// acquireOrRenewLease either races to acquire a new master lease, or update the existing master's lease
// returns true if we have the lease, and an error if one occurs.
// TODO: use the master election utility once it is merged in.
func (c *Config) acquireOrRenewLease(etcdClient *etcd.Client) (bool, error) {
result, err := etcdClient.Get(c.key, false, false)
if err != nil {
if tools.IsEtcdNotFound(err) {
// there is no current master, try to become master, create will fail if the key already exists
_, err := etcdClient.Create(c.key, c.whoami, c.ttl)
if err != nil {
return false, err
}
c.lastLease = time.Now()
return true, nil
}
return false, err
}
if result.Node.Value == c.whoami {
glog.Infof("key already exists, we are the master (%s)", result.Node.Value)
// we extend our lease @ 1/2 of the existing TTL, this ensures the master doesn't flap around
if result.Node.Expiration.Sub(time.Now()) < time.Duration(c.ttl/2)*time.Second {
_, err := etcdClient.CompareAndSwap(c.key, c.whoami, c.ttl, c.whoami, result.Node.ModifiedIndex)
if err != nil {
return false, err
}
}
c.lastLease = time.Now()
return true, nil
}
glog.Infof("key already exists, the master is %s, sleeping.", result.Node.Value)
return false, nil
}
// setCommandFunc executes the "set" command.
func setCommandFunc(cmd *cobra.Command, args []string, client *etcd.Client) (*etcd.Response, error) {
if len(args) == 0 {
return nil, errors.New("Key required")
}
key := args[0]
value, err := argOrStdin(args, os.Stdin, 1)
if err != nil {
return nil, errors.New("Value required")
}
ttl := ttlFlag
prevValue := swapWithValueFlag
prevIndex := swapWithIndexFlag
if prevValue == "" && prevIndex == 0 {
return client.Set(key, value, uint64(ttl))
} else {
return client.CompareAndSwap(key, value, uint64(ttl), prevValue, uint64(prevIndex))
}
}
func CASEpoch(client *etcd.Client, appname string, prevEpoch, epoch uint64) error {
prevEpochStr := strconv.FormatUint(prevEpoch, 10)
epochStr := strconv.FormatUint(epoch, 10)
_, err := client.CompareAndSwap(EpochPath(appname), epochStr, 0, prevEpochStr, 0)
return err
}