harness-drone/pubsub/hub_redis.go

124 lines
2.9 KiB
Go

// 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.
// +build !oss
package pubsub
import (
"context"
"encoding/json"
"fmt"
"os"
"sync"
"github.com/drone/drone/core"
"github.com/drone/drone/service/redisdb"
)
const (
redisPubSubEvents = "drone-events"
redisPubSubCapacity = 100
)
func newHubRedis(r redisdb.RedisDB) core.Pubsub {
h := &hubRedis{
rdb: r,
subscribers: make(map[chan<- *core.Message]struct{}),
}
go r.Subscribe(context.Background(), redisPubSubEvents, redisPubSubCapacity, h)
return h
}
type hubRedis struct {
sync.Mutex
rdb redisdb.RedisDB
subscribers map[chan<- *core.Message]struct{}
}
// Publish publishes a new message. All subscribers will get it.
func (h *hubRedis) Publish(ctx context.Context, e *core.Message) (err error) {
client := h.rdb.Client()
data, err := json.Marshal(e)
if err != nil {
return
}
_, err = client.Publish(ctx, redisPubSubEvents, data).Result()
if err != nil {
return
}
return
}
// Subscribe add a new subscriber. The subscriber gets event until its context is not finished.
func (h *hubRedis) Subscribe(ctx context.Context) (<-chan *core.Message, <-chan error) {
chMessage := make(chan *core.Message, redisPubSubCapacity)
chErr := make(chan error)
h.Lock()
h.subscribers[chMessage] = struct{}{}
h.Unlock()
go func() {
<-ctx.Done()
h.Lock()
delete(h.subscribers, chMessage)
h.Unlock()
close(chMessage)
close(chErr)
}()
return chMessage, chErr
}
// Subscribers returns number of subscribers.
func (h *hubRedis) Subscribers() (int, error) {
h.Lock()
n := len(h.subscribers)
h.Unlock()
return n, nil
}
// ProcessMessage relays the message to all subscribers listening to drone events.
// It is a part of redisdb.PubSubProcessor implementation and it's called internally by redisdb.Subscribe.
func (h *hubRedis) ProcessMessage(s string) {
message := &core.Message{}
err := json.Unmarshal([]byte(s), message)
if err != nil {
// Ignore invalid messages. This is a "should not happen" situation,
// because messages are encoded as json in Publish().
_, _ = fmt.Fprintf(os.Stderr, "pubsub/redis: failed to unmarshal a message. %s\n", err)
return
}
h.Lock()
for ss := range h.subscribers {
select {
case ss <- message:
default: // messages are lost if a subscriber channel reaches its capacity
}
}
h.Unlock()
}
// ProcessError is a part of redisdb.PubSubProcessor implementation.
func (h *hubRedis) ProcessError(error) {}