support parsing client-cache invalidation messages

pubsub.go

@@ -409,6 +409,20 @@ func (c *PubSub) newMessage(reply interface{}) (interface{}, error) {
 			return &Pong{
 				Payload: reply[1].(string),
 			}, nil
+		case "invalidate":
+			switch payload := reply[1].(type) {
+			case []interface{}:
+				s := make([]string, len(payload))
+				for idx := range payload {
+					s[idx] = payload[idx].(string)
+				}
+				return &Message{
+					Channel:      "invalidate",
+					PayloadSlice: s,
+				}, nil
+			default:
+				return nil, fmt.Errorf("redis: unsupported invalidate message payload: %#v", payload)
+			}
 		default:
 			return nil, fmt.Errorf("redis: unsupported pubsub message: %q", kind)
 		}

pubsub_test.go

@@ -1,6 +1,8 @@
 package redis_test
 
 import (
+	"context"
+	"fmt"
 	"io"
 	"net"
 	"sync"
@@ -567,4 +569,99 @@ var _ = Describe("PubSub", func() {
 		Expect(msg.Channel).To(Equal("mychannel"))
 		Expect(msg.Payload).To(Equal(text))
 	})
+
+	It("supports client-cache invalidation messages", func() {
+		ch := make(chan []string, 2)
+		defer close(ch)
+		client := redis.NewClient(getOptsWithTracking(redisOptions(), func(keys []string) error {
+			ch <- keys
+			return nil
+		}))
+		defer client.Close()
+
+		v1 := client.Get(context.Background(), "foo")
+		Expect(v1.Val()).To(Equal(""))
+		s1 := client.Set(context.Background(), "foo", "bar", time.Duration(time.Minute))
+		Expect(s1.Val()).To(Equal("OK"))
+		v2 := client.Get(context.Background(), "foo")
+		Expect(v2.Val()).To(Equal("bar"))
+		// sleep a little to allow time for the first invalidation message to come through
+		time.Sleep(time.Second)
+		s2 := client.Set(context.Background(), "foo", "foobar", time.Duration(time.Minute))
+		Expect(s2.Val()).To(Equal("OK"))
+
+		for i := 0; i < 2; i++ {
+			select {
+			case keys := <-ch:
+				Expect(keys).ToNot(BeEmpty())
+				Expect(keys[0]).To(Equal("foo"))
+			case <-time.After(10 * time.Second):
+				// fail on timeouts
+				Fail("invalidation message wait timed out")
+			}
+		}
+	})
+
 })
+
+func getOptsWithTracking(opt *redis.Options, processInvalidKeysFunc func([]string) error) *redis.Options {
+	var mu sync.Mutex
+	invalidateClientID := int64(-1)
+	invalidateOpts := *opt
+	invalidateOpts.OnConnect = func(ctx context.Context, conn *redis.Conn) (err error) {
+		invalidateClientID, err = conn.ClientID(ctx).Result()
+		return
+	}
+
+	startBackgroundInvalidationSubscription := func(ctx context.Context) int64 {
+		mu.Lock()
+		defer mu.Unlock()
+
+		if invalidateClientID != -1 {
+			return invalidateClientID
+		}
+
+		invalidateClient := redis.NewClient(&invalidateOpts)
+		invalidations := invalidateClient.Subscribe(ctx, "__redis__:invalidate")
+
+		go func() {
+			defer func() {
+				invalidations.Close()
+				invalidateClient.Close()
+
+				mu.Lock()
+				invalidateClientID = -1
+				mu.Unlock()
+			}()
+
+			for {
+				msg, err := invalidations.ReceiveMessage(context.Background())
+				if err == io.EOF || err == context.Canceled {
+					return
+				} else if err != nil {
+					fmt.Printf("warning: subscription on key invalidations aborted: %s\n", err.Error())
+					// send back empty []string to fail the test
+					processInvalidKeysFunc([]string{})
+					return
+				}
+
+				processInvalidKeysFunc(msg.PayloadSlice)
+			}
+		}()
+
+		return invalidateClientID
+	}
+
+	opt.OnConnect = func(ctx context.Context, conn *redis.Conn) error {
+		invalidateClientID := startBackgroundInvalidationSubscription(ctx)
+		return conn.Process(
+			ctx,
+			redis.NewBoolCmd(
+				ctx,
+				"CLIENT", "TRACKING", "on",
+				"REDIRECT", fmt.Sprintf("%d", invalidateClientID),
+			),
+		)
+	}
+	return opt
+}