Updated documentation.

README.md

@@ -3,13 +3,15 @@ If you'd like to play with the backend code seriously, please read the detailed
 
 There could be some left over wechat-game related code pieces, but they're neither meant to work nor supported anymore. 
 
-# 1. Database Server
+# 1. Building & running
 
-The database product to be used for this project is MySQL 5.7.
+## 1.1 Golang1.19.1
+Documentation TBD.
 
-We use [skeema](https://github.com/skeema/skeema) for schematic synchronization under `<proj-root>/database/skeema-repo-root/` which intentionally doesn't contain a `.skeema` file. Please read [this tutorial](https://shimo.im/doc/wQ0LvB0rlZcbHF5V) for more information.
+## 1.2 MySQL 
+The database product to be used for this project is MySQL 5.7, you can install and manage `MySQL` server by [these scripts](https://github.com/genxium/Ubuntu14InitScripts/tree/master/database/mysql).
 
-You can use [this node module (still under development)](https://github.com/genxium/node-mysqldiff-bridge) instead under `Windows10`, other versions of Windows are not yet tested for compatibility.
+We use [skeema](https://github.com/skeema/skeema) for schematic synchronization under `<proj-root>/database/skeema-repo-root/` which intentionally doesn't contain a `.skeema` file. Please read [this tutorial](https://shimo.im/doc/wQ0LvB0rlZcbHF5V) for more information. For `Windows 10/11`, you can compile `skeema` from source and config the host to be `127.0.0.1` instead of `localhost` to use it, i.e. circumventing the pitfall for MySQL unix socket connection on Windows.
 
 The following command(s)
 ```
@@ -21,33 +23,25 @@ user@proj-root/database/skeema-repo-root> skeema diff
 ```
 is recommended to be used for checking difference from your "live MySQL server" to the latest expected schema tracked in git.
 
-# 2. Building & running
+## 1.3 Required Config Files
 
-## 2.1 Golang1.11
+### 1.3.1 Backend 
-See https://github.com/genxium/Go111ModulePrac for details.
-
-## 2.2 MySQL 
-On a product machine, you can install and manage `MySQL` server by [these scripts](https://github.com/genxium/Ubuntu14InitScripts/tree/master/database/mysql).
-
-## 2.3 Required Config Files
-
-### 2.3.1 Backend 
 - It needs `<proj-root>/battle_srv/configs/*` which is generated by `cd <proj-root>/battle_srv && cp -r ./configs.template ./configs` and necessary customization.
 
-### 2.3.2 Frontend 
+### 1.3.2 Frontend 
 - It needs CocosCreator v2.2.1 to build.
 - A required "CocosCreator plugin `i18n`" is already enclosed in the project, if you have a globally installed "CocosCreator plugin `i18n`"(often located at `$HOME/.CocosCreator/packages/`) they should be OK to co-exist.
 - It needs `<proj-root>/frontend/assets/plugin_scripts/conf.js` which is generated by `cd <proj-root>/frontend/assets/plugin_scripts && cp conf.js.template conf.js`.
 
-## 2.4 Troubleshooting
+## 1.4 Troubleshooting
 
-### 2.4.1 Redis snapshot writing failure
+### 1.4.1 Redis snapshot writing failure
 ```
 ErrFatal        {"err": "MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error."}
 ```
 
 Just restart your `redis-server` process.
 
-# 3. Git configs cautions
+# 2. Git configs cautions
 
 Please make sure that you've set `ignorecase = false` in your `[core] section of <proj-root>/.git/config`.

battle_srv/go.mod

@@ -1,38 +1,46 @@
 module server
 
+go 1.19
+
 require (
 	github.com/ByteArena/box2d v1.0.2
-	github.com/ChimeraCoder/gojson v1.0.0 // indirect
 	github.com/Masterminds/squirrel v0.0.0-20180815162352-8a7e65843414
 	github.com/davecgh/go-spew v1.1.1
-	github.com/fatih/color v1.7.0 // indirect
 	github.com/gin-contrib/cors v0.0.0-20180514151808-6f0a820f94be
-	github.com/gin-contrib/sse v0.0.0-20170109093832-22d885f9ecc7 // indirect
 	github.com/gin-gonic/gin v1.3.0
-	github.com/githubnemo/CompileDaemon v1.0.0 // indirect
 	github.com/go-redis/redis v6.13.2+incompatible
 	github.com/go-sql-driver/mysql v1.4.0
 	github.com/golang/protobuf v1.5.2
-	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/gorilla/websocket v1.2.0
 	github.com/hashicorp/go-cleanhttp v0.0.0-20171218145408-d5fe4b57a186
-	github.com/howeyc/fsnotify v0.9.0 // indirect
 	github.com/imdario/mergo v0.3.6
 	github.com/jmoiron/sqlx v0.0.0-20180614180643-0dae4fefe7c0
-	github.com/lann/builder v0.0.0-20180802200727-47ae307949d0 // indirect
-	github.com/lann/ps v0.0.0-20150810152359-62de8c46ede0 // indirect
 	github.com/logrusorgru/aurora v0.0.0-20181002194514-a7b3b318ed4e
-	github.com/mattn/go-colorable v0.0.9 // indirect
-	github.com/mattn/go-isatty v0.0.3 // indirect
-	github.com/mattn/go-sqlite3 v1.9.0
 	github.com/robfig/cron v0.0.0-20180505203441-b41be1df6967
 	github.com/solarlune/resolv v0.5.1
 	github.com/thoas/go-funk v0.0.0-20180716193722-1060394a7713
+	go.uber.org/zap v1.9.1
+	google.golang.org/protobuf v1.28.1
+)
+
+require (
+	github.com/ChimeraCoder/gojson v1.0.0 // indirect
+	github.com/fatih/color v1.7.0 // indirect
+	github.com/gin-contrib/sse v0.0.0-20170109093832-22d885f9ecc7 // indirect
+	github.com/githubnemo/CompileDaemon v1.0.0 // indirect
+	github.com/google/go-cmp v0.5.9 // indirect
+	github.com/howeyc/fsnotify v0.9.0 // indirect
+	github.com/kvartborg/vector v0.0.0-20200419093813-2cba0cabb4f0 // indirect
+	github.com/lann/builder v0.0.0-20180802200727-47ae307949d0 // indirect
+	github.com/lann/ps v0.0.0-20150810152359-62de8c46ede0 // indirect
+	github.com/mattn/go-isatty v0.0.16 // indirect
+	github.com/mattn/go-sqlite3 v1.14.15 // indirect
 	github.com/ugorji/go v1.1.1 // indirect
 	go.uber.org/atomic v1.3.2 // indirect
 	go.uber.org/multierr v1.1.0 // indirect
-	go.uber.org/zap v1.9.1
+	golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab // indirect
-	google.golang.org/protobuf v1.28.1
+	golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 // indirect
+	gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 // indirect
 	gopkg.in/go-playground/validator.v8 v8.18.2 // indirect
 	gopkg.in/yaml.v2 v2.2.1 // indirect
 )

