perf: parse chain-id from big genesis file could be slow

CHANGELOG.md

@@ -67,6 +67,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (rpc) [#17470](https://github.com/cosmos/cosmos-sdk/pull/17470) Avoid open 0.0.0.0 to public by default and add `listen-ip-address` argument for `testnet init-files` cmd.
 * (types) [#17670](https://github.com/cosmos/cosmos-sdk/pull/17670) Use `ctx.CometInfo` in place of `ctx.VoteInfos`
 * [#17733](https://github.com/cosmos/cosmos-sdk/pull/17733) Ensure `buf export` exports all proto dependencies
+* [#18204](https://github.com/cosmos/cosmos-sdk/pull/18204) Use streaming json parser to parse chain-id from genesis file.
 
 ### Bug Fixes
 

go.mod

@@ -14,6 +14,7 @@ require (
 	cosmossdk.io/x/protocolpool v0.0.0-20230925135524-a1bc045b3190
 	cosmossdk.io/x/tx v0.11.0
 	github.com/99designs/keyring v1.2.1
+	github.com/bcicen/jstream v1.0.1
 	github.com/bgentry/speakeasy v0.1.1-0.20220910012023-760eaf8b6816
 	github.com/bits-and-blooms/bitset v1.10.0
 	github.com/chzyer/readline v1.5.1
@@ -173,6 +174,7 @@ replace cosmossdk.io/x/protocolpool => ./x/protocolpool
 replace (
 	// use cosmos fork of keyring
 	github.com/99designs/keyring => github.com/cosmos/keyring v1.2.0
+	github.com/bcicen/jstream => github.com/yihuang/jstream v0.0.0-20231023072018-cb6eaf5ca571
 	// dgrijalva/jwt-go is deprecated and doesn't receive security updates.
 	// TODO: remove it: https://github.com/cosmos/cosmos-sdk/issues/13134
 	github.com/dgrijalva/jwt-go => github.com/golang-jwt/jwt/v4 v4.4.2

go.sum

@@ -792,6 +792,8 @@ github.com/urfave/cli v1.20.0/go.mod h1:70zkFmudgCuE/ngEzBv17Jvp/497gISqfk5gWijb
 github.com/urfave/cli v1.22.1/go.mod h1:Gos4lmkARVdJ6EkW0WaNv/tZAAMe9V7XWyB60NtXRu0=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
+github.com/yihuang/jstream v0.0.0-20231023072018-cb6eaf5ca571 h1:J0wQbFhjC6ZLJlNCIcWSEpWuiBQ/wdvaDXJSBzpoeyQ=
+github.com/yihuang/jstream v0.0.0-20231023072018-cb6eaf5ca571/go.mod h1:9ielPxqFry7Y4Tg3j4BfjPocfJ3TbsRtXOAYXYmRuAQ=
 github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=

server/util.go

@@ -37,7 +37,6 @@
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/mempool"
 	"github.com/cosmos/cosmos-sdk/version"
-	genutiltypes "github.com/cosmos/cosmos-sdk/x/genutil/types"
 )
 
 // ServerContextKey defines the context key used to retrieve a server.Context from
@@ -485,12 +484,16 @@
 	chainID := cast.ToString(appOpts.Get(flags.FlagChainID))
 	if chainID == "" {
 		// fallback to genesis chain-id
-		appGenesis, err := genutiltypes.AppGenesisFromFile(filepath.Join(homeDir, "config", "genesis.json"))
+		reader, err := os.Open(filepath.Join(homeDir, "config", "genesis.json"))
 		if err != nil {
 			panic(err)
 		}
+		defer reader.Close()
 
-		chainID = appGenesis.ChainID
+		chainID, err = sdk.ParseChainIDFromGenesis(reader)
+		if err != nil {
+			panic(fmt.Errorf("failed to parse chain-id from genesis file: %w", err))
+		}
 	}
 
 	snapshotStore, err := GetSnapshotStore(appOpts)

types/chain_id.go

@@ -0,0 +1,40 @@
+package types
+
+import (
+	"errors"
+	"io"
+
+	"github.com/bcicen/jstream"
+)
+
+const ChainIDFieldName = "chain_id"
+
+// ParseChainIDFromGenesis parses the chain-id from the genesis file using constant memory.
+//
+// TODO consider [encoding/json/v2](https://github.com/golang/go/discussions/63397) when it's ready.
+func ParseChainIDFromGenesis(reader io.Reader) (string, error) {
+	decoder := jstream.NewDecoder(reader, 1).EmitKV()
+	var (
+		chain_id string
+		ok       bool
+	)
+	err := decoder.Decode(func(mv *jstream.MetaValue) bool {
+		if kv, ok := mv.Value.(jstream.KV); ok {
+			if kv.Key == ChainIDFieldName {
+				chain_id, ok = kv.Value.(string)
+				return false
+			}
+		}
+		return true
+	})
+	if len(chain_id) > 0 {
+		return chain_id, nil
+	}
+	if !ok {
+		return "", errors.New("chain-id is not a string")
+	}
+	if err == nil {
+		return "", errors.New("chain-id not found in genesis file")
+	}
+	return "", err
+}