@@ -0,0 +1,126 @@
+package events
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+	"gitlab.com/tozd/go/errors"
+	"go.alanpearce.eu/x/log"
+	"go.uber.org/zap"
+)
+
+const db = 0
+const key = "run_id"
+const fallbackRunID uint64 = 210
+
+type RedisOptions struct {
+	Enabled    bool   `conf:"default:false"`
+	Address    string `conf:"default:localhost:6379"`
+	Username   string `conf:"default:default"`
+	Password   string `conf:"default:default"`
+	TLSEnabled bool   `conf:"default:false"`
+}
+
+type Logger struct {
+	log *zap.SugaredLogger
+}
+
+func (l *Logger) Printf(_ context.Context, format string, v ...interface{}) {
+	l.log.Infof(format, v...)
+}
+
+type RedisListener struct {
+	client *redis.Client
+	log    *log.Logger
+}
+
+func NewRedisListener(opts *RedisOptions, log *log.Logger) (*RedisListener, error) {
+	clientConfig := &redis.Options{
+		Addr:     opts.Address,
+		Username: opts.Username,
+		Password: opts.Password,
+	}
+	if opts.TLSEnabled {
+		clientConfig.TLSConfig = &tls.Config{
+			InsecureSkipVerify: false,
+			MinVersion:         tls.VersionTLS13,
+		}
+	}
+	redis.SetLogger(&Logger{log: log.GetLogger().Sugar()})
+	client := redis.NewClient(clientConfig)
+
+	log.Debug(
+		"connecting to redis",
+		"address",
+		opts.Address,
+		"username",
+		opts.Username,
+		"tls",
+		opts.TLSEnabled,
+	)
+
+	return &RedisListener{
+		client: client,
+		log:    log,
+	}, nil
+}
+
+func (rl *RedisListener) GetLatestRunID() (uint64, error) {
+	ctx, cancel := context.WithTimeout(context.TODO(), 2*time.Second)
+	defer cancel()
+
+	payload, err := rl.client.Get(ctx, key).Result()
+	if err != nil {
+		return fallbackRunID, errors.WithMessage(err, "could not get latest run ID")
+	}
+
+	runID, err := strconv.ParseUint(payload, 10, 64)
+	if err != nil {
+		return fallbackRunID, errors.WithMessage(err, "could not parse latest run ID")
+	}
+
+	rl.log.Debug("redis response", "payload", payload, "run_id", runID)
+
+	return runID, nil
+}
+
+// requires `redis-cli config set notify-keyspace-events KEA`
+func getKeyspaceName(key string) string {
+	return fmt.Sprintf("__keyspace@%d__:%s", db, key)
+}
+
+func (rl *RedisListener) Subscribe() (<-chan Event, error) {
+	events := make(chan Event, 1)
+	ctx := context.TODO()
+	channel := getKeyspaceName(key)
+	pubsub := rl.client.Subscribe(ctx, channel)
+	rl.log.Debug("subscribing", "channel", channel)
+
+	_, err := pubsub.Receive(ctx)
+	if err != nil {
+		return nil, errors.WithMessage(err, "could not subscribe to channel")
+	}
+
+	go func(ch <-chan *redis.Message) {
+		for msg := range ch {
+			rl.log.Debug("got event", "payload", msg.Payload)
+
+			runID, err := rl.GetLatestRunID()
+			if err != nil {
+				rl.log.Warn("could not get latest run ID")
+			}
+
+			events <- Event{
+				CIEvent: CIEvent{
+					RunID: runID,
+				},
+			}
+		}
+	}(pubsub.Channel())
+
+	return events, nil
+}