battle_srv/go.sum

@@ -57,8 +57,12 @@ github.com/mattn/go-colorable v0.0.9 h1:UVL0vNpWh04HeJXV0KLcaT7r06gOH2l4OW6ddYRU
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
 github.com/mattn/go-isatty v0.0.3 h1:ns/ykhmWi7G9O+8a448SecJU3nSMBXJfqQkl0upE1jI=
 github.com/mattn/go-isatty v0.0.3/go.mod h1:M+lRXTBqGeGNdLjl/ufCoiOlB5xdOkqRJdNxMWT7Zi4=
+github.com/mattn/go-isatty v0.0.16 h1:bq3VjFmv/sOjHtdEhmkEV4x1AJtvUvOJ2PFAZ5+peKQ=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
 github.com/mattn/go-sqlite3 v1.9.0 h1:pDRiWfl+++eC2FEFRy6jXmQlvp4Yh3z1MJKg4UeYM/4=
 github.com/mattn/go-sqlite3 v1.9.0/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
+github.com/mattn/go-sqlite3 v1.14.15 h1:vfoHhTN1af61xCRSWzFIWzx2YskyMTwHLrExkBOjvxI=
+github.com/mattn/go-sqlite3 v1.14.15/go.mod h1:2eHXhiwb8IkHr+BDWZGa96P6+rkvnG63S2DGjv9HUNg=
 github.com/op/go-logging v0.0.0-20160315200505-970db520ece7 h1:lDH9UUVJtmYCjyT0CI4q8xvlXPxeZ0gYCVvWbmPlp88=
 github.com/op/go-logging v0.0.0-20160315200505-970db520ece7/go.mod h1:HzydrMdWErDVzsI23lYNej1Htcns9BCg93Dk0bBINWk=
 github.com/robfig/cron v0.0.0-20180505203441-b41be1df6967 h1:x7xEyJDP7Hv3LVgvWhzioQqbC/KtuUhTigKlH/8ehhE=
@@ -75,6 +79,8 @@ go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/zap v1.9.1 h1:XCJQEf3W6eZaVwhRBof6ImoYGJSITeKWsyeh3HFu/5o=
 go.uber.org/zap v1.9.1/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab h1:2QkjZIsXupsJbJIdSjjUOgWK3aEtzyuh2mPt3l/CkeU=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20220907171357-04be3eba64a2/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=

battle_srv/models/room.go

@@ -159,7 +159,8 @@ type Room struct {
 	EffectivePlayerCount                   int32
 	DismissalWaitGroup                     sync.WaitGroup
 	Barriers                               map[int32]*Barrier
-	AllPlayerInputsBuffer                  *RingBuffer
+	InputsBuffer                           *RingBuffer // Indices are STRICTLY consecutive
+	DiscreteInputsBuffer                   sync.Map    // Indices are NOT NECESSARILY consecutive
 	RenderFrameBuffer                      *RingBuffer
 	LastAllConfirmedInputFrameId           int32
 	LastAllConfirmedInputFrameIdWithChange int32
@@ -357,16 +358,16 @@ func (pR *Room) RenderFrameBufferString() string {
 	return fmt.Sprintf("{renderFrameId: %d, stRenderFrameId: %d, edRenderFrameId: %d, lastAllConfirmedRenderFrameId: %d}", pR.RenderFrameId, pR.RenderFrameBuffer.StFrameId, pR.RenderFrameBuffer.EdFrameId, pR.CurDynamicsRenderFrameId)
 }
 
-func (pR *Room) AllPlayerInputsBufferString(allDetails bool) string {
+func (pR *Room) InputsBufferString(allDetails bool) string {
 	if allDetails {
 		// Appending of the array of strings can be very SLOW due to on-demand heap allocation! Use this printing with caution.
 		s := make([]string, 0)
-		s = append(s, fmt.Sprintf("{renderFrameId: %v, stInputFrameId: %v, edInputFrameId: %v, lastAllConfirmedInputFrameIdWithChange: %v, lastAllConfirmedInputFrameId: %v}", pR.RenderFrameId, pR.AllPlayerInputsBuffer.StFrameId, pR.AllPlayerInputsBuffer.EdFrameId, pR.LastAllConfirmedInputFrameIdWithChange, pR.LastAllConfirmedInputFrameId))
+		s = append(s, fmt.Sprintf("{renderFrameId: %v, stInputFrameId: %v, edInputFrameId: %v, lastAllConfirmedInputFrameIdWithChange: %v, lastAllConfirmedInputFrameId: %v}", pR.RenderFrameId, pR.InputsBuffer.StFrameId, pR.InputsBuffer.EdFrameId, pR.LastAllConfirmedInputFrameIdWithChange, pR.LastAllConfirmedInputFrameId))
 		for playerId, player := range pR.Players {
 			s = append(s, fmt.Sprintf("{playerId: %v, ackingFrameId: %v, ackingInputFrameId: %v, lastSentInputFrameId: %v}", playerId, player.AckingFrameId, player.AckingInputFrameId, player.LastSentInputFrameId))
 		}
-		for i := pR.AllPlayerInputsBuffer.StFrameId; i < pR.AllPlayerInputsBuffer.EdFrameId; i++ {
+		for i := pR.InputsBuffer.StFrameId; i < pR.InputsBuffer.EdFrameId; i++ {
-			tmp := pR.AllPlayerInputsBuffer.GetByFrameId(i)
+			tmp := pR.InputsBuffer.GetByFrameId(i)
 			if nil == tmp {
 				break
 			}
@@ -376,7 +377,7 @@ func (pR *Room) AllPlayerInputsBufferString(allDetails bool) string {
 
 		return strings.Join(s, "; ")
 	} else {
-		return fmt.Sprintf("{renderFrameId: %d, stInputFrameId: %d, edInputFrameId: %d, lastAllConfirmedInputFrameIdWithChange: %d, lastAllConfirmedInputFrameId: %d}", pR.RenderFrameId, pR.AllPlayerInputsBuffer.StFrameId, pR.AllPlayerInputsBuffer.EdFrameId, pR.LastAllConfirmedInputFrameIdWithChange, pR.LastAllConfirmedInputFrameId)
+		return fmt.Sprintf("{renderFrameId: %d, stInputFrameId: %d, edInputFrameId: %d, lastAllConfirmedInputFrameIdWithChange: %d, lastAllConfirmedInputFrameId: %d}", pR.RenderFrameId, pR.InputsBuffer.StFrameId, pR.InputsBuffer.EdFrameId, pR.LastAllConfirmedInputFrameIdWithChange, pR.LastAllConfirmedInputFrameId)
 	}
 }
 
@@ -424,7 +425,7 @@ func (pR *Room) StartBattle() {
 			stCalculation := utils.UnixtimeNano()
 
 			if totalElapsedNanos > pR.BattleDurationNanos {
-				Logger.Info(fmt.Sprintf("The `battleMainLoop` for roomId=%v is stopped:\n%v", pR.Id, pR.AllPlayerInputsBufferString(true)))
+				Logger.Info(fmt.Sprintf("The `battleMainLoop` for roomId=%v is stopped:\n%v", pR.Id, pR.InputsBufferString(true)))
 				pR.StopBattleForSettlement()
 			}
 
@@ -452,50 +453,9 @@ func (pR *Room) StartBattle() {
 			}
 
 			upperToSendInputFrameId := atomic.LoadInt32(&(pR.LastAllConfirmedInputFrameId))
-			for playerId, player := range pR.Players {
-				if swapped := atomic.CompareAndSwapInt32(&player.BattleState, PlayerBattleStateIns.ACTIVE, PlayerBattleStateIns.ACTIVE); !swapped {
-					// [WARNING] DON'T send anything if the player is disconnected, because it could jam the channel and cause significant delay upon "battle recovery for reconnected player".
-					continue
-				}
-				if 0 == pR.RenderFrameId {
-					kickoffFrame := pR.RenderFrameBuffer.GetByFrameId(0).(*pb.RoomDownsyncFrame)
-					pR.sendSafely(kickoffFrame, nil, DOWNSYNC_MSG_ACT_BATTLE_START, playerId)
-				} else {
-					// [WARNING] Websocket is TCP-based, thus no need to re-send a previously sent inputFrame to a same player!
-					toSendInputFrames := make([]*pb.InputFrameDownsync, 0, pR.AllPlayerInputsBuffer.Cnt)
-					candidateToSendInputFrameId := atomic.LoadInt32(&(pR.Players[playerId].LastSentInputFrameId)) + 1
-					if candidateToSendInputFrameId < pR.AllPlayerInputsBuffer.StFrameId {
-						// [WARNING] As "player.LastSentInputFrameId <= lastAllConfirmedInputFrameIdWithChange" for each iteration, and "lastAllConfirmedInputFrameIdWithChange <= lastAllConfirmedInputFrameId" where the latter is used to "applyInputFrameDownsyncDynamics" and then evict "pR.AllPlayerInputsBuffer", thus there's a very high possibility that "player.LastSentInputFrameId" is already evicted.
-						// Logger.Debug(fmt.Sprintf("LastSentInputFrameId already popped: roomId=%v, playerId=%v, lastSentInputFrameId=%v, playerAckingInputFrameId=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, candidateToSendInputFrameId-1, player.AckingInputFrameId, pR.AllPlayerInputsBufferString(false)))
-						candidateToSendInputFrameId = pR.AllPlayerInputsBuffer.StFrameId
-					}
-
-					// [WARNING] EDGE CASE HERE: Upon initialization, all of "lastAllConfirmedInputFrameId", "lastAllConfirmedInputFrameIdWithChange" and "anchorInputFrameId" are "-1", thus "candidateToSendInputFrameId" starts with "0", however "inputFrameId: 0" might not have been all confirmed!
-
-					for candidateToSendInputFrameId <= upperToSendInputFrameId {
-						tmp := pR.AllPlayerInputsBuffer.GetByFrameId(candidateToSendInputFrameId)
-						if nil == tmp {
-							panic(fmt.Sprintf("Required inputFrameId=%v for roomId=%v, playerId=%v doesn't exist! AllPlayerInputsBuffer=%v", candidateToSendInputFrameId, pR.Id, playerId, pR.AllPlayerInputsBufferString(false)))
-						}
-						f := tmp.(*pb.InputFrameDownsync)
-						if pR.inputFrameIdDebuggable(candidateToSendInputFrameId) {
-							Logger.Debug("inputFrame lifecycle#3[sending]:", zap.Any("roomId", pR.Id), zap.Any("playerId", playerId), zap.Any("playerAckingInputFrameId", player.AckingInputFrameId), zap.Any("inputFrameId", candidateToSendInputFrameId), zap.Any("inputFrameId-doublecheck", f.InputFrameId), zap.Any("AllPlayerInputsBuffer", pR.AllPlayerInputsBufferString(false)), zap.Any("ConfirmedList", f.ConfirmedList))
-						}
-						toSendInputFrames = append(toSendInputFrames, f)
-						candidateToSendInputFrameId++
-					}
-
-					if 0 >= len(toSendInputFrames) {
-						// [WARNING] When sending DOWNSYNC_MSG_ACT_FORCED_RESYNC, there MUST BE accompanying "toSendInputFrames" for calculating "refRenderFrameId"!
-						continue
-					}
-
-					indiceInJoinIndexBooleanArr := uint32(player.JoinIndex - 1)
-					var joinMask uint64 = (1 << indiceInJoinIndexBooleanArr)
-					if 0 < (unconfirmedMask & joinMask) {
 			/*
 			   [WARNING]
-						   "refRenderFrameId" MUST BE CAPPED somehow by "candidateToSendInputFrameId-1", if frontend resyncs itself to a more advanced value than given below, upon the next renderFrame tick on the frontend it might generate non-consecutive "nextInputFrameId > frontend.recentInputCache.edFrameId+1".
+			   Upon resynced on frontend, "refRenderFrameId" MUST BE CAPPED somehow by "upperToSendInputFrameId", if frontend resyncs itself to a more advanced value than given below, upon the next renderFrame tick on the frontend it might generate non-consecutive "nextInputFrameId > frontend.recentInputCache.edFrameId+1".
 
 			   If "NstDelayFrames" becomes larger, "pR.RenderFrameId - refRenderFrameId" possibly becomes larger because the force confirmation is delayed more.
 
@@ -509,9 +469,50 @@ func (pR *Room) StartBattle() {
 			if refRenderFrameId > pR.CurDynamicsRenderFrameId {
 				refRenderFrameId = pR.CurDynamicsRenderFrameId
 			}
+			for playerId, player := range pR.Players {
+				if swapped := atomic.CompareAndSwapInt32(&player.BattleState, PlayerBattleStateIns.ACTIVE, PlayerBattleStateIns.ACTIVE); !swapped {
+					// [WARNING] DON'T send anything if the player is disconnected, because it could jam the channel and cause significant delay upon "battle recovery for reconnected player".
+					continue
+				}
+				if 0 == pR.RenderFrameId {
+					kickoffFrame := pR.RenderFrameBuffer.GetByFrameId(0).(*pb.RoomDownsyncFrame)
+					pR.sendSafely(kickoffFrame, nil, DOWNSYNC_MSG_ACT_BATTLE_START, playerId)
+				} else {
+					// [WARNING] Websocket is TCP-based, thus no need to re-send a previously sent inputFrame to a same player!
+					toSendInputFrames := make([]*pb.InputFrameDownsync, 0, pR.InputsBuffer.Cnt)
+					candidateToSendInputFrameId := atomic.LoadInt32(&(pR.Players[playerId].LastSentInputFrameId)) + 1
+					if candidateToSendInputFrameId < pR.InputsBuffer.StFrameId {
+						// [WARNING] As "player.LastSentInputFrameId <= lastAllConfirmedInputFrameIdWithChange" for each iteration, and "lastAllConfirmedInputFrameIdWithChange <= lastAllConfirmedInputFrameId" where the latter is used to "applyInputFrameDownsyncDynamics" and then evict "pR.InputsBuffer", thus there's a very high possibility that "player.LastSentInputFrameId" is already evicted.
+						// Logger.Debug(fmt.Sprintf("LastSentInputFrameId already popped: roomId=%v, playerId=%v, lastSentInputFrameId=%v, playerAckingInputFrameId=%v, InputsBuffer=%v", pR.Id, playerId, candidateToSendInputFrameId-1, player.AckingInputFrameId, pR.InputsBufferString(false)))
+						candidateToSendInputFrameId = pR.InputsBuffer.StFrameId
+					}
+
+					// [WARNING] EDGE CASE HERE: Upon initialization, all of "lastAllConfirmedInputFrameId", "lastAllConfirmedInputFrameIdWithChange" and "anchorInputFrameId" are "-1", thus "candidateToSendInputFrameId" starts with "0", however "inputFrameId: 0" might not have been all confirmed!
+
+					for candidateToSendInputFrameId <= upperToSendInputFrameId {
+						tmp := pR.InputsBuffer.GetByFrameId(candidateToSendInputFrameId)
+						if nil == tmp {
+							panic(fmt.Sprintf("Required inputFrameId=%v for roomId=%v, playerId=%v doesn't exist! InputsBuffer=%v", candidateToSendInputFrameId, pR.Id, playerId, pR.InputsBufferString(false)))
+						}
+						f := tmp.(*pb.InputFrameDownsync)
+						if pR.inputFrameIdDebuggable(candidateToSendInputFrameId) {
+							Logger.Debug("inputFrame lifecycle#3[sending]:", zap.Any("roomId", pR.Id), zap.Any("playerId", playerId), zap.Any("playerAckingInputFrameId", player.AckingInputFrameId), zap.Any("inputFrameId", candidateToSendInputFrameId), zap.Any("inputFrameId-doublecheck", f.InputFrameId), zap.Any("InputsBuffer", pR.InputsBufferString(false)), zap.Any("ConfirmedList", f.ConfirmedList))
+						}
+						toSendInputFrames = append(toSendInputFrames, f)
+						candidateToSendInputFrameId++
+					}
+
+					if 0 >= len(toSendInputFrames) {
+						// [WARNING] When sending DOWNSYNC_MSG_ACT_FORCED_RESYNC, there MUST BE accompanying "toSendInputFrames" for calculating "refRenderFrameId"!
+						continue
+					}
+
+					indiceInJoinIndexBooleanArr := uint32(player.JoinIndex - 1)
+					var joinMask uint64 = (1 << indiceInJoinIndexBooleanArr)
+					if 0 < (unconfirmedMask & joinMask) {
 						tmp := pR.RenderFrameBuffer.GetByFrameId(refRenderFrameId)
 						if nil == tmp {
-							panic(fmt.Sprintf("Required refRenderFrameId=%v for roomId=%v, playerId=%v, candidateToSendInputFrameId=%v doesn't exist! AllPlayerInputsBuffer=%v, RenderFrameBuffer=%v", refRenderFrameId, pR.Id, playerId, candidateToSendInputFrameId, pR.AllPlayerInputsBufferString(false), pR.RenderFrameBufferString()))
+							panic(fmt.Sprintf("Required refRenderFrameId=%v for roomId=%v, playerId=%v, candidateToSendInputFrameId=%v doesn't exist! InputsBuffer=%v, RenderFrameBuffer=%v", refRenderFrameId, pR.Id, playerId, candidateToSendInputFrameId, pR.InputsBufferString(false), pR.RenderFrameBufferString()))
 						}
 						refRenderFrame := tmp.(*pb.RoomDownsyncFrame)
 						pR.sendSafely(refRenderFrame, toSendInputFrames, DOWNSYNC_MSG_ACT_FORCED_RESYNC, playerId)
@@ -522,23 +523,17 @@ func (pR *Room) StartBattle() {
 				}
 			}
 
-			renderFrameBuffLowerBound := pR.ConvertToGeneratingRenderFrameId(upperToSendInputFrameId) + (1 << pR.InputScaleFrames) - 1
+			// Evict no longer required "RenderFrameBuffer"
-			if renderFrameBuffLowerBound > pR.RenderFrameId {
+			for pR.RenderFrameBuffer.N < pR.RenderFrameBuffer.Cnt || (0 < pR.RenderFrameBuffer.Cnt && pR.RenderFrameBuffer.StFrameId < refRenderFrameId) {
-				renderFrameBuffLowerBound = pR.RenderFrameId
-			}
-			if renderFrameBuffLowerBound > pR.CurDynamicsRenderFrameId {
-				renderFrameBuffLowerBound = pR.CurDynamicsRenderFrameId
-			}
-			for 0 < pR.RenderFrameBuffer.Cnt && pR.RenderFrameBuffer.StFrameId < renderFrameBuffLowerBound {
 				_ = pR.RenderFrameBuffer.Pop()
 			}
 
-			toApplyInputFrameId := pR.ConvertToInputFrameId(pR.CurDynamicsRenderFrameId, pR.InputDelayFrames)
+			toApplyInputFrameId := pR.ConvertToInputFrameId(refRenderFrameId, pR.InputDelayFrames)
-			for 0 < pR.AllPlayerInputsBuffer.Cnt && pR.AllPlayerInputsBuffer.StFrameId < toApplyInputFrameId {
+			for pR.InputsBuffer.N < pR.InputsBuffer.Cnt || (0 < pR.InputsBuffer.Cnt && pR.InputsBuffer.StFrameId < toApplyInputFrameId) {
-				f := pR.AllPlayerInputsBuffer.Pop().(*pb.InputFrameDownsync)
+				f := pR.InputsBuffer.Pop().(*pb.InputFrameDownsync)
 				if pR.inputFrameIdDebuggable(f.InputFrameId) {
 					// Popping of an "inputFrame" would be AFTER its being all being confirmed, because it requires the "inputFrame" to be all acked
-					Logger.Debug("inputFrame lifecycle#4[popped]:", zap.Any("roomId", pR.Id), zap.Any("inputFrameId", f.InputFrameId), zap.Any("AllPlayerInputsBuffer", pR.AllPlayerInputsBufferString(false)))
+					Logger.Debug("inputFrame lifecycle#4[popped]:", zap.Any("roomId", pR.Id), zap.Any("inputFrameId", f.InputFrameId), zap.Any("InputsBuffer", pR.InputsBufferString(false)))
 				}
 			}
 
@@ -558,13 +553,16 @@ func (pR *Room) StartBattle() {
 	})
 }
 
+func (pR *Room) toDiscreteInputsBufferIndex(inputFrameId int32, joinIndex int32) int32 {
+	return (inputFrameId << 2) + joinIndex // allowing joinIndex upto 15
+}
+
 func (pR *Room) OnBattleCmdReceived(pReq *pb.WsReq) {
 	if swapped := atomic.CompareAndSwapInt32(&pR.State, RoomBattleStateIns.IN_BATTLE, RoomBattleStateIns.IN_BATTLE); !swapped {
 		return
 	}
 
 	playerId := pReq.PlayerId
-	indiceInJoinIndexBooleanArr := uint32(pReq.JoinIndex - 1)
 	inputFrameUpsyncBatch := pReq.InputFrameUpsyncBatch
 	ackingFrameId := pReq.AckingFrameId
 	ackingInputFrameId := pReq.AckingInputFrameId
@@ -584,49 +582,16 @@ func (pR *Room) OnBattleCmdReceived(pReq *pb.WsReq) {
 
 	for _, inputFrameUpsync := range inputFrameUpsyncBatch {
 		clientInputFrameId := inputFrameUpsync.InputFrameId
-		if clientInputFrameId < pR.AllPlayerInputsBuffer.StFrameId {
+		if clientInputFrameId < pR.InputsBuffer.StFrameId {
-			// Obsolete is actually not as concerned as advanced inputFrame.
+			// The updates to "pR.InputsBuffer.StFrameId" is monotonically increasing, thus if "clientInputFrameId < pR.InputsBuffer.StFrameId" at any moment of time, it is obsolete in the future.
-			Logger.Debug(fmt.Sprintf("Obsolete inputFrameUpsync: roomId=%v, playerId=%v, clientInputFrameId=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, clientInputFrameId, pR.AllPlayerInputsBufferString(false)))
+			Logger.Debug(fmt.Sprintf("Omitting obsolete inputFrameUpsync: roomId=%v, playerId=%v, clientInputFrameId=%v, InputsBuffer=%v", pR.Id, playerId, clientInputFrameId, pR.InputsBufferString(false)))
-			return
+			continue
 		}
 
-		var joinMask uint64 = (1 << indiceInJoinIndexBooleanArr)
+		bufIndex := pR.toDiscreteInputsBufferIndex(clientInputFrameId, pReq.JoinIndex)
-		encodedInput := pR.EncodeUpsyncCmd(inputFrameUpsync)
+		pR.DiscreteInputsBuffer.Store(bufIndex, inputFrameUpsync)
 
-		if clientInputFrameId >= pR.AllPlayerInputsBuffer.EdFrameId {
+		// TODO: "pR.DiscreteInputsBuffer" might become too large with outdated "inputFrameUpsync" items, maintain another queue orderd by timestamp to evict them
-			Logger.Warn(fmt.Sprintf("inputFrame too advanced! is the player cheating? roomId=%v, playerId=%v, clientInputFrameId=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, clientInputFrameId, pR.AllPlayerInputsBufferString(false)))
-			return
-		}
-		tmp2 := pR.AllPlayerInputsBuffer.GetByFrameId(clientInputFrameId)
-		if nil == tmp2 {
-			// This shouldn't happen due to the previous 2 checks
-			Logger.Warn(fmt.Sprintf("Mysterious error getting an input frame: roomId=%v, playerId=%v, clientInputFrameId=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, clientInputFrameId, pR.AllPlayerInputsBufferString(false)))
-			return
-		}
-		inputFrameDownsync := tmp2.(*pb.InputFrameDownsync)
-		oldConfirmedList := atomic.LoadUint64(&(inputFrameDownsync.ConfirmedList))
-		if (oldConfirmedList & joinMask) > 0 {
-			Logger.Debug(fmt.Sprintf("Cmd already confirmed but getting set attempt, omitting this upsync cmd: roomId=%v, playerId=%v, clientInputFrameId=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, clientInputFrameId, pR.AllPlayerInputsBufferString(false)))
-			return
-		}
-
-		// In Golang 1.12, there's no "compare-and-swap primitive" on a custom struct (or it's pointer, unless it's an unsafe pointer https://pkg.go.dev/sync/atomic@go1.12#CompareAndSwapPointer). Although CAS on custom struct is possible in Golang 1.19 https://pkg.go.dev/sync/atomic@go1.19.1#Value.CompareAndSwap, using a single word is still faster whenever possible.
-
-		// [WARNING] No need to use CAS for updating "inputFrameDownsync.InputList[indiceInJoinIndexBooleanArr]", the upsync from frontend takes top priority.
-		atomic.StoreUint64(&inputFrameDownsync.InputList[indiceInJoinIndexBooleanArr], encodedInput)
-
-		newConfirmedList := (oldConfirmedList | joinMask)
-		if swapped := atomic.CompareAndSwapUint64(&(inputFrameDownsync.ConfirmedList), oldConfirmedList, newConfirmedList); !swapped {
-			// [WARNING] Upon this error, the actual input has already been updated, which is an expected result if it caused by the force confirmation from "battleMainLoop".
-			Logger.Warn(fmt.Sprintf("Failed confirm CAS, might've been forced to all-confirmed: roomId=%v, playerId=%v, clientInputFrameId=%v", pR.Id, playerId, clientInputFrameId))
-			return
-		}
-
-		totPlayerCnt := uint32(pR.Capacity)
-		allConfirmedMask := uint64((1 << totPlayerCnt) - 1)
-		if allConfirmedMask == newConfirmedList {
-			pR.onInputFrameDownsyncAllConfirmed(inputFrameDownsync, playerId)
-		}
 	}
 }
 
