// Create a node if it doesn't exist, otherwise do nothing
func (zk *ZkConn) Touch(nodePath string) (string, error) {
if stat, err := zk.Exists(nodePath); err == nil && stat != nil {
return nodePath, nil
}
// touch all directores above nodePath because zookeeper sucks
dir := path.Dir(nodePath)
if dir != "/" && dir != "." {
zk.Touch(dir)
}
return zk.Create(nodePath, "", 0, gozk.WorldACL(gozk.PERM_ALL))
}
func rlock(conn *gozk.Conn, basePath, prefix string, checkPrefix []string) (lock string, err error) {
// step 1
lock, err = conn.Create(path.Join(basePath, prefix), "", gozk.EPHEMERAL|gozk.SEQUENCE,
gozk.WorldACL(gozk.PERM_ALL))
if err != nil {
return lock, err
}
for {
// step 2
children, _, err := conn.Children(basePath)
if err != nil {
return lock, err
}
// step 3
if children == nil || len(children) == 0 {
return lock, errors.New("get children didn't return my lock")
}
// filter out non-lock children and extract sequence numbers
filteredChildren := map[string]string{}
filteredChildrenKeys := []string{}
for _, v := range children {
for _, pfx := range checkPrefix {
if strings.HasPrefix(v, pfx) {
seqNum := strings.Replace(v, pfx, "", 1)
filteredChildren[seqNum] = v
filteredChildrenKeys = append(filteredChildrenKeys, seqNum)
break
}
}
}
sort.Strings(filteredChildrenKeys)
prevLock := ""
for _, seqNum := range filteredChildrenKeys {
if path.Base(lock) == filteredChildren[seqNum] {
break
}
prevLock = path.Join(basePath, filteredChildren[seqNum])
}
if prevLock == "" {
return lock, nil
}
// step 4
stat, watchCh, err := conn.ExistsW(prevLock)
if err != nil {
return lock, err
}
// step 5
if stat == nil {
continue
}
<-watchCh
}
return lock, nil
}