
+	default:
+		return nil, fmt.Errorf("unknown replicator type in config: %q", config.Type)
+	}
+}
+
+// newFileReplicatorFromConfig returns a new instance of FileReplicator build from config.
+func newFileReplicatorFromConfig(db *litestream.DB, config *ReplicaConfig) (*litestream.FileReplicator, error) {
+	if config.Path == "" {
+		return nil, fmt.Errorf("file replicator path require for db %q", db.Path())
+	}
+	return litestream.NewFileReplicator(db, config.Name, config.Path), nil
+}

cmd/litestream/replicate.go

@@ -54,10 +54,17 @@ func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 		return errors.New("configuration must specify at least one database")
 	}
 
-	for _, dbc := range config.DBs {
-		if err := c.openDB(dbc); err != nil {
+	for _, dbConfig := range config.DBs {
+		db, err := newDBFromConfig(dbConfig)
+		if err != nil {
 			return err
 		}
+
+		// Open database & attach to program.
+		if err := db.Open(); err != nil {
+			return err
+		}
+		c.DBs = append(c.DBs, db)
 	}
 
 	// Notify user that initialization is done.
@@ -76,47 +83,6 @@ func (c *ReplicateCommand) Run(ctx context.Context, args []string) (err error) {
 	return nil
 }
 
-// openDB instantiates and initializes a DB based on a configuration.
-func (c *ReplicateCommand) openDB(config *DBConfig) error {
-	// Initialize database with given path.
-	db := litestream.NewDB(config.Path)
-
-	// Instantiate and attach replicators.
-	for _, rconfig := range config.Replicas {
-		r, err := c.createReplicator(db, rconfig)
-		if err != nil {
-			return err
-		}
-		db.Replicators = append(db.Replicators, r)
-	}
-
-	// Open database & attach to program.
-	if err := db.Open(); err != nil {
-		return err
-	}
-	c.DBs = append(c.DBs, db)
-
-	return nil
-}
-
-// createReplicator instantiates a replicator for a DB based on a config.
-func (c *ReplicateCommand) createReplicator(db *litestream.DB, config *ReplicaConfig) (litestream.Replicator, error) {
-	switch config.Type {
-	case "", "file":
-		return c.createFileReplicator(db, config)
-	default:
-		return nil, fmt.Errorf("unknown replicator type in config: %q", config.Type)
-	}
-}
-
-// createFileReplicator returns a new instance of FileReplicator build from config.
-func (c *ReplicateCommand) createFileReplicator(db *litestream.DB, config *ReplicaConfig) (*litestream.FileReplicator, error) {
-	if config.Path == "" {
-		return nil, fmt.Errorf("file replicator path require for db %q", db.Path())
-	}
-	return litestream.NewFileReplicator(db, config.Name, config.Path), nil
-}
-
 // Close closes all open databases.
 func (c *ReplicateCommand) Close() (err error) {
 	for _, db := range c.DBs {
@@ -131,7 +97,7 @@ func (c *ReplicateCommand) Close() (err error) {
 }
 
 func (c *ReplicateCommand) Usage() {
-	fmt.Println(`
+	fmt.Printf(`
 The replicate command starts a server to monitor & replicate databases 
 specified in your configuration file.
 
@@ -142,7 +108,7 @@ Usage:
 Arguments:
 
 	-config PATH
-	    Specifies the configuration file. Defaults to ~/litestream.yml
+	    Specifies the configuration file. Defaults to %s
 
-`[1:])
+`[1:], DefaultConfigPath)
 }

db.go

@@ -190,6 +190,26 @@ func (db *DB) Close() (err error) {
 	return err
 }
 
+// UpdatedAt returns the last modified time of the database or WAL file.
+func (db *DB) UpdatedAt() (time.Time, error) {
+	// Determine database modified time.
+	fi, err := os.Stat(db.Path())
+	if err != nil {
+		return time.Time{}, err
+	}
+	t := fi.ModTime().UTC()
+
+	// Use WAL modified time, if available & later.
+	if fi, err := os.Stat(db.WALPath()); os.IsNotExist(err) {
+		return t, nil
+	} else if err != nil {
+		return t, err
+	} else if fi.ModTime().After(t) {
+		t = fi.ModTime().UTC()
+	}
+	return t, nil
+}
+
 // Init initializes the connection to the database.
 // Skipped if already initialized or if the database file does not exist.
 func (db *DB) Init() (err error) {

litestream.go

@@ -138,6 +138,34 @@ func removeTmpFiles(root string) error {
 	})
 }
 
+// IsGenerationName returns true if s is the correct length and is only lowercase hex characters.
+func IsGenerationName(s string) bool {
+	if len(s) != GenerationNameLen {
+		return false
+	}
+	for _, ch := range s {
+		if !isHexChar(ch) {
+			return false
+		}
+	}
+	return true
+}
+
+// IsSnapshotPath returns true if s is a path to a snapshot file.
+func IsSnapshotPath(s string) bool {
+	return strings.HasSuffix(s, SnapshotExt) || strings.HasSuffix(s, SnapshotExt+".gz")
+}
+
+// IsWALPath returns true if s is a path to a WAL file.
+func IsWALPath(s string) bool {
+	return strings.HasSuffix(s, WALExt) || strings.HasSuffix(s, WALExt+".gz")
+}
+
+// isHexChar returns true if ch is a lowercase hex character.
+func isHexChar(ch rune) bool {
+	return (ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f')
+}
+
 // HexDump returns hexdump output but with duplicate lines removed.
 func HexDump(b []byte) string {
 	const prefixN = len("00000000")

replicator.go

@@ -12,14 +12,29 @@ import (
 	"sort"
 	"strings"
 	"sync"
+	"time"
 )
 
