discovery

README

Curator Service Discovery (for Go)

Implement Curator-sytle service discovery in Go -- both server-side registration as well as client-side discovery.

Server-side

First, create teh service-discovery framework (passing it a connected curator) and call MaintainRegistrations() to start its connection monitor:

  s := discovery.NewServiceDiscovery(c, "/path/to/services")
  s.MaintainRegistrations()

Then register some services:

  reg := discovery.NewSimpleServiceInstance("baz", "127.0.0.1", 8080)
  ...
  if err := s.Register(reg); err != nil {
    log.Fatal("failed to register: ", err)
  }
  defer s.Unregister(reg)

Client-side

First, create a service-discovery framework (passing it a connected curator) and call Watch() to start watching for changes.

Use Provider(service) to get a provider, which can be used to get a registered instance (via GetInstance()) whenever one is needed.

The default strategy used when creating providers is to randomly select a registed node. Use ProviderWithStrategy(name, strategy) to pass a different ProviderStrategy, such as the RoundRobinProvider.

  s := discovery.NewServiceDiscovery(c, "/path/to/services")
  s.Watch()

  bazProvider := s.Provider("baz")
  ...

  def HandleReq() {
  ...
    hostForThisReq := bazProvider.GetInstance().Spec()
    http.Get(fmt.Sprintf("http://%s/path/to/resource", hostForThisReq))
  ...
  }

Testing

The tests use zk.StartTestCluster to get a testing zookeeper instance. This requires you have zookeeper installed locally (it searches a few relative and system paths). On OSX, brew install zookeeper is enough to get it working.

Authors

• David Taylor

Documentation

Index

• func NewServiceDiscoveryAndConn(connString, basePath string) (*ServiceDiscovery, Conn, error)
• type Conn
  • func DefaultConn(conn string) (Conn, error)
• type FixedSetInstanceProvider
  • func (p *FixedSetInstanceProvider) GetAllInstances() ([]*ServiceInstance, error)
• type InstanceProvider
• type InstanceSerializer
• type JsonInstanceSerializer
  • func (s *JsonInstanceSerializer) Deserialize(b []byte) (*ServiceInstance, error)
  • func (s *JsonInstanceSerializer) Serialize(i *ServiceInstance) ([]byte, error)
• type ProviderStrategy
• type RandomProvider
  • func NewRandomProvider() *RandomProvider
  • func (r RandomProvider) GetInstance(ip InstanceProvider) (*ServiceInstance, error)
• type RoundRobinProvider
  • func NewRoundRobinProvider() *RoundRobinProvider
  • func (r *RoundRobinProvider) GetInstance(ip InstanceProvider) (*ServiceInstance, error)
• type ServiceDiscovery
  • func NewServiceDiscovery(client Conn, basePath string) *ServiceDiscovery
  • func (s *ServiceDiscovery) MaintainRegistrations() error
  • func (s *ServiceDiscovery) Provider(name string) ServiceProvider
  • func (s *ServiceDiscovery) ProviderWithStrategy(name string, strat ProviderStrategy) ServiceProvider
  • func (s *ServiceDiscovery) Register(service *ServiceInstance) error
  • func (s *ServiceDiscovery) ReregisterAll() error
  • func (s *ServiceDiscovery) StateChanged(c curator.CuratorFramework, n curator.ConnectionState)
  • func (s *ServiceDiscovery) Unregister(service *ServiceInstance) error
  • func (s *ServiceDiscovery) UnregisterAll() error
  • func (s *ServiceDiscovery) Watch() error
• type ServiceDiscoveryInstanceProvider
  • func (s *ServiceDiscoveryInstanceProvider) GetAllInstances() ([]*ServiceInstance, error)
  • func (s *ServiceDiscoveryInstanceProvider) GetInstance() (*ServiceInstance, error)
• type ServiceInstance
  • func NewServiceInstance(name, address string, port, ssl *int, payload *string) *ServiceInstance
  • func NewSimpleServiceInstance(name, address string, port int) *ServiceInstance
  • func (i *ServiceInstance) Spec() string
• type ServiceProvider
• type ServiceType
• type TreeCache
  • func NewTreeCache(s *ServiceDiscovery) *TreeCache
  • func (t *TreeCache) Start()

Functions

func NewServiceDiscoveryAndConn

func NewServiceDiscoveryAndConn(connString, basePath string) (*ServiceDiscovery, Conn, error)

