zk

Documentation

Overview

Package zk provides Instancer and Registrar implementations for ZooKeeper.

Index

• Constants
• Variables
• type Client
  • func NewClient(servers []string, logger log.Logger, options ...Option) (Client, error)
• type Instancer
  • func NewInstancer(c Client, path string, logger log.Logger) (*Instancer, error)
  • func (s *Instancer) Deregister(ch chan<- sd.Event)
  • func (s *Instancer) Register(ch chan<- sd.Event)
  • func (s *Instancer) Stop()
• type Option
  • func ACL(acl []zk.ACL) Option
  • func ConnectTimeout(t time.Duration) Option
  • func Credentials(user, pass string) Option
  • func EventHandler(handler func(zk.Event)) Option
  • func Payload(payload [][]byte) Option
  • func SessionTimeout(t time.Duration) Option
• type Registrar
  • func NewRegistrar(client Client, service Service, logger log.Logger) *Registrar
  • func (r *Registrar) Deregister()
  • func (r *Registrar) Register()
• type Service

Constants

const (
	// DefaultConnectTimeout is the default timeout to establish a connection to
	// a ZooKeeper node.
	DefaultConnectTimeout = 2 * time.Second
	// DefaultSessionTimeout is the default timeout to keep the current
	// ZooKeeper session alive during a temporary disconnect.
	DefaultSessionTimeout = 5 * time.Second
)

Variables

var (
	DefaultACL            = zk.WorldACL(zk.PermAll)
	ErrInvalidCredentials = errors.New("invalid credentials provided")
	ErrClientClosed       = errors.New("client service closed")
	ErrNotRegistered      = errors.New("not registered")
	ErrNodeNotFound       = errors.New("node not found")
)

DefaultACL is the default ACL to use for creating znodes.

Types

type Client

type Client interface {
	// GetEntries should query the provided path in ZooKeeper, place a watch on
	// it and retrieve data from its current child nodes.
	GetEntries(path string) ([]string, <-chan zk.Event, error)
	// CreateParentNodes should try to create the path in case it does not exist
	// yet on ZooKeeper.
	CreateParentNodes(path string) error
	// Register a service with ZooKeeper.
	Register(s *Service) error
	// Deregister a service with ZooKeeper.
	Deregister(s *Service) error
	// Stop should properly shutdown the client implementation
	Stop()
}

Client is a wrapper around a lower level ZooKeeper client implementation.

func NewClient

func NewClient(servers []string, logger log.Logger, options ...Option) (Client, error)

NewClient returns a ZooKeeper client with a connection to the server cluster. It will return an error if the server cluster cannot be resolved.

type Instancer

type Instancer struct {
	// contains filtered or unexported fields
}

Instancer yield instances stored in a certain ZooKeeper path. Any kind of change in that path is watched and will update the subscribers.

func NewInstancer

func NewInstancer(c Client, path string, logger log.Logger) (*Instancer, error)

NewInstancer returns a ZooKeeper Instancer. ZooKeeper will start watching the given path for changes and update the Instancer endpoints.

func (*Instancer) Deregister

func (s *Instancer) Deregister(ch chan<- sd.Event)

Deregister implements Instancer.

func (*Instancer) Register

func (s *Instancer) Register(ch chan<- sd.Event)

Register implements Instancer.

func (*Instancer) Stop

func (s *Instancer) Stop()

Stop terminates the Instancer.

type Option

type Option func(*clientConfig) error

Option functions enable friendly APIs.

func ACL

func ACL(acl []zk.ACL) Option

ACL returns an Option specifying a non-default ACL for creating parent nodes.

func ConnectTimeout

func ConnectTimeout(t time.Duration) Option

ConnectTimeout returns an Option specifying a non-default connection timeout when we try to establish a connection to a ZooKeeper server.

func Credentials

func Credentials(user, pass string) Option

Credentials returns an Option specifying a user/password combination which the client will use to authenticate itself with.

func EventHandler

func EventHandler(handler func(zk.Event)) Option

EventHandler returns an Option specifying a callback function to handle incoming zk.Event payloads (ZooKeeper connection events).

func Payload

func Payload(payload [][]byte) Option

Payload returns an Option specifying non-default data values for each znode created by CreateParentNodes.

func SessionTimeout

func SessionTimeout(t time.Duration) Option

SessionTimeout returns an Option specifying a non-default session timeout.

type Registrar

type Registrar struct {
	// contains filtered or unexported fields
}

Registrar registers service instance liveness information to ZooKeeper.

func NewRegistrar

func NewRegistrar(client Client, service Service, logger log.Logger) *Registrar

NewRegistrar returns a ZooKeeper Registrar acting on the provided catalog registration.

func (*Registrar) Deregister

func (r *Registrar) Deregister()

Deregister implements sd.Registrar interface.

func (*Registrar) Register

func (r *Registrar) Register()

Register implements sd.Registrar interface.

type Service

type Service struct {
	Path string // discovery namespace, example: /myorganization/myplatform/
	Name string // service name, example: addscv
	Data []byte // instance data to store for discovery, example: 10.0.2.10:80
	// contains filtered or unexported fields
}

Service holds the root path, service name and instance identifying data you want to publish to ZooKeeper.