[DO NOT MERGE] Refactor - Move command execution responsibility to CommandHandler from IOThread

config/config.go

@@ -168,6 +168,7 @@ type performance struct {
 	ShardCronFrequency     time.Duration `config:"shard_cron_frequency" default:"1s"`
 	MultiplexerPollTimeout time.Duration `config:"multiplexer_poll_timeout" default:"100ms"`
 	MaxClients             int32         `config:"max_clients" default:"20000" validate:"min=0"`
+	MaxCmdHandlers         int32         `config:"max_cmd_handlers" default:"20000" validate:"min=0"`
 	StoreMapInitSize       int           `config:"store_map_init_size" default:"1024000"`
 	AdhocReqChanBufSize    int           `config:"adhoc_req_chan_buf_size" default:"20"`
 	EnableProfiling        bool          `config:"profiling" default:"false"`

integration_tests/commands/resp/setup.go

@@ -29,6 +29,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/dicedb/dice/internal/commandhandler"
 	"github.com/dicedb/dice/internal/iothread"
 	"github.com/dicedb/dice/internal/server/resp"
 	"github.com/dicedb/dice/internal/wal"
@@ -211,10 +212,12 @@ func RunTestServer(wg *sync.WaitGroup, opt TestServerOptions) {
 	cmdWatchSubscriptionChan := make(chan watchmanager.WatchSubscription)
 	gec := make(chan error)
 	shardManager := shard.NewShardManager(1, cmdWatchChan, gec)
-	ioThreadManager := iothread.NewManager(20000, shardManager)
+	ioThreadManager := iothread.NewManager(20000)
+	cmdHandlerManager := commandhandler.NewManager(20000, shardManager)
+
 	// Initialize the RESP Server
 	wl, _ := wal.NewNullWAL()
-	testServer := resp.NewServer(shardManager, ioThreadManager, cmdWatchSubscriptionChan, cmdWatchChan, gec, wl)
+	testServer := resp.NewServer(shardManager, ioThreadManager, cmdHandlerManager, cmdWatchSubscriptionChan, cmdWatchChan, gec, wl)
 
 	ctx, cancel := context.WithCancel(context.Background())
 	fmt.Println("Starting the test server on port", config.DiceConfig.RespServer.Port)

internal/iothread/cmd_compose.go → internal/commandhandler/cmd_compose.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-package iothread
+package commandhandler
 
 import (
 	"math"
@@ -24,7 +24,7 @@ import (
 	"github.com/dicedb/dice/internal/ops"
 )
 
-// This file contains functions used by the IOThread to handle and process responses
+// This file contains functions used by the CommandHandler to handle and process responses
 // from multiple shards during distributed operations. For commands that are executed
 // across several shards, such as MultiShard commands, dedicated functions are responsible
 // for aggregating and managing the results.

internal/iothread/cmd_custom.go → internal/commandhandler/cmd_custom.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-package iothread
+package commandhandler
 
 import (
 	"fmt"
@@ -28,7 +28,7 @@ import (
 
 // RespAuth returns with an encoded "OK" if the user is authenticated
 // If the user is not authenticated, it returns with an encoded error message
-func (t *BaseIOThread) RespAuth(args []string) interface{} {
+func (h *BaseCommandHandler) RespAuth(args []string) interface{} {
 	// Check for incorrect number of arguments (arity error).
 	if len(args) < 1 || len(args) > 2 {
 		return diceerrors.ErrWrongArgumentCount("AUTH")
@@ -47,7 +47,7 @@ func (t *BaseIOThread) RespAuth(args []string) interface{} {
 		username, password = args[0], args[1]
 	}
 
-	if err := t.Session.Validate(username, password); err != nil {
+	if err := h.Session.Validate(username, password); err != nil {
 		return err
 	}
 

internal/iothread/cmd_decompose.go → internal/commandhandler/cmd_decompose.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-package iothread
+package commandhandler
 
 import (
 	"context"
@@ -28,7 +28,7 @@ import (
 	"github.com/dicedb/dice/internal/store"
 )
 
