// 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.WorldACL(zookeeper.PERM_ALL))
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)
}
// WaitForMastership is part of the topo.MasterParticipation interface.
func (mp *zkMasterParticipation) WaitForMastership() (context.Context, error) {
electionPath := path.Join(GlobalElectionPath, mp.name)
// fast path if Stop was already called
select {
case <-mp.stop:
close(mp.done)
return nil, topo.ErrInterrupted
default:
}
// create the current proposal
proposal, err := mp.zkts.zconn.Create(electionPath+"/", mp.id, zookeeper.FlagSequence|zookeeper.FlagEphemeral, zookeeper.WorldACL(zk.PermFile))
if err != nil {
return nil, fmt.Errorf("cannot create proposal file in %v: %v", electionPath, err)
}
// Wait until we are it, or we are interrupted. Using a
// small-ish time out so it gets exercised faster (as opposed
// to crashing after a day of use).
for {
err = zk.ObtainQueueLock(mp.zkts.zconn, proposal, 5*time.Minute, mp.stop)
if err == nil {
// we got the lock, move on
break
}
if err == zk.ErrInterrupted {
// mp.stop is closed, we should return
close(mp.done)
return nil, topo.ErrInterrupted
}
if err == zk.ErrTimeout {
// we try again
continue
}
// something else went wrong
return nil, err
}
// we got the lock, create our background context
ctx, cancel := context.WithCancel(context.Background())
go mp.watchMastership(proposal, cancel)
return ctx, nil
}
func cmdQlock(args []string) {
zkPath := fixZkPath(args[0])
timeout, err := time.ParseDuration(*lockWaitTimeout)
if err != nil {
log.Fatalf("qlock: invalid timeout %v: %v", *lockWaitTimeout, err)
}
sigRecv := make(chan os.Signal, 1)
interrupted := make(chan struct{})
signal.Notify(sigRecv, os.Interrupt)
go func() {
<-sigRecv
close(interrupted)
}()
err = zk.ObtainQueueLock(zconn, zkPath, timeout, interrupted)
if err != nil {
log.Fatalf("qlock: error %v: %v", zkPath, err)
}
fmt.Printf("qlock: locked %v\n", zkPath)
}
// 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(ctx context.Context, actionDir, contents string) (string, error) {
// create the action path
actionPath, err := zkts.zconn.Create(actionDir, contents, zookeeper.FlagSequence|zookeeper.FlagEphemeral, zookeeper.WorldACL(zk.PermFile))
if err != nil {
return "", convertError(err)
}
// get the timeout from the context
var timeout time.Duration
deadline, ok := ctx.Deadline()
if !ok {
// enforce a default timeout
timeout = 30 * time.Second
} else {
timeout = deadline.Sub(time.Now())
}
// get the interrupted channel from context or don't interrupt
interrupted := ctx.Done()
if interrupted == nil {
interrupted = make(chan struct{})
}
err = zk.ObtainQueueLock(zkts.zconn, actionPath, timeout, interrupted)
if err != nil {
var errToReturn error
switch err {
case zk.ErrTimeout:
errToReturn = topo.ErrTimeout
case zk.ErrInterrupted:
// the context failed, get the error from it
if ctx.Err() == context.DeadlineExceeded {
errToReturn = topo.ErrTimeout
} else {
errToReturn = topo.ErrInterrupted
}
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
}