-Re: zookeeper leadership election example application
Ted Dunning 2011-11-26, 07:37
I think that the code also needs:
* comments. You need to put some java docs in that say what the different
classes and methods are intended to do. External documentation is nice,
but hardly sufficient.
* global handling of disconnection and pausing of masters during a
* a description of how you think you are handling error conditions
* tests that demonstrate that you handle error conditions
I would also take issue with Jordan's suggestion for retry logic. With
ephemeral sequential node, retries are very dangerous in certain corner
failure modes. This is the primary reason that I prefer the single file
leader election method. With a reasonable number of masters (the most
common case) this is completely sufficient since the herd effect isn't a
problem for such a small herd.
On Fri, Nov 25, 2011 at 10:17 PM, Jordan Zimmerman
> A few comments:
> * NodeMonitor.createRootIfNotExists() should catch NodeExists. In the case
> of multiple clients, this is a possibility.
> * I'd add a start method and create the ZooKeeper instance there. This
> gives users a chance to set a listener so as to receive all messages.
> * All ZooKeeper operations should be in some kind of retry loop. The
> client can lose connection to a given server but successfully reconnect to
> another one in the cluster.
> * When creating the Znode, it can succeed on the server but fail to return
> the result to the client. On a Disconnect/Session exception, you should
> retry and then call getChildren and search for your node.
> On 11/25/11 2:45 AM, "Olivier Van Acker" <[EMAIL PROTECTED]> wrote:
> >I've written a example app on how to do implement leadership election in
> >with zookeeper
> >Is there anyone on the list who'd like to review my app and if it needs
> >improvement or not?
> >the app is on github:
> >and explained how it works on my blog: