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disco.go
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disco.go
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package disco
import (
"crypto/rand"
"io"
"encoding/json"
"fmt"
"sync/atomic"
"time"
"expvar"
"strings"
"sync"
"bytes"
"encoding/binary"
"sort"
"github.com/signalfx/golib/errors"
"github.com/samuel/go-zookeeper/zk"
"github.com/signalfx/golib/log"
"github.com/signalfx/golib/logkey"
"github.com/signalfx/golib/pointer"
"github.com/signalfx/golib/zkplus"
)
// ServiceInstance defines a remote service and is similar to
// https://curator.apache.org/apidocs/org/apache/curator/x/discovery/ServiceInstanceBuilder.html
type ServiceInstance struct {
ID string `json:"id"`
Name string `json:"name"`
Payload interface{} `json:"payload,omitempty"`
Address string `json:"address"`
Port uint16 `json:"port"`
RegistrationTimeUTC int64 `json:"registrationTimeUTC"`
SslPort *uint16 `json:"sslPort"`
ServiceType string `json:"serviceType"`
URISpec *string `json:"uriSpec"`
}
func (s *ServiceInstance) uniqueHash() []byte {
buf := new(bytes.Buffer)
errors.PanicIfErrWrite(buf.Write([]byte(s.ID)))
log.IfErr(log.Panic, binary.Write(buf, binary.BigEndian, s.RegistrationTimeUTC))
return buf.Bytes()
}
// DialString is a string that net.Dial() can accept that will connect to this service's Port
func (s *ServiceInstance) DialString() string {
return fmt.Sprintf("%s:%d", s.Address, s.Port)
}
// ChangeWatch is a callback you can register on a service that is executed whenever the service's
// instances change
type ChangeWatch func()
// Service is a set of ServiceInstance that describe a discovered service
type Service struct {
services atomic.Value // []ServiceInstance
name string
ignoreUpdates int64
stateLog log.Logger
watchLock sync.Mutex
watches []ChangeWatch
}
// ZkConn does zookeeper connections
type ZkConn interface {
GetW(path string) ([]byte, *zk.Stat, <-chan zk.Event, error)
Create(path string, data []byte, flags int32, acl []zk.ACL) (string, error)
ChildrenW(path string) ([]string, *zk.Stat, <-chan zk.Event, error)
ExistsW(path string) (bool, *zk.Stat, <-chan zk.Event, error)
Delete(path string, version int32) error
Close()
}
// ZkConnCreator creates Zk connections for disco to use.
type ZkConnCreator interface {
Connect() (ZkConn, <-chan zk.Event, error)
}
// ZkConnCreatorFunc gives you a ZkConnCreator out of a function
type ZkConnCreatorFunc func() (ZkConn, <-chan zk.Event, error)
// Connect to a zookeeper endpoint
func (z ZkConnCreatorFunc) Connect() (ZkConn, <-chan zk.Event, error) {
return z()
}
// Disco is a service discovery framework orchestrated via zookeeper
type Disco struct {
zkConnCreator ZkConnCreator
zkConn ZkConn
eventChan <-chan zk.Event
GUIDbytes [16]byte
publishAddress string
myAdvertisedServices map[string]ServiceInstance
myEphemeralNodes map[string][]byte
shouldQuit chan struct{}
eventLoopDone chan struct{}
ninjaMode bool
watchedMutex sync.RWMutex
watchedServices map[string]*Service
manualEvents chan zk.Event
stateLog log.Logger
jsonMarshal func(v interface{}) ([]byte, error)
}
// BuilderConnector satisfies the disco zk connect interface for a zkplus.Builder
func BuilderConnector(b *zkplus.Builder) ZkConnCreator {
return ZkConnCreatorFunc(func() (ZkConn, <-chan zk.Event, error) {
return b.BuildDirect()
})
}
// Config controls optional parameters for disco
type Config struct {
RandomSource io.Reader
Logger log.Logger
}
// DefaultConfig is used if any config values are nil
var DefaultConfig = &Config{
RandomSource: rand.Reader,
Logger: log.DefaultLogger.CreateChild(),
