Add support for graceful halt via server config

.pending/features/sdk/3981-Add-support-to-gracefully-halt-a-node-at-a-given-height

@@ -0,0 +1,2 @@
+#3981 Add support to gracefully halt a node at a given height
+via the node's `halt-height` config or CLI value.

baseapp/baseapp.go

@@ -3,6 +3,7 @@ package baseapp
 import (
 	"fmt"
 	"io"
+	"os"
 	"reflect"
 	"runtime/debug"
 	"strings"
@@ -81,6 +82,9 @@ type BaseApp struct {
 
 	// flag for sealing options and parameters to a BaseApp
 	sealed bool
+
+	// height at which to halt the chain and gracefully shutdown
+	haltHeight uint64
 }
 
 var _ abci.Application = (*BaseApp)(nil)
@@ -230,6 +234,10 @@ func (app *BaseApp) setMinGasPrices(gasPrices sdk.DecCoins) {
 	app.minGasPrices = gasPrices
 }
 
+func (app *BaseApp) setHaltHeight(height uint64) {
+	app.haltHeight = height
+}
+
 // Router returns the router of the BaseApp.
 func (app *BaseApp) Router() Router {
 	if app.sealed {
@@ -885,7 +893,13 @@ func (app *BaseApp) EndBlock(req abci.RequestEndBlock) (res abci.ResponseEndBloc
 	return
 }
 
-// Commit implements the ABCI interface.
+// Commit implements the ABCI interface. It will commit all state that exists in
+// the deliver state's multi-store and includes the resulting commit ID in the
+// returned abci.ResponseCommit. Commit will set the check state based on the
+// latest header and reset the deliver state. Also, if a non-zero halt height is
+// defined in config, Commit will execute a deferred function call to check
+// against that height and gracefully halt if it matches the latest committed
+// height.
 func (app *BaseApp) Commit() (res abci.ResponseCommit) {
 	header := app.deliverState.ctx.BlockHeader()
 
@@ -896,13 +910,20 @@ func (app *BaseApp) Commit() (res abci.ResponseCommit) {
 
 	// Reset the Check state to the latest committed.
 	//
-	// NOTE: safe because Tendermint holds a lock on the mempool for Commit.
-	// Use the header from this latest block.
+	// NOTE: This is safe because Tendermint holds a lock on the mempool for
+	// Commit. Use the header from this latest block.
 	app.setCheckState(header)
 
 	// empty/reset the deliver state
 	app.deliverState = nil
 
+	defer func() {
+		if app.haltHeight > 0 && uint64(header.Height) == app.haltHeight {
+			app.logger.Info("halting node per configuration", "height", app.haltHeight)
+			os.Exit(0)
+		}
+	}()
+
 	return abci.ResponseCommit{
 		Data: commitID.Hash,
 	}

baseapp/options.go

@@ -28,6 +28,11 @@ func SetMinGasPrices(gasPricesStr string) func(*BaseApp) {
 	return func(bap *BaseApp) { bap.setMinGasPrices(gasPrices) }
 }
 
+// SetHaltHeight returns a BaseApp option function that sets the halt height.
+func SetHaltHeight(height uint64) func(*BaseApp) {
+	return func(bap *BaseApp) { bap.setHaltHeight(height) }
+}
+
 func (app *BaseApp) SetName(name string) {
 	if app.sealed {
 		panic("SetName() on sealed BaseApp")

cmd/gaia/cmd/gaiad/main.go

@@ -70,6 +70,7 @@ func newApp(logger log.Logger, db dbm.DB, traceStore io.Writer) abci.Application
 		logger, db, traceStore, true, invCheckPeriod,
 		baseapp.SetPruning(store.NewPruningOptionsFromString(viper.GetString("pruning"))),
 		baseapp.SetMinGasPrices(viper.GetString(server.FlagMinGasPrices)),
+		baseapp.SetHaltHeight(uint64(viper.GetInt(server.FlagHaltHeight))),
 	)
 }
 

cmd/gaia/init/testnet.go

@@ -236,6 +236,8 @@ func initTestnet(config *tmconfig.Config, cdc *codec.Codec) error {
 			return err
 		}
 
