// lockForAction creates the action node in zookeeper, waits for the
// queue lock, displays a nice error message if it cant get it
func (zkts *Server) lockForAction(actionDir, contents string, timeout time.Duration, interrupted chan struct{}) (string, error) {
// create the action path
actionPath, err := zkts.zconn.Create(actionDir, contents, zookeeper.SEQUENCE|zookeeper.EPHEMERAL, zookeeper.WorldACL(zk.PERM_FILE))
if err != nil {
return "", err
}
err = zk.ObtainQueueLock(zkts.zconn, actionPath, timeout, interrupted)
if err != nil {
var errToReturn error
switch err {
case zk.ErrInterrupted:
errToReturn = topo.ErrInterrupted
case zk.ErrTimeout:
errToReturn = topo.ErrTimeout
default:
errToReturn = fmt.Errorf("failed to obtain action lock: %v %v", actionPath, err)
}
// Regardless of the reason, try to cleanup.
log.Warningf("Failed to obtain action lock: %v", err)
zkts.zconn.Delete(actionPath, -1)
// Show the other actions in the directory
dir := path.Dir(actionPath)
children, _, err := zkts.zconn.Children(dir)
if err != nil {
log.Warningf("Failed to get children of %v: %v", dir, err)
return "", errToReturn
}
if len(children) == 0 {
log.Warningf("No other action running, you may just try again now.")
return "", errToReturn
}
childPath := path.Join(dir, children[0])
data, _, err := zkts.zconn.Get(childPath)
if err != nil {
log.Warningf("Failed to get first action node %v (may have just ended): %v", childPath, err)
return "", errToReturn
}
log.Warningf("------ Most likely blocking action: %v\n%v", childPath, data)
return "", errToReturn
}
return actionPath, nil
}
func cmdQlock(subFlags *flag.FlagSet, args []string) {
var (
lockWaitTimeout = subFlags.Duration("lock-wait-timeout", 0, "wait for a lock for the specified duration")
)
subFlags.Parse(args)
zkPath := fixZkPath(subFlags.Arg(0))
sigRecv := make(chan os.Signal, 1)
interrupted := make(chan struct{})
signal.Notify(sigRecv, os.Interrupt)
go func() {
<-sigRecv
close(interrupted)
}()
if err := zk.ObtainQueueLock(zconn, zkPath, *lockWaitTimeout, interrupted); err != nil {
log.Fatalf("qlock: error %v: %v", zkPath, err)
}
fmt.Printf("qlock: locked %v\n", zkPath)
}