Periodically write a database backup. (#76)

.gitignore

@@ -1,2 +1,3 @@
 vspd
 /database/test.db
+/database/test.db-backup

README.md

@@ -67,7 +67,13 @@ libraries:
 
 ## Backup
 
-- Regular backups of bbolt database and feexpub.
+The bbolt database file used by vspd is stored in the process home directory, at
+the path `{homedir}/data/{network}/vspd.db`. vspd keeps a file lock on this
+file, so it cannot be opened by any other processes while vspd is running.
+
+To facilitate back-ups, vspd will write periodically write a copy of the bbolt
+database to the path `{homedir}/data/{network}/vspd.db-backup`. A copy of the
+database file will also be written to this path when vspd shuts down.
 
 ## Issue Tracker
 

config.go

@@ -10,6 +10,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"time"
 
 	"github.com/decred/dcrd/dcrutil/v3"
 	"github.com/decred/dcrd/hdkeychain/v3"
@@ -27,27 +28,29 @@ var (
 	defaultDcrdHost       = "127.0.0.1"
 	defaultWalletHost     = "127.0.0.1"
 	defaultWebServerDebug = false
+	defaultBackupInterval = time.Minute * 3
 )
 
 // config defines the configuration options for the VSP.
 type config struct {
-	Listen         string  `long:"listen" ini-name:"listen" description:"The ip:port to listen for API requests."`
+	Listen         string        `long:"listen" ini-name:"listen" description:"The ip:port to listen for API requests."`
-	LogLevel       string  `long:"loglevel" ini-name:"loglevel" description:"Logging level." choice:"trace" choice:"debug" choice:"info" choice:"warn" choice:"error" choice:"critical"`
+	LogLevel       string        `long:"loglevel" ini-name:"loglevel" description:"Logging level." choice:"trace" choice:"debug" choice:"info" choice:"warn" choice:"error" choice:"critical"`
-	Network        string  `long:"network" ini-name:"network" description:"Decred network to use." choice:"testnet" choice:"mainnet" choice:"simnet"`
+	Network        string        `long:"network" ini-name:"network" description:"Decred network to use." choice:"testnet" choice:"mainnet" choice:"simnet"`
-	FeeXPub        string  `long:"feexpub" ini-name:"feexpub" description:"Cold wallet xpub used for collecting fees."`
+	FeeXPub        string        `long:"feexpub" ini-name:"feexpub" description:"Cold wallet xpub used for collecting fees."`
-	VSPFee         float64 `long:"vspfee" ini-name:"vspfee" description:"Fee percentage charged for VSP use. eg. 0.01 (1%), 0.05 (5%)."`
+	VSPFee         float64       `long:"vspfee" ini-name:"vspfee" description:"Fee percentage charged for VSP use. eg. 0.01 (1%), 0.05 (5%)."`
-	HomeDir        string  `long:"homedir" ini-name:"homedir" no-ini:"true" description:"Path to application home directory. Used for storing VSP database and logs."`
+	HomeDir        string        `long:"homedir" ini-name:"homedir" no-ini:"true" description:"Path to application home directory. Used for storing VSP database and logs."`
-	ConfigFile     string  `long:"configfile" ini-name:"configfile" no-ini:"true" description:"Path to configuration file."`