}
// New creates a disco discovery/publishing service
func New(zkConnCreator ZkConnCreator, publishAddress string, config *Config) (*Disco, error) {
conf := pointer.FillDefaultFrom(config, DefaultConfig).(*Config)
var GUID [16]byte
_, err := io.ReadFull(conf.RandomSource, GUID[:16])
if err != nil {
return nil, errors.Annotate(err, "cannot create random GUID")
}
d := &Disco{
zkConnCreator: zkConnCreator,
myAdvertisedServices: make(map[string]ServiceInstance),
myEphemeralNodes: make(map[string][]byte),
GUIDbytes: GUID,
jsonMarshal: json.Marshal,
publishAddress: publishAddress,
shouldQuit: make(chan struct{}),
eventLoopDone: make(chan struct{}),
watchedServices: make(map[string]*Service),
manualEvents: make(chan zk.Event),
}
d.stateLog = log.NewContext(conf.Logger).With(logkey.GUID, d.GUID())
d.zkConn, d.eventChan, err = zkConnCreator.Connect()
if err != nil {
return nil, errors.Annotate(err, "cannot create first zk connection")
}
go d.eventLoop()
return d, nil
}
// NinjaMode will have future Advertise() calls no-op. This is useful when
// connecting an application to a production or testing tier and not wanting to advertise yourself
// for incomming connections,
func (d *Disco) NinjaMode(ninjaMode bool) {
d.ninjaMode = ninjaMode
}
func isServiceModificationEvent(eventType zk.EventType) bool {
return eventType == zk.EventNodeDataChanged || eventType == zk.EventNodeDeleted || eventType == zk.EventNodeCreated || eventType == zk.EventNodeChildrenChanged
}
func (d *Disco) eventLoop() {
defer close(d.eventLoopDone)
for {
select {
case <-d.shouldQuit:
return
case e := <-d.manualEvents:
log.IfErr(d.stateLog, d.processZkEvent(&e))
case e := <-d.eventChan:
log.IfErr(d.stateLog, d.processZkEvent(&e))
}
}
}
var errServiceDoesNotExist = errors.New("could not find service to refresh")
func (d *Disco) logInfoState(e *zk.Event) bool {
if e.State == zk.StateDisconnected {
d.stateLog.Log(logkey.ZkEvent, e, "Disconnected from zookeeper. Will attempt to remake connection.")
return true
}
if e.State == zk.StateConnecting {
d.stateLog.Log(logkey.ZkEvent, e, "Server is now attempting to reconnect.")
return true
}
return false
}
func (d *Disco) processZkEvent(e *zk.Event) error {
d.stateLog.Log(logkey.ZkEvent, e, "disco event seen")
d.logInfoState(e)
if e.State == zk.StateHasSession {
return d.refreshAll()
}
serviceName := ""
if isServiceModificationEvent(e.Type) {
// serviceName is in () /(___)/___
serviceName = e.Path
if serviceName[0] == '/' {
serviceName = serviceName[1:]
}
parts := strings.SplitN(serviceName, "/", 2)
serviceName = parts[0]
}
if serviceName != "" {
d.stateLog.Log(logkey.DiscoService, serviceName, "refresh on service")
service, err := func() (*Service, error) {
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
s, exist := d.watchedServices[serviceName]
if exist {
return s, nil
}
return nil, errServiceDoesNotExist
}()
if err != nil {
d.stateLog.Log(logkey.ZkEvent, e, logkey.DiscoService, serviceName, log.Err, err, "Unable to find parent")
} else {
d.stateLog.Log(logkey.DiscoService, service, "refreshing")
return service.refresh(d.zkConn)
}
}
return nil
}
// DeleteAdvertisedServices deletes all advertised services
func (d *Disco) DeleteAdvertisedServices() {
d.watchedMutex.RLock()
services := make([]string, 0, len(d.myAdvertisedServices))
for s := range d.myAdvertisedServices {
services = append(services, s)
}
d.watchedMutex.RUnlock()
for _, serviceName := range services {
d.DeleteAdvertisedService(serviceName)
}
}
// DeleteAdvertisedService deletes a specific advertised service name
func (d *Disco) DeleteAdvertisedService(serviceName string) {
