Package org.apache.solr.cloud

Class ZkShardTerms

java.lang.Object
org.apache.solr.cloud.ZkShardTerms
All Implemented Interfaces:
AutoCloseable
public class ZkShardTerms extends Object implements AutoCloseable
Class used for interact with a ZK term node. Each ZK term node relates to a shard of a collection and have this format (in json)

{ "replicaNodeName1" : 1, "replicaNodeName2" : 2, .. }

The values correspond to replicas are called terms. Only replicas with highest term value are considered up to date and be able to become leader and serve queries.

Terms can only updated in two strict ways:

  • A replica sets its term equals to leader's term
  • The leader increase its term and some other replicas by 1
This class should not be reused after Watcher.Event.KeeperState.Expired event

  • Constructor Details

    • ZkShardTerms

      public ZkShardTerms(String collection, String shard, org.apache.solr.common.cloud.SolrZkClient zkClient)

  • Method Details

    • ensureTermsIsHigher

      public void ensureTermsIsHigher(String leader, Set<String> replicasNeedingRecovery)
      Ensure that terms are higher than some replica's terms. If the current leader is attempting to give up leadership and included in replicasNeedingRecovery, then other replicas that are in sync will have higher terms, while the leader will stay where it is.
      Parameters:
      leader - coreNodeName of leader
      replicasNeedingRecovery - set of replicas in which their terms should be lower than leader's term

    • getShardTerms

      public ShardTerms getShardTerms()

    • canBecomeLeader

      public boolean canBecomeLeader(String coreNodeName)
      Can this replica become leader?
      Parameters:
      coreNodeName - of the replica
      Returns:
      true if this replica can become leader, false if otherwise

    • skipSendingUpdatesTo

      public boolean skipSendingUpdatesTo(String coreNodeName)
      Should leader skip sending updates to this replica?
      Parameters:
      coreNodeName - of the replica
      Returns:
      true if this replica has term equals to leader's term, false if otherwise

    • registered

      public boolean registered(String coreNodeName)
      Did this replica registered its term? This is a sign to check f
      Parameters:
      coreNodeName - of the replica
      Returns:
      true if this replica registered its term, false if otherwise

    • close

      public void close()
      Specified by:
      close in interface AutoCloseable

    • setTermEqualsToLeader

      public void setTermEqualsToLeader(String coreNodeName)
      Set a replica's term equals to leader's term, and remove recovering flag of a replica. This call should only be used by CollectionParams.CollectionAction.FORCELEADER
      Parameters:
      coreNodeName - of the replica

    • setTermToZero

      public void setTermToZero(String coreNodeName)
      Set a replica's term to 0. If the term does not exist, create it.
      Parameters:
      coreNodeName - of the replica

    • startRecovering

      public void startRecovering(String coreNodeName)
      Mark coreNodeName as recovering

    • doneRecovering

      public void doneRecovering(String coreNodeName)
      Mark coreNodeName as finished recovering

    • isRecovering

      public boolean isRecovering(String name)

    • ensureHighestTermsAreNotZero

      public void ensureHighestTermsAreNotZero()
      When first updates come in, all replicas have some data now, so we must switch from term 0 (registered) to 1 (have some data)

    • getHighestTerm

      public long getHighestTerm()

    • getTerm

      public long getTerm(String coreNodeName)

    • refreshTerms

      public void refreshTerms()
      Fetch latest terms from ZK