Class LeaderElector

  • public class LeaderElector
    extends Object
    Leader Election process. This class contains the logic by which a leader is chosen. First call * setup(ElectionContext) to ensure the election process is init'd. Next call joinElection(ElectionContext, boolean) to start the leader election. The implementation follows the classic ZooKeeper recipe of creating an ephemeral, sequential node for each candidate and then looking at the set of such nodes - if the created node is the lowest sequential node, the candidate that created the node is the leader. If not, the candidate puts a watch on the next lowest node it finds, and if that node goes down, starts the whole process over by checking if it's the lowest sequential node, etc.
    • Constructor Detail

      • LeaderElector

        public LeaderElector​(SolrZkClient zkClient)
      • LeaderElector

        public LeaderElector​(SolrZkClient zkClient,
                             Map<,​ElectionContext> electionContexts)
    • Method Detail

      • getSeq

        public static int getSeq​(String nStringSequence)
        Returns int given String of form n_0000000001 or n_0000000003, etc.
        sequence number
      • getNodeName

        public static String getNodeName​(String nStringSequence)
      • joinElection

        public int joinElection​(ElectionContext context,
                                boolean replacement,
                                boolean joinAtHead)
                         throws org.apache.zookeeper.KeeperException,
        Begin participating in the election process. Gets a new sequential number and begins watching the node with the sequence number before it, unless it is the lowest number, in which case, initiates the leader process. If the node that is watched goes down, check if we are the new lowest node, else watch the next lowest numbered node.
        sequential node number
      • sortSeqs

        public static void sortSeqs​(List<String> seqs)
        Sort n string sequence list.