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Add pro-active TTL based lease releasing when we can't communicate with etcd.

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This commit is contained in:
Brendan Burns 2015-06-03 21:37:04 -07:00
parent fc742f8c13
commit 6b837ae004
1 changed files with 20 additions and 7 deletions
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27
contrib/pod-master/podmaster.go
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@ -42,6 +42,7 @@ type Config struct {
src string src string
dest string dest string
sleep time.Duration sleep time.Duration
lastLease time.Time
} }
// runs the election loop. never returns. // runs the election loop. never returns.
@ -50,7 +51,13 @@ func (c *Config) leaseAndUpdateLoop(etcdClient *etcd.Client) {
master, err := c.acquireOrRenewLease(etcdClient) master, err := c.acquireOrRenewLease(etcdClient)
if err != nil { if err != nil {
glog.Errorf("Error in master election: %v", err) glog.Errorf("Error in master election: %v", err)
continue if uint64(time.Now().Sub(c.lastLease).Seconds()) < c.ttl {
continue
}
// Our lease has expired due to our own accounting, pro-actively give it
// up, even if we couldn't contact etcd.
glog.Infof("Too much time has elapsed, giving up lease.")
master = false
} }
if err := c.update(master); err != nil { if err := c.update(master); err != nil {
glog.Errorf("Error updating files: %v", err) glog.Errorf("Error updating files: %v", err)
@ -64,13 +71,17 @@ func (c *Config) leaseAndUpdateLoop(etcdClient *etcd.Client) {
// TODO: use the master election utility once it is merged in. // TODO: use the master election utility once it is merged in.
func (c *Config) acquireOrRenewLease(etcdClient *etcd.Client) (bool, error) { func (c *Config) acquireOrRenewLease(etcdClient *etcd.Client) (bool, error) {
result, err := etcdClient.Get(c.key, false, false) result, err := etcdClient.Get(c.key, false, false)
if tools.IsEtcdNotFound(err) { if err != nil {
// there is no current master, try to become master, create will fail if the key already exists if tools.IsEtcdNotFound(err) {
_, err := etcdClient.Create(c.key, c.whoami, c.ttl) // there is no current master, try to become master, create will fail if the key already exists
if err != nil { _, err := etcdClient.Create(c.key, c.whoami, c.ttl)
return false, err if err != nil {
return false, err
}
c.lastLease = time.Now()
return true, nil
} }
return true, nil return false, err
} }
if result.Node.Value == c.whoami { if result.Node.Value == c.whoami {
glog.Infof("key already exists, we are the master (%s)", result.Node.Value) glog.Infof("key already exists, we are the master (%s)", result.Node.Value)
@ -81,6 +92,7 @@ func (c *Config) acquireOrRenewLease(etcdClient *etcd.Client) (bool, error) {
return false, err return false, err
} }
} }
c.lastLease = time.Now()
return true, nil return true, nil
} }
glog.Infof("key already exists, the master is %s, sleeping.", result.Node.Value) glog.Infof("key already exists, the master is %s, sleeping.", result.Node.Value)
@ -97,6 +109,7 @@ func (c *Config) update(master bool) error {
switch { switch {
case master && !exists: case master && !exists:
return copyFile(c.src, c.dest) return copyFile(c.src, c.dest)
// TODO: validate sha hash for the two files and overwrite if dest is different than src.
case !master && exists: case !master && exists:
return os.Remove(c.dest) return os.Remove(c.dest)
} }