ZOOKEEPER-3414 sync api throws NoNodeException when path is non-existent

[rabi-kumar]

As per ticket ZOOKEEPER-3414 while executing sync cmd NoNodeException should be thrown when path doesn't exist. To implement this I have used CliWrapperException and KeeperException.NoNodeException in the else condition of exec() present in SyncCommand.java

Please do let me know if the changes made make sense or if I have missed something.

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[HorizonNet]

Left some NITs

[anmolnar]

@ravowlga123 Issue has been reported my @maoling .
I had the assumption of this should be implemented on server side. There's no guarantee of somebody not deleting the node after getData call.

[rabi-kumar]

Hi @anmolnar if changes are not sufficient then I will look into zookeeper-server. Also would appreciate feedback from @maoling regarding this.

[maoling]

I had the assumption of this should be implemented on server side. There's no guarantee of somebody not deleting the node after getData call.

• Yes, it is. Implementing on client side really has that side effect, especially a delete after sync by another client, just before getData.

• Overall, sync + getData isn't a good api design and some issues in it(e.g sync isn't a quorum operation and cannot get updated data when network partitioned, so I create ZOOKEEPER-3600 to depreciate it by a new Linearizability Read api.)

• A base summary of current sync implementation, when the client calls the sync api to a follower server, follower pends the requestA(in the pendingSyncs) and forwards requestA to leader. when leader has no outstanding proposals(outstandingProposals), leader will send a SYNC message to follower, follower will commit requestA util it receives the SYNC from leader.

• For the server side fix:

FinalRequestProcessor
            case OpCode.sync: {
                xxxxxxxxxxxxxxxxxxxxxxxxxx
                path = syncRequest.getPath();
                DataNode n = zks.getZKDatabase().getNode(path);
                if (n == null) {
                    throw new KeeperException.NoNodeException();
                }
                rsp = new SyncResponse(path);
                xxxxxxxxxxxxxxxxxxxxxxxxxx
            }
SyncCommand:
            } else if (resultCode == KeeperException.Code.NONODE.intValue()) {
                throw new KeeperException.NoNodeException(path);
            } else

[rabi-kumar]

Hi @maoling Thank You for the detailed explanation. I really appreciate it. I will update the changes shortly as per your explanation.