add --nocache option to disable compact block file cache

This fixes issue #480. Enabling this option decreases the performance of
gRPCs GetBlock and GetBlockRange, but conserves disk space (the size of
the database is currently around 17GB).

Note, specifying this option will also delete the existing cache (so if
you start again without --nocache, the cache will need to be recreated).

cmd/root.go

@@ -55,6 +55,7 @@ var rootCmd = &cobra.Command{
 			GenCertVeryInsecure: viper.GetBool("gen-cert-very-insecure"),
 			DataDir:             viper.GetString("data-dir"),
 			Redownload:          viper.GetBool("redownload"),
+			NoCache:             viper.GetBool("nocache"),
 			SyncFromHeight:      viper.GetInt("sync-from-height"),
 			PingEnable:          viper.GetBool("ping-very-insecure"),
 			Darkside:            viper.GetBool("darkside-very-insecure"),
@@ -240,13 +241,22 @@ func startServer(opts *common.Options) error {
 		os.Stderr.WriteString(fmt.Sprintf("\n  ** Can't create db directory: %s\n\n", dbPath))
 		os.Exit(1)
 	}
-	syncFromHeight := opts.SyncFromHeight
-	if opts.Redownload {
-		syncFromHeight = 0
+	var cache *common.BlockCache
+	if opts.NoCache {
+		lengthsName, blocksName := common.DbFileNames(dbPath, chainName)
+		os.Remove(lengthsName)
+		os.Remove(blocksName)
+	} else {
+		syncFromHeight := opts.SyncFromHeight
+		if opts.Redownload {
+			syncFromHeight = 0
+		}
+		cache = common.NewBlockCache(dbPath, chainName, saplingHeight, syncFromHeight)
 	}
-	cache := common.NewBlockCache(dbPath, chainName, saplingHeight, syncFromHeight)
 	if !opts.Darkside {
-		go common.BlockIngestor(cache, 0 /*loop forever*/)
+		if !opts.NoCache {
+			go common.BlockIngestor(cache, 0 /*loop forever*/)
+		}
 	} else {
 		// Darkside wants to control starting the block ingestor.
 		common.DarksideInit(cache, int(opts.DarksideTimeout))
@@ -330,6 +340,7 @@ func init() {
 	rootCmd.Flags().Bool("no-tls-very-insecure", false, "run without the required TLS certificate, only for debugging, DO NOT use in production")
 	rootCmd.Flags().Bool("gen-cert-very-insecure", false, "run with self-signed TLS certificate, only for debugging, DO NOT use in production")
 	rootCmd.Flags().Bool("redownload", false, "re-fetch all blocks from zcashd; reinitialize local cache files")
+	rootCmd.Flags().Bool("nocache", false, "don't maintain a compact blocks disk cache (to reduce storage)")
 	rootCmd.Flags().Int("sync-from-height", -1, "re-fetch blocks from zcashd start at this height")
 	rootCmd.Flags().String("data-dir", "/var/lib/lightwalletd", "data directory (such as db)")
 	rootCmd.Flags().Bool("ping-very-insecure", false, "allow Ping GRPC for testing")
@@ -362,6 +373,8 @@ func init() {
 	viper.SetDefault("gen-cert-very-insecure", false)
 	viper.BindPFlag("redownload", rootCmd.Flags().Lookup("redownload"))
 	viper.SetDefault("redownload", false)
+	viper.BindPFlag("nocache", rootCmd.Flags().Lookup("nocache"))
+	viper.SetDefault("nocache", false)
 	viper.BindPFlag("sync-from-height", rootCmd.Flags().Lookup("sync-from-height"))
 	viper.SetDefault("sync-from-height", -1)
 	viper.BindPFlag("data-dir", rootCmd.Flags().Lookup("data-dir"))

common/cache.go

@@ -195,7 +195,7 @@ func NewBlockCache(dbPath string, chainName string, startHeight int, syncFromHei
 	c := &BlockCache{}
 	c.firstBlock = startHeight
 	c.nextBlock = startHeight
-	c.lengthsName, c.blocksName = dbFileNames(dbPath, chainName)
+	c.lengthsName, c.blocksName = DbFileNames(dbPath, chainName)
 	var err error
 	if err := os.MkdirAll(filepath.Join(dbPath, chainName), 0755); err != nil {
 		Log.Fatal("mkdir ", dbPath, " failed: ", err)
@@ -250,7 +250,7 @@ func NewBlockCache(dbPath string, chainName string, startHeight int, syncFromHei
 	return c
 }
 
-func dbFileNames(dbPath string, chainName string) (string, string) {
+func DbFileNames(dbPath string, chainName string) (string, string) {
 	return filepath.Join(dbPath, chainName, "lengths"),
 		filepath.Join(dbPath, chainName, "blocks")
 }

common/common.go

@@ -43,6 +43,7 @@ type Options struct {
 	NoTLSVeryInsecure   bool   `json:"no_tls_very_insecure,omitempty"`
 	GenCertVeryInsecure bool   `json:"gen_cert_very_insecure,omitempty"`
 	Redownload          bool   `json:"redownload"`
+	NoCache             bool   `json:"nocache"`
 	SyncFromHeight      int    `json:"sync_from_height"`
 	DataDir             string `json:"data_dir"`
 	PingEnable          bool   `json:"ping_enable"`
@@ -476,9 +477,12 @@ func BlockIngestor(c *BlockCache, rep int) {
 // nil if no block exists at this height.
 func GetBlock(cache *BlockCache, height int) (*walletrpc.CompactBlock, error) {
 	// First, check the cache to see if we have the block
-	block := cache.Get(height)
-	if block != nil {
-		return block, nil
+	var block *walletrpc.CompactBlock
+	if cache != nil {
+		block := cache.Get(height)
+		if block != nil {
+			return block, nil
+		}
 	}
 
 	// Not in the cache