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, snitch`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `NetworkTopologyStrategy(java.lang.String keyspaceName, TokenMetadata tokenMetadata, IEndpointSnitch snitch, java.util.Map<java.lang.String,java.lang.String> configOptions)`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `java.util.List<java.net.InetAddress>` | `calculateNaturalEndpoints(Token searchToken, TokenMetadata tokenMetadata)` calculate endpoints in one pass through the tokens by tracking our progress in each DC.
    `java.util.Set<java.lang.String>` | `getDatacenters()`
    `int` | `getReplicationFactor()` calculate the RF based on strategy_options.
    `int` | `getReplicationFactor(java.lang.String dc)`
    `boolean` | `hasSameSettings(AbstractReplicationStrategy other)`
    `void` | `validateOptions()`

    - ### Methods inherited from class org.apache.cassandra.locator.AbstractReplicationStrategy

      `createReplicationStrategy, getAddressRanges, getAddressRanges, getCachedEndpoints, getClass, getNaturalEndpoints, getPendingAddressRanges, getPendingAddressRanges, getRangeAddresses, getWriteResponseHandler, recognizedOptions, validateReplicationFactor, validateReplicationStrategy`

    - ### 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 keyspaceName,
                                         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)

      calculate endpoints in one pass through the tokens by tracking our progress in each DC.
      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.RingPosition)`

    - #### 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`

    - #### hasSameSettings

          public boolean hasSameSettings(AbstractReplicationStrategy other)

      Overrides:
        `hasSameSettings` in class `AbstractReplicationStrategy`

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