404 lines
6.7 KiB
Go
404 lines
6.7 KiB
Go
// Package cache provides a registry cache
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package cache
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import (
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"math"
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"math/rand"
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"sync"
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"time"
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"github.com/micro/go-micro/registry"
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log "github.com/micro/go-micro/util/log"
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)
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// Cache is the registry cache interface
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type Cache interface {
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// embed the registry interface
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registry.Registry
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// stop the cache watcher
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Stop()
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}
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type Options struct {
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// TTL is the cache TTL
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TTL time.Duration
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}
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type Option func(o *Options)
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type cache struct {
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registry.Registry
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opts Options
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// registry cache
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sync.RWMutex
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cache map[string][]*registry.Service
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ttls map[string]time.Time
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watched map[string]bool
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exit chan bool
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}
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var (
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DefaultTTL = time.Minute
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)
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func backoff(attempts int) time.Duration {
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if attempts == 0 {
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return time.Duration(0)
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}
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return time.Duration(math.Pow(10, float64(attempts))) * time.Millisecond
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}
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// isValid checks if the service is valid
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func (c *cache) isValid(services []*registry.Service, ttl time.Time) bool {
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// no services exist
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if len(services) == 0 {
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return false
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}
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// ttl is invalid
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if ttl.IsZero() {
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return false
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}
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// time since ttl is longer than timeout
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if time.Since(ttl) > c.opts.TTL {
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return false
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}
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// ok
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return true
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}
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func (c *cache) quit() bool {
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select {
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case <-c.exit:
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return true
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default:
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return false
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}
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}
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func (c *cache) del(service string) {
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delete(c.cache, service)
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delete(c.ttls, service)
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}
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func (c *cache) get(service string) ([]*registry.Service, error) {
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// read lock
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c.RLock()
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// check the cache first
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services := c.cache[service]
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// get cache ttl
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ttl := c.ttls[service]
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// got services && within ttl so return cache
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if c.isValid(services, ttl) {
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// make a copy
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cp := registry.Copy(services)
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// unlock the read
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c.RUnlock()
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// return servics
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return cp, nil
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}
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// get does the actual request for a service and cache it
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get := func(service string) ([]*registry.Service, error) {
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// ask the registry
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services, err := c.Registry.GetService(service)
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if err != nil {
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return nil, err
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}
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// cache results
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c.Lock()
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c.set(service, registry.Copy(services))
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c.Unlock()
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return services, nil
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}
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// watch service if not watched
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if _, ok := c.watched[service]; !ok {
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go c.run(service)
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}
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// unlock the read lock
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c.RUnlock()
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// get and return services
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return get(service)
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}
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func (c *cache) set(service string, services []*registry.Service) {
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c.cache[service] = services
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c.ttls[service] = time.Now().Add(c.opts.TTL)
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}
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func (c *cache) update(res *registry.Result) {
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if res == nil || res.Service == nil {
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return
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}
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c.Lock()
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defer c.Unlock()
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services, ok := c.cache[res.Service.Name]
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if !ok {
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// we're not going to cache anything
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// unless there was already a lookup
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return
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}
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if len(res.Service.Nodes) == 0 {
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switch res.Action {
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case "delete":
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c.del(res.Service.Name)
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}
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return
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}
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// existing service found
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var service *registry.Service
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var index int
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for i, s := range services {
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if s.Version == res.Service.Version {
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service = s
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index = i
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}
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}
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switch res.Action {
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case "create", "update":
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if service == nil {
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c.set(res.Service.Name, append(services, res.Service))
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return
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}
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// append old nodes to new service
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for _, cur := range service.Nodes {
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var seen bool
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for _, node := range res.Service.Nodes {
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if cur.Id == node.Id {
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seen = true
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break
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}
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}
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if !seen {
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res.Service.Nodes = append(res.Service.Nodes, cur)
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}
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}
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services[index] = res.Service
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c.set(res.Service.Name, services)
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case "delete":
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if service == nil {
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return
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}
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var nodes []*registry.Node
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// filter cur nodes to remove the dead one
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for _, cur := range service.Nodes {
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var seen bool
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for _, del := range res.Service.Nodes {
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if del.Id == cur.Id {
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seen = true
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break
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}
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}
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if !seen {
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nodes = append(nodes, cur)
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}
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}
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// still got nodes, save and return
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if len(nodes) > 0 {
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service.Nodes = nodes
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services[index] = service
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c.set(service.Name, services)
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return
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}
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// zero nodes left
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// only have one thing to delete
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// nuke the thing
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if len(services) == 1 {
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c.del(service.Name)
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return
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}
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// still have more than 1 service
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// check the version and keep what we know
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var srvs []*registry.Service
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for _, s := range services {
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if s.Version != service.Version {
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srvs = append(srvs, s)
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}
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}
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// save
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c.set(service.Name, srvs)
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}
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}
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// run starts the cache watcher loop
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// it creates a new watcher if there's a problem
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func (c *cache) run(service string) {
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// set watcher
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c.Lock()
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c.watched[service] = true
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c.Unlock()
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// delete watcher on exit
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defer func() {
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c.Lock()
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delete(c.watched, service)
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c.Unlock()
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}()
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var a, b int
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for {
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// exit early if already dead
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if c.quit() {
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return
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}
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// jitter before starting
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j := rand.Int63n(100)
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time.Sleep(time.Duration(j) * time.Millisecond)
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// create new watcher
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w, err := c.Registry.Watch(
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registry.WatchService(service),
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)
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if err != nil {
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if c.quit() {
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return
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}
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d := backoff(a)
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if a > 3 {
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log.Log("rcache: ", err, " backing off ", d)
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a = 0
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}
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time.Sleep(d)
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a++
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continue
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}
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// reset a
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a = 0
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// watch for events
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if err := c.watch(w); err != nil {
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if c.quit() {
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return
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}
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d := backoff(b)
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if b > 3 {
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log.Log("rcache: ", err, " backing off ", d)
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b = 0
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}
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time.Sleep(d)
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b++
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continue
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}
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// reset b
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b = 0
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}
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}
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// watch loops the next event and calls update
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// it returns if there's an error
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func (c *cache) watch(w registry.Watcher) error {
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// used to stop the watch
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stop := make(chan bool)
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// manage this loop
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go func() {
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defer w.Stop()
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select {
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// wait for exit
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case <-c.exit:
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return
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// we've been stopped
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case <-stop:
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return
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}
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}()
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for {
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res, err := w.Next()
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if err != nil {
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close(stop)
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return err
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}
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c.update(res)
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}
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}
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func (c *cache) GetService(service string) ([]*registry.Service, error) {
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// get the service
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services, err := c.get(service)
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if err != nil {
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return nil, err
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}
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// if there's nothing return err
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if len(services) == 0 {
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return nil, registry.ErrNotFound
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}
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// return services
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return services, nil
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}
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func (c *cache) Stop() {
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select {
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case <-c.exit:
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return
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default:
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close(c.exit)
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}
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}
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func (c *cache) String() string {
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return "rcache"
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}
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// New returns a new cache
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func New(r registry.Registry, opts ...Option) Cache {
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rand.Seed(time.Now().UnixNano())
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options := Options{
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TTL: DefaultTTL,
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}
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for _, o := range opts {
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o(&options)
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}
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return &cache{
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Registry: r,
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opts: options,
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watched: make(map[string]bool),
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cache: make(map[string][]*registry.Service),
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ttls: make(map[string]time.Time),
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exit: make(chan bool),
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}
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}
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