@@ -634,9 +599,9 @@ func (pR *Room) onInputFrameDownsyncAllConfirmed(inputFrameDownsync *pb.InputFra
 	inputFrameId := inputFrameDownsync.InputFrameId
 	if -1 == pR.LastAllConfirmedInputFrameIdWithChange || false == pR.equalInputLists(inputFrameDownsync.InputList, pR.LastAllConfirmedInputList) {
 		if -1 == playerId {
-			Logger.Info(fmt.Sprintf("Key inputFrame change: roomId=%v, newInputFrameId=%v, lastInputFrameId=%v, newInputList=%v, lastInputList=%v, AllPlayerInputsBuffer=%v", pR.Id, inputFrameId, pR.LastAllConfirmedInputFrameId, inputFrameDownsync.InputList, pR.LastAllConfirmedInputList, pR.AllPlayerInputsBufferString(false)))
+			Logger.Info(fmt.Sprintf("Key inputFrame change: roomId=%v, newInputFrameId=%v, lastInputFrameId=%v, newInputList=%v, lastInputList=%v, InputsBuffer=%v", pR.Id, inputFrameId, pR.LastAllConfirmedInputFrameId, inputFrameDownsync.InputList, pR.LastAllConfirmedInputList, pR.InputsBufferString(false)))
 		} else {
-			Logger.Info(fmt.Sprintf("Key inputFrame change: roomId=%v, playerId=%v, newInputFrameId=%v, lastInputFrameId=%v, newInputList=%v, lastInputList=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, inputFrameId, pR.LastAllConfirmedInputFrameId, inputFrameDownsync.InputList, pR.LastAllConfirmedInputList, pR.AllPlayerInputsBufferString(false)))
+			Logger.Info(fmt.Sprintf("Key inputFrame change: roomId=%v, playerId=%v, newInputFrameId=%v, lastInputFrameId=%v, newInputList=%v, lastInputList=%v, InputsBuffer=%v", pR.Id, playerId, inputFrameId, pR.LastAllConfirmedInputFrameId, inputFrameDownsync.InputList, pR.LastAllConfirmedInputList, pR.InputsBufferString(false)))
 		}
 		atomic.StoreInt32(&(pR.LastAllConfirmedInputFrameIdWithChange), inputFrameId)
 	}
@@ -646,9 +611,9 @@ func (pR *Room) onInputFrameDownsyncAllConfirmed(inputFrameDownsync *pb.InputFra
 		pR.LastAllConfirmedInputList[i] = v
 	}
 	if -1 == playerId {
-		Logger.Debug(fmt.Sprintf("inputFrame lifecycle#2[forced-allconfirmed]: roomId=%v, AllPlayerInputsBuffer=%v", pR.Id, pR.AllPlayerInputsBufferString(false)))
+		Logger.Debug(fmt.Sprintf("inputFrame lifecycle#2[forced-allconfirmed]: roomId=%v, InputsBuffer=%v", pR.Id, pR.InputsBufferString(false)))
 	} else {
-		Logger.Info(fmt.Sprintf("inputFrame lifecycle#2[allconfirmed]: roomId=%v, playerId=%v, AllPlayerInputsBuffer=%v", pR.Id, playerId, pR.AllPlayerInputsBufferString(false)))
+		Logger.Info(fmt.Sprintf("inputFrame lifecycle#2[allconfirmed]: roomId=%v, playerId=%v, InputsBuffer=%v", pR.Id, playerId, pR.InputsBufferString(false)))
 	}
 }
 
@@ -786,7 +751,8 @@ func (pR *Room) OnDismissed() {
 	pR.PlayerSignalToCloseDict = make(map[int32]SignalToCloseConnCbType)
 	pR.JoinIndexBooleanArr = make([]bool, pR.Capacity)
 	pR.Barriers = make(map[int32]*Barrier)
-	pR.AllPlayerInputsBuffer = NewRingBuffer(1024)
+	pR.InputsBuffer = NewRingBuffer(1024)
+	pR.DiscreteInputsBuffer = sync.Map{}
 	pR.RenderFrameBuffer = NewRingBuffer(1024)
 
 	pR.LastAllConfirmedInputFrameId = -1
@@ -1045,16 +1011,16 @@ func (pR *Room) prefabInputFrameDownsync(inputFrameId int32) *pb.InputFrameDowns
 	*/
 	var currInputFrameDownsync *pb.InputFrameDownsync = nil
 
-	if 0 == inputFrameId && 0 == pR.AllPlayerInputsBuffer.Cnt {
+	if 0 == inputFrameId && 0 == pR.InputsBuffer.Cnt {
 		currInputFrameDownsync = &pb.InputFrameDownsync{
 			InputFrameId:  0,
 			InputList:     make([]uint64, pR.Capacity),
 			ConfirmedList: uint64(0),
 		}
 	} else {
-		tmp := pR.AllPlayerInputsBuffer.GetByFrameId(inputFrameId - 1)
+		tmp := pR.InputsBuffer.GetByFrameId(inputFrameId - 1)
 		if nil == tmp {
-			panic(fmt.Sprintf("Error prefabbing inputFrameDownsync: roomId=%v, AllPlayerInputsBuffer=%v", pR.Id, pR.AllPlayerInputsBufferString(false)))
+			panic(fmt.Sprintf("Error prefabbing inputFrameDownsync: roomId=%v, InputsBuffer=%v", pR.Id, pR.InputsBufferString(false)))
 		}
 		prevInputFrameDownsync := tmp.(*pb.InputFrameDownsync)
 		currInputList := prevInputFrameDownsync.InputList // Would be a clone of the values
@@ -1065,7 +1031,26 @@ func (pR *Room) prefabInputFrameDownsync(inputFrameId int32) *pb.InputFrameDowns
 		}
 	}
 
-	pR.AllPlayerInputsBuffer.Put(currInputFrameDownsync)
+	for _, player := range pR.Players {
+		// Enrich by already arrived player upsync commands
+		bufIndex := pR.toDiscreteInputsBufferIndex(currInputFrameDownsync.InputFrameId, player.JoinIndex)
+		tmp, loaded := pR.DiscreteInputsBuffer.LoadAndDelete(bufIndex)
+		if !loaded {
+			continue
+		}
+		inputFrameUpsync := tmp.(*pb.InputFrameUpsync)
+		indiceInJoinIndexBooleanArr := uint32(player.JoinIndex - 1)
+		currInputFrameDownsync.InputList[indiceInJoinIndexBooleanArr] = pR.EncodeUpsyncCmd(inputFrameUpsync)
+		currInputFrameDownsync.ConfirmedList |= (1 << indiceInJoinIndexBooleanArr)
+	}
+
+	totPlayerCnt := uint32(pR.Capacity)
+	allConfirmedMask := uint64((1 << totPlayerCnt) - 1)
+	if currInputFrameDownsync.ConfirmedList == allConfirmedMask {
+		pR.onInputFrameDownsyncAllConfirmed(currInputFrameDownsync, -1)
+	}
+
+	pR.InputsBuffer.Put(currInputFrameDownsync)
 	return currInputFrameDownsync
 }
 
@@ -1087,9 +1072,9 @@ func (pR *Room) forceConfirmationIfApplicable() uint64 {
 		Logger.Debug(fmt.Sprintf("inputFrameId2=%v is already all-confirmed for roomId=%v[type#1], no need to force confirmation of it", inputFrameId2, pR.Id))
 		return 0
 	}
-	tmp := pR.AllPlayerInputsBuffer.GetByFrameId(inputFrameId2)
+	tmp := pR.InputsBuffer.GetByFrameId(inputFrameId2)
 	if nil == tmp {
-		panic(fmt.Sprintf("inputFrameId2=%v doesn't exist for roomId=%v, this is abnormal because the server should prefab inputFrameDownsync in a most advanced pace, check the prefab logic! AllPlayerInputsBuffer=%v", inputFrameId2, pR.Id, pR.AllPlayerInputsBufferString(false)))
+		panic(fmt.Sprintf("inputFrameId2=%v doesn't exist for roomId=%v, this is abnormal because the server should prefab inputFrameDownsync in a most advanced pace, check the prefab logic! InputsBuffer=%v", inputFrameId2, pR.Id, pR.InputsBufferString(false)))
 	}
 	inputFrame2 := tmp.(*pb.InputFrameDownsync)
 