 // Replicator represents a method for replicating the snapshot & WAL data to
 // a remote destination.
 type Replicator interface {
+	// The name of the replicator. Defaults to type if no name specified.
 	Name() string
+
+	// String identifier for the type of replicator ("file", "s3", etc).
 	Type() string
+
+	// Returns a list of generation names for the replicator.
+	Generations() ([]string, error)
+
+	// Returns basic information about a generation including the number of
+	// snapshot & WAL files as well as the time range covered.
+	GenerationStats(generation string) (GenerationStats, error)
+
+	// Starts replicating in a background goroutine.
 	Start(ctx context.Context)
+
+	// Stops all replication processing. Blocks until processing stopped.
 	Stop()
 }
 
@@ -71,6 +86,112 @@ func (r *FileReplicator) WALPath(generation string, index int) string {
 	return filepath.Join(r.dst, "generations", generation, "wal", fmt.Sprintf("%016x.wal", index))
 }
 
+// Generations returns a list of available generation names.
+func (r *FileReplicator) Generations() ([]string, error) {
+	fis, err := ioutil.ReadDir(filepath.Join(r.dst, "generations"))
+	if os.IsNotExist(err) {
+		return nil, nil
+	} else if err != nil {
+		return nil, err
+	}
+
+	var generations []string
+	for _, fi := range fis {
+		if !IsGenerationName(fi.Name()) {
+			continue
+		} else if !fi.IsDir() {
+			continue
+		}
+		generations = append(generations, fi.Name())
+	}
+	return generations, nil
+}
+
+// GenerationStats returns stats for a generation.
+func (r *FileReplicator) GenerationStats(generation string) (stats GenerationStats, err error) {
+	// Determine stats for all snapshots.
+	n, min, max, err := r.snapshotStats(generation)
+	if err != nil {
+		return stats, err
+	}
+	stats.SnapshotN = n
+	stats.CreatedAt, stats.UpdatedAt = min, max
+
+	// Update stats if we have WAL files.
+	n, min, max, err = r.walStats(generation)
+	if err != nil {
+		return stats, err
+	} else if n == 0 {
+		return stats, nil
+	}
+
+	stats.WALN = n
+	if stats.CreatedAt.IsZero() || min.Before(stats.CreatedAt) {
+		stats.CreatedAt = min
+	}
+	if stats.UpdatedAt.IsZero() || max.After(stats.UpdatedAt) {
+		stats.UpdatedAt = max
+	}
+	return stats, nil
+}
+
+func (r *FileReplicator) snapshotStats(generation string) (n int, min, max time.Time, err error) {
+	fis, err := ioutil.ReadDir(filepath.Join(r.dst, "generations", generation, "snapshots"))
+	if os.IsNotExist(err) {
+		return n, min, max, nil
+	} else if err != nil {
+		return n, min, max, err
+	}
+
+	for _, fi := range fis {
+		if !IsSnapshotPath(fi.Name()) {
+			continue
+		}
+		modTime := fi.ModTime().UTC()
+
+		n++
+		if min.IsZero() || modTime.Before(min) {
+			min = modTime
+		}
+		if max.IsZero() || modTime.After(max) {
+			max = modTime
+		}
+	}
+	return n, min, max, nil
+}
+
+func (r *FileReplicator) walStats(generation string) (n int, min, max time.Time, err error) {
+	fis, err := ioutil.ReadDir(filepath.Join(r.dst, "generations", generation, "wal"))
+	if os.IsNotExist(err) {
+		return n, min, max, nil
+	} else if err != nil {
+		return n, min, max, err
+	}
+
+	for _, fi := range fis {
+		if !IsWALPath(fi.Name()) {
+			continue
+		}
+		modTime := fi.ModTime().UTC()
+
+		n++
+		if min.IsZero() || modTime.Before(min) {
+			min = modTime
+		}
+		if max.IsZero() || modTime.After(max) {
+			max = modTime
+		}
+	}
+	return n, min, max, nil
+}
+
+type GenerationStats struct {
+	SnapshotN int
+	WALN      int
+	CreatedAt time.Time
+	UpdatedAt time.Time
+}
+
 // Start starts replication for a given generation.
 func (r *FileReplicator) Start(ctx context.Context) {
 	// Stop previous replication.