l := log.NewContext(d.stateLog).With(logkey.DiscoService, serviceName)
servicePath := d.servicePath(serviceName)
exists, stat, _, err := d.zkConn.ExistsW(servicePath)
if err == nil && exists {
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
l.Log(logkey.Name, serviceName, "deleting advertised service")
log.IfErr(l, d.zkConn.Delete(servicePath, stat.Version))
delete(d.myAdvertisedServices, serviceName)
}
}
// Close any open disco connections making this disco unreliable for future updates
func (d *Disco) Close() {
d.DeleteAdvertisedServices()
close(d.shouldQuit)
<-d.eventLoopDone
d.zkConn.Close()
}
func (d *Disco) servicePath(serviceName string) string {
return fmt.Sprintf("/%s/%s", serviceName, d.GUID())
}
// GUID that this disco advertises itself as
func (d *Disco) GUID() string {
return fmt.Sprintf("%x", d.GUIDbytes)
}
func (d *Disco) myServiceData(serviceName string, payload interface{}, port uint16) ServiceInstance {
return ServiceInstance{
ID: d.GUID(),
Name: serviceName,
Payload: payload,
Address: d.publishAddress,
Port: port,
RegistrationTimeUTC: time.Now().UnixNano() / int64(time.Millisecond),
SslPort: nil,
ServiceType: "DYNAMIC",
URISpec: nil,
}
}
func (d *Disco) refreshAll() error {
d.stateLog.Log("Refreshing all zk services")
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
for serviceName, serviceInstance := range d.myAdvertisedServices {
l := log.NewContext(d.stateLog).With(logkey.DiscoService, serviceName)
l.Log("refresh for service")
log.IfErr(l, d.advertiseInZK(false, serviceName, serviceInstance))
}
for path, payload := range d.myEphemeralNodes {
l := log.NewContext(d.stateLog).With(logkey.DiscoService, path)
l.Log("refresh for node")
log.IfErr(l, d.createInZk(false, path, payload))
}
for _, service := range d.watchedServices {
log.IfErr(d.stateLog, service.refresh(d.zkConn))
}
return nil
}
func (d *Disco) createInZk(deleteIfExists bool, pathDirectory string, instanceBytes []byte) error {
servicePath := d.servicePath(pathDirectory)
exists, stat, _, err := d.zkConn.ExistsW(servicePath)
if err != nil {
return errors.Annotatef(err, "cannot ExistsW %s", servicePath)
}
if !deleteIfExists && exists {
d.stateLog.Log("Service already exists. Will not delete it")
return nil
}
if exists {
d.stateLog.Log(logkey.ZkPath, servicePath, "Clearing out old service path")
// clear out the old version
if err = d.zkConn.Delete(servicePath, stat.Version); err != nil {
return errors.Annotatef(err, "unhandled ZK Delete of %s", servicePath)
}
}
_, err = d.zkConn.Create(servicePath, instanceBytes, zk.FlagEphemeral, zk.WorldACL(zk.PermAll))
return err
}
func (d *Disco) advertiseInZK(deleteIfExists bool, serviceName string, instanceData ServiceInstance) error {
// Need to create service root node
_, err := d.zkConn.Create(fmt.Sprintf("/%s", serviceName), []byte{}, 0, zk.WorldACL(zk.PermAll))
if err != nil && errors.Tail(err) != zk.ErrNodeExists {
return errors.Annotatef(err, "unhandled ZK error on Create of %s", serviceName)
}
instanceBytes, err := d.jsonMarshal(instanceData)
if err != nil {
return errors.Annotatef(err, "cannot JSON marshal data %v", instanceData)
}
if err = d.createInZk(deleteIfExists, serviceName, instanceBytes); err != nil {
return errors.Annotatef(err, "cannot create node to advertise myself in disco")
}
return nil
}
// ErrDuplicateAdvertise is returned by Advertise if users try to Advertise the same service name
// twice
var ErrDuplicateAdvertise = errors.New("service name already advertised")
func (d *Disco) innerPreable(path string, err *error) func() {
if d.ninjaMode {
