53 lines
1.7 KiB
Go
53 lines
1.7 KiB
Go
/*
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Package stream provides a publish/subscribe system for events produced by changes
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to the state store.
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*/
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package stream
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import "fmt"
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// Topic is an identifier that partitions events. A subscription will only receive
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// events which match the Topic.
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type Topic fmt.Stringer
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// Event is a structure with identifiers and a payload. Events are Published to
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// EventPublisher and returned to Subscribers.
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type Event struct {
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Topic Topic
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Key string
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Index uint64
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Payload interface{}
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}
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// IsEndOfSnapshot returns true if this is a framing event that indicates the
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// snapshot has completed. Subsequent events from Subscription.Next will be
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// streamed as they occur.
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func (e Event) IsEndOfSnapshot() bool {
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return e.Payload == endOfSnapshot{}
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}
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// IsNewSnapshotToFollow returns true if this is a framing event that indicates
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// that the clients view is stale, and must be reset. Subsequent events from
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// Subscription.Next will be a new snapshot, followed by an EndOfSnapshot event.
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func (e Event) IsNewSnapshotToFollow() bool {
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return e.Payload == newSnapshotToFollow{}
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}
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type endOfSnapshot struct{}
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type newSnapshotToFollow struct{}
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type closeSubscriptionPayload struct {
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tokensSecretIDs []string
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}
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// NewCloseSubscriptionEvent returns a special Event that is handled by the
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// stream package, and is never sent to subscribers. EventProcessor handles
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// these events, and closes any subscriptions which were created using a token
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// which matches any of the tokenSecretIDs.
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//
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// tokenSecretIDs may contain duplicate IDs.
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func NewCloseSubscriptionEvent(tokenSecretIDs []string) Event {
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return Event{Payload: closeSubscriptionPayload{tokensSecretIDs: tokenSecretIDs}}
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}
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