watch

Documentation

Overview

Package watch contains a generic watchable interface, and a fake for testing code that uses the watch interface.

Index

• type Broadcaster
  • func NewBroadcaster(queueLength int, fullChannelBehavior FullChannelBehavior) *Broadcaster
  • func (m *Broadcaster) Action(action EventType, obj runtime.Object)
  • func (m *Broadcaster) Shutdown()
  • func (m *Broadcaster) Watch() Interface
  • func (m *Broadcaster) WatchWithPrefix(queuedEvents []Event) Interface
• type ConditionFunc
• type Decoder
• type Event
  • func Until(timeout time.Duration, watcher Interface, conditions ...ConditionFunc) (*Event, error)
• type EventType
• type FakeWatcher
  • func NewFake() *FakeWatcher
  • func (f *FakeWatcher) Action(action EventType, obj runtime.Object)
  • func (f *FakeWatcher) Add(obj runtime.Object)
  • func (f *FakeWatcher) Delete(lastValue runtime.Object)
  • func (f *FakeWatcher) Error(errValue runtime.Object)
  • func (f *FakeWatcher) Modify(obj runtime.Object)
  • func (f *FakeWatcher) ResultChan() <-chan Event
  • func (f *FakeWatcher) Stop()
• type FilterFunc
• type FullChannelBehavior
• type Interface
  • func Filter(w Interface, f FilterFunc) Interface
  • func NewEmptyWatch() Interface
• type StreamWatcher
  • func NewStreamWatcher(d Decoder) *StreamWatcher
  • func (sw *StreamWatcher) ResultChan() <-chan Event
  • func (sw *StreamWatcher) Stop()

Types

type Broadcaster

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

Broadcaster distributes event notifications among any number of watchers. Every event is delivered to every watcher.

func NewBroadcaster

func NewBroadcaster(queueLength int, fullChannelBehavior FullChannelBehavior) *Broadcaster

NewBroadcaster creates a new Broadcaster. queueLength is the maximum number of events to queue per watcher. It is guaranteed that events will be distributed in the order in which they occur, but the order in which a single event is distributed among all of the watchers is unspecified.

func (*Broadcaster) Action

func (m *Broadcaster) Action(action EventType, obj runtime.Object)

Action distributes the given event among all watchers.

func (*Broadcaster) Shutdown

func (m *Broadcaster) Shutdown()

Shutdown disconnects all watchers (but any queued events will still be distributed). You must not call Action or Watch* after calling Shutdown. This call blocks until all events have been distributed through the outbound channels. Note that since they can be buffered, this means that the watchers might not have received the data yet as it can remain sitting in the buffered channel.

func (*Broadcaster) Watch

func (m *Broadcaster) Watch() Interface

Watch adds a new watcher to the list and returns an Interface for it. Note: new watchers will only receive new events. They won't get an entire history of previous events.

func (*Broadcaster) WatchWithPrefix

func (m *Broadcaster) WatchWithPrefix(queuedEvents []Event) Interface

WatchWithPrefix adds a new watcher to the list and returns an Interface for it. It sends queuedEvents down the new watch before beginning to send ordinary events from Broadcaster. The returned watch will have a queue length that is at least large enough to accommodate all of the items in queuedEvents.

type ConditionFunc

type ConditionFunc func(event Event) (bool, error)

ConditionFunc returns true if the condition has been reached, false if it has not been reached yet, or an error if the condition cannot be checked and should terminate. In general, it is better to define level driven conditions over edge driven conditions (pod has ready=true, vs pod modified and ready changed from false to true).

type Decoder

type Decoder interface {
	// Decode should return the type of event, the decoded object, or an error.
	// An error will cause StreamWatcher to call Close(). Decode should block until
	// it has data or an error occurs.
	Decode() (action EventType, object runtime.Object, err error)

	// Close should close the underlying io.Reader, signalling to the source of
	// the stream that it is no longer being watched. Close() must cause any
	// outstanding call to Decode() to return with an error of some sort.
	Close()
}

Decoder allows StreamWatcher to watch any stream for which a Decoder can be written.

