Support Monitor Command (#2830)

* Add monitor command

* Add monitor commadn and tests

* insure goroutine shutdown

* fix data race

* linting

* change timeout explanation

---------

Co-authored-by: Chayim <chayim@users.noreply.github.com>

Author: ofekshenawa

command.go

@@ -8,6 +8,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/redis/go-redis/v9/internal"
@@ -5381,3 +5382,85 @@ func (cmd *InfoCmd) Item(section, key string) string {
 		return cmd.val[section][key]
 	}
 }
+
+type MonitorStatus int
+
+const (
+	monitorStatusIdle MonitorStatus = iota
+	monitorStatusStart
+	monitorStatusStop
+)
+
+type MonitorCmd struct {
+	baseCmd
+	ch     chan string
+	status MonitorStatus
+	mu     sync.Mutex
+}
+
+func newMonitorCmd(ctx context.Context, ch chan string) *MonitorCmd {
+	return &MonitorCmd{
+		baseCmd: baseCmd{
+			ctx:  ctx,
+			args: []interface{}{"monitor"},
+		},
+		ch:     ch,
+		status: monitorStatusIdle,
+		mu:     sync.Mutex{},
+	}
+}
+
+func (cmd *MonitorCmd) String() string {
+	return cmdString(cmd, nil)
+}
+
+func (cmd *MonitorCmd) readReply(rd *proto.Reader) error {
+	ctx, cancel := context.WithCancel(cmd.ctx)
+	go func(ctx context.Context) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				err := cmd.readMonitor(rd, cancel)
+				if err != nil {
+					cmd.err = err
+					return
+				}
+			}
+		}
+	}(ctx)
+	return nil
+}
+
+func (cmd *MonitorCmd) readMonitor(rd *proto.Reader, cancel context.CancelFunc) error {
+	for {
+		cmd.mu.Lock()
+		st := cmd.status
+		cmd.mu.Unlock()
+		if pk, _ := rd.Peek(1); len(pk) != 0 && st == monitorStatusStart {
+			line, err := rd.ReadString()
+			if err != nil {
+				return err
+			}
+			cmd.ch <- line
+		}
+		if st == monitorStatusStop {
+			cancel()
+			break
+		}
+	}
+	return nil
+}
+
+func (cmd *MonitorCmd) Start() {
+	cmd.mu.Lock()
+	defer cmd.mu.Unlock()
+	cmd.status = monitorStatusStart
+}
+
+func (cmd *MonitorCmd) Stop() {
+	cmd.mu.Lock()
+	defer cmd.mu.Unlock()
+	cmd.status = monitorStatusStop
+}

commands.go

@@ -204,7 +204,6 @@ type Cmdable interface {
 	SlowLogGet(ctx context.Context, num int64) *SlowLogCmd
 	Time(ctx context.Context) *TimeCmd
 	DebugObject(ctx context.Context, key string) *StringCmd
-
 	MemoryUsage(ctx context.Context, key string, samples ...int) *IntCmd
 
 	ModuleLoadex(ctx context.Context, conf *ModuleLoadexConfig) *StringCmd
@@ -700,3 +699,20 @@ func (c cmdable) ModuleLoadex(ctx context.Context, conf *ModuleLoadexConfig) *St
 	_ = c(ctx, cmd)
 	return cmd
 }
+
+/*
+Monitor - represents a Redis MONITOR command, allowing the user to capture
+and process all commands sent to a Redis server. This mimics the behavior of
+MONITOR in the redis-cli.
+
+Notes:
+- Using MONITOR blocks the connection to the server for itself. It needs a dedicated connection
+- The user should create a channel of type string
+- This runs concurrently in the background. Trigger via the Start and Stop functions
+See further: Redis MONITOR command: https://redis.io/commands/monitor
+*/
+func (c cmdable) Monitor(ctx context.Context, ch chan string) *MonitorCmd {
+	cmd := newMonitorCmd(ctx, ch)
+	_ = c(ctx, cmd)
+	return cmd
+}

main_test.go

@@ -41,6 +41,11 @@ var (
 	redisAddr = ":" + redisPort
 )
 
+var (
+	rediStackPort = "6379"
+	rediStackAddr = ":" + rediStackPort
+)
+
 var (
 	sentinelAddrs = []string{":" + sentinelPort1, ":" + sentinelPort2, ":" + sentinelPort3}
 

monitor_test.go

@@ -0,0 +1,48 @@
+package redis_test
+
+import (
+	"context"
+	"time"
+
+	. "github.com/bsm/ginkgo/v2"
+	. "github.com/bsm/gomega"
+
+	"github.com/redis/go-redis/v9"
+)
+
+var _ = Describe("Monitor command", Label("monitor"), func() {
+	ctx := context.TODO()
+	var client *redis.Client
+
+	BeforeEach(func() {
+		client = redis.NewClient(&redis.Options{Addr: ":6379"})
+		Expect(client.FlushDB(ctx).Err()).NotTo(HaveOccurred())
+	})
+
+	AfterEach(func() {
+		Expect(client.Close()).NotTo(HaveOccurred())
+	})
+
+	It("should monitor", Label("monitor"), func() {
+		ress := make(chan string)
+		client1 := redis.NewClient(&redis.Options{Addr: rediStackAddr})
+		mn := client1.Monitor(ctx, ress)
+		mn.Start()
+		// Wait for the Redis server to be in monitoring mode.
+		time.Sleep(100 * time.Millisecond)
+		client.Set(ctx, "foo", "bar", 0)
+		client.Set(ctx, "bar", "baz", 0)
+		client.Set(ctx, "bap", 8, 0)
+		client.Get(ctx, "bap")
+		lst := []string{}
+		for i := 0; i < 5; i++ {
+			s := <-ress
+			lst = append(lst, s)
+		}
+		mn.Stop()
+		Expect(lst[0]).To(ContainSubstring("OK"))
+		Expect(lst[1]).To(ContainSubstring(`"set" "foo" "bar"`))
+		Expect(lst[2]).To(ContainSubstring(`"set" "bar" "baz"`))
+		Expect(lst[3]).To(ContainSubstring(`"set" "bap" "8"`))
+	})
+})