This is a known bug in helix. https://issues.apache.org/jira/browse/HELIX-123
The problem is we are comparing the instance name of the controller but not the session id, so if you start two controllers of the same name, isLeader() return true. We will fix it shortly. Thanks, Jason From: Lance Co Ting Keh <[email protected]<mailto:[email protected]>> Reply-To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Date: Friday, June 21, 2013 1:39 PM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: Re: Controller fault tolerance Hi Kishore, I tried starting two controllers programmatically like you mentioned: controllerManager = HelixControllerMain.startHelixController(zkAddress, clusterName, "controller", HelixControllerMain.STANDALONE); I then called isLeader() on the both managers (http://helix.incubator.apache.org/apidocs/reference/org/apache/helix/HelixManager.html#isLeader()). and both of them returned true. They're obviously both on the same zookeeper instance, and on the same cluster. The controllers are running and so im not sure whether or not its actually leader electing properly, or I'm misinterpreting the isLeader() function Thanks Lance On Mon, Jun 17, 2013 at 9:22 AM, Manikumar Reddy <[email protected]<mailto:[email protected]>> wrote: Hi Kishore, Thanks for the quick response. Regards, Kumar On Mon, Jun 17, 2013 at 8:18 PM, kishore g <[email protected]<mailto:[email protected]>> wrote: Hi Kumar, You can start multiple controllers and only one of them will be active and rest of them will be in standby mode. If the active controller fails, one of the standby will become active and start managing the cluster. You can start the controllers either using command line or programmatically. command line ./run-helix-controller.sh --zkSvr localhost:2199 --cluster <clustername> using Helix api controllerManager = HelixControllerMain.startHelixController(zkAddress, clusterName, "controller", HelixControllerMain.STANDALONE); Hope this helps. thanks, Kishore G On Mon, Jun 17, 2013 at 7:01 AM, Manikumar Reddy <[email protected]<mailto:[email protected]>> wrote: Hi, I am trying to understand the Helix Controller/Cluster manager fault tolerance mechanism. Single Controller will become Single-Point-Failure. So what are the available options/techniques to achieve controller fault tolerance? Any pointers/recipes/code snippets? Regards, Kumar
