fix(hotkeys): read the CPU time reply fields (#4206)

HOTKEYS GET reports the session CPU time as total-cpu-time-user-ms and
total-cpu-time-sys-ms, which is how src/hotkeys.c and the command docs name
them. readReply looked up used-cpu-user-ms and used-cpu-sys-ms instead, so
UsedCPUUser and UsedCPUSys stayed zero for every reply.

command.go

@@ -6903,10 +6903,11 @@ func (cmd *HotKeysCmd) readReply(rd *proto.Reader) error {
 	if v, ok := data["collection-duration-ms"].(int64); ok {
 		result.CollectionDuration = time.Duration(v) * time.Millisecond
 	}
-	if v, ok := data["used-cpu-sys-ms"].(int64); ok {
+	// The server names these total-cpu-time-*-ms, not after the fields below.
+	if v, ok := data["total-cpu-time-sys-ms"].(int64); ok {
 		result.UsedCPUSys = time.Duration(v) * time.Millisecond
 	}
-	if v, ok := data["used-cpu-user-ms"].(int64); ok {
+	if v, ok := data["total-cpu-time-user-ms"].(int64); ok {
 		result.UsedCPUUser = time.Duration(v) * time.Millisecond
 	}
 	if v, ok := data["total-net-bytes"].(int64); ok {

hotkeys_commands_unit_test.go

@@ -0,0 +1,74 @@
+package redis
+
+import (
+	"context"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/redis/go-redis/v9/internal/proto"
+)
+
+// HOTKEYS GET answers with an array holding a single map. The CPU totals are
+// named total-cpu-time-user-ms and total-cpu-time-sys-ms by the server, so the
+// reply must be read under those names. RESP2 sends the same fields as a flat
+// array of name/value pairs.
+func TestHotKeysCmdReadReplyCPUFields(t *testing.T) {
+	fields := [][2]string{
+		{"tracking-active", ":1\r\n"},
+		{"sample-ratio", ":1\r\n"},
+		{"selected-slots", "*1\r\n*2\r\n:0\r\n:16383\r\n"},
+		{"all-commands-all-slots-us", ":103\r\n"},
+		{"net-bytes-all-commands-all-slots", ":2042\r\n"},
+		{"collection-start-time-unix-ms", ":1770824933147\r\n"},
+		{"collection-duration-ms", ":0\r\n"},
+		{"total-cpu-time-user-ms", ":23\r\n"},
+		{"total-cpu-time-sys-ms", ":7\r\n"},
+		{"total-net-bytes", ":2038\r\n"},
+		{"by-cpu-time-us", "*2\r\n" + hotKeysBulkTestString("hotkey_001_counter") + ":29\r\n"},
+		{"by-net-bytes", "*2\r\n" + hotKeysBulkTestString("hotkey_001") + ":446\r\n"},
+	}
+
+	var body strings.Builder
+	for _, field := range fields {
+		body.WriteString(hotKeysBulkTestString(field[0]))
+		body.WriteString(field[1])
+	}
+	resp3 := "*1\r\n%" + strconv.Itoa(len(fields)) + "\r\n" + body.String()
+	resp2 := "*1\r\n*" + strconv.Itoa(2*len(fields)) + "\r\n" + body.String()
+
+	for _, reply := range []string{resp3, resp2} {
+		cmd := NewHotKeysCmd(context.Background(), "hotkeys", "get")
+		if err := cmd.readReply(proto.NewReader(strings.NewReader(reply))); err != nil {
+			t.Fatalf("readReply(%.80q): %v", reply, err)
+		}
+
+		val := cmd.Val()
+		if val == nil {
+			t.Fatalf("readReply(%.80q) left no result", reply)
+		}
+		if got := val.UsedCPUUser; got != 23*time.Millisecond {
+			t.Errorf("UsedCPUUser for %.80q = %v; want 23ms", reply, got)
+		}
+		if got := val.UsedCPUSys; got != 7*time.Millisecond {
+			t.Errorf("UsedCPUSys for %.80q = %v; want 7ms", reply, got)
+		}
+		if !val.TrackingActive {
+			t.Errorf("TrackingActive for %.80q = false; want true", reply)
+		}
+		if got := val.TotalNetBytes; got != 2038 {
+			t.Errorf("TotalNetBytes for %.80q = %d; want 2038", reply, got)
+		}
+		if got := val.AllCommandsAllSlots; got != 103*time.Microsecond {
+			t.Errorf("AllCommandsAllSlots for %.80q = %v; want 103us", reply, got)
+		}
+		if got := val.ByCPUTime; len(got) != 1 || got[0].Key != "hotkey_001_counter" || got[0].Value != int64(29) {
+			t.Errorf("ByCPUTime for %.80q = %v; want one hotkey_001_counter entry of 29", reply, got)
+		}
+	}
+}
+
+func hotKeysBulkTestString(s string) string {
+	return "$" + strconv.Itoa(len(s)) + "\r\n" + s + "\r\n"
+}