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zookeeper.go
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zookeeper.go
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/*
package zookeeper contains definition of discovery logic to announce rpc
instances in zookeeper and resolve them.
*/
package zookeeper
import (
"strings"
"sync"
"time"
log "github.com/Sirupsen/logrus"
"github.com/mouadino/go-nano/discovery"
"github.com/mouadino/go-nano/serializer"
"github.com/samuel/go-zookeeper/zk"
)
type zookeeperAnnounceResolver struct {
logger *log.Logger
endpoints []string
serial serializer.Serializer
timeout time.Duration
chroot string
conn *zk.Conn
perms int32
mu sync.RWMutex
cache map[string]*discovery.Service
}
// Timeout option configure connection timeout to zookeeper, default 3 seconds.
func Timeout(timeout time.Duration) func(z *zookeeperAnnounceResolver) {
return func(z *zookeeperAnnounceResolver) {
z.timeout = timeout
}
}
// Chroot option configure zookeeper path chroot, default "nano-services".
func Chroot(chroot string) func(z *zookeeperAnnounceResolver) {
return func(z *zookeeperAnnounceResolver) {
z.chroot = chroot
}
}
// Perms option configure zookeeper path permission, default to open for all.
func Perms(perms int32) func(z *zookeeperAnnounceResolver) {
return func(z *zookeeperAnnounceResolver) {
z.perms = perms
}
}
// Serializer option configure serializer to use when reading values instance data
// from zookeeper, default to json serializer.
func Serializer(serial serializer.Serializer) func(z *zookeeperAnnounceResolver) {
return func(z *zookeeperAnnounceResolver) {
z.serial = serial
}
}
// New creates a AnnounceResolver for zookeeper.
func New(endpoints []string, options ...func(z *zookeeperAnnounceResolver)) discovery.AnnounceResolver {
z := &zookeeperAnnounceResolver{
endpoints: endpoints,
logger: log.New(),
chroot: "nano-services",
timeout: 3 * time.Second,
perms: zk.PermAll,
serial: serializer.JSONSerializer{},
cache: make(map[string]*discovery.Service),
}
for _, opt := range options {
opt(z)
}
return z
}
// Resolve the given service name to a Service structure.
func (z *zookeeperAnnounceResolver) Resolve(name string) (*discovery.Service, error) {
err := z.ensureConn()
if err != nil {
return nil, err
}
z.mu.RLock()
s, ok := z.cache[name]
z.mu.RUnlock()
if ok {
return s, nil
}
s, err = z.resolve(name)
if err != nil {
z.mu.Lock()
z.cache[name] = s
z.mu.Unlock()
}
return s, err
}
func (z *zookeeperAnnounceResolver) resolve(name string) (*discovery.Service, error) {
children, _, events, err := z.conn.ChildrenW(z.getPath(name))
if err != nil {
return nil, err
}
service := &discovery.Service{
Name: name,
Instances: z.getInstances(name, children),
}
go z.watchEvents(events, func(ev zk.Event) {
z.onPathChange(ev, service)
})
return service, nil
}
func (z *zookeeperAnnounceResolver) getInstances(name string, children []string) []discovery.Instance {
instances := []discovery.Instance{}
for _, id := range children {
meta, err := z.getInstanceData(name, id)
if err != nil {
continue
}
instances = append(instances, discovery.Instance{
ID: id,
Endpoint: meta["endpoint"].(string),
Meta: meta,
})
}
return instances
}
func (z *zookeeperAnnounceResolver) getInstanceData(name, id string) (discovery.InstanceMeta, error) {
data, _, err := z.conn.Get(z.getPath(name, id))
if err != nil {
z.logger.Errorf("zookeeper get failed for %s: %s", id, err)
return nil, err
}
var meta discovery.InstanceMeta
err = z.serial.Decode(data, &meta)
if err != nil {
z.logger.Errorf("zookeeper metadata parse failed for %s: %s", id, err)
return nil, err
}
return meta, nil
}
func (z *zookeeperAnnounceResolver) onPathChange(ev zk.Event, service *discovery.Service) {
z.logger.WithFields(log.Fields{
"event": ev.Type,
"name": service.Name,
"path": ev.Path,
}).Debug("zookeeper path changed")
children, _, err := z.conn.Children(z.getPath(service.Name))
if err != nil {
z.logger.Debug("zookeeper error getting children ", err)
return
}
service.Instances = z.getInstances(service.Name, children)
}
// Announce instance for discovery in zookeeper under given name.
func (z *zookeeperAnnounceResolver) Announce(name string, instance discovery.Instance) error {
err := z.ensureConn()
if err != nil {
return err
}
metadata, err := z.serial.Encode(instance.Meta)
if err != nil {
return err
}
return z.createNode(z.getPath(name, instance.ID), metadata)
}
func (z *zookeeperAnnounceResolver) ensureConn() error {
if z.conn != nil {
return nil
}
conn, events, err := zk.Connect(z.endpoints, z.timeout)
if err != nil {
return err
}
go z.watchEvents(events, func(ev zk.Event) {
z.logger.WithFields(log.Fields{
"event": ev.Type,
}).Debug("zookeeper changed state")
})
z.conn = conn
z.conn.SetLogger(z.logger)
return err
}
func (z *zookeeperAnnounceResolver) watchEvents(events <-chan zk.Event, callback func(zk.Event)) {
for ev := range events {
callback(ev)
}
}
func (z *zookeeperAnnounceResolver) getPath(keys ...string) string {
path := append([]string{z.chroot}, keys...)
return "/" + strings.Join(path, "/")
}
func (z *zookeeperAnnounceResolver) createNode(path string, data []byte) error {
acl := zk.WorldACL(z.perms)
flags := int32(0)
// TODO: Refactor me.
keys := strings.Split(path, "/")
d := []byte{}
var p string
for i, _ := range keys {
p = strings.Join(keys[:i+1], "/")
if p == "" {
continue
}
if p == path {
d = data
flags = int32(zk.FlagEphemeral)
}
_, err := z.conn.Create(p, d, flags, acl)
if err != nil && err != zk.ErrNodeExists {
return err
}
}
return nil
}