package com.lambdaworks.redis;
import java.util.List;
import com.lambdaworks.redis.models.role.RedisNodeDescription;
/**
* Defines from which Redis nodes data is read.
*
* @author Mark Paluch
* @since 4.0
*/
public abstract class ReadFrom {
/**
* Setting to read from the master only.
*/
public static final ReadFrom MASTER = new ReadFromImpl.ReadFromMaster();
/**
* Setting to read preferred from the master and fall back to a slave if the master is not available.
*/
public static final ReadFrom MASTER_PREFERRED = new ReadFromImpl.ReadFromMasterPreferred();
/**
* Setting to read from the slave only.
*/
public static final ReadFrom SLAVE = new ReadFromImpl.ReadFromSlave();
/**
* Setting to read from the nearest node.
*/
public static final ReadFrom NEAREST = new ReadFromImpl.ReadFromNearest();
/**
* Chooses the nodes from the matching Redis nodes that match this read selector.
*
* @param nodes set of nodes that are suitable for reading
* @return List of {@link RedisNodeDescription}s that are selected for reading
*/
public abstract List<RedisNodeDescription> select(Nodes nodes);
/**
* Retrieve the {@link ReadFrom} preset by name.
*
* @param name the name of the read from setting
* @return the {@link ReadFrom} preset
* @throws IllegalArgumentException if {@code name} is empty, {@literal null} or the {@link ReadFrom} preset is unknown.
*/
public static ReadFrom valueOf(String name) {
if (LettuceStrings.isEmpty(name)) {
throw new IllegalArgumentException("Name must not be empty");
}
if (name.equalsIgnoreCase("master")) {
return MASTER;
}
if (name.equalsIgnoreCase("masterPreferred")) {
return MASTER_PREFERRED;
}
if (name.equalsIgnoreCase("slave")) {
return SLAVE;
}
if (name.equalsIgnoreCase("nearest")) {
return NEAREST;
}
throw new IllegalArgumentException("ReadFrom " + name + " not supported");
}
/**
* Descriptor of nodes that are available for the current read operation.
*/
public interface Nodes extends Iterable<RedisNodeDescription> {
/**
* Returns the list of nodes that are applicable for the read operation. The list is ordered by latency.
*
* @return the collection of nodes that are applicable for reading.
*
*/
List<RedisNodeDescription> getNodes();
}
}