+		// TODO: Rename config file to server.toml as it's not particular to Gaia
+		// (REF: https://github.com/cosmos/cosmos-sdk/issues/4125).
 		gaiaConfigFilePath := filepath.Join(nodeDir, "config/gaiad.toml")
 		srvconfig.WriteConfigFile(gaiaConfigFilePath, gaiaConfig)
 	}

docs/cosmos-hub/validators/validator-setup.md

@@ -165,6 +165,15 @@ You should also be able to see your validator on the [Explorer](https://explorec
 To be in the validator set, you need to have more total voting power than the 100th validator.
 :::
 
+## Halting Your Validator
+
+When attempting to perform routine maintenance or planning for an upcoming coordinated
+upgrade, it can be useful to have your validator systematically and gracefully halt.
+You can achieve this by either setting the `halt-height` to the height at which
+you want your node to shutdown or by passing the `--halt-height` flag to `gaiad`.
+The node will shutdown with a zero exit code at that given height after committing
+the block.
+
 ## Common Problems
 
 ### Problem #1: My validator has `voting_power: 0`

server/config/config.go

@@ -17,6 +17,10 @@ type BaseConfig struct {
 	// transaction. A transaction's fees must meet the minimum of any denomination
 	// specified in this config (e.g. 0.25token1;0.0001token2).
 	MinGasPrices string `mapstructure:"minimum-gas-prices"`
+
+	// HaltHeight contains a non-zero height at which a node will gracefully halt
+	// and shutdown that can be used to assist upgrades and testing.
+	HaltHeight uint64 `mapstructure:"halt-height"`
 }
 
 // Config defines the server's top level configuration
@@ -56,6 +60,7 @@ func DefaultConfig() *Config {
 	return &Config{
 		BaseConfig{
 			MinGasPrices: defaultMinGasPrices,
+			HaltHeight:   0,
 		},
 	}
 }

server/config/toml.go

@@ -17,6 +17,10 @@ const defaultConfigTemplate = `# This is a TOML config file.
 # transaction. A transaction's fees must meet the minimum of any denomination
 # specified in this config (e.g. 0.25token1;0.0001token2).
 minimum-gas-prices = "{{ .BaseConfig.MinGasPrices }}"
+
+# HaltHeight contains a non-zero height at which a node will gracefully halt
+# and shutdown that can be used to assist upgrades and testing.
+halt-height = {{ .BaseConfig.HaltHeight }}
 `
 
 var configTemplate *template.Template

server/start.go

@@ -23,6 +23,7 @@ const (
 	flagTraceStore     = "trace-store"
 	flagPruning        = "pruning"
 	FlagMinGasPrices   = "minimum-gas-prices"
+	FlagHaltHeight     = "halt-height"
 )
 
 // StartCmd runs the service passed in, either stand-alone or in-process with
@@ -53,6 +54,7 @@ func StartCmd(ctx *Context, appCreator AppCreator) *cobra.Command {
 		FlagMinGasPrices, "",
 		"Minimum gas prices to accept for transactions; Any fee in a tx must meet this minimum (e.g. 0.01photino;0.0001stake)",
 	)
+	cmd.Flags().Uint64(FlagHaltHeight, 0, "Height at which to gracefully halt the chain and shutdown the node")
 
 	// add support for all Tendermint-specific command line options
 	tcmd.AddNodeFlags(cmd)

server/util.go

@@ -105,7 +105,10 @@ func interceptLoadConfig() (conf *cfg.Config, err error) {
 		conf, err = tcmd.ParseConfig() // NOTE: ParseConfig() creates dir/files as necessary.
 	}
 
-	// create a default gaia config file if it does not exist
+	// create a default Gaia config file if it does not exist
+	//
+	// TODO: Rename config file to server.toml as it's not particular to Gaia
+	// (REF: https://github.com/cosmos/cosmos-sdk/issues/4125).
 	gaiaConfigFilePath := filepath.Join(rootDir, "config/gaiad.toml")
 	if _, err := os.Stat(gaiaConfigFilePath); os.IsNotExist(err) {
 		gaiaConf, _ := config.ParseConfig()