+	ConfigFile     string        `long:"configfile" ini-name:"configfile" no-ini:"true" description:"Path to configuration file."`
-	DcrdHost       string  `long:"dcrdhost" ini-name:"dcrdhost" description:"The ip:port to establish a JSON-RPC connection with dcrd. Should be the same host where vspd is running."`
+	DcrdHost       string        `long:"dcrdhost" ini-name:"dcrdhost" description:"The ip:port to establish a JSON-RPC connection with dcrd. Should be the same host where vspd is running."`
-	DcrdUser       string  `long:"dcrduser" ini-name:"dcrduser" description:"Username for dcrd RPC connections."`
+	DcrdUser       string        `long:"dcrduser" ini-name:"dcrduser" description:"Username for dcrd RPC connections."`
-	DcrdPass       string  `long:"dcrdpass" ini-name:"dcrdpass" description:"Password for dcrd RPC connections."`
+	DcrdPass       string        `long:"dcrdpass" ini-name:"dcrdpass" description:"Password for dcrd RPC connections."`
-	DcrdCert       string  `long:"dcrdcert" ini-name:"dcrdcert" description:"The dcrd RPC certificate file."`
+	DcrdCert       string        `long:"dcrdcert" ini-name:"dcrdcert" description:"The dcrd RPC certificate file."`
-	WalletHost     string  `long:"wallethost" ini-name:"wallethost" description:"The ip:port to establish a JSON-RPC connection with voting dcrwallet."`
+	WalletHost     string        `long:"wallethost" ini-name:"wallethost" description:"The ip:port to establish a JSON-RPC connection with voting dcrwallet."`
-	WalletUser     string  `long:"walletuser" ini-name:"walletuser" description:"Username for dcrwallet RPC connections."`
+	WalletUser     string        `long:"walletuser" ini-name:"walletuser" description:"Username for dcrwallet RPC connections."`
-	WalletPass     string  `long:"walletpass" ini-name:"walletpass" description:"Password for dcrwallet RPC connections."`
+	WalletPass     string        `long:"walletpass" ini-name:"walletpass" description:"Password for dcrwallet RPC connections."`
-	WalletCert     string  `long:"walletcert" ini-name:"walletcert" description:"The dcrwallet RPC certificate file."`
+	WalletCert     string        `long:"walletcert" ini-name:"walletcert" description:"The dcrwallet RPC certificate file."`
-	WebServerDebug bool    `long:"webserverdebug" ini-name:"webserverdebug" description:"Enable web server debug mode (verbose logging to terminal and live-reloading templates)."`
+	WebServerDebug bool          `long:"webserverdebug" ini-name:"webserverdebug" description:"Enable web server debug mode (verbose logging to terminal and live-reloading templates)."`
-	SupportEmail   string  `long:"supportemail" ini-name:"supportemail" description:"Email address for users in need of support."`
+	SupportEmail   string        `long:"supportemail" ini-name:"supportemail" description:"Email address for users in need of support."`
+	BackupInterval time.Duration `long:"backupinterval" ini-name:"backupinterval" description:"Time period between automatic database backups. Valid time units are {s,m,h}. Minimum 30 seconds."`
 