-// This file is utilized by the IOThread to decompose commands that need to be executed
+// This file is utilized by the CommandHandler to decompose commands that need to be executed
 // across multiple shards. For commands that operate on multiple keys or necessitate
 // distribution across shards (e.g., MultiShard commands), a Breakup function is invoked
 // to transform the original command into multiple smaller commands, each directed at
@@ -41,13 +41,13 @@ import (
 // decomposeRename breaks down the RENAME command into separate DELETE and SET commands.
 // It first waits for the result of a GET command from shards. If successful, it removes
 // the old key using a DEL command and sets the new key with the retrieved value using a SET command.
-func decomposeRename(ctx context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeRename(ctx context.Context, h *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	// Waiting for GET command response
 	var val string
 	select {
 	case <-ctx.Done():
-		slog.Error("IOThread timed out waiting for response from shards", slog.String("id", thread.id), slog.Any("error", ctx.Err()))
-	case preProcessedResp, ok := <-thread.preprocessingChan:
+		slog.Error("CommandHandler timed out waiting for response from shards", slog.String("id", h.id), slog.Any("error", ctx.Err()))
+	case preProcessedResp, ok := <-h.preprocessingChan:
 		if ok {
 			evalResp := preProcessedResp.EvalResponse
 			if evalResp.Error != nil {
@@ -85,13 +85,13 @@ func decomposeRename(ctx context.Context, thread *BaseIOThread, cd *cmd.DiceDBCm
 // decomposeCopy breaks down the COPY command into a SET command that copies a value from
 // one key to another. It first retrieves the value of the original key from shards, then
 // sets the value to the destination key using a SET command.
-func decomposeCopy(ctx context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeCopy(ctx context.Context, h *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	// Waiting for GET command response
 	var resp *ops.StoreResponse
 	select {
 	case <-ctx.Done():
-		slog.Error("IOThread timed out waiting for response from shards", slog.String("id", thread.id), slog.Any("error", ctx.Err()))
-	case preProcessedResp, ok := <-thread.preprocessingChan:
+		slog.Error("CommandHandler timed out waiting for response from shards", slog.String("id", h.id), slog.Any("error", ctx.Err()))
+	case preProcessedResp, ok := <-h.preprocessingChan:
 		if ok {
 			resp = preProcessedResp
 		}
@@ -124,7 +124,7 @@ func decomposeCopy(ctx context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd)
 // decomposeMSet decomposes the MSET (Multi-set) command into individual SET commands.
 // It expects an even number of arguments (key-value pairs). For each pair, it creates
 // a separate SET command to store the value at the given key.
-func decomposeMSet(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeMSet(_ context.Context, _ *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args)%2 != 0 {
 		return nil, diceerrors.ErrWrongArgumentCount("MSET")
 	}
@@ -148,7 +148,7 @@ func decomposeMSet(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cm
 // decomposeMGet decomposes the MGET (Multi-get) command into individual GET commands.
 // It expects a list of keys, and for each key, it creates a separate GET command to
 // retrieve the value associated with that key.
-func decomposeMGet(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeMGet(_ context.Context, _ *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) < 1 {
 		return nil, diceerrors.ErrWrongArgumentCount("MGET")
 	}
@@ -164,7 +164,7 @@ func decomposeMGet(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cm
 	return decomposedCmds, nil
 }
 
-func decomposeSInter(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeSInter(_ context.Context, _ *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) < 1 {
 		return nil, diceerrors.ErrWrongArgumentCount("SINTER")
 	}
@@ -180,7 +180,7 @@ func decomposeSInter(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*
 	return decomposedCmds, nil
 }
 
-func decomposeSDiff(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeSDiff(_ context.Context, _ *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) < 1 {
 		return nil, diceerrors.ErrWrongArgumentCount("SDIFF")
 	}
@@ -196,7 +196,7 @@ func decomposeSDiff(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*c
 	return decomposedCmds, nil
 }
 
-func decomposeJSONMget(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeJSONMget(_ context.Context, _ *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) < 2 {
 		return nil, diceerrors.ErrWrongArgumentCount("JSON.MGET")
 	}
@@ -215,7 +215,7 @@ func decomposeJSONMget(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([
 	return decomposedCmds, nil
 }
 