d.stateLog.Log(logkey.DiscoService, path, "Not advertising because disco is in ninja mode")
return nil
}
return func() {
d.stateLog.Log(log.Err, *err, "advertised result")
if *err == nil {
d.manualEvents <- zk.Event{
Type: zk.EventNodeChildrenChanged,
State: zk.StateConnected,
Path: path,
}
}
}
}
// Advertise yourself as hosting a service
func (d *Disco) Advertise(serviceName string, payload interface{}, port uint16) (err error) {
f := d.innerPreable(serviceName, &err)
if f == nil {
return nil
}
// Note: Important to defer after we release the mutex since the chan send could be a blocking
// operation
defer f()
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
d.stateLog.Log(logkey.DiscoService, serviceName, "Advertising myself on a service")
_, exists := d.myAdvertisedServices[serviceName]
if exists {
return ErrDuplicateAdvertise
}
service := d.myServiceData(serviceName, payload, port)
if err := d.advertiseInZK(true, serviceName, service); err != nil {
return errors.Annotatef(err, "cannot advertise %s in disco", serviceName)
}
d.myAdvertisedServices[serviceName] = service
return nil
}
// CreatePersistentEphemeralNode creates a persistent ephemeral node
func (d *Disco) CreatePersistentEphemeralNode(path string, payload []byte) (err error) {
f := d.innerPreable(path, &err)
if f == nil {
return nil
}
// Note: Important to defer after we release the mutex since the chan send could be a blocking
// operation
defer f()
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
_, err = d.zkConn.Create(fmt.Sprintf("/%s", path), []byte{}, 0, zk.WorldACL(zk.PermAll))
if err != nil && errors.Tail(err) != zk.ErrNodeExists {
return errors.Annotatef(err, "unhandled ZK error on Create of %s", path)
}
if err = d.createInZk(true, path, payload); err != nil {
return errors.Annotatef(err, "cannot create persistent ephemeral node")
}
d.myEphemeralNodes[path] = payload
return nil
}
// Var returns an expvar variable that shows all the current disco services and the current
// list of endpoints seen for each service
func (d *Disco) Var() expvar.Var {
return expvar.Func(func() interface{} {
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
ret := make(map[string][]ServiceInstance)
for serviceName, service := range d.watchedServices {
ret[serviceName] = service.ServiceInstances()
}
return ret
})
}
// Services advertising for serviceName
func (d *Disco) Services(serviceName string) (*Service, error) {
d.watchedMutex.Lock()
defer d.watchedMutex.Unlock()
s, exist := d.watchedServices[serviceName]
if exist {
return s, nil
}
ret := &Service{
name: serviceName,
stateLog: log.NewContext(d.stateLog).With(logkey.DiscoService, serviceName),
}
ret.services.Store([]ServiceInstance{})
refreshRes := ret.refresh(d.zkConn)
if refreshRes == nil {
d.watchedServices[serviceName] = ret
return ret, nil
}
return nil, errors.Annotatef(refreshRes, "cannot refresh service %s", serviceName)
}
type serviceInstanceList []ServiceInstance
func (x serviceInstanceList) Len() int {
return len(x)
}
func (x serviceInstanceList) Less(i, j int) bool {
return x[i].RegistrationTimeUTC < x[j].RegistrationTimeUTC
}
func (x serviceInstanceList) Swap(i, j int) {
x[i], x[j] = x[j], x[i]
}
// ServiceInstances that represent instances of this service in your system
func (s *Service) ServiceInstances() []ServiceInstance {
svcs := s.services.Load().([]ServiceInstance)
ret := make([]ServiceInstance, len(svcs))
copy(ret, svcs)
sort.Sort(serviceInstanceList(ret))
return ret
}
// ForceInstances overrides a disco service to have exactly the passed instances forever. Useful
// for debugging.
