Merge Pull Request #3777: Fix export panic

Author: jackzampolin

PENDING.md

@@ -89,6 +89,8 @@ decoded automatically.
 
 ### Gaia
 
+* [\#3777](https://github.com/cosmso/cosmos-sdk/pull/3777) `gaiad export` no longer panics when the database is empty
+
 ### SDK
 
 * \#3728 Truncate decimal multiplication & division in distribution to ensure

server/export.go

@@ -10,9 +10,9 @@ import (
 	"github.com/spf13/viper"
 
 	"io/ioutil"
-	"path"
 
 	"github.com/tendermint/tendermint/libs/cli"
+	dbm "github.com/tendermint/tendermint/libs/db"
 	tmtypes "github.com/tendermint/tendermint/types"
 
 	"github.com/cosmos/cosmos-sdk/codec"
@@ -34,35 +34,35 @@ func ExportCmd(ctx *Context, cdc *codec.Codec, appExporter AppExporter) *cobra.C
 			config.SetRoot(viper.GetString(cli.HomeFlag))
 
 			traceWriterFile := viper.GetString(flagTraceStore)
-			emptyState, err := isEmptyState(config.RootDir)
+
+			db, err := openDB(config.RootDir)
 			if err != nil {
 				return err
 			}
 
-			if emptyState || appExporter == nil {
-				_, err := fmt.Fprintln(os.Stderr, "WARNING: State is not initialized. Returning genesis file.")
-				if err != nil {
+			if isEmptyState(db) || appExporter == nil {
+				if _, err := fmt.Fprintln(os.Stderr, "WARNING: State is not initialized. Returning genesis file."); err != nil {
 					return err
 				}
+
 				genesis, err := ioutil.ReadFile(config.GenesisFile())
 				if err != nil {
 					return err
 				}
+
 				fmt.Println(string(genesis))
 				return nil
 			}
 
-			db, err := openDB(config.RootDir)
-			if err != nil {
-				return err
-			}
 			traceWriter, err := openTraceWriter(traceWriterFile)
 			if err != nil {
 				return err
 			}
+
 			height := viper.GetInt64(flagHeight)
 			forZeroHeight := viper.GetBool(flagForZeroHeight)
 			jailWhiteList := viper.GetStringSlice(flagJailWhitelist)
+
 			appState, validators, err := appExporter(ctx.Logger, db, traceWriter, height, forZeroHeight, jailWhiteList)
 			if err != nil {
 				return fmt.Errorf("error exporting state: %v", err)
@@ -85,17 +85,16 @@ func ExportCmd(ctx *Context, cdc *codec.Codec, appExporter AppExporter) *cobra.C
 			return nil
 		},
 	}
+
 	cmd.Flags().Int64(flagHeight, -1, "Export state from a particular height (-1 means latest height)")
 	cmd.Flags().Bool(flagForZeroHeight, false, "Export state to start at height zero (perform preproccessing)")
 	cmd.Flags().StringSlice(flagJailWhitelist, []string{}, "List of validators to not jail state export")
 	return cmd
 }
 
-func isEmptyState(home string) (bool, error) {
-	files, err := ioutil.ReadDir(path.Join(home, "data"))
-	if err != nil {
-		return false, err
+func isEmptyState(db dbm.DB) bool {
+	if db.Stats()["leveldb.sstables"] != "" {
+		return false
 	}
-
-	return len(files) == 0, nil
+	return true
 }