## org.apache.cassandra.locator
Class NetworkTopologyStrategy

    java.lang.Object
      org.apache.cassandra.locator.AbstractReplicationStrategy
          org.apache.cassandra.locator.NetworkTopologyStrategy

    public class NetworkTopologyStrategy

extends AbstractReplicationStrategy

This Replication Strategy takes a property file that gives the intended replication factor in each datacenter. The sum total of the datacenter replication factor values should be equal to the keyspace replication factor.

So for example, if the keyspace replication factor is 6, the datacenter replication factors could be 3, 2, and 1 - so 3 replicas in one datacenter, 2 in another, and 1 in another - totalling 6.

This class also caches the Endpoints and invalidates the cache if there is a change in the number of tokens.

Field Summary

Fields inherited from class org.apache.cassandra.locator.AbstractReplicationStrategy
`configOptions, table`

Constructor Summary
`NetworkTopologyStrategy(java.lang.String table, TokenMetadata tokenMetadata, IEndpointSnitch snitch, java.util.Map<java.lang.String,java.lang.String> configOptions)`

Method Summary
`java.util.List<java.net.InetAddress>` `calculateNaturalEndpoints(Token searchToken, TokenMetadata tokenMetadata)` calculate the natural endpoints for the given token
`java.util.Set<java.lang.String>` `getDatacenters()`
`int` `getReplicationFactor()` calculate the RF based on strategy_options.
`int` `getReplicationFactor(java.lang.String dc)`
`void` `validateOptions()`

Methods inherited from class org.apache.cassandra.locator.AbstractReplicationStrategy
`cacheEndpoint, clearEndpointCache, createReplicationStrategy, createReplicationStrategy, getAddressRanges, getAddressRanges, getCachedEndpoints, getClass, getNaturalEndpoints, getPendingAddressRanges, getRangeAddresses, getWriteResponseHandler, invalidateCachedTokenEndpointValues, validateReplicationFactor`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### NetworkTopologyStrategy

    public NetworkTopologyStrategy(java.lang.String table,
                                   TokenMetadata tokenMetadata,
                                   IEndpointSnitch snitch,
                                   java.util.Map<java.lang.String,java.lang.String> configOptions)
                            throws ConfigurationException

Throws:
  `ConfigurationException`

Method Detail

### calculateNaturalEndpoints

    public java.util.List<java.net.InetAddress> calculateNaturalEndpoints(Token searchToken,
                                                                          TokenMetadata tokenMetadata)

  Description copied from class: `AbstractReplicationStrategy`
  calculate the natural endpoints for the given token

  Specified by:
    `calculateNaturalEndpoints` in class `AbstractReplicationStrategy`
  Parameters:
    `searchToken` - the token the natural endpoints are requested for
  Returns:
    a copy of the natural endpoints for the given token
  See Also:
    `AbstractReplicationStrategy.getNaturalEndpoints(org.apache.cassandra.dht.Token)`

### getReplicationFactor

    public int getReplicationFactor()

  Description copied from class: `AbstractReplicationStrategy`
  calculate the RF based on strategy_options. When overwriting, ensure that this get() is FAST, as this is called often.

  Specified by:
    `getReplicationFactor` in class `AbstractReplicationStrategy`
  Returns:
    the replication factor

### getReplicationFactor

    public int getReplicationFactor(java.lang.String dc)

### getDatacenters

    public java.util.Set<java.lang.String> getDatacenters()

### validateOptions

    public void validateOptions()
                         throws ConfigurationException

  Specified by:
    `validateOptions` in class `AbstractReplicationStrategy`
  Throws:
    `ConfigurationException`

Copyright © 2012 The Apache Software Foundation