Documentation
¶
Overview ¶
Package abstractlist provides a utility for managing peer availability with a separate implementation of peer selection from just among available peers. The peer list implements the peer.ChooserList interface and accepts an abstractlist.Implementation to provide the implementation-specific concern of, for example, a *roundrobin.List.
The example is an implementation of peer.ChooserList using a random peer selection strategy, returned by newRandomListImplementation(), implementing abstractlist.Implementation.
type List struct {
*abstractlist.List
}
func New(transport peer.Transport) *List {
return &List{
List: abstractlist.New(
"random",
transport,
newRandomListImplementation(),
),
}
}
The abstract peer list is designed to take responsibility for concurrently communicating with three parties: the outbound (which sees it as a peer.Chooser), the peer list updater (which see it as a peer.List), and the transport (which sees it as a bank of peer.Subscriber). By taking care of concurrency, the abstract peer list frees the Implementation from the concern of thread safety.
Index ¶
- type Implementation
- type List
- func (pl *List) Available(pid peer.Identifier) bool
- func (pl *List) Choose(ctx context.Context, req *transport.Request) (peer.Peer, func(error), error)
- func (pl *List) Introspect() introspection.ChooserStatus
- func (pl *List) IsRunning() bool
- func (pl *List) Name() string
- func (pl *List) NotifyStatusChanged(pid peer.Identifier)
- func (pl *List) NumAvailable() int
- func (pl *List) NumUnavailable() int
- func (pl *List) NumUninitialized() int
- func (pl *List) Peers() []peer.StatusPeer
- func (pl *List) Start() error
- func (pl *List) Stop() error
- func (pl *List) Transport() peer.Transport
- func (pl *List) Uninitialized(pid peer.Identifier) bool
- func (pl *List) Update(updates peer.ListUpdates) error
- type Option
- type Subscriber
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Implementation ¶
type Implementation interface {
Add(peer.StatusPeer, peer.Identifier) Subscriber
Remove(peer.StatusPeer, peer.Identifier, Subscriber)
Choose(*transport.Request) peer.StatusPeer
}
Implementation is a collection of available peers, with its own subscribers for pending request count change notifications. The abstract list uses the implementation to track peers that can be returned by Choose, as opposed to those that were added but reported unavailable by the underlying transport. Use "go.uber.org/yarpc/peer/abstractlist".List in conjunction with an Implementation to produce a "go.uber.org/yarpc/api/peer".ChooserList.
The abstractlist.List calls Add, Remove, and Choose under a write lock so the implementation is free to perform mutations on its own data without locks.
It should be noted that since the abstractlist.List is using a write lock for Add, Remove and Choose, performances of the abstract.List might be limited for a given implementation. For instance, a tworandomchoices implementation would not need a write lock for the method Choose but only a read lock.
Choose must return nil immediately if the collection is empty. The abstractlist.List guarantees that peers will only be added if they're absent, and only removed they are present. Choose should not block.
type List ¶
type List struct {
// contains filtered or unexported fields
}
List is an abstract peer list, backed by an Implementation to determine which peer to choose among available peers. The abstract list manages available versus unavailable peers, intercepting these notifications from the transport's concrete implementation of peer.StatusPeer with the peer.Subscriber API. The peer list will not choose an unavailable peer, prefering to block until one becomes available.
The list is a suitable basis for concrete implementations like round-robin.
This abstract list does not participate in the transport’s pending request count tracking. The list tracks pending request counts for the peers that it chooses, does not inform the transport of these choices, and ignores notifications from the transport about choices other peer lists that share the same peers have made.
func New ¶
func New(name string, transport peer.Transport, implementation Implementation, opts ...Option) *List
New creates a new peer list with an identifier chooser for available peers.
func (*List) Available ¶
func (pl *List) Available(pid peer.Identifier) bool
Available returns whether the identifier peer is available for traffic.
func (*List) Introspect ¶
func (pl *List) Introspect() introspection.ChooserStatus
Introspect returns a ChooserStatus with a summary of the Peers.
func (*List) NotifyStatusChanged ¶
func (pl *List) NotifyStatusChanged(pid peer.Identifier)
NotifyStatusChanged receives status change notifications for peers in the list.
This function exists only as is necessary for dispatching connection status changes from tests.
func (*List) NumAvailable ¶
NumAvailable returns how many peers are available.
func (*List) NumUnavailable ¶
NumUnavailable returns how many peers are unavailable while the list is running.
func (*List) NumUninitialized ¶
NumUninitialized returns how many peers are unavailable because the peer list was stopped or has not yet started.
func (*List) Peers ¶
func (pl *List) Peers() []peer.StatusPeer
Peers returns a snapshot of all retained (available and unavailable) peers.
func (*List) Transport ¶
Transport returns the underlying transport for retaining and releasing peers.
func (*List) Uninitialized ¶
func (pl *List) Uninitialized(pid peer.Identifier) bool
Uninitialized returns whether the identifier peer is present but uninitialized.
func (*List) Update ¶
func (pl *List) Update(updates peer.ListUpdates) error
Update applies the additions and removals of peer Identifiers to the list it returns a multi-error result of every failure that happened without circuit breaking due to failures.
Updates must be serialized so no peer is removed if it is absent and no peer is added if it is present. Updates should not have overlapping additions and removals, but the list will tollerate this case, but may cause existing connections to close and be replaced.
Update will return errors if its invariants are violated, regardless of whether updates are sent while the list is running. Updates may be interleaved with Start and Stop in any order any number of times.
type Option ¶
type Option interface {
// contains filtered or unexported methods
}
Option customizes the behavior of a list.
func Capacity ¶
Capacity specifies the default capacity of the underlying data structures for this list
Defaults to 10.
func DefaultChooseTimeout ¶ added in v1.46.0
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() Option
FailFast indicates that the peer list should not wait for peers to be added, when choosing a peer.
This option is particularly useful for proxies.
type Subscriber ¶
type Subscriber interface {
UpdatePendingRequestCount(int)
}
Subscriber is a callback that implementations of peer list data structures must provide.
The peer list uses the Subscriber to send notifications when a peer’s pending request count changes. A peer list implementation may have a single subscriber or a subscriber for each peer. UpdatePendingRequestCount is thread safe to be called
Source Files