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Add -if-db-not-exists restore flag

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This commit adds a flag to `litestream restore` to skip the restore
if the database file already exists. It is useful when using the
official Litestream Docker image and you don't have the ability to
add a script to check for the existence of the file.
This commit is contained in:
Ben Johnson
2021-05-31 14:46:15 -06:00
parent 59b025d3da
commit 88909e3bd0
1 changed files with 30 additions and 4 deletions
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34
cmd/litestream/restore.go
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@@ -28,6 +28,7 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
fs.StringVar(&opt.Generation, "generation", "", "generation name")
fs.Var((*indexVar)(&opt.Index), "index", "wal index")
fs.IntVar(&opt.Parallelism, "parallelism", opt.Parallelism, "parallelism")
ifDBNotExists := fs.Bool("if-db-not-exists", false, "")
ifReplicaExists := fs.Bool("if-replica-exists", false, "")
timestampStr := fs.String("timestamp", "", "timestamp")
verbose := fs.Bool("v", false, "verbose output")
@@ -58,14 +59,20 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
if *configPath != "" {
return fmt.Errorf("cannot specify a replica URL and the -config flag")
}
if r, err = c.loadFromURL(ctx, fs.Arg(0), &opt); err != nil {
if r, err = c.loadFromURL(ctx, fs.Arg(0), *ifDBNotExists, &opt); err == errSkipDBExists {
fmt.Println("database already exists, skipping")
return nil
} else if err != nil {
return err
}
} else {
if *configPath == "" {
*configPath = DefaultConfigPath()
}
if r, err = c.loadFromConfig(ctx, fs.Arg(0), *configPath, !*noExpandEnv, &opt); err != nil {
if r, err = c.loadFromConfig(ctx, fs.Arg(0), *configPath, !*noExpandEnv, *ifDBNotExists, &opt); err == errSkipDBExists {
fmt.Println("database already exists, skipping")
return nil
} else if err != nil {
return err
}
}
@@ -84,7 +91,16 @@ func (c *RestoreCommand) Run(ctx context.Context, args []string) (err error) {
}
// loadFromURL creates a replica & updates the restore options from a replica URL.
func (c *RestoreCommand) loadFromURL(ctx context.Context, replicaURL string, opt *litestream.RestoreOptions) (*litestream.Replica, error) {
func (c *RestoreCommand) loadFromURL(ctx context.Context, replicaURL string, ifDBNotExists bool, opt *litestream.RestoreOptions) (*litestream.Replica, error) {
if opt.OutputPath == "" {
return nil, fmt.Errorf("output path required")
}
// Exit successfully if the output file already exists.
if _, err := os.Stat(opt.OutputPath); !os.IsNotExist(err) && ifDBNotExists {
return nil, errSkipDBExists
}
syncInterval := litestream.DefaultSyncInterval
r, err := NewReplicaFromConfig(&ReplicaConfig{
URL: replicaURL,
@@ -98,7 +114,7 @@ func (c *RestoreCommand) loadFromURL(ctx context.Context, replicaURL string, opt
}
// loadFromConfig returns a replica & updates the restore options from a DB reference.
func (c *RestoreCommand) loadFromConfig(ctx context.Context, dbPath, configPath string, expandEnv bool, opt *litestream.RestoreOptions) (*litestream.Replica, error) {
func (c *RestoreCommand) loadFromConfig(ctx context.Context, dbPath, configPath string, expandEnv, ifDBNotExists bool, opt *litestream.RestoreOptions) (*litestream.Replica, error) {
// Load configuration.
config, err := ReadConfigFile(configPath, expandEnv)
if err != nil {
@@ -123,6 +139,11 @@ func (c *RestoreCommand) loadFromConfig(ctx context.Context, dbPath, configPath
opt.OutputPath = dbPath
}
// Exit successfully if the output file already exists.
if _, err := os.Stat(opt.OutputPath); !os.IsNotExist(err) && ifDBNotExists {
return nil, errSkipDBExists
}
// Determine the appropriate replica & generation to restore from,
r, generation, err := db.CalcRestoreTarget(ctx, *opt)
if err != nil {
@@ -173,6 +194,9 @@ Arguments:
Output path of the restored database.
Defaults to original DB path.
-if-db-not-exists
Returns exit code of 0 if the database already exists.
-if-replica-exists
Returns exit code of 0 if no backups found.
@@ -205,3 +229,5 @@ Examples:
DefaultConfigPath(),
)
}
var errSkipDBExists = errors.New("database already exists, skipping")