fix: use correct config key for db_backend (backport #17406) (#17411)

Co-authored-by: Julien Robert <julien@rbrt.fr>

CHANGELOG.md

@@ -47,6 +47,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* (server) [#17181](https://github.com/cosmos/cosmos-sdk/pull/17181) Fix `db_backend` lookup fallback from `config.toml`.
 * (runtime) [#17284](https://github.com/cosmos/cosmos-sdk/pull/17284) Properly allow to combine depinject-enabled modules and non-depinject-enabled modules in app v2.
 * (baseapp) [#17159](https://github.com/cosmos/cosmos-sdk/pull/17159) Validators can propose blocks that exceed the gas limit.
 * (baseapp) [#16547](https://github.com/cosmos/cosmos-sdk/pull/16547) Ensure a transaction's gas limit cannot exceed the block gas limit.

server/config/toml.go

@@ -83,8 +83,7 @@ iavl-lazy-loading = {{ .BaseConfig.IAVLLazyLoading }}
 
 # AppDBBackend defines the database backend type to use for the application and snapshots DBs.
 # An empty string indicates that a fallback will be used.
-# First fallback is the deprecated compile-time types.DBBackend value.
-# Second fallback (if the types.DBBackend also isn't set), is the db-backend value set in Tendermint's config.toml.
+# The fallback is the db_backend value set in Tendermint's config.toml.
 app-db-backend = "{{ .BaseConfig.AppDBBackend }}"
 
 ###############################################################################

server/util.go

@@ -392,7 +392,7 @@ func WaitForQuitSignals() ErrorCode {
 func GetAppDBBackend(opts types.AppOptions) dbm.BackendType {
 	rv := cast.ToString(opts.Get("app-db-backend"))
 	if len(rv) == 0 {
-		rv = cast.ToString(opts.Get("db-backend"))
+		rv = cast.ToString(opts.Get("db_backend"))
 	}
 	if len(rv) != 0 {
 		return dbm.BackendType(rv)

server/util_test.go

@@ -10,8 +10,10 @@ import (
 	"strings"
 	"testing"
 
+	db "github.com/cometbft/cometbft-db"
 	tmcfg "github.com/cometbft/cometbft/config"
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 	"github.com/stretchr/testify/require"
 
 	"github.com/cosmos/cosmos-sdk/client"
@@ -38,6 +40,15 @@ func preRunETestImpl(cmd *cobra.Command, args []string) error {
 	return cancelledInPreRun
 }
 
+func TestGetAppDBBackend(t *testing.T) {
+	v := viper.New()
+	require.Equal(t, server.GetAppDBBackend(v), db.GoLevelDBBackend)
+	v.Set("db_backend", "dbtype1") // value from CometBFT config
+	require.Equal(t, server.GetAppDBBackend(v), db.BackendType("dbtype1"))
+	v.Set("app-db-backend", "dbtype2") // value from app.toml
+	require.Equal(t, server.GetAppDBBackend(v), db.BackendType("dbtype2"))
+}
+
 func TestInterceptConfigsPreRunHandlerCreatesConfigFilesWhenMissing(t *testing.T) {
 	tempDir := t.TempDir()
 	cmd := server.StartCmd(nil, "/foobar")