type Event

type Event struct {
	Type EventType

	// Object is:
	//  * If Type is Added or Modified: the new state of the object.
	//  * If Type is Deleted: the state of the object immediately before deletion.
	//  * If Type is Error: *api.Status is recommended; other types may make sense
	//    depending on context.
	Object runtime.Object
}

Event represents a single event to a watched resource.

func Until

func Until(timeout time.Duration, watcher Interface, conditions ...ConditionFunc) (*Event, error)

Until reads items from the watch until each provided condition succeeds, and then returns the last watch encountered. The first condition that returns an error terminates the watch (and the event is also returned). If no event has been received, the returned event will be nil. Conditions are satisfied sequentially so as to provide a useful primitive for higher level composition.

type EventType

type EventType string

EventType defines the possible types of events.

const (
	Added    EventType = "ADDED"
	Modified EventType = "MODIFIED"
	Deleted  EventType = "DELETED"
	Error    EventType = "ERROR"
)

type FakeWatcher

type FakeWatcher struct {
	Stopped bool
	sync.Mutex
	// contains filtered or unexported fields
}

FakeWatcher lets you test anything that consumes a watch.Interface; threadsafe.

func NewFake

func NewFake() *FakeWatcher

func (*FakeWatcher) Action

func (f *FakeWatcher) Action(action EventType, obj runtime.Object)

Action sends an event of the requested type, for table-based testing.

func (*FakeWatcher) Add

func (f *FakeWatcher) Add(obj runtime.Object)

Add sends an add event.

func (*FakeWatcher) Delete

func (f *FakeWatcher) Delete(lastValue runtime.Object)

Delete sends a delete event.

func (*FakeWatcher) Error

func (f *FakeWatcher) Error(errValue runtime.Object)

Error sends an Error event.

func (*FakeWatcher) Modify

func (f *FakeWatcher) Modify(obj runtime.Object)

Modify sends a modify event.

func (*FakeWatcher) ResultChan

func (f *FakeWatcher) ResultChan() <-chan Event

func (*FakeWatcher) Stop

func (f *FakeWatcher) Stop()

Stop implements Interface.Stop().

type FilterFunc

type FilterFunc func(in Event) (out Event, keep bool)

FilterFunc should take an event, possibly modify it in some way, and return the modified event. If the event should be ignored, then return keep=false.

type FullChannelBehavior

type FullChannelBehavior int

FullChannelBehavior controls how the Broadcaster reacts if a watcher's watch channel is full.

const (
	WaitIfChannelFull FullChannelBehavior = iota
	DropIfChannelFull
)

type Interface

type Interface interface {
	// Stops watching. Will close the channel returned by ResultChan(). Releases
	// any resources used by the watch.
	Stop()

	// Returns a chan which will receive all the events. If an error occurs
	// or Stop() is called, this channel will be closed, in which case the
	// watch should be completely cleaned up.
	ResultChan() <-chan Event
}

Interface can be implemented by anything that knows how to watch and report changes.

func Filter

func Filter(w Interface, f FilterFunc) Interface

Filter passes all events through f before allowing them to pass on. Putting a filter on a watch, as an unavoidable side-effect due to the way go channels work, effectively causes the watch's event channel to have its queue length increased by one.

WARNING: filter has a fatal flaw, in that it can't properly update the Type field (Add/Modified/Deleted) to reflect items beginning to pass the filter when they previously didn't.

func NewEmptyWatch

func NewEmptyWatch() Interface

NewEmptyWatch returns a watch interface that returns no results and is closed. May be used in certain error conditions where no information is available but an error is not warranted.

type StreamWatcher

type StreamWatcher struct {
	sync.Mutex
	// contains filtered or unexported fields
}

StreamWatcher turns any stream for which you can write a Decoder interface into a watch.Interface.

func NewStreamWatcher

func NewStreamWatcher(d Decoder) *StreamWatcher

NewStreamWatcher creates a StreamWatcher from the given decoder.

func (*StreamWatcher) ResultChan

func (sw *StreamWatcher) ResultChan() <-chan Event

ResultChan implements Interface.

func (*StreamWatcher) Stop

func (sw *StreamWatcher) Stop()

Stop implements Interface.