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watch.go
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watch.go
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// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package subnet
import (
"time"
log "github.com/coreos/flannel/Godeps/_workspace/src/github.com/golang/glog"
"github.com/coreos/flannel/Godeps/_workspace/src/golang.org/x/net/context"
)
// WatchLeases performs a long term watch of the given network's subnet leases
// and communicates addition/deletion events on receiver channel. It takes care
// of handling "fall-behind" logic where the history window has advanced too far
// and it needs to diff the latest snapshot with its saved state and generate events
func WatchLeases(ctx context.Context, sm Manager, network string, receiver chan []Event) {
lw := &leaseWatcher{}
var cursor interface{}
for {
res, err := sm.WatchLeases(ctx, network, cursor)
if err != nil {
if err == context.Canceled || err == context.DeadlineExceeded {
return
}
log.Errorf("Watch subnets: %v", err)
time.Sleep(time.Second)
continue
}
cursor = res.Cursor
batch := []Event{}
if len(res.Snapshot) > 0 {
batch = lw.reset(res.Snapshot)
} else {
batch = lw.update(res.Events)
}
if batch != nil {
receiver <- batch
}
}
}
type leaseWatcher struct {
leases []Lease
}
func (lw *leaseWatcher) reset(leases []Lease) []Event {
batch := []Event{}
for _, nl := range leases {
found := false
for i, ol := range lw.leases {
if ol.Subnet.Equal(nl.Subnet) {
lw.leases = deleteLease(lw.leases, i)
found = true
break
}
}
if !found {
// new lease
batch = append(batch, Event{SubnetAdded, nl})
}
}
// everything left in sm.leases has been deleted
for _, l := range lw.leases {
batch = append(batch, Event{SubnetRemoved, l})
}
lw.leases = leases
return batch
}
func (lw *leaseWatcher) update(events []Event) []Event {
batch := []Event{}
for _, e := range events {
switch e.Type {
case SubnetAdded:
batch = append(batch, lw.add(&e.Lease))
case SubnetRemoved:
batch = append(batch, lw.remove(&e.Lease))
}
}
return batch
}
func (lw *leaseWatcher) add(lease *Lease) Event {
for i, l := range lw.leases {
if l.Subnet.Equal(lease.Subnet) {
lw.leases[i] = *lease
return Event{SubnetAdded, lw.leases[i]}
}
}
lw.leases = append(lw.leases, *lease)
return Event{SubnetAdded, lw.leases[len(lw.leases)-1]}
}
func (lw *leaseWatcher) remove(lease *Lease) Event {
for i, l := range lw.leases {
if l.Subnet.Equal(lease.Subnet) {
lw.leases = deleteLease(lw.leases, i)
return Event{SubnetRemoved, l}
}
}
log.Errorf("Removed subnet (%s) was not found", lease.Subnet)
return Event{SubnetRemoved, *lease}
}
func deleteLease(l []Lease, i int) []Lease {
l[i], l = l[len(l)-1], l[:len(l)-1]
return l
}