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pacemaker.go
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pacemaker.go
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package hotstuff
import (
"time"
"github.com/onflow/flow-go/consensus/hotstuff/model"
"github.com/onflow/flow-go/model/flow"
)
// PaceMaker for HotStuff. The component is passive in that it only reacts to method calls.
// The PaceMaker does not perform state transitions on its own. Timeouts are emitted through
// channels. Each timeout has its own dedicated channel, which is garbage collected after the
// respective state has been passed. It is the EventHandler's responsibility to pick up
// timeouts from the currently active TimeoutChannel process them first and subsequently inform the
// PaceMaker about processing the timeout. Specifically, the intended usage pattern for the
// TimeoutChannels is as follows:
//
// • Each time the PaceMaker starts a new timeout, it created a new TimeoutChannel
//
// • The channel for the CURRENTLY ACTIVE timeout is returned by PaceMaker.TimeoutChannel()
//
// • Each time the EventHandler processes an event, the EventHandler might call into PaceMaker
// potentially resulting in a state transition and the PaceMaker starting a new timeout
//
// • Hence, after processing any event, EventHandler should retrieve the current TimeoutChannel
// from the PaceMaker.
//
// For Example:
//
// for {
// timeoutChannel := el.eventHandler.TimeoutChannel()
// select {
// case <-timeoutChannel:
// el.eventHandler.OnLocalTimeout()
// case <other events>
// }
// }
type PaceMaker interface {
// CurView returns the current view.
CurView() uint64
// UpdateCurViewWithQC will check if the given QC will allow PaceMaker to fast
// forward to QC.view+1. If PaceMaker incremented the current View, a NewViewEvent will be returned.
UpdateCurViewWithQC(qc *flow.QuorumCertificate) (*model.NewViewEvent, bool)
// UpdateCurViewWithBlock will check if the given block will allow PaceMaker to fast forward
// to the BlockProposal's view. If yes, the PaceMaker will update it's internal value for
// CurView and return a NewViewEvent.
//
// The parameter `nextPrimary` indicates to the PaceMaker whether or not this replica is the
// primary for the NEXT view taking block.view as reference.
// True corresponds to this replica being the next primary.
UpdateCurViewWithBlock(block *model.Block, isLeaderForNextView bool) (*model.NewViewEvent, bool)
// TimeoutChannel returns the timeout channel for the CURRENTLY ACTIVE timeout.
// Each time the pace maker starts a new timeout, this channel is replaced.
TimeoutChannel() <-chan time.Time
// OnTimeout is called when a timeout, which was previously created by the PaceMaker, has
// looped through the event loop. When used correctly, OnTimeout will always return
// a NewViewEvent.
// It is the responsibility of the calling code to ensure that NO STALE timeouts are
// delivered to the PaceMaker.
OnTimeout() *model.NewViewEvent
// Start starts the PaceMaker (i.e. the timeout for the configured starting value for view).
Start()
// BlockRateDelay
BlockRateDelay() time.Duration
}