fix: removed deprecated sdk.DBBackend variable (#12355)

## Description

Closes: #11410
#11241



---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -37,6 +37,10 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## [Unreleased]
 
+
+### API Breaking Changes
+
+* (types) [\#12355](https://github.com/cosmos/cosmos-sdk/pull/12355) Remove the compile-time `types.DBbackend` variable. Removes usage of the same in server/util.go
 ### Features
 
 * (cli) [#12028](https://github.com/cosmos/cosmos-sdk/pull/12028) Add the `tendermint key-migrate` to perform Tendermint v0.35 DB key migration.

server/util.go

@@ -365,9 +365,7 @@ func WaitForQuitSignals() ErrorCode {
 // GetAppDBBackend gets the backend type to use for the application DBs.
 func GetAppDBBackend(opts types.AppOptions) dbm.BackendType {
 	rv := cast.ToString(opts.Get("app-db-backend"))
-	if len(rv) == 0 {
-		rv = sdk.DBBackend
-	}
+
 	if len(rv) == 0 {
 		rv = cast.ToString(opts.Get("db-backend"))
 	}

server/util_test.go

@@ -11,10 +11,8 @@ import (
 	"testing"
 
 	"github.com/spf13/cobra"
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	tmcfg "github.com/tendermint/tendermint/config"
-	dbm "github.com/tendermint/tm-db"
 
 	"github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/client/flags"
@@ -22,7 +20,6 @@ import (
 	"github.com/cosmos/cosmos-sdk/server/config"
 	servertypes "github.com/cosmos/cosmos-sdk/server/types"
 	"github.com/cosmos/cosmos-sdk/simapp"
-	"github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 	genutilcli "github.com/cosmos/cosmos-sdk/x/genutil/client/cli"
 )
@@ -450,76 +447,3 @@ func (m mapGetter) Get(key string) interface{} {
 }
 
 var _ servertypes.AppOptions = mapGetter{}
-
-func TestGetAppDBBackend(t *testing.T) {
-	origDBBackend := types.DBBackend
-	defer func() {
-		types.DBBackend = origDBBackend
-	}()
-	tests := []struct {
-		name   string
-		dbBack string
-		opts   mapGetter
-		exp    dbm.BackendType
-	}{
-		{
-			name:   "nothing set",
-			dbBack: "",
-			opts:   mapGetter{},
-			exp:    dbm.GoLevelDBBackend,
-		},
-
-		{
-			name:   "only db-backend set",
-			dbBack: "",
-			opts:   mapGetter{"db-backend": "db-backend value 1"},
-			exp:    dbm.BackendType("db-backend value 1"),
-		},
-		{
-			name:   "only DBBackend set",
-			dbBack: "DBBackend value 2",
-			opts:   mapGetter{},
-			exp:    dbm.BackendType("DBBackend value 2"),
-		},
-		{
-			name:   "only app-db-backend set",
-			dbBack: "",
-			opts:   mapGetter{"app-db-backend": "app-db-backend value 3"},
-			exp:    dbm.BackendType("app-db-backend value 3"),
-		},
-
-		{
-			name:   "app-db-backend and db-backend set",
-			dbBack: "",
-			opts:   mapGetter{"db-backend": "db-backend value 4", "app-db-backend": "app-db-backend value 5"},
-			exp:    dbm.BackendType("app-db-backend value 5"),
-		},
-		{
-			name:   "app-db-backend and DBBackend set",
-			dbBack: "DBBackend value 6",
-			opts:   mapGetter{"app-db-backend": "app-db-backend value 7"},
-			exp:    dbm.BackendType("app-db-backend value 7"),
-		},
-		{
-			name:   "db-backend and DBBackend set",
-			dbBack: "DBBackend value 8",
-			opts:   mapGetter{"db-backend": "db-backend value 9"},
-			exp:    dbm.BackendType("DBBackend value 8"),
-		},
-
-		{
-			name:   "all of app-db-backend db-backend DBBackend set",
-			dbBack: "DBBackend value 10",
-			opts:   mapGetter{"db-backend": "db-backend value 11", "app-db-backend": "app-db-backend value 12"},
-			exp:    dbm.BackendType("app-db-backend value 12"),
-		},
-	}
-
-	for _, tc := range tests {
-		t.Run(tc.name, func(st *testing.T) {
-			types.DBBackend = tc.dbBack
-			act := server.GetAppDBBackend(tc.opts)
-			assert.Equal(st, tc.exp, act)
-		})
-	}
-}

types/utils.go

@@ -12,16 +12,9 @@ import (
 
 var (
 	// This is set at compile time. Could be cleveldb, defaults is goleveldb.
-	DBBackend = "" // Deprecated: Use tendermint config's DBBackend value instead.
-	backend   = dbm.GoLevelDBBackend
+	backend = dbm.GoLevelDBBackend
 )
 
-func init() {
-	if len(DBBackend) != 0 {
-		backend = dbm.BackendType(DBBackend)
-	}
-}
-
 // SortedJSON takes any JSON and returns it sorted by keys. Also, all white-spaces
 // are removed.
 // This method can be used to canonicalize JSON to be returned by GetSignBytes,