package cache import ( "log" "sync" "time" "github.com/micro/go-micro/registry" "github.com/micro/go-micro/selector" ) /* Cache selector is a selector which uses the registry.Watcher to Cache service entries. It defaults to a TTL for 1 minute and causes a cache miss on the next request. */ type cacheSelector struct { so selector.Options ttl time.Duration // registry cache sync.Mutex cache map[string][]*registry.Service ttls map[string]time.Time // used to close or reload watcher reload chan bool exit chan bool } var ( DefaultTTL = time.Minute ) func (c *cacheSelector) quit() bool { select { case <-c.exit: return true default: return false } } // cp copies a service. Because we're caching handing back pointers would // create a race condition, so we do this instead // its fast enough func (c *cacheSelector) cp(current []*registry.Service) []*registry.Service { var services []*registry.Service for _, service := range current { // copy service s := new(registry.Service) *s = *service // copy nodes var nodes []*registry.Node for _, node := range service.Nodes { n := new(registry.Node) *n = *node nodes = append(nodes, n) } s.Nodes = nodes // copy endpoints var eps []*registry.Endpoint for _, ep := range service.Endpoints { e := new(registry.Endpoint) *e = *ep eps = append(eps, e) } s.Endpoints = eps // append service services = append(services, s) } return services } func (c *cacheSelector) del(service string) { delete(c.cache, service) delete(c.ttls, service) } func (c *cacheSelector) get(service string) ([]*registry.Service, error) { c.Lock() defer c.Unlock() // check the cache first services, ok := c.cache[service] ttl, kk := c.ttls[service] // got results, copy and return if ok && len(services) > 0 { // only return if its less than the ttl if kk && time.Since(ttl) < c.ttl { return c.cp(services), nil } } // cache miss or ttl expired // now ask the registry services, err := c.so.Registry.GetService(service) if err != nil { return nil, err } // we didn't have any results so cache c.cache[service] = c.cp(services) c.ttls[service] = time.Now().Add(c.ttl) return services, nil } func (c *cacheSelector) set(service string, services []*registry.Service) { c.cache[service] = services c.ttls[service] = time.Now().Add(c.ttl) } func (c *cacheSelector) update(res *registry.Result) { if res == nil || res.Service == nil { return } c.Lock() defer c.Unlock() services, ok := c.cache[res.Service.Name] if !ok { // we're not going to cache anything // unless there was already a lookup return } if len(res.Service.Nodes) == 0 { switch res.Action { case "delete": c.del(res.Service.Name) } return } // existing service found var service *registry.Service var index int for i, s := range services { if s.Version == res.Service.Version { service = s index = i } } switch res.Action { case "create", "update": if service == nil { c.set(res.Service.Name, append(services, res.Service)) return } // append old nodes to new service for _, cur := range service.Nodes { var seen bool for _, node := range res.Service.Nodes { if cur.Id == node.Id { seen = true break } } if !seen { res.Service.Nodes = append(res.Service.Nodes, cur) } } services[index] = res.Service c.set(res.Service.Name, services) case "delete": if service == nil { return } var nodes []*registry.Node // filter cur nodes to remove the dead one for _, cur := range service.Nodes { var seen bool for _, del := range res.Service.Nodes { if del.Id == cur.Id { seen = true break } } if !seen { nodes = append(nodes, cur) } } // still got nodes, save and return if len(nodes) > 0 { service.Nodes = nodes services[index] = service c.set(service.Name, services) return } // zero nodes left // only have one thing to delete // nuke the thing if len(services) == 1 { c.del(service.Name) return } // still have more than 1 service // check the version and keep what we know var srvs []*registry.Service for _, s := range services { if s.Version != service.Version { srvs = append(srvs, s) } } // save c.set(service.Name, srvs) } } // run starts the cache watcher loop // it creates a new watcher if there's a problem // reloads the watcher if Init is called // and returns when Close is called func (c *cacheSelector) run() { go c.tick() for { // exit early if already dead if c.quit() { return } // create new watcher w, err := c.so.Registry.Watch() if err != nil { log.Println(err) time.Sleep(time.Second) continue } // watch for events if err := c.watch(w); err != nil { log.Println(err) continue } } } // check cache and expire on each tick func (c *cacheSelector) tick() { t := time.NewTicker(time.Minute) for { select { case <-t.C: c.Lock() for service, expiry := range c.ttls { if d := time.Since(expiry); d > c.ttl { // TODO: maybe refresh the cache rather than blowing it away c.del(service) } } c.Unlock() case <-c.exit: return } } } // watch loops the next event and calls update // it returns if there's an error func (c *cacheSelector) watch(w registry.Watcher) error { defer w.Stop() // manage this loop go func() { // wait for exit or reload signal select { case <-c.exit: case <-c.reload: } // stop the watcher w.Stop() }() for { res, err := w.Next() if err != nil { return err } c.update(res) } } func (c *cacheSelector) Init(opts ...selector.Option) error { for _, o := range opts { o(&c.so) } // reload the watcher go func() { select { case <-c.exit: return default: c.reload <- true } }() return nil } func (c *cacheSelector) Options() selector.Options { return c.so } func (c *cacheSelector) Select(service string, opts ...selector.SelectOption) (selector.Next, error) { sopts := selector.SelectOptions{ Strategy: c.so.Strategy, } for _, opt := range opts { opt(&sopts) } // get the service // try the cache first // if that fails go directly to the registry services, err := c.get(service) if err != nil { return nil, err } // apply the filters for _, filter := range sopts.Filters { services = filter(services) } // if there's nothing left, return if len(services) == 0 { return nil, selector.ErrNotFound } return sopts.Strategy(services), nil } func (c *cacheSelector) Mark(service string, node *registry.Node, err error) { return } func (c *cacheSelector) Reset(service string) { c.Lock() c.del(service) c.Unlock() } // Close stops the watcher and destroys the cache func (c *cacheSelector) Close() error { c.Lock() c.cache = make(map[string][]*registry.Service) c.Unlock() select { case <-c.exit: return nil default: close(c.exit) } return nil } func (c *cacheSelector) String() string { return "cache" } func NewSelector(opts ...selector.Option) selector.Selector { sopts := selector.Options{ Strategy: selector.Random, } for _, opt := range opts { opt(&sopts) } if sopts.Registry == nil { sopts.Registry = registry.DefaultRegistry } ttl := DefaultTTL if sopts.Context != nil { if t, ok := sopts.Context.Value(ttlKey{}).(time.Duration); ok { ttl = t } } c := &cacheSelector{ so: sopts, ttl: ttl, cache: make(map[string][]*registry.Service), ttls: make(map[string]time.Time), reload: make(chan bool, 1), exit: make(chan bool), } go c.run() return c }