pubsub: redis implementation

cmd/drone-server/config/config.go

@@ -63,6 +63,7 @@ type (
 		Logging      Logging
 		Prometheus   Prometheus
 		Proxy        Proxy
+		Redis        Redis
 		Registration Registration
 		Registries   Registries
 		Repository   Repository
@@ -166,6 +167,11 @@ type (
 		EnableAnonymousAccess bool `envconfig:"DRONE_PROMETHEUS_ANONYMOUS_ACCESS" default:"false"`
 	}
 
+	// Redis provides the redis configuration.
+	Redis struct {
+		ConnectionString string `envconfig:"DRONE_REDIS_CONNECTION"`
+	}
+
 	// Repository provides the repository configuration.
 	Repository struct {
 		Filter     []string `envconfig:"DRONE_REPOSITORY_FILTER"`

cmd/drone-server/inject_store.go

@@ -34,6 +34,7 @@ import (
 	"github.com/drone/drone/store/template"
 	"github.com/drone/drone/store/user"
 
+	"github.com/go-redis/redis/v8"
 	"github.com/google/wire"
 	"github.com/sirupsen/logrus"
 )
@@ -55,6 +56,7 @@ var storeSet = wire.NewSet(
 	global.New,
 	step.New,
 	template.New,
+	provideRedisClient,
 )
 
 // provideDatabase is a Wire provider function that provides a
@@ -177,3 +179,18 @@ func provideUserStore(db *db.DB, enc encrypt.Encrypter, config config.Config) co
 	metric.UserCount(users)
 	return users
 }
+
+func provideRedisClient(config config.Config) (rdb *redis.Client, err error) {
+	if config.Redis.ConnectionString == "" {
+		return
+	}
+
+	options, err := redis.ParseURL(config.Redis.ConnectionString)
+	if err != nil {
+		return
+	}
+
+	rdb = redis.NewClient(options)
+
+	return
+}

cmd/drone-server/wire_gen.go

@@ -55,7 +55,14 @@ func InitializeApplication(config2 config.Config) (application, error) {
 	cronStore := cron.New(db)
 	repositoryStore := provideRepoStore(db)
 	buildStore := provideBuildStore(db)
-	corePubsub := pubsub.New()
+	redisClient, err := provideRedisClient(config2)
+	if err != nil {
+		return application{}, err
+	}
+	corePubsub, err := pubsub.New(redisClient)
+	if err != nil {
+		return application{}, err
+	}
 	stageStore := provideStageStore(db)
 	scheduler := provideScheduler(stageStore, config2)
 	statusService := provideStatusService(client, renewer, config2)

pubsub/hub.go

@@ -27,8 +27,8 @@ type hub struct {
 	subs map[*subscriber]struct{}
 }
 
-// New creates a new publish subscriber.
-func New() core.Pubsub {
+// newHub creates a new publish subscriber.
+func newHub() core.Pubsub {
 	return &hub{
 		subs: map[*subscriber]struct{}{},
 	}

pubsub/pubsub.go

@@ -0,0 +1,31 @@
+// Copyright 2021 Drone IO, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pubsub
+
+import (
+	"github.com/drone/drone/core"
+
+	"github.com/go-redis/redis/v8"
+)
+
+// New creates a new publish subscriber. If Redis client passed as parameter is not nil it uses
+// a Redis implementation, otherwise it uses an in-memory implementation.
+func New(rdb *redis.Client) (core.Pubsub, error) {
+	if rdb != nil {
+		return newRedis(rdb)
+	}
+
+	return newHub(), nil
+}

pubsub/redis.go

@@ -0,0 +1,126 @@
+// Copyright 2021 Drone IO, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pubsub
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/drone/drone/core"
+
+	"github.com/go-redis/redis/v8"
+)
+
+const channelPubSub = "drone-events"
+
+type hubRedis struct {
+	rdb *redis.Client
+}
+
+func (h *hubRedis) Publish(ctx context.Context, e *core.Message) (err error) {
+	data, err := json.Marshal(e)
+	if err != nil {
+		return
+	}
+
+	_, err = h.rdb.Publish(ctx, channelPubSub, data).Result()
+	if err != nil {
+		return
+	}
+
+	return
+}
+
+func (h *hubRedis) Subscribe(ctx context.Context) (<-chan *core.Message, <-chan error) {
+	messageCh := make(chan *core.Message, 100)
+	errCh := make(chan error)
+
+	go func() {
+		pubsub := h.rdb.Subscribe(ctx, channelPubSub)
+		ch := pubsub.Channel(redis.WithChannelSize(100))
+
+		defer func() {
+			_ = pubsub.Close()
+			close(messageCh)
+			close(errCh)
+		}()
+
+		err := pubsub.Ping(ctx)
+		if err != nil {
+			errCh <- err
+			return
+		}
+
+		for {
+			select {
+			case m, ok := <-ch:
+				if ok {
+					message := &core.Message{}
+					err = json.Unmarshal([]byte(m.Payload), message)
+					if err != nil {
+						fmt.Printf("error@pubsub: failed to unmarshal a message. %s\n", err)
+						continue
+					}
+					messageCh <- message
+				} else {
+					errCh <- fmt.Errorf("redis pubsub channel=%s closed", channelPubSub)
+					return
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return messageCh, errCh
+}
+
+func (h *hubRedis) Subscribers() int {
+	ctx, cancelFunc := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancelFunc()
+
+	v, err := h.rdb.Do(ctx, "pubsub", "numsub", channelPubSub).Result()
+	if err != nil {
+		fmt.Printf("error@pubsub: failed to get number of subscribers. %s\n", err)
+		return -1
+	}
+
+	values, ok := v.([]interface{}) // the result should be: [<channel name, string>, <subscriber count, int64>]
+	if !ok || len(values) != 2 {
+		return 0
+	}
+
+	if subscriberCount, ok := values[1].(int64); ok {
+		return int(subscriberCount)
+	}
+
+	return 0
+}
+
+func newRedis(rdb *redis.Client) (ps core.Pubsub, err error) {
+	_, err = rdb.Ping(context.Background()).Result()
+	if err != nil {
+		err = fmt.Errorf("redis not accessibe: %w", err)
+		return
+	}
+
+	ps = &hubRedis{
+		rdb: rdb,
+	}
+
+	return
+}