func (s *Service) ForceInstances(instances []ServiceInstance) {
atomic.StoreInt64(&s.ignoreUpdates, 1)
s.watchLock.Lock()
defer s.watchLock.Unlock()
s.services.Store(instances)
for _, watch := range s.watches {
watch()
}
}
// Watch for changes to the members of this service
func (s *Service) Watch(watch ChangeWatch) {
s.watchLock.Lock()
defer s.watchLock.Unlock()
s.watches = append(s.watches, watch)
}
func (s *Service) String() string {
s.watchLock.Lock()
defer s.watchLock.Unlock()
return fmt.Sprintf("name=%s|len(watch)=%d|instances=%v", s.name, len(s.watches), s.services.Load())
}
func (s *Service) byteHashes() string {
all := []string{}
for _, i := range s.ServiceInstances() {
all = append(all, string(i.uniqueHash()))
}
slice := sort.StringSlice(all)
slice.Sort()
r := ""
for _, s := range all {
r += s
}
return r
}
func childrenServices(logger log.Logger, serviceName string, children []string, zkConn ZkConn) ([]ServiceInstance, error) {
logger.Log("getting services")
ret := make([]ServiceInstance, len(children))
allErrors := make([]error, 0, len(children))
var wg sync.WaitGroup
for index, child := range children {
wg.Add(1)
go func(child string, instanceAddr *ServiceInstance) {
defer wg.Done()
var bytes []byte
var err2 error
bytes, _, _, err2 = zkConn.GetW(fmt.Sprintf("/%s/%s", serviceName, child))
if err2 != nil {
allErrors = append(allErrors, errors.Annotatef(err2, "fail to GetW %s/%s", serviceName, child))
return
}
err2 = json.Unmarshal(bytes, instanceAddr)
if err2 != nil {
allErrors = append(allErrors, errors.Annotatef(err2, "cannot unmarshal %s from %v", child, bytes))
return
}
}(child, &ret[index]) // <--- Important b/c inside range
}
wg.Wait()
return ret, errors.NewMultiErr(allErrors)
}
func (s *Service) refresh(zkConn ZkConn) error {
if atomic.LoadInt64(&s.ignoreUpdates) != 0 {
s.stateLog.Log("refresh flag set. Ignoring refresh")
return nil
}
s.stateLog.Log("refresh called")
oldHash := s.byteHashes()
children, _, _, err := zkConn.ChildrenW(fmt.Sprintf("/%s", s.name))
if err != nil && errors.Tail(err) != zk.ErrNoNode {
s.stateLog.Log(log.Err, err, "Error getting children")
return errors.Annotatef(err, "unexpected zk error on childrenw")
}
if errors.Tail(err) == zk.ErrNoNode {
exists, _, _, err := zkConn.ExistsW(fmt.Sprintf("/%s", s.name))
if exists || err != nil {
s.stateLog.Log(log.Err, err, "Unable to register exists watch!")
}
s.services.Store(make([]ServiceInstance, 0))
} else {
services, err := childrenServices(s.stateLog, s.name, children, zkConn)
if err != nil {
return err
}
s.services.Store(services)
}
s.watchLock.Lock()
defer s.watchLock.Unlock()
newHash := s.byteHashes()
if oldHash != newHash {
for _, w := range s.watches {
w()
}
}
return nil
}