chore(txPipeline): refactor slottedCommands impl

Author: ndyakov

osscluster.go

@@ -1526,102 +1526,78 @@ func (c *ClusterClient) processTxPipeline(ctx context.Context, cmds []Cmder) err
 		return err
 	}
 
-	cmdsMap := map[int][]Cmder{}
+	keyedCmdsBySlot := c.slottedKeyedCommands(cmds)
 	slot := -1
-	// get only the keyed commands
-	keyedCmds := c.keyedCmds(cmds)
-	if len(keyedCmds) == 0 {
-		// no keyed commands try random slot
+	switch len(keyedCmdsBySlot) {
+	case 0:
 		slot = hashtag.RandomSlot()
-	} else {
-		// keyed commands, get slot from them
-		// if more than one slot, return cross slot error
-		cmdsBySlot := c.mapCmdsBySlot(keyedCmds)
-		if len(cmdsBySlot) > 1 {
-			// cross slot error, we have more than one slot for keyed commands
-			setCmdsErr(cmds, ErrCrossSlot)
-			return ErrCrossSlot
-		}
-		// get the slot, should be only one
-		for sl := range cmdsBySlot {
+	case 1:
+		for sl := range keyedCmdsBySlot {
 			slot = sl
 			break
 		}
-	}
-	// slot was not determined, try random one
-	if slot == -1 {
-		slot = hashtag.RandomSlot()
-	}
-	cmdsMap[slot] = cmds
-
-	// TxPipeline does not support cross slot transaction.
-	// double check the commands are in the same slot
-	if len(cmdsMap) > 1 {
+	default:
+		// TxPipeline does not support cross slot transaction.
 		setCmdsErr(cmds, ErrCrossSlot)
 		return ErrCrossSlot
 	}
 
-	for slot, cmds := range cmdsMap {
-		node, err := state.slotMasterNode(slot)
-		if err != nil {
-			setCmdsErr(cmds, err)
-			continue
-		}
+	node, err := state.slotMasterNode(slot)
+	if err != nil {
+		setCmdsErr(cmds, err)
+		return err
+	}
 
-		cmdsMap := map[*clusterNode][]Cmder{node: cmds}
-		for attempt := 0; attempt <= c.opt.MaxRedirects; attempt++ {
-			if attempt > 0 {
-				if err := internal.Sleep(ctx, c.retryBackoff(attempt)); err != nil {
-					setCmdsErr(cmds, err)
-					return err
-				}
+	cmdsMap := map[*clusterNode][]Cmder{node: cmds}
+	for attempt := 0; attempt <= c.opt.MaxRedirects; attempt++ {
+		if attempt > 0 {
+			if err := internal.Sleep(ctx, c.retryBackoff(attempt)); err != nil {
+				setCmdsErr(cmds, err)
+				return err
 			}
+		}
 
-			failedCmds := newCmdsMap()
-			var wg sync.WaitGroup
+		failedCmds := newCmdsMap()
+		var wg sync.WaitGroup
 
-			for node, cmds := range cmdsMap {
-				wg.Add(1)
-				go func(node *clusterNode, cmds []Cmder) {
-					defer wg.Done()
-					c.processTxPipelineNode(ctx, node, cmds, failedCmds)
-				}(node, cmds)
-			}
+		for node, cmds := range cmdsMap {
+			wg.Add(1)
+			go func(node *clusterNode, cmds []Cmder) {
+				defer wg.Done()
+				c.processTxPipelineNode(ctx, node, cmds, failedCmds)
+			}(node, cmds)
+		}
 
-			wg.Wait()
-			if len(failedCmds.m) == 0 {
-				break
-			}
-			cmdsMap = failedCmds.m
+		wg.Wait()
+		if len(failedCmds.m) == 0 {
+			break
 		}
+		cmdsMap = failedCmds.m
 	}
 
 	return cmdsFirstErr(cmds)
 }
 
-func (c *ClusterClient) mapCmdsBySlot(cmds []Cmder) map[int][]Cmder {
-	cmdsMap := make(map[int][]Cmder)
-	preferredRandomSlot := -1
+// slottedKeyedCommands returns a map of slot to commands taking into account
+// only commands that have keys.
+func (c *ClusterClient) slottedKeyedCommands(cmds []Cmder) map[int][]Cmder {
+	cmdsSlots := map[int][]Cmder{}
+
+	prefferedRandomSlot := -1
 	for _, cmd := range cmds {
-		slot := c.cmdSlot(cmd, preferredRandomSlot)
-		if preferredRandomSlot == -1 {
-			preferredRandomSlot = slot
+		if cmdFirstKeyPos(cmd) == 0 {
+			continue
 		}
-		cmdsMap[slot] = append(cmdsMap[slot], cmd)
-	}
-	return cmdsMap
-}
 
-// keyedCmds returns all the keyed commands from the cmds slice
-// it determines keyed commands by checking if the command has a first key position
-func (c *ClusterClient) keyedCmds(cmds []Cmder) []Cmder {
-	keyedCmds := make([]Cmder, 0, len(cmds))
-	for _, cmd := range cmds {
-		if cmdFirstKeyPos(cmd) != 0 {
-			keyedCmds = append(keyedCmds, cmd)
+		slot := c.cmdSlot(cmd, prefferedRandomSlot)
+		if prefferedRandomSlot == -1 {
+			prefferedRandomSlot = slot
 		}
+
+		cmdsSlots[slot] = append(cmdsSlots[slot], cmd)
 	}
-	return keyedCmds
+
+	return cmdsSlots
 }
 
 func (c *ClusterClient) processTxPipelineNode(