Types

type Conn

type Conn interface {
	curator.CuratorFramework
}

func DefaultConn

func DefaultConn(conn string) (Conn, error)

type FixedSetInstanceProvider

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

func (*FixedSetInstanceProvider) GetAllInstances

func (p *FixedSetInstanceProvider) GetAllInstances() ([]*ServiceInstance, error)

type InstanceProvider

type InstanceProvider interface {
	/**
	 * Return the current available set of instances <b>IMPORTANT: </b> users
	 * should not hold on to the instance returned. They should always get a fresh list.
	 */
	GetAllInstances() ([]*ServiceInstance, error)
}

type InstanceSerializer

type InstanceSerializer interface {
	Serialize(i *ServiceInstance) ([]byte, error)
	Deserialize(b []byte) (*ServiceInstance, error)
}

type JsonInstanceSerializer

type JsonInstanceSerializer struct {
}

func (*JsonInstanceSerializer) Deserialize

func (s *JsonInstanceSerializer) Deserialize(b []byte) (*ServiceInstance, error)

func (*JsonInstanceSerializer) Serialize

func (s *JsonInstanceSerializer) Serialize(i *ServiceInstance) ([]byte, error)

type ProviderStrategy

type ProviderStrategy interface {
	// Given a source of instances, return one of them for a single use.
	GetInstance(instanceProvider InstanceProvider) (*ServiceInstance, error)
}

type RandomProvider

type RandomProvider struct {
	*rand.Rand
}

func NewRandomProvider

func NewRandomProvider() *RandomProvider

func (RandomProvider) GetInstance

func (r RandomProvider) GetInstance(ip InstanceProvider) (*ServiceInstance, error)

type RoundRobinProvider

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

func NewRoundRobinProvider

func NewRoundRobinProvider() *RoundRobinProvider

func (*RoundRobinProvider) GetInstance

func (r *RoundRobinProvider) GetInstance(ip InstanceProvider) (*ServiceInstance, error)

type ServiceDiscovery

type ServiceDiscovery struct {

	// Cache of watched services
	Services map[string][]*ServiceInstance
	// contains filtered or unexported fields
}

func NewServiceDiscovery

func NewServiceDiscovery(client Conn, basePath string) *ServiceDiscovery

func (*ServiceDiscovery) MaintainRegistrations

func (s *ServiceDiscovery) MaintainRegistrations() error

func (*ServiceDiscovery) Provider

func (s *ServiceDiscovery) Provider(name string) ServiceProvider

func (*ServiceDiscovery) ProviderWithStrategy

func (s *ServiceDiscovery) ProviderWithStrategy(name string, strat ProviderStrategy) ServiceProvider

func (*ServiceDiscovery) Register

func (s *ServiceDiscovery) Register(service *ServiceInstance) error

func (*ServiceDiscovery) ReregisterAll

func (s *ServiceDiscovery) ReregisterAll() error

func (*ServiceDiscovery) StateChanged

func (s *ServiceDiscovery) StateChanged(c curator.CuratorFramework, n curator.ConnectionState)

func (*ServiceDiscovery) Unregister

func (s *ServiceDiscovery) Unregister(service *ServiceInstance) error

func (*ServiceDiscovery) UnregisterAll

func (s *ServiceDiscovery) UnregisterAll() error

func (*ServiceDiscovery) Watch

func (s *ServiceDiscovery) Watch() error

type ServiceDiscoveryInstanceProvider

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

func (*ServiceDiscoveryInstanceProvider) GetAllInstances

func (s *ServiceDiscoveryInstanceProvider) GetAllInstances() ([]*ServiceInstance, error)

func (*ServiceDiscoveryInstanceProvider) GetInstance

func (s *ServiceDiscoveryInstanceProvider) GetInstance() (*ServiceInstance, error)

type ServiceInstance

type ServiceInstance struct {
	Name                string      `json:"name"`
	Id                  string      `json:"id"`
	Address             string      `json:"address"`
	Port                *int        `json:"port"`
	SslPort             *int        `json:"sslPort"`
	Payload             *string     `json:"payload"`
	RegistrationTimeUTC int64       `json:"registrationTimeUTC"`
	ServiceType         ServiceType `json:"serviceType"`
	UriSpec             *string     `json:"uriSpec"`
}

func NewServiceInstance

func NewServiceInstance(name, address string, port, ssl *int, payload *string) *ServiceInstance

func NewSimpleServiceInstance

func NewSimpleServiceInstance(name, address string, port int) *ServiceInstance

func (*ServiceInstance) Spec

func (i *ServiceInstance) Spec() string

type ServiceProvider

type ServiceProvider interface {
	InstanceProvider
	/**
	 * Return an instance for a single use. <b>IMPORTANT: </b> users
	 * should not hold on to the instance returned. They should always get a fresh instance.
	 */
	GetInstance() (*ServiceInstance, error)
}

type ServiceType

type ServiceType string

const (
	DYNAMIC   ServiceType = "DYNAMIC"
	STATIC    ServiceType = "STATIC"
	PERMANENT ServiceType = "PERMANENT"
)

type TreeCache

type TreeCache struct {
	*ServiceDiscovery
	// contains filtered or unexported fields
}

func NewTreeCache

func NewTreeCache(s *ServiceDiscovery) *TreeCache

func (*TreeCache) Start

func (t *TreeCache) Start()