 	dbPath     string
 	netParams  *netParams
@@ -152,6 +155,7 @@ func loadConfig() (*config, error) {
 		DcrdHost:       defaultDcrdHost,
 		WalletHost:     defaultWalletHost,
 		WebServerDebug: defaultWebServerDebug,
+		BackupInterval: defaultBackupInterval,
 	}
 
 	// Pre-parse the command line options to see if an alternative config
@@ -241,6 +245,11 @@ func loadConfig() (*config, error) {
 		cfg.netParams = &simNetParams
 	}
 
+	// Ensure backup interval is greater than 30 seconds.
+	if cfg.BackupInterval < time.Second*30 {
+		return nil, errors.New("minimum backupinterval is 30 seconds")
+	}
+
 	// Ensure the support email address is set.
 	if cfg.SupportEmail == "" {
 		return nil, errors.New("the supportemail option is not set")

database/database.go

@@ -6,6 +6,7 @@ import (
 	"crypto/rand"
 	"encoding/binary"
 	"fmt"
+	"os"
 	"sync"
 	"time"
 
@@ -33,9 +34,38 @@ var (
 	lastAddressIndexK = []byte("lastaddressindex")
 )
 
+// backupMtx protects writeBackup, to ensure only one backup file is written at
+// a time.
+var backupMtx sync.Mutex
+
+func writeBackup(db *bolt.DB, dbFile string) error {
+	backupMtx.Lock()
+	defer backupMtx.Unlock()
+
+	backupPath := dbFile + "-backup"
+	tempPath := backupPath + "~"
+
+	// Write backup to temporary file.
+	err := db.View(func(tx *bolt.Tx) error {
+		return tx.CopyFile(tempPath, 0600)
+	})
+	if err != nil {
+		return fmt.Errorf("tx.CopyFile: %v", err)
+	}
+
+	// Rename temporary file to actual backup file.
+	err = os.Rename(tempPath, backupPath)
+	if err != nil {
+		return fmt.Errorf("os.Rename: %v", err)
+	}
+
+	log.Debugf("Database backup written to %s", backupPath)
+	return err
+}
+
 // Open initializes and returns an open database. If no database file is found
 // at the provided path, a new one will be created.
-func Open(ctx context.Context, shutdownWg *sync.WaitGroup, dbFile string) (*VspDatabase, error) {
+func Open(ctx context.Context, shutdownWg *sync.WaitGroup, dbFile string, backupInterval time.Duration) (*VspDatabase, error) {
 
 	db, err := bolt.Open(dbFile, 0600, &bolt.Options{Timeout: 1 * time.Second})
 	if err != nil {
@@ -51,7 +81,13 @@ func Open(ctx context.Context, shutdownWg *sync.WaitGroup, dbFile string) (*VspD
 		<-ctx.Done()
 
 		log.Debug("Closing database...")
-		err := db.Close()
+
+		err := writeBackup(db, dbFile)
+		if err != nil {
+			log.Errorf("Failed to write database backup: %v", err)
+		}
+
+		err = db.Close()
 		if err != nil {
 			log.Errorf("Error closing database: %v", err)
 		} else {
@@ -60,6 +96,25 @@ func Open(ctx context.Context, shutdownWg *sync.WaitGroup, dbFile string) (*VspD
 		shutdownWg.Done()
 	}()
 
+	// Start a ticker to update the backup file at the specified interval.
+	shutdownWg.Add(1)
+	backupTicker := time.NewTicker(backupInterval)
+	go func() {
+		for {
+			select {
+			case <-backupTicker.C:
+				err := writeBackup(db, dbFile)
+				if err != nil {
+					log.Errorf("Failed to write database backup: %v", err)
+				}
+			case <-ctx.Done():
+				backupTicker.Stop()
+				shutdownWg.Done()
+				return
+			}
+		}
+	}()
+
 	// Create all storage buckets of the VSP if they don't already exist.
 	err = db.Update(func(tx *bolt.Tx) error {
 		if tx.Bucket(vspBktK) == nil {

database/database_test.go

@@ -5,17 +5,20 @@ import (
 	"os"
 	"sync"
 	"testing"
+	"time"
 )
 
 var (
-	testDb = "test.db"
+	testDb   = "test.db"
-	db     *VspDatabase
+	backupDb = "test.db-backup"
+	db       *VspDatabase
 )
 
 // TestDatabase runs all database tests.
 func TestDatabase(t *testing.T) {
 	// Ensure we are starting with a clean environment.
 	os.Remove(testDb)
+	os.Remove(backupDb)
 
 	// All sub-tests to run.
 	tests := map[string]func(*testing.T){
@@ -31,7 +34,7 @@ func TestDatabase(t *testing.T) {
 		var err error
 		var wg sync.WaitGroup
 		ctx, cancel := context.WithCancel(context.TODO())
-		db, err = Open(ctx, &wg, testDb)
+		db, err = Open(ctx, &wg, testDb, time.Hour)
 		if err != nil {
 			t.Fatalf("error creating test database: %v", err)
 		}
@@ -44,6 +47,7 @@ func TestDatabase(t *testing.T) {
 		wg.Wait()
 
 		os.Remove(testDb)
+		os.Remove(backupDb)
 	}
 }
 

main.go

@@ -49,7 +49,7 @@ func run(ctx context.Context) error {
 	defer log.Info("Shutdown complete")
 
 	// Open database.
-	db, err := database.Open(ctx, &shutdownWg, cfg.dbPath)
+	db, err := database.Open(ctx, &shutdownWg, cfg.dbPath, cfg.BackupInterval)
 	if err != nil {
 		log.Errorf("Database error: %v", err)
 		requestShutdown()