func (c *Connection) CreateEphemeral(path string, node client.Node) (string, error) {
if c.conn == nil {
return "", client.ErrConnectionClosed
}
p := join(c.basePath, path)
bytes, err := json.Marshal(node)
if err != nil {
return "", client.ErrSerialization
}
path, err = c.conn.CreateProtectedEphemeralSequential(p, bytes, zklib.WorldACL(zklib.PermAll))
if err == zklib.ErrNoNode {
// Create parent node.
parts := strings.Split(p, "/")
pth := ""
if len(parts) > 1 {
for _, p := range parts[1 : len(parts)-1] {
pth += "/" + p
_, err = c.conn.Create(pth, []byte{}, 0, zklib.WorldACL(zklib.PermAll))
if err != nil && err != zklib.ErrNodeExists {
return "", xlateError(err)
}
}
path, err = c.conn.CreateProtectedEphemeralSequential(p, bytes, zklib.WorldACL(zklib.PermAll))
}
}
if err == nil {
node.SetVersion(&zklib.Stat{})
}
return path, xlateError(err)
}
// Create places data at the node at the given path.
func (c *Connection) Create(path string, node client.Node) error {
if c.conn == nil {
return client.ErrConnectionClosed
}
p := join(c.basePath, path)
bytes, err := json.Marshal(node)
if err != nil {
return client.ErrSerialization
}
_, err = c.conn.Create(p, bytes, 0, zklib.WorldACL(zklib.PermAll))
if err == zklib.ErrNoNode {
// Create parent node.
parts := strings.Split(p, "/")
pth := ""
for _, p := range parts[1:] {
pth += "/" + p
_, err = c.conn.Create(pth, []byte{}, 0, zklib.WorldACL(zklib.PermAll))
if err != nil && err != zklib.ErrNodeExists {
return xlateError(err)
}
}
}
if err == nil {
node.SetVersion(&zklib.Stat{})
}
return xlateError(err)
}
// TakeLead attempts to aquire the leader role. When aquired it return a
// channel on the leader node so the caller can react to changes in zookeeper
func (l *Leader) TakeLead() (echan <-chan client.Event, err error) {
if l.lockPath != "" {
return nil, ErrDeadlock
}
prefix := l.prefix()
data, err := json.Marshal(l.node)
if err != nil {
return nil, xlateError(err)
}
path := ""
for i := 0; i < 3; i++ {
if l.c.conn == nil {
// TODO: race condition exists
return nil, fmt.Errorf("connection lost")
}
path, err = l.c.conn.CreateProtectedEphemeralSequential(prefix, data, zklib.WorldACL(zklib.PermAll))
if err == zklib.ErrNoNode {
// Create parent node.
parts := strings.Split(l.path, "/")
pth := ""
for _, p := range parts[1:] {
pth += "/" + p
if l.c.conn == nil {
// TODO: race condition exists
return nil, fmt.Errorf("connection lost")
}
_, err := l.c.conn.Create(pth, []byte{}, 0, zklib.WorldACL(zklib.PermAll))
if err != nil && err != zklib.ErrNodeExists {
return nil, xlateError(err)
}
}
} else if err == nil {
break
} else {
return nil, xlateError(err)
}
}
if err != nil {
return nil, xlateError(err)
}
seq, err := parseSeq(path)
if err != nil {
return nil, xlateError(err)
}
// This implements the leader election recipe recommeded by ZooKeeper
// https://zookeeper.apache.org/doc/trunk/recipes.html#sc_leaderElection
for {
children, _, err := l.c.conn.Children(l.path)
if err != nil {
return nil, xlateError(err)
}
lowestSeq := seq
var prevSeq uint64
prevSeqPath := ""
// find the lowest sequenced node
for _, p := range children {
s, err := parseSeq(p)
if err != nil {
return nil, xlateError(err)
}
if s < lowestSeq {
lowestSeq = s
}
if s < seq && s > prevSeq {
prevSeq = s
prevSeqPath = p
}
}
if seq == lowestSeq {
// Acquired the lock
break
}
// Wait on the node next in line for the lock
_, _, ch, err := l.c.conn.GetW(l.path + "/" + prevSeqPath)
if err != nil && err != zklib.ErrNoNode {
return nil, xlateError(err)
} else if err != nil && err == zklib.ErrNoNode {
// try again
continue
}
ev := <-ch
if ev.Err != nil {
return nil, xlateError(ev.Err)
}
}
glog.Infof("w %s", path)
_, _, event, err := l.c.conn.GetW(path)
glog.Infof("calling wait on %s: %s", path, err)
if err == nil {
l.seq = seq
l.lockPath = path
} else {
l.c.Delete(path)
}
return toClientEvent(event), xlateError(err)
}
// NewLock returns a managed lock object at the given path bound to the current
// connection.
func (c *Connection) NewLock(path string) client.Lock {
return &Lock{
lock: zklib.NewLock(c.conn, join(c.basePath, path), zklib.WorldACL(zklib.PermAll)),
}
}