feat: support dynamic app db backend flag (#1226)

* support dynamic app db backend

* address pr reviews

* add comment

* Update server/start.go

Co-authored-by: Federico Kunze Küllmer <31522760+fedekunze@users.noreply.github.com>

CHANGELOG.md

@@ -54,6 +54,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### Improvements
 
 * (feemarket) [\#1165](https://github.com/evmos/ethermint/pull/1165) Add hint in specs about different gas terminology for gas in Cosmos and Ethereum.
+* (cli) [#1226](https://github.com/evmos/ethermint/pull/1226) Add custom app db backend flag.
 
 ### Bug Fixes
 

Makefile

@@ -15,6 +15,9 @@ HTTPS_GIT := https://github.com/evmos/ethermint.git
 PROJECT_NAME = $(shell git remote get-url origin | xargs basename -s .git)
 DOCKER := $(shell which docker)
 DOCKER_BUF := $(DOCKER) run --rm -v $(CURDIR):/workspace --workdir /workspace bufbuild/buf:1.0.0-rc8
+# RocksDB is a native dependency, so we don't assume the library is installed.
+# Instead, it must be explicitly enabled and we warn when it is not.
+ENABLE_ROCKSDB ?= false
 
 export GO111MODULE = on
 
@@ -49,9 +52,6 @@ ifeq ($(LEDGER_ENABLED),true)
   endif
 endif
 
-ifeq (cleveldb,$(findstring cleveldb,$(COSMOS_BUILD_OPTIONS)))
-  build_tags += gcc
-endif
 build_tags += $(BUILD_TAGS)
 build_tags := $(strip $(build_tags))
 
@@ -69,23 +69,31 @@ ldflags = -X github.com/cosmos/cosmos-sdk/version.Name=ethermint \
 			-X "github.com/cosmos/cosmos-sdk/version.BuildTags=$(build_tags_comma_sep)" \
 			-X github.com/tendermint/tendermint/version.TMCoreSemVer=$(TMVERSION)
 
+ifeq ($(ENABLE_ROCKSDB),true)
+  BUILD_TAGS += rocksdb_build
+  test_tags += rocksdb_build
+else
+  $(warning RocksDB support is disabled; to build and test with RocksDB support, set ENABLE_ROCKSDB=true)
+endif
+
 # DB backend selection
 ifeq (cleveldb,$(findstring cleveldb,$(COSMOS_BUILD_OPTIONS)))
-  ldflags += -X github.com/cosmos/cosmos-sdk/types.DBBackend=cleveldb
+  BUILD_TAGS += gcc
 endif
 ifeq (badgerdb,$(findstring badgerdb,$(COSMOS_BUILD_OPTIONS)))
-  ldflags += -X github.com/cosmos/cosmos-sdk/types.DBBackend=badgerdb
+  BUILD_TAGS += badgerdb
 endif
 # handle rocksdb
 ifeq (rocksdb,$(findstring rocksdb,$(COSMOS_BUILD_OPTIONS)))
+  ifneq ($(ENABLE_ROCKSDB),true)
+    $(error Cannot use RocksDB backend unless ENABLE_ROCKSDB=true)
+  endif
   CGO_ENABLED=1
   BUILD_TAGS += rocksdb
-  ldflags += -X github.com/cosmos/cosmos-sdk/types.DBBackend=rocksdb
 endif
 # handle boltdb
 ifeq (boltdb,$(findstring boltdb,$(COSMOS_BUILD_OPTIONS)))
   BUILD_TAGS += boltdb
-  ldflags += -X github.com/cosmos/cosmos-sdk/types.DBBackend=boltdb
 endif
 
 ifeq (,$(findstring nostrip,$(COSMOS_BUILD_OPTIONS)))
@@ -94,6 +102,9 @@ endif
 ldflags += $(LDFLAGS)
 ldflags := $(strip $(ldflags))
 
+build_tags += $(BUILD_TAGS)
+build_tags := $(strip $(build_tags))
+
 BUILD_FLAGS := -tags "$(build_tags)" -ldflags '$(ldflags)'
 # check for nostrip option
 ifeq (,$(findstring nostrip,$(COSMOS_BUILD_OPTIONS)))

cmd/ethermintd/root.go

@@ -210,6 +210,10 @@ func (a appCreator) newApp(logger tmlog.Logger, db dbm.DB, traceStore io.Writer,
 	}
 
 	snapshotDir := filepath.Join(cast.ToString(appOpts.Get(flags.FlagHome)), "data", "snapshots")
+	if err = os.MkdirAll(snapshotDir, os.ModePerm); err != nil {
+		panic(err)
+	}
+
 	snapshotDB, err := dbm.NewDB("metadata", sdkserver.GetAppDBBackend(appOpts), snapshotDir)
 	if err != nil {
 		panic(err)

server/flags/flags.go

@@ -7,13 +7,15 @@ import (
 	"github.com/spf13/viper"
 )
 
-// Tendermint full-node start flags
+// Tendermint/cosmos-sdk full-node start flags
 const (
 	WithTendermint = "with-tendermint"
 	Address        = "address"
 	Transport      = "transport"
 	TraceStore     = "trace-store"
 	CPUProfile     = "cpu-profile"
+	// The type of database for application and snapshots databases
+	AppDBBackend = "app-db-backend"
 )
 
 // GRPC-related flags.

server/start.go

@@ -141,6 +141,7 @@ which accepts a path for the resulting pprof file.
 	cmd.Flags().Uint64(server.FlagPruningInterval, 0, "Height interval at which pruned heights are removed from disk (ignored if pruning is not 'custom')")
 	cmd.Flags().Uint(server.FlagInvCheckPeriod, 0, "Assert registered invariants every N blocks")
 	cmd.Flags().Uint64(server.FlagMinRetainBlocks, 0, "Minimum block height offset during ABCI commit to prune Tendermint blocks")
+	cmd.Flags().String(srvflags.AppDBBackend, "", "The type of database for application and snapshots databases")
 
 	cmd.Flags().Bool(srvflags.GRPCEnable, true, "Define if the gRPC server should be enabled")
 	cmd.Flags().String(srvflags.GRPCAddress, serverconfig.DefaultGRPCAddress, "the gRPC server address to listen on")