add -nocache to disable compact block file cache

This fixes issue zcash#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).

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)
@@ -257,7 +257,7 @@ 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