@@ -1123,11 +1108,11 @@ func (pR *Room) applyInputFrameDownsyncDynamics(fromRenderFrameId int32, toRende
 		delayedInputFrameId := pR.ConvertToInputFrameId(collisionSysRenderFrameId, pR.InputDelayFrames)
 		if 0 <= delayedInputFrameId {
 			if delayedInputFrameId > pR.LastAllConfirmedInputFrameId {
-				panic(fmt.Sprintf("delayedInputFrameId=%v is not yet all-confirmed for roomId=%v, this is abnormal because it's to be used for applying dynamics to [fromRenderFrameId:%v, toRenderFrameId:%v) @ collisionSysRenderFrameId=%v! AllPlayerInputsBuffer=%v", delayedInputFrameId, pR.Id, fromRenderFrameId, toRenderFrameId, collisionSysRenderFrameId, pR.AllPlayerInputsBufferString(false)))
+				panic(fmt.Sprintf("delayedInputFrameId=%v is not yet all-confirmed for roomId=%v, this is abnormal because it's to be used for applying dynamics to [fromRenderFrameId:%v, toRenderFrameId:%v) @ collisionSysRenderFrameId=%v! InputsBuffer=%v", delayedInputFrameId, pR.Id, fromRenderFrameId, toRenderFrameId, collisionSysRenderFrameId, pR.InputsBufferString(false)))
 			}
-			tmp := pR.AllPlayerInputsBuffer.GetByFrameId(delayedInputFrameId)
+			tmp := pR.InputsBuffer.GetByFrameId(delayedInputFrameId)
 			if nil == tmp {
-				panic(fmt.Sprintf("delayedInputFrameId=%v doesn't exist for roomId=%v, this is abnormal because it's to be used for applying dynamics to [fromRenderFrameId:%v, toRenderFrameId:%v) @ collisionSysRenderFrameId=%v! AllPlayerInputsBuffer=%v", delayedInputFrameId, pR.Id, fromRenderFrameId, toRenderFrameId, collisionSysRenderFrameId, pR.AllPlayerInputsBufferString(false)))
+				panic(fmt.Sprintf("delayedInputFrameId=%v doesn't exist for roomId=%v, this is abnormal because it's to be used for applying dynamics to [fromRenderFrameId:%v, toRenderFrameId:%v) @ collisionSysRenderFrameId=%v! InputsBuffer=%v", delayedInputFrameId, pR.Id, fromRenderFrameId, toRenderFrameId, collisionSysRenderFrameId, pR.InputsBufferString(false)))
 			}
 			delayedInputFrame := tmp.(*pb.InputFrameDownsync)
 			// [WARNING] It's possible that by now "allConfirmedMask != delayedInputFrame.ConfirmedList && delayedInputFrameId <= pR.LastAllConfirmedInputFrameId", we trust "pR.LastAllConfirmedInputFrameId" as the TOP AUTHORITY.
@@ -1143,6 +1128,7 @@ func (pR *Room) applyInputFrameDownsyncDynamics(fromRenderFrameId int32, toRende
 				baseChange := player.Speed * pR.RollbackEstimatedDt * decodedInputSpeedFactor
 				dx := baseChange * float64(decodedInput[0])
 				dy := baseChange * float64(decodedInput[1])
+
                 /*
 				// The collision lib seems very slow at worst cases, omitting for now
 				collisionPlayerIndex := COLLISION_PLAYER_INDEX_PREFIX + joinIndex

frontend/assets/scenes/login.fire

@@ -440,7 +440,7 @@
       "array": [
         0,
         0,
-        216.6425019058577,
+        210.74654679407692,
         0,
         0,
         0,

frontend/assets/scripts/Map.js

@@ -547,20 +547,23 @@ cc.Class({
     this._inputControlEnabled = false;
   },
 
-  onBattleStartedOrResynced(rdf) {
+  onRoomDownsyncFrame(rdf) {
     // This function is also applicable to "re-joining".
     const self = window.mapIns;
+    if (rdf.id < self.lastAllConfirmedRenderFrameId) {
+      return window.RING_BUFF_FAILED_TO_SET;
+    }
     const dumpRenderCacheRet = self.dumpToRenderCache(rdf);
     if (window.RING_BUFF_FAILED_TO_SET == dumpRenderCacheRet) {
       console.error("Something is wrong while setting the RingBuffer by frameId!");
       return dumpRenderCacheRet;
     }
     if (window.MAGIC_ROOM_DOWNSYNC_FRAME_ID.BATTLE_START < rdf.id && window.RING_BUFF_CONSECUTIVE_SET == dumpRenderCacheRet) {
-      if (rdf.id < self.chaserRenderFrameId) {
+      /*
-        // This "rdf.id = backend.refRenderFrameId" could be small, see comments around "room.go".
+      Don't change 
-        self.chaserRenderFrameId = rdf.id;
+      - lastAllConfirmedRenderFrameId, it's updated only in "rollbackAndChase > _createRoomDownsyncFrameLocally" (except for when RING_BUFF_NON_CONSECUTIVE_SET) 
-      }
+      - chaserRenderFrameId, it's updated only in "onInputFrameDownsyncBatch" (except for when RING_BUFF_NON_CONSECUTIVE_SET)
-      // In this case, we'll also got proper all-confirmed inputFrames for advancing the renderFrames in the coming "update(dt)" 
+      */
       return dumpRenderCacheRet;
     }
 
@@ -569,6 +572,7 @@ cc.Class({
 
     self.renderFrameId = rdf.id;
     self.lastRenderFrameIdTriggeredAt = performance.now();
+    // In this case it must be true that "rdf.id > chaserRenderFrameId >= lastAllConfirmedRenderFrameId".
     self.lastAllConfirmedRenderFrameId = rdf.id;
     self.chaserRenderFrameId = rdf.id;
 
@@ -623,6 +627,9 @@ cc.Class({
     for (let k in batch) {
       const inputFrameDownsync = batch[k];
       const inputFrameDownsyncId = inputFrameDownsync.inputFrameId;
+      if (inputFrameDownsyncId < self.lastAllConfirmedInputFrameId) {
+        continue;
+      }
       if (window.RING_BUFF_NON_CONSECUTIVE_SET == dumpRenderCacheRet) {
         // Deliberately left blank, in this case "chaserRenderFrameId" is already reset to proper value.
       } else {
@@ -767,8 +774,9 @@ cc.Class({
         // Use "fractional-frame-chasing" to guarantee that "self.update(dt)" is not jammed by a "large range of frame-chasing". See `<proj-root>/ConcerningEdgeCases.md` for the motivation. 
         const prevChaserRenderFrameId = self.chaserRenderFrameId;
         let nextChaserRenderFrameId = (prevChaserRenderFrameId + self.maxChasingRenderFramesPerUpdate);
-        if (nextChaserRenderFrameId > self.renderFrameId)
+        if (nextChaserRenderFrameId > self.renderFrameId) {
           nextChaserRenderFrameId = self.renderFrameId;
+        }
         self.rollbackAndChase(prevChaserRenderFrameId, nextChaserRenderFrameId, self.chaserCollisionSys, self.chaserCollisionSysMap);
         self.chaserRenderFrameId = nextChaserRenderFrameId; // Move the cursor "self.chaserRenderFrameId", keep in mind that "self.chaserRenderFrameId" is not monotonic!
         let t2 = performance.now();
@@ -975,29 +983,27 @@ cc.Class({
   },
 
