dtm/dtmsvr/topics.go

package dtmsvr

import (
	"errors"

	"github.com/dtm-labs/dtm/client/dtmcli/dtmimp"
	"github.com/dtm-labs/dtm/client/dtmcli/logger"
)

const (
	topicsCat = "topics"
)

var topicsMap = map[string]Topic{}

// Topic define topic info
type Topic struct {
	Name        string       `json:"k"`
	Subscribers []Subscriber `json:"v"`
	Version     uint64       `json:"version"`
}

// Subscriber define subscriber info
type Subscriber struct {
	URL    string `json:"url"`
	Remark string `json:"remark"`
}

func topic2urls(topic string) []string {
	urls := make([]string, len(topicsMap[topic].Subscribers))
	for k, subscriber := range topicsMap[topic].Subscribers {
		urls[k] = subscriber.URL
	}
	return urls
}

// Subscribe subscribes topic, create topic if not exist
func Subscribe(topic, url, remark string) error {
	if topic == "" {
		return errors.New("empty topic")
	}
	if url == "" {
		return errors.New("empty url")
	}

	newSubscriber := Subscriber{
		URL:    url,
		Remark: remark,
	}
	kvs := GetStore().FindKV(topicsCat, topic)
	if len(kvs) == 0 {
		return GetStore().CreateKV(topicsCat, topic, dtmimp.MustMarshalString([]Subscriber{newSubscriber}))
	}

	subscribers := []Subscriber{}
	dtmimp.MustUnmarshalString(kvs[0].V, &subscribers)
	for _, subscriber := range subscribers {
		if subscriber.URL == url {
			return errors.New("this url exists")
		}
	}
	subscribers = append(subscribers, newSubscriber)
	kvs[0].V = dtmimp.MustMarshalString(subscribers)
	return GetStore().UpdateKV(&kvs[0])
}

// Unsubscribe unsubscribes the topic
func Unsubscribe(topic, url string) error {
	if topic == "" {
		return errors.New("empty topic")
	}
	if url == "" {
		return errors.New("empty url")
	}

	kvs := GetStore().FindKV(topicsCat, topic)
	if len(kvs) == 0 {
		return errors.New("no such a topic")
	}
	subscribers := []Subscriber{}
	dtmimp.MustUnmarshalString(kvs[0].V, &subscribers)
	if len(subscribers) == 0 {
		return errors.New("this topic is empty")
	}
	n := len(subscribers)
	for k, subscriber := range subscribers {
		if subscriber.URL == url {
			subscribers = append(subscribers[:k], subscribers[k+1:]...)
			break
		}
	}
	if len(subscribers) == n {
		return errors.New("no such an url ")
	}
	kvs[0].V = dtmimp.MustMarshalString(subscribers)
	return GetStore().UpdateKV(&kvs[0])
}

// updateTopicsMap updates the topicsMap variable, unsafe for concurrent
func updateTopicsMap() {
	kvs := GetStore().FindKV(topicsCat, "")
	for _, kv := range kvs {
		topic := topicsMap[kv.K]
		if topic.Version >= kv.Version {
			continue
		}
		newTopic := Topic{}
		newTopic.Name = kv.K
		newTopic.Version = kv.Version
		dtmimp.MustUnmarshalString(kv.V, &newTopic.Subscribers)
		topicsMap[kv.K] = newTopic
		logger.Infof("topic updated. old topic:%v new topic:%v", topicsMap[kv.K], newTopic)
	}
	logger.Debugf("all topic updated. topic:%v", topicsMap)
}