本篇将讲解registration_db.go文件。
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package nsqlookupd import ( "fmt" "sync" "time" ) //定义了类型RegistrationDB，按字面意思：注册数据库，可理解为保存注册信息的数据库。 type RegistrationDB struct { //嵌入了RWMutex，所以在后面在方法中才可以调用Lock和Unlock方法 sync.RWMutex //一个MAP，以Registration为键，Producers为值 //看下面的代码中Producers的定义，它是Producer的slice，从中可看出Registration和Producer是一对多的关系 registrationMap map[Registration]Producers } //定义类型Registration， type Registration struct { Category string Key string SubKey string } //定义类型Registrations为Registration的slice type Registrations []Registration //定义类型PeerInfo type PeerInfo struct { id string RemoteAddress string `json:"remote_address"` Hostname string `json:"hostname"` BroadcastAddress string `json:"broadcast_address"` TcpPort int `json:"tcp_port"` HttpPort int `json:"http_port"` Version string `json:"version"` lastUpdate time.Time } //定义类型Producer type Producer struct { //PeerInfo的指针 peerInfo *PeerInfo //是否要被移除（tombstoned） tombstoned bool //移除时间 tombstonedAt time.Time } //定义类型Producers为Producer的slice type Producers []*Producer //Producer的String方法 func (p *Producer) String() string { return fmt.Sprintf("%s [%d, %d]", p.peerInfo.BroadcastAddress, p.peerInfo.TcpPort, p.peerInfo.HttpPort) } //本方法将Producer标记为墓碑状态 func (p *Producer) Tombstone() { p.tombstoned = true p.tombstonedAt = time.Now() } //被标记为墓碑状态,同时距标记时间小于lifetime值。 //比如：在0分0秒时调用了上一个函数Tombstone(),在0分1秒时调用函数IsTombstoned(5)，返回结果为true func (p *Producer) IsTombstoned(lifetime time.Duration) bool { return p.tombstoned && time.Now().Sub(p.tombstonedAt) < lifetime } //新建RegistrationDB类型的变量 func NewRegistrationDB() *RegistrationDB { return &RegistrationDB{ //make一个map registrationMap: make(map[Registration]Producers), } } //添加一个registration的key，只是把map的key设置了，value为一个空的Producers slice func (r *RegistrationDB) AddRegistration(k Registration) { r.Lock() defer r.Unlock() _, ok := r.registrationMap[k] if !ok { r.registrationMap[k] = make(Producers, 0) } } //将一个Producer添加到指定的Registration里 func (r *RegistrationDB) AddProducer(k Registration, p *Producer) bool { r.Lock() defer r.Unlock() //producers是一个slice producers := r.registrationMap[k] //遍历producers，看这个要添加的Producer是否已经存在了 found := false for _, producer := range producers { //通过producer.peerInfo.id来判断是否为同一个Producer if producer.peerInfo.id == p.peerInfo.id { found = true } } //只有要添加的Producer不存在时，才添加到Registration里 if found == false { r.registrationMap[k] = append(producers, p) } return !found } // 根据producer.peerInfo.id从registration里删除一个Producer func (r *RegistrationDB) RemoveProducer(k Registration, id string) (bool, int) { r.Lock() defer r.Unlock() //map中不存在key为k的Registration记录，所以也就无需删除了。 producers, ok := r.registrationMap[k] if !ok { return false, 0 } removed := false //创建空的Producers slice，所有不需要删除的Producer都移动这个slice里，并在移除完成后重新赋值给Registration //注意学习这种从slice中移除一个元素的方式 cleaned := make(Producers, 0) for _, producer := range producers { //id不相同，不是要删除的producer，移到cleaned slice里 if producer.peerInfo.id != id { cleaned = append(cleaned, producer) } else { removed = true } } // Note: this leaves keys in the DB even if they have empty lists //重新赋值，这确保了即使cleaned是一个空slice,键值k仍然会在RegistrationDB中存在 r.registrationMap[k] = cleaned //返回两个值，是否删除，新slice的长度 return removed, len(cleaned) } // 删除Registration和它对应的Producers func (r *RegistrationDB) RemoveRegistration(k Registration) { r.Lock() defer r.Unlock() delete(r.registrationMap, k) } //查找Registrations，可以看到，传入参数的三个变量与Registration类型里的三个值是对应的 func (r *RegistrationDB) FindRegistrations(category string, key string, subkey string) Registrations { r.RLock() defer r.RUnlock() results := make(Registrations, 0) for k := range r.registrationMap { //找出registrationMap中所有category，key，subkey与入参相同的Registration //IsMatch方法在后面的代码中定义 if !k.IsMatch(category, key, subkey) { continue } results = append(results, k) } return results } //根据category key subkey查找所有的Producer func (r *RegistrationDB) FindProducers(category string, key string, subkey string) Producers { r.RLock() defer r.RUnlock() results := make(Producers, 0) //遍历map for k, producers := range r.registrationMap { if !k.IsMatch(category, key, subkey) { continue } //遍历每个registration下的producers for _, producer := range producers { found := false //判断producer是否已经存在了，如果存在的话，就不添加了 for _, p := range results { if producer.peerInfo.id == p.peerInfo.id { found = true } } if found == false { results = append(results, producer) } } } return results } //根据producer.peerInfo.id查找所属的registration key func (r *RegistrationDB) LookupRegistrations(id string) Registrations { r.RLock() defer r.RUnlock() results := make(Registrations, 0) //遍历map for k, producers := range r.registrationMap { //遍历每个registration下的producers for _, p := range producers { if p.peerInfo.id == id { results = append(results, k) break } } } return results } //依据Registration类型里的三个变量，判断是否与Registration匹配 func (k Registration) IsMatch(category string, key string, subkey string) bool { if category != k.Category { return false } if key != "*" && k.Key != key { return false } if subkey != "*" && k.SubKey != subkey { return false } return true } //过滤获取所有与输入参数匹配的Registration func (rr Registrations) Filter(category string, key string, subkey string) Registrations { output := make(Registrations, 0) for _, k := range rr { if k.IsMatch(category, key, subkey) { output = append(output, k) } } return output } //获取MAP中所有Registration的key func (rr Registrations) Keys() []string { keys := make([]string, len(rr)) for i, k := range rr { keys[i] = k.Key } return keys } //获取MAP中所有Registration的subkey func (rr Registrations) SubKeys() []string { subkeys := make([]string, len(rr)) for i, k := range rr { subkeys[i] = k.SubKey } return subkeys } //获取所有可用的Producer func (pp Producers) FilterByActive(inactivityTimeout time.Duration, tombstoneLifetime time.Duration) Producers { now := time.Now() results := make(Producers, 0) for _, p := range pp { //满足以下两个判断条件的producer被忽略 //1 超过了活跃时间，在inactivityTimeout时间内没有与nsqlookupd交互 //2 被标记为墓碑状态，在tombstoneLifetime时间内标记的producer将被过滤掉 if now.Sub(p.peerInfo.lastUpdate) > inactivityTimeout || p.IsTombstoned(tombstoneLifetime) { continue } results = append(results, p) } return results } //获取Producers中所有的PeerInfo func (pp Producers) PeerInfo() []*PeerInfo { results := make([]*PeerInfo, 0) for _, p := range pp { results = append(results, p.peerInfo) } return results } |
读过上述代码，可总结出，registration_db.go文件用MAP以一对多的形式保存Producer，并提供一系列增、删、改、查的操作封装。同时使用RWMutex做并发控制。
