Hi I am pretty new to the concept of Hadoop High Availability,I have done all the basic configurations needed for High Availability.When I manually killed the namenode process in one machine,the other node became active and this node went to standby mode.But when I shutdown the machine which has active node running,other node is not going to active state. Any help is appreciated
thanks in advance.
It may be that when you kill the process, the name node goes into graceful shutdown which includes notifying the other name node to take it's place, which the other one does immediately.
On the other hand, when you shut down the machine, it may be that graceful shut down of name node is not executed, and so the other name node does not yet know that it should take over. Given enough time though, it should.
As far as I am concerned, if the node 'dies' in a unspected way, it will stop sending the heartbeat to it's zookeeper, so you must give enough time to that process (Zookeeper) to ensure the active NameNode is dead.
On a scenario with only NameNode process dying, there is another process in that machine, 'Failover controller' that will notify of NameNode death to the passive one, that is why it is a fast thing.
Please take a look at this thread, since it is well written.