-func decomposeTouch(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeTouch(_ context.Context, _ *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) == 0 {
 		return nil, diceerrors.ErrWrongArgumentCount("TOUCH")
 	}
@@ -232,13 +232,13 @@ func decomposeTouch(_ context.Context, _ *BaseIOThread, cd *cmd.DiceDBCmd) ([]*c
 	return decomposedCmds, nil
 }
 
-func decomposeDBSize(_ context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeDBSize(_ context.Context, h *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) > 0 {
 		return nil, diceerrors.ErrWrongArgumentCount("DBSIZE")
 	}
 
 	decomposedCmds := make([]*cmd.DiceDBCmd, 0, len(cd.Args))
-	for i := uint8(0); i < uint8(thread.shardManager.GetShardCount()); i++ {
+	for i := uint8(0); i < uint8(h.shardManager.GetShardCount()); i++ {
 		decomposedCmds = append(decomposedCmds,
 			&cmd.DiceDBCmd{
 				Cmd:  store.SingleShardSize,
@@ -249,13 +249,13 @@ func decomposeDBSize(_ context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd)
 	return decomposedCmds, nil
 }
 
-func decomposeKeys(_ context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeKeys(_ context.Context, h *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) != 1 {
 		return nil, diceerrors.ErrWrongArgumentCount("KEYS")
 	}
 
 	decomposedCmds := make([]*cmd.DiceDBCmd, 0, len(cd.Args))
-	for i := uint8(0); i < uint8(thread.shardManager.GetShardCount()); i++ {
+	for i := uint8(0); i < uint8(h.shardManager.GetShardCount()); i++ {
 		decomposedCmds = append(decomposedCmds,
 			&cmd.DiceDBCmd{
 				Cmd:  store.SingleShardKeys,
@@ -266,13 +266,13 @@ func decomposeKeys(_ context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd) (
 	return decomposedCmds, nil
 }
 
-func decomposeFlushDB(_ context.Context, thread *BaseIOThread, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
+func decomposeFlushDB(_ context.Context, h *BaseCommandHandler, cd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error) {
 	if len(cd.Args) > 1 {
 		return nil, diceerrors.ErrWrongArgumentCount("FLUSHDB")
 	}
 
 	decomposedCmds := make([]*cmd.DiceDBCmd, 0, len(cd.Args))
-	for i := uint8(0); i < uint8(thread.shardManager.GetShardCount()); i++ {
+	for i := uint8(0); i < uint8(h.shardManager.GetShardCount()); i++ {
 		decomposedCmds = append(decomposedCmds,
 			&cmd.DiceDBCmd{
 				Cmd:  store.FlushDB,

internal/iothread/cmd_meta.go → internal/commandhandler/cmd_meta.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-package iothread
+package commandhandler
 
 import (
 	"context"
@@ -213,12 +213,12 @@ const (
 
 type CmdMeta struct {
 	CmdType
-	Cmd             string
-	IOThreadHandler func([]string) []byte
+	Cmd                string
+	CmdHandlerFunction func([]string) []byte
 
 	// decomposeCommand is a function that takes a DiceDB command and breaks it down into smaller,
 	// manageable DiceDB commands for each shard processing. It returns a slice of DiceDB commands.
-	decomposeCommand func(ctx context.Context, thread *BaseIOThread, DiceDBCmd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error)
+	decomposeCommand func(ctx context.Context, h *BaseCommandHandler, DiceDBCmd *cmd.DiceDBCmd) ([]*cmd.DiceDBCmd, error)
 
 	// composeResponse is a function that combines multiple responses from the execution of commands
 	// into a single response object. It accepts a variadic parameter of EvalResponse objects
@@ -233,10 +233,10 @@ type CmdMeta struct {
 
