roundrobin

Documentation

Index

• func NewImplementation(opts ...Option) abstractlist.Implementation
• func Spec() yarpcconfig.PeerListSpec
• func SpecWithOptions(options ...ListOption) yarpcconfig.PeerListSpec
• type Configuration
• type List
  • func New(transport peer.Transport, opts ...ListOption) *List
  • func (l *List) Choose(ctx context.Context, req *transport.Request) (peer peer.Peer, onFinish func(error), err error)
  • func (l *List) Introspect() introspection.ChooserStatus
  • func (l *List) IsRunning() bool
  • func (l *List) NotifyStatusChanged(pid peer.Identifier)
  • func (l *List) Peers() []peer.StatusPeer
  • func (l *List) Start() error
  • func (l *List) Stop() error
  • func (l *List) Update(updates peer.ListUpdates) error
• type ListOption
  • func Capacity(capacity int) ListOption
  • func DefaultChooseTimeout(timeout time.Duration) ListOption
  • func FailFast() ListOption
  • func Logger(logger *zap.Logger) ListOption
• type Option

Functions

func NewImplementation

func NewImplementation(opts ...Option) abstractlist.Implementation

NewImplementation creates a new round-robin abstractlist.Implementation.

Use this constructor instead of NewList, when wanting to do custom peer connection management.

func Spec

func Spec() yarpcconfig.PeerListSpec

Spec returns a configuration specification for the round-robin peer list implementation, making it possible to select the least recently chosen peer with transports that use outbound peer list configuration (like HTTP).

cfg := yarpcconfig.New()
cfg.MustRegisterPeerList(roundrobin.Spec())

This enables the round-robin peer list:

outbounds:
  otherservice:
    unary:
      http:
        url: https://host:port/rpc
        round-robin:
          peers:
            - 127.0.0.1:8080
            - 127.0.0.1:8081

Other than a specific peer or peers list, use any peer list updater registered with a yarpc Configurator. The configuration allows for alternative initial allocation capacity and a fail-fast option. With fail-fast enabled, the peer list will return an error immediately if no peers are available (connected) at the time the request is sent. The default choose timeout enables calls without deadlines, ie streaming, to choose peers without waiting indefinitely.

round-robin:
  peers:
    - 127.0.0.1:8080
  capacity: 1
  failFast: true
  defaultChooseTimeout: 1s

func SpecWithOptions

func SpecWithOptions(options ...ListOption) yarpcconfig.PeerListSpec

SpecWithOptions accepts additional list constructor options.

Types

type Configuration

type Configuration struct {
	Capacity *int `config:"capacity"`
	FailFast bool `config:"failFast"`
	// DefaultChooseTimeout specifies the deadline to add to Choose calls if not
	// present. This enables calls without deadlines, ie streaming, to choose
	// peers without waiting indefinitely.
	DefaultChooseTimeout *time.Duration `config:"defaultChooseTimeout"`
}

Configuration descripes how to build a round-robin peer list.

type List

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

List is a PeerList which rotates which peers are to be selected in a circle

func New

func New(transport peer.Transport, opts ...ListOption) *List

New creates a new round robin peer list.

func (*List) Choose

func (l *List) Choose(ctx context.Context, req *transport.Request) (peer peer.Peer, onFinish func(error), err error)

Choose returns a peer, suitable for sending a request.

The peer is not guaranteed to be connected and available, but the peer list makes every attempt to ensure this and minimize the probability that a chosen peer will fail to carry a request.

func (*List) Introspect

func (l *List) Introspect() introspection.ChooserStatus

Introspect reveals information about the list to the internal YARPC introspection system.

func (*List) IsRunning

func (l *List) IsRunning() bool

IsRunning returns whether the list has started and not yet stopped.

func (*List) NotifyStatusChanged

func (l *List) NotifyStatusChanged(pid peer.Identifier)

NotifyStatusChanged forwards a status change notification to an individual peer in the list.

This satisfies the peer.Subscriber interface and should only be used to send notifications in tests. The list's RetainPeer and ReleasePeer methods deal with an individual peer.Subscriber instance for each peer in the list, avoiding a map lookup.

func (*List) Peers

func (l *List) Peers() []peer.StatusPeer

Peers produces a slice of all retained peers.

func (*List) Start

func (l *List) Start() error

Start causes the peer list to start.

Starting will retain all peers that have been added but not removed the first time it is called.

Start may be called any number of times and in any order in relation to Stop but will only cause the list to start the first time, and only if it has not already been stopped.

func (*List) Stop

func (l *List) Stop() error

Stop causes the peer list to stop.

Stopping will release all retained peers to the underlying transport.

Stop may be called any number of times and in order in relation to Start but will only cause the list to stop the first time, and only if it has previously been started.

func (*List) Update

func (l *List) Update(updates peer.ListUpdates) error

Update may add and remove logical peers in the list.

The peer list uses a transport to obtain a physical peer for each logical peer. The transport is responsible for informing the peer list whether the peer is available or unavailable, but cannot guarantee that the peer will still be available after it is chosen.

type ListOption

type ListOption func(*listConfig)

ListOption customizes the behavior of a roundrobin list.

func Capacity

func Capacity(capacity int) ListOption

Capacity specifies the default capacity of the underlying data structures for this list.

Defaults to 10.

func DefaultChooseTimeout

func DefaultChooseTimeout(timeout time.Duration) ListOption

DefaultChooseTimeout specifies the default timeout to add to 'Choose' calls without context deadlines. This prevents long-lived streams from setting calling deadlines.

Defaults to 500ms.

func FailFast

func FailFast() ListOption

FailFast indicates that the peer list should not wait for a peer to become available when choosing a peer.

This option is preferrable when the better failure mode is to retry from the origin, since another proxy instance might already have a connection.

func Logger

func Logger(logger *zap.Logger) ListOption

Logger specifies a logger.

type Option

type Option interface {
	// contains filtered or unexported methods
}

Option configures the peer list implementation constructor.