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package engine
import (
"context"
"sync"
"github.com/google/uuid"
"github.com/target/goalert/validation"
)
const cycleHist = 10
type cycleMonitor struct {
mx sync.Mutex
cycles map[uuid.UUID]chan struct{}
history [cycleHist]uuid.UUID
}
func newCycleMonitor() *cycleMonitor {
m := &cycleMonitor{
cycles: make(map[uuid.UUID]chan struct{}, cycleHist),
}
m._newID()
return m
}
func (c *cycleMonitor) _newID() {
// remove oldest cycle
delete(c.cycles, c.history[cycleHist-1])
// shift history
copy(c.history[:], c.history[1:])
// add new cycle
c.history[0] = uuid.New()
c.cycles[c.history[0]] = make(chan struct{})
}
// startNextCycle marks the beginning of the next engine cycle.
// It returns a func that should be called when the cycle is finished.
func (c *cycleMonitor) startNextCycle() func() {
c.mx.Lock()
defer c.mx.Unlock()
ch := c.cycles[c.history[0]]
c._newID()
return func() { close(ch) }
}
// WaitCycleID waits for the engine cycle with the given UUID to finish.
func (c *cycleMonitor) WaitCycleID(ctx context.Context, cycleID uuid.UUID) error {
if c == nil {
// engine is disabled
return validation.NewGenericError("engine is disabled")
}
c.mx.Lock()
ch, ok := c.cycles[cycleID]
c.mx.Unlock()
if !ok {
return validation.NewGenericError("unknown cycle ID")
}
select {
case <-ch:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
// NextCycleID returns the UUID of the next engine cycle.
func (c *cycleMonitor) NextCycleID() uuid.UUID {
if c == nil {
// engine is disabled
return uuid.Nil
}
c.mx.Lock()
defer c.mx.Unlock()
return c.history[0]
}
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