   rollbackAndChase(renderFrameIdSt, renderFrameIdEd, collisionSys, collisionSysMap) {
-    if (renderFrameIdSt >= renderFrameIdEd) {
-      return;
-    }
-
     const self = this;
-    const renderFrameSt = self.recentRenderCache.getByFrameId(renderFrameIdSt); // typed "RoomDownsyncFrame"
+    let latestRdf = self.recentRenderCache.getByFrameId(renderFrameIdSt); // typed "RoomDownsyncFrame"
-    if (null == renderFrameSt) {
+    if (null == latestRdf) {
       console.error("Couldn't find renderFrameId=", renderFrameIdSt, " to rollback, lastAllConfirmedRenderFrameId=", self.lastAllConfirmedRenderFrameId, ", lastAllConfirmedInputFrameId=", self.lastAllConfirmedInputFrameId, ", recentRenderCache=", self._stringifyRecentRenderCache(false), ", recentInputCache=", self._stringifyRecentInputCache(false));
     }
+
+    if (renderFrameIdSt >= renderFrameIdEd) {
+      return latestRdf;
+    }
     /* 
-    Reset "position" of players in "collisionSys" according to "renderFrameSt". The easy part is that we don't have path-dependent-integrals to worry about like that of thermal dynamics.
+    Reset "position" of players in "collisionSys" according to "renderFrameIdSt". The easy part is that we don't have path-dependent-integrals to worry about like that of thermal dynamics.
     */
     self.playerRichInfoDict.forEach((playerRichInfo, playerId) => {
       const joinIndex = playerRichInfo.joinIndex;
       const collisionPlayerIndex = self.collisionPlayerIndexPrefix + joinIndex;
       const playerCollider = collisionSysMap.get(collisionPlayerIndex);
-      const player = renderFrameSt.players[playerId];
+      const player = latestRdf.players[playerId];
       playerCollider.x = player.x;
       playerCollider.y = player.y;
     });
 
-    // [WARNING] Traverse in the order of joinIndices to guarantee determinism.
-
     /*
     This function eventually calculates a "RoomDownsyncFrame" where "RoomDownsyncFrame.id == renderFrameIdEd".
     */
@@ -1009,6 +1015,7 @@ cc.Class({
         console.error("Failed to get cached inputFrameDownsync for renderFrameId=", i, ", inputFrameId=", j, "lastAllConfirmedRenderFrameId=", self.lastAllConfirmedRenderFrameId, ", lastAllConfirmedInputFrameId=", self.lastAllConfirmedInputFrameId, ", recentRenderCache=", self._stringifyRecentRenderCache(false), ", recentInputCache=", self._stringifyRecentInputCache(false));
       }
       const inputList = inputFrameDownsync.inputList;
+      // [WARNING] Traverse in the order of joinIndices to guarantee determinism.
       for (let j in self.playerRichInfoArr) {
         const joinIndex = parseInt(j) + 1;
         const playerId = self.playerRichInfoArr[j].id;
@@ -1038,9 +1045,11 @@ cc.Class({
           playerCollider.y -= result.overlap * result.overlap_y;
         }
       }
+
+      latestRdf = self._createRoomDownsyncFrameLocally(i+1, collisionSys, collisionSysMap);
     }
 
-    return self._createRoomDownsyncFrameLocally(renderFrameIdEd, collisionSys, collisionSysMap);
+    return latestRdf;
   },
 
   _initPlayerRichInfoDict(players, playerMetas) {

frontend/assets/scripts/RingBuffer.js

@@ -68,7 +68,7 @@ RingBuffer.prototype.getByFrameId = function(frameId) {
 // [WARNING] During a battle, frontend could receive non-consecutive frames (either renderFrame or inputFrame) due to resync, the buffer should handle these frames properly. 
 RingBuffer.prototype.setByFrameId = function(item, frameId) {
   if (frameId < this.stFrameId) {
-    console.error("Invalid putByFrameId#1: stFrameId=", stFrameId, ", edFrameId=", edFrameId, ", incoming item=", item);
+    console.error("Invalid putByFrameId#1: stFrameId=", this.stFrameId, ", edFrameId=", this.edFrameId, ", incoming item=", item);
     return window.RING_BUFF_FAILED_TO_SET;
   }
   const arrIdx = this.getArrIdxByOffset(frameId - this.stFrameId);

frontend/assets/scripts/WsSessionMgr.js

@@ -171,7 +171,7 @@ window.initPersistentSessionClient = function(onopenCb, expectedRoomId) {
           mapIns.onBattleReadyToStart(resp.rdf.playerMetas, false);
           break;
         case window.DOWNSYNC_MSG_ACT_BATTLE_START:
-          mapIns.onBattleStartedOrResynced(resp.rdf);
+          mapIns.onRoomDownsyncFrame(resp.rdf);
           break;
         case window.DOWNSYNC_MSG_ACT_BATTLE_STOPPED:
           mapIns.onBattleStopped();
@@ -180,9 +180,9 @@ window.initPersistentSessionClient = function(onopenCb, expectedRoomId) {
           mapIns.onInputFrameDownsyncBatch(resp.inputFrameDownsyncBatch);
           break;
         case window.DOWNSYNC_MSG_ACT_FORCED_RESYNC:
-          console.warn("Got forced resync:", JSON.stringify(resp), " @localRenderFrameId=", mapIns.renderFrameId, ", @localRecentInputCache=", mapIns._stringifyRecentInputCache(false));
+          console.warn("Got forced resync@localRenderFrameId=", mapIns.renderFrameId, ", @lastAllConfirmedRenderFrameId=", mapIns.lastAllConfirmedRenderFrameId, "@lastAllConfirmedInputFrameId=", mapIns.lastAllConfirmedInputFrameId, ", @localRecentInputCache=", mapIns._stringifyRecentInputCache(false), ", the incoming resp=\n", JSON.stringify(resp));
           // The following order of execution is important, because "onInputFrameDownsyncBatch" is only available when state is IN_BATTLE 
-          const dumpRenderCacheRet = mapIns.onBattleStartedOrResynced(resp.rdf);
+          const dumpRenderCacheRet = mapIns.onRoomDownsyncFrame(resp.rdf);
           mapIns.onInputFrameDownsyncBatch(resp.inputFrameDownsyncBatch, dumpRenderCacheRet);
           break;
         default: