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service.go
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service.go
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package discovery
import (
"log"
"time"
"github.com/curator-go/curator"
)
type ServiceDiscovery struct {
client curator.CuratorFramework
// Cache of watched services
Services map[string][]*ServiceInstance
// Maintained service registrations
maintain map[string]*ServiceInstance
tree *TreeCache
// path under which to read/create registrations (/base/servicename/instance-id)
basePath string
serializer InstanceSerializer
connChanges chan bool
}
type Conn interface {
curator.CuratorFramework
}
func DefaultConn(conn string) (Conn, error) {
retryPolicy := curator.NewExponentialBackoffRetry(time.Second, 3, 15*time.Second)
client := curator.NewClient(conn, retryPolicy)
if err := client.Start(); err != nil {
return nil, err
}
return client, nil
}
func NewServiceDiscoveryAndConn(connString, basePath string) (*ServiceDiscovery, Conn, error) {
client, err := DefaultConn(connString)
if err != nil {
return nil, nil, err
}
return NewServiceDiscovery(client, basePath), client, nil
}
func NewServiceDiscovery(client Conn, basePath string) *ServiceDiscovery {
s := new(ServiceDiscovery)
s.client = client
s.basePath = basePath
s.maintain = make(map[string]*ServiceInstance)
s.serializer = &JsonInstanceSerializer{}
s.connChanges = make(chan bool, 10)
s.Services = make(map[string][]*ServiceInstance)
return s
}
func (s *ServiceDiscovery) MaintainRegistrations() error {
go s.maintainConn()
s.client.ConnectionStateListenable().AddListener(s)
return nil
}
func (s *ServiceDiscovery) Watch() error {
if err := curator.NewEnsurePath(s.basePath).Ensure(s.client.ZookeeperClient()); err != nil {
return err
}
s.tree = NewTreeCache(s)
s.tree.Start()
return nil
}
func (s *ServiceDiscovery) StateChanged(c curator.CuratorFramework, n curator.ConnectionState) {
s.connChanges <- n.Connected()
}
func (s *ServiceDiscovery) maintainConn() {
prev := false
for {
// wait for conn change
c, ok := getMostRecentBool(s.connChanges)
if !ok {
break
}
if c && c != prev {
log.Println("Reconnected. Re-registering services.")
s.ReregisterAll()
}
prev = c
}
}
func (s *ServiceDiscovery) pathForName(name string) string {
return curator.JoinPath(s.basePath, name)
}
func (s *ServiceDiscovery) pathForInstance(name, id string) string {
return curator.JoinPath(s.pathForName(name), id)
}
func (s *ServiceDiscovery) Register(service *ServiceInstance) error {
b, err := s.serializer.Serialize(service)
if err != nil {
return err
}
p := s.pathForInstance(service.Name, service.Id)
m := curator.PERSISTENT
if service.ServiceType == DYNAMIC {
m = curator.EPHEMERAL
}
for i := 0; i < 3; i++ {
log.Printf("Creating %s registration %s (attempt %d): %s\n", service.Name, service.Spec(), i+1, p)
_, err = s.client.Create().CreatingParentsIfNeeded().WithMode(m).ForPathWithData(p, b)
if err == nil {
s.maintain[service.Id] = service
return nil
}
}
return err
}
func (s *ServiceDiscovery) Unregister(service *ServiceInstance) error {
p := s.pathForInstance(service.Name, service.Id)
delete(s.maintain, service.Id)
log.Printf("Deleting %s registration %s: %s\n", service.Name, service.Spec(), p)
return s.client.Delete().ForPath(p)
}
func (s *ServiceDiscovery) ReregisterAll() error {
for _, i := range s.maintain {
if err := s.Register(i); err != nil {
return err
}
}
return nil
}
func (s *ServiceDiscovery) UnregisterAll() error {
for _, i := range s.maintain {
if err := s.Unregister(i); err != nil {
return err
}
}
return nil
}
type ServiceDiscoveryInstanceProvider struct {
name string
disco *ServiceDiscovery
strat ProviderStrategy
}
func (s *ServiceDiscoveryInstanceProvider) GetAllInstances() ([]*ServiceInstance, error) {
return s.disco.Services[s.name], nil
}
func (s *ServiceDiscoveryInstanceProvider) GetInstance() (*ServiceInstance, error) {
return s.strat.GetInstance(s)
}
func (s *ServiceDiscovery) Provider(name string) ServiceProvider {
return s.ProviderWithStrategy(name, NewRandomProvider())
}
func (s *ServiceDiscovery) ProviderWithStrategy(name string, strat ProviderStrategy) ServiceProvider {
return &ServiceDiscoveryInstanceProvider{name, s, strat}
}