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tree_cache.go
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tree_cache.go
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package discovery
import (
"log"
"github.com/curator-go/curator"
"github.com/samuel/go-zookeeper/zk"
)
type TreeCache struct {
*ServiceDiscovery
existing map[string]map[string]*ServiceInstance
serviceListChanges chan bool
instanceListChanges chan string
}
func NewTreeCache(s *ServiceDiscovery) *TreeCache {
existing := make(map[string]map[string]*ServiceInstance)
return &TreeCache{s, existing, make(chan bool, 10), make(chan string, 10)}
}
func (t *TreeCache) Start() {
t.processServiceChanges()
go t.processInstanceChanges()
}
func (t *TreeCache) processInstanceChanges() {
for {
s, ok := getMostRecentString(t.instanceListChanges)
if !ok {
break
}
t.readAndWatch(s, "restarting")
}
log.Println("Done watching for instance changes")
}
func (t *TreeCache) readAndWatch(service, verb string) {
p := t.pathForName(service)
w := curator.NewWatcher(func(e *zk.Event) { t.instanceListChanges <- service })
children, err := t.client.GetChildren().UsingWatcher(w).ForPath(p)
if err != nil {
log.Printf("Error %s watch for %s: %s\n", verb, service, err)
} else {
t.readInstanceList(service, children)
}
}
func (t *TreeCache) readInstanceList(s string, children []string) {
instances := make([]*ServiceInstance, 0, len(children))
existing, ok := t.existing[s]
if !ok {
existing = make(map[string]*ServiceInstance)
}
for _, id := range children {
if e, found := existing[id]; found {
instances = append(instances, e)
continue
}
p := t.pathForInstance(s, id)
data, err := t.client.GetData().ForPath(p)
if err != nil {
log.Printf("Error fetching instance info for %s-%s (%s): %s\n", s, id, p, err)
continue
}
i, err := t.serializer.Deserialize(data)
if err != nil {
log.Printf("Error decoding instance info for %s-%s (%s): %s\n", s, id, p, err)
continue
}
i.Id = id // Just in case, since we treat use path for caching.
log.Printf("New instance for %s in %s (%s)\n", s, i.Spec(), id)
existing[id] = i
instances = append(instances, i)
}
t.existing[s] = existing
t.Services[s] = instances
}
func (t *TreeCache) processServiceChanges() {
watching := make(map[string]bool)
go func() {
for {
_, cont := getMostRecentBool(t.serviceListChanges)
if !cont {
break
}
t.readServices(watching)
}
log.Println("Done watching for service changes")
}()
t.readServices(watching)
}
func (t *TreeCache) readServices(watching map[string]bool) {
w := curator.NewWatcher(func(*zk.Event) { t.serviceListChanges <- true })
children, err := t.client.GetChildren().UsingWatcher(w).ForPath(t.basePath)
if err != nil {
log.Println("Error reading service list: ", err)
return
}
found := make(map[string]bool)
for _, i := range children {
found[i] = true
if !watching[i] {
t.readAndWatch(i, "starting")
watching[i] = true
}
}
for i, _ := range t.Services {
if !found[i] {
delete(t.Services, i)
}
}
}