 	// preProcessResponse is a function that handles the preprocessing of a DiceDB command by
 	// preparing the necessary operations (e.g., fetching values from shards) before the command
-	// is executed. It takes the io-thread and the original DiceDB command as parameters and
+	// is executed. It takes the CommandHandler and the original DiceDB command as parameters and
 	// ensures that any required information is retrieved and processed in advance. Use this when set
 	// preProcessingReq = true.
-	preProcessResponse func(thread *BaseIOThread, DiceDBCmd *cmd.DiceDBCmd) error
+	preProcessResponse func(h *BaseCommandHandler, DiceDBCmd *cmd.DiceDBCmd) error
 }
 
 var CommandsMeta = map[string]CmdMeta{
@@ -691,8 +691,8 @@ func init() {
 func validateCmdMeta(c string, meta CmdMeta) error {
 	switch meta.CmdType {
 	case Global:
-		if meta.IOThreadHandler == nil {
-			return fmt.Errorf("global command %s must have IOThreadHandler function", c)
+		if meta.CmdHandlerFunction == nil {
+			return fmt.Errorf("global command %s must have CmdHandlerFunction function", c)
 		}
 	case MultiShard, AllShard:
 		if meta.decomposeCommand == nil || meta.composeResponse == nil {

internal/iothread/cmd_preprocess.go → internal/commandhandler/cmd_preprocess.go

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
-package iothread
+package commandhandler
 
 import (
 	"github.com/dicedb/dice/internal/cmd"
@@ -25,13 +25,13 @@ import (
 // preProcessRename prepares the RENAME command for preprocessing by sending a GET command
 // to retrieve the value of the original key. The retrieved value is used later in the
 // decomposeRename function to delete the old key and set the new key.
-func preProcessRename(thread *BaseIOThread, diceDBCmd *cmd.DiceDBCmd) error {
+func preProcessRename(h *BaseCommandHandler, diceDBCmd *cmd.DiceDBCmd) error {
 	if len(diceDBCmd.Args) < 2 {
 		return diceerrors.ErrWrongArgumentCount("RENAME")
 	}
 
 	key := diceDBCmd.Args[0]
-	sid, rc := thread.shardManager.GetShardInfo(key)
+	sid, rc := h.shardManager.GetShardInfo(key)
 
 	preCmd := cmd.DiceDBCmd{
 		Cmd:  "RENAME",
@@ -42,7 +42,7 @@ func preProcessRename(thread *BaseIOThread, diceDBCmd *cmd.DiceDBCmd) error {
 		SeqID:         0,
 		RequestID:     GenerateUniqueRequestID(),
 		Cmd:           &preCmd,
-		IOThreadID:    thread.id,
+		CmdHandlerID:  h.id,
 		ShardID:       sid,
 		Client:        nil,
 		PreProcessing: true,
@@ -54,12 +54,12 @@ func preProcessRename(thread *BaseIOThread, diceDBCmd *cmd.DiceDBCmd) error {
 // preProcessCopy prepares the COPY command for preprocessing by sending a GET command
 // to retrieve the value of the original key. The retrieved value is used later in the
 // decomposeCopy function to copy the value to the destination key.
-func customProcessCopy(thread *BaseIOThread, diceDBCmd *cmd.DiceDBCmd) error {
+func customProcessCopy(h *BaseCommandHandler, diceDBCmd *cmd.DiceDBCmd) error {
 	if len(diceDBCmd.Args) < 2 {
 		return diceerrors.ErrWrongArgumentCount("COPY")
 	}
 
-	sid, rc := thread.shardManager.GetShardInfo(diceDBCmd.Args[0])
+	sid, rc := h.shardManager.GetShardInfo(diceDBCmd.Args[0])
 
 	preCmd := cmd.DiceDBCmd{
 		Cmd:  "COPY",
@@ -71,7 +71,7 @@ func customProcessCopy(thread *BaseIOThread, diceDBCmd *cmd.DiceDBCmd) error {
 		SeqID:         0,
 		RequestID:     GenerateUniqueRequestID(),
 		Cmd:           &preCmd,
-		IOThreadID:    thread.id,
+		CmdHandlerID:  h.id,
 		ShardID:       sid,
 		Client:        nil,
 		PreProcessing: true,