org.apache.zookeeper.server.quorum.flexible
Class QuorumHierarchical

java.lang.Object
  org.apache.zookeeper.server.quorum.flexible.QuorumHierarchical

All Implemented Interfaces:

QuorumVerifier

public class QuorumHierarchical
extends Object
implements QuorumVerifier

This class implements a validator for hierarchical quorums. With this construction, zookeeper servers are split into disjoint groups, and each server has a weight. We obtain a quorum if we get more than half of the total weight of a group for a majority of groups. The configuration of quorums uses two parameters: group and weight. Groups are sets of ZooKeeper servers, and we set a group by passing a colon-separated list of server ids. It is also necessary to assign weights to server. Here is an example of a configuration that creates three groups and assigns a weight of 1 to each server: group.1=1:2:3 group.2=4:5:6 group.3=7:8:9 weight.1=1 weight.2=1 weight.3=1 weight.4=1 weight.5=1 weight.6=1 weight.7=1 weight.8=1 weight.9=1 Note that it is still necessary to define peers using the server keyword.

Constructor Summary

QuorumHierarchical(int numGroups, HashMap<Long,Long> serverWeight, HashMap<Long,Long> serverGroup)
This contructor takes the two hash maps needed to enable validating quorums.

QuorumHierarchical(Properties qp)
This constructor takes a set of properties.

QuorumHierarchical(String filename)
This contructor requires the quorum configuration to be declared in a separate file, and it takes the file as an input parameter.

Method Summary

boolean	containsQuorum(HashSet<Long> set) Verifies if a given set is a quorum.
long	getWeight(long id) Returns the weight of a server.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

QuorumHierarchical

public QuorumHierarchical(String filename)
                   throws QuorumPeerConfig.ConfigException

This contructor requires the quorum configuration to be declared in a separate file, and it takes the file as an input parameter.

Throws:

QuorumPeerConfig.ConfigException

QuorumHierarchical

public QuorumHierarchical(Properties qp)
                   throws QuorumPeerConfig.ConfigException

This constructor takes a set of properties. We use it in the unit test for this feature.

Throws:

QuorumPeerConfig.ConfigException

QuorumHierarchical

public QuorumHierarchical(int numGroups,
                          HashMap<Long,Long> serverWeight,
                          HashMap<Long,Long> serverGroup)

This contructor takes the two hash maps needed to enable validating quorums. We use it with QuorumPeerConfig. That is, we declare weights and groups in the server configuration file along with the other parameters.

Parameters:

numGroups -

serverWeight -

serverGroup -

Method Detail

getWeight

public long getWeight(long id)

Returns the weight of a server.

Specified by:

getWeight in interface QuorumVerifier

Parameters:

id -

containsQuorum

public boolean containsQuorum(HashSet<Long> set)

Verifies if a given set is a quorum.

Specified by:

containsQuorum in interface QuorumVerifier