forked from coreos/fleet
/
engine.go
101 lines (84 loc) · 2.2 KB
/
engine.go
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package engine
import (
"fmt"
"time"
log "github.com/coreos/fleet/Godeps/_workspace/src/github.com/golang/glog"
"github.com/coreos/fleet/machine"
"github.com/coreos/fleet/registry"
)
const (
// time between triggering reconciliation routine
reconcileInterval = 2 * time.Second
// name of role that represents the lead engine in a cluster
engineRoleName = "engine-leader"
// time the role will be leased before the lease must be renewed
engineRoleLeasePeriod = 10 * time.Second
)
type Engine struct {
rec Reconciler
registry registry.Registry
machine machine.Machine
lease registry.Lease
}
func New(reg registry.Registry, mach machine.Machine) *Engine {
rec := &dumbReconciler{reg, mach}
return &Engine{rec, reg, mach, nil}
}
func (e *Engine) Run(stop chan bool) {
ticker := time.Tick(reconcileInterval)
machID := e.machine.State().ID
for {
select {
case <-stop:
log.V(1).Info("Engine exiting due to stop signal")
return
case <-ticker:
log.V(1).Info("Engine tick")
e.lease = ensureLeader(e.lease, e.registry, machID)
if e.lease == nil {
continue
}
start := time.Now()
e.rec.Reconcile()
elapsed := time.Now().Sub(start)
msg := fmt.Sprintf("Engine completed reconciliation in %s", elapsed)
if elapsed > reconcileInterval {
log.Warning(msg)
} else {
log.V(1).Info(msg)
}
}
}
}
func (e *Engine) Purge() {
if e.lease == nil {
return
}
err := e.lease.Release()
if err != nil {
log.Errorf("Failed to release lease: %v", err)
}
}
// ensureLeader will attempt to renew a non-nil Lease, falling back to
// acquiring a new Lease on the lead engine role.
func ensureLeader(prev registry.Lease, reg registry.Registry, machID string) (cur registry.Lease) {
if prev != nil {
err := prev.Renew(engineRoleLeasePeriod)
if err == nil {
cur = prev
return
} else {
log.Errorf("Engine leadership could not be renewed: %v", err)
}
}
var err error
cur, err = reg.LeaseRole(engineRoleName, machID, engineRoleLeasePeriod)
if err != nil {
log.Errorf("Failed acquiring engine leadership: %v", err)
} else if cur == nil {
log.V(1).Infof("Unable to acquire engine leadership")
} else {
log.Infof("Acquired engine leadership")
}
return
}