R4R: Support export at specific height

PENDING.md

@@ -29,6 +29,7 @@ FEATURES
   * [stake][cli] [\#2027] Add CLI query command for getting all delegations to a specific validator.
 
 * Gaia
+  * [app] \#2791 Support export at a specific height, with `gaiad export --height=HEIGHT`.
   * [x/gov] [#2479](https://github.com/cosmos/cosmos-sdk/issues/2479) Implemented querier
   for getting governance parameters.
 

cmd/gaia/app/app.go

@@ -322,6 +322,11 @@ func (app *GaiaApp) ExportAppStateAndValidators() (appState json.RawMessage, val
 	return appState, validators, nil
 }
 
+// load a particular height
+func (app *GaiaApp) LoadHeight(height int64) error {
+	return app.LoadVersion(height, app.keyMain)
+}
+
 //______________________________________________________________________________________________
 
 // Combined Staking Hooks

cmd/gaia/cmd/gaiad/main.go

@@ -64,8 +64,14 @@ func newApp(logger log.Logger, db dbm.DB, traceStore io.Writer) abci.Application
 }
 
 func exportAppStateAndTMValidators(
-	logger log.Logger, db dbm.DB, traceStore io.Writer,
+	logger log.Logger, db dbm.DB, traceStore io.Writer, height int64,
 ) (json.RawMessage, []tmtypes.GenesisValidator, error) {
 	gApp := app.NewGaiaApp(logger, db, traceStore)
+	if height != -1 {
+		err := gApp.LoadHeight(height)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
 	return gApp.ExportAppStateAndValidators()
 }

docs/getting-started/join-testnet.md

@@ -127,6 +127,21 @@ gaiacli status
 
 View the status of the network with the [Cosmos Explorer](https://explorecosmos.network). Once your full node syncs up to the current block height, you should see it appear on the [list of full nodes](https://explorecosmos.network/validators). If it doesn't show up, that's ok--the Explorer does not connect to every node.
 
+## Export State
+
+Gaia can dump the entire application state to a JSON file, which could be useful for manual analysis and can also be used as the genesis file of a new network.
+
+Export state with:
+
+```bash
+gaiad export > [filename].json
+```
+
+You can also export state from a particular height (at the end of processing the block of that height):
+
+```bash
+gaiad export --height=[height] > [filename].json
+```
 
 ## Upgrade to Validator Node
 

examples/basecoin/cmd/basecoind/main.go

@@ -126,7 +126,7 @@ func newApp(logger log.Logger, db dbm.DB, storeTracer io.Writer) abci.Applicatio
 	return app.NewBasecoinApp(logger, db, baseapp.SetPruning(viper.GetString("pruning")))
 }
 
-func exportAppStateAndTMValidators(logger log.Logger, db dbm.DB, storeTracer io.Writer) (
+func exportAppStateAndTMValidators(logger log.Logger, db dbm.DB, storeTracer io.Writer, _ int64) (
 	json.RawMessage, []tmtypes.GenesisValidator, error) {
 	bapp := app.NewBasecoinApp(logger, db)
 	return bapp.ExportAppStateAndValidators()

examples/democoin/cmd/democoind/main.go

@@ -133,7 +133,7 @@ func newApp(logger log.Logger, db dbm.DB, _ io.Writer) abci.Application {
 	return app.NewDemocoinApp(logger, db)
 }
 
-func exportAppStateAndTMValidators(logger log.Logger, db dbm.DB, _ io.Writer) (
+func exportAppStateAndTMValidators(logger log.Logger, db dbm.DB, _ io.Writer, _ int64) (
 	json.RawMessage, []tmtypes.GenesisValidator, error) {
 	dapp := app.NewDemocoinApp(logger, db)
 	return dapp.ExportAppStateAndValidators()

server/constructors.go

@@ -19,7 +19,7 @@ type (
 
 	// AppExporter is a function that dumps all app state to
 	// JSON-serializable structure and returns the current validator set.
-	AppExporter func(log.Logger, dbm.DB, io.Writer) (json.RawMessage, []tmtypes.GenesisValidator, error)
+	AppExporter func(log.Logger, dbm.DB, io.Writer, int64) (json.RawMessage, []tmtypes.GenesisValidator, error)
 )
 
 func openDB(rootDir string) (dbm.DB, error) {

server/export.go

@@ -13,9 +13,13 @@ import (
 	"path"
 )
 
+const (
+	flagHeight = "height"
+)
+
 // ExportCmd dumps app state to JSON.
 func ExportCmd(ctx *Context, cdc *codec.Codec, appExporter AppExporter) *cobra.Command {
-	return &cobra.Command{
+	cmd := &cobra.Command{
 		Use:   "export",
 		Short: "Export state to JSON",
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -45,7 +49,8 @@ func ExportCmd(ctx *Context, cdc *codec.Codec, appExporter AppExporter) *cobra.C
 			if err != nil {
 				return err
 			}
-			appState, validators, err := appExporter(ctx.Logger, db, traceWriter)
+			height := viper.GetInt64(flagHeight)
+			appState, validators, err := appExporter(ctx.Logger, db, traceWriter, height)
 			if err != nil {
 				return errors.Errorf("error exporting state: %v\n", err)
 			}
@@ -67,6 +72,8 @@ 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)")
+	return cmd
 }
 
 func isEmptyState(home string) (bool, error) {