ReadFrom (Lettuce 6.5.5.RELEASE API)

java.lang.Object
- io.lettuce.core.ReadFrom

```
public abstract class ReadFrom
extends Object
```
Defines from which Redis nodes data is read.

Since:

4.0

Author:

Mark Paluch, Ryosuke Hasebe, Omer Cilingir, Yohei Ueki

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static interface ReadFrom.Nodes
Descriptor of nodes that are available for the current read operation.

Nested Classes
Modifier and Type	Class and Description
`static interface`	`ReadFrom.Nodes` Descriptor of nodes that are available for the current read operation.

Field Summary

Fields
Modifier and Type	Field and Description
`static ReadFrom`	`ANY` Setting to read from any node.
`static ReadFrom`	`ANY_REPLICA` Setting to read from any replica node.
`static ReadFrom`	`LOWEST_LATENCY` Setting to read from the node with the lowest latency during topology discovery.
`static ReadFrom`	`MASTER` Setting to read from the upstream only.
`static ReadFrom`	`MASTER_PREFERRED` Setting to read preferred from the upstream and fall back to a replica if the master is not available.
`static ReadFrom`	`NEAREST` Deprecated. since 6.1.7 as we're renaming this setting to `LOWEST_LATENCY` for more clarity what this setting actually represents.
`static ReadFrom`	`REPLICA` Setting to read from the replica only.
`static ReadFrom`	`REPLICA_PREFERRED` Setting to read preferred from replica and fall back to upstream if no replica is available.
`static ReadFrom`	`SLAVE` Deprecated. renamed to `REPLICA`.
`static ReadFrom`	`SLAVE_PREFERRED` Deprecated. Renamed to `REPLICA_PREFERRED`.
`static ReadFrom`	`UPSTREAM` Setting to read from the upstream only.
`static ReadFrom`	`UPSTREAM_PREFERRED` Setting to read preferred from the upstream and fall back to a replica if the upstream is not available.

Constructor Summary

Constructors
Constructor and Description

ReadFrom()

Constructors
Constructor and Description
`ReadFrom()`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`protected boolean`	`isOrderSensitive()` Returns whether this `ReadFrom` requires ordering of the resulting `nodes`.
`static ReadFrom`	`regex(Pattern pattern)` Read from any node that has `RedisURI` matching with the given pattern.
`static ReadFrom`	`regex(Pattern pattern, boolean orderSensitive)` Read from any node that has `RedisURI` matching with the given pattern.
`abstract List<RedisNodeDescription>`	`select(ReadFrom.Nodes nodes)` Chooses the nodes from the matching Redis nodes that match this read selector.
`static ReadFrom`	`subnet(String... cidrNotations)` Setting to read from any node in the subnets.
`static ReadFrom`	`valueOf(String name)` Retrieve the `ReadFrom` preset by name.

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

- Field Detail
  - MASTER
```
public static final ReadFrom MASTER
```
    Setting to read from the upstream only.
  - MASTER_PREFERRED
```
public static final ReadFrom MASTER_PREFERRED
```
    Setting to read preferred from the upstream and fall back to a replica if the master is not available.
  - UPSTREAM
```
public static final ReadFrom UPSTREAM
```
    Setting to read from the upstream only.
    
    Since:
    
    6.0
  - UPSTREAM_PREFERRED
```
public static final ReadFrom UPSTREAM_PREFERRED
```
    Setting to read preferred from the upstream and fall back to a replica if the upstream is not available.
    
    Since:
    
    6.0
  - REPLICA_PREFERRED
```
public static final ReadFrom REPLICA_PREFERRED
```
    Setting to read preferred from replica and fall back to upstream if no replica is available.
    
    Since:
    
    5.2
  - SLAVE_PREFERRED
```
@Deprecated
public static final ReadFrom SLAVE_PREFERRED
```
    Deprecated. Renamed to REPLICA_PREFERRED.
    
    Setting to read preferred from replicas and fall back to upstream if no replica is available.
    
    Since:
    
    4.4
  - REPLICA
```
public static final ReadFrom REPLICA
```
    Setting to read from the replica only.
    
    Since:
    
    5.2
  - SLAVE
```
@Deprecated
public static final ReadFrom SLAVE
```
    Deprecated. renamed to REPLICA.
    
    Setting to read from the replica only.
  - LOWEST_LATENCY
```
public static final ReadFrom LOWEST_LATENCY
```
    Setting to read from the node with the lowest latency during topology discovery. Note that latency measurements are momentary snapshots that can change in rapid succession. Requires dynamic refresh sources to obtain topologies and latencies from all nodes in the cluster.
    
    Since:
    
    6.1.7
  - NEAREST
```
@Deprecated
public static final ReadFrom NEAREST
```
    Deprecated. since 6.1.7 as we're renaming this setting to LOWEST_LATENCY for more clarity what this setting actually represents.
    
    Setting to read from the node with the lowest latency during topology discovery. Note that latency measurements are momentary snapshots that can change in rapid succession. Requires dynamic refresh sources to obtain topologies and latencies from all nodes in the cluster.
  - ANY
```
public static final ReadFrom ANY
```
    Setting to read from any node.
    
    Since:
    
    5.2
  - ANY_REPLICA
```
public static final ReadFrom ANY_REPLICA
```
    Setting to read from any replica node.
    
    Since:
    
    6.0.1
- Constructor Detail
  - ReadFrom
```
public ReadFrom()
```
- Method Detail
  - subnet
```
public static ReadFrom subnet(String... cidrNotations)
```
    Setting to read from any node in the subnets.
    
    Parameters:
    
    cidrNotations - CIDR-block notation strings, e.g., "192.168.0.0/16", "2001:db8:abcd:0000::/52". Must not be null.
    
    Returns:
    
    an instance of ReadFromImpl.ReadFromSubnet.
    
    Since:
    
    6.1
  - regex
```
public static ReadFrom regex(Pattern pattern)
```
    Read from any node that has RedisURI matching with the given pattern.
    
    Parameters:
    
    pattern - regex pattern, e.g., Pattern.compile(".*region-1.*"). Must not be null.
    
    Returns:
    
    an instance of ReadFromImpl.ReadFromRegex.
    
    Since:
    
    6.1
  - regex
```
public static ReadFrom regex(Pattern pattern,
                             boolean orderSensitive)
```
    Read from any node that has RedisURI matching with the given pattern.
    
    Parameters:
    
    pattern - regex pattern, e.g., Pattern.compile(".*region-1.*"). Must not be null.
    
    orderSensitive - true to attempt reads in the order of hosts returned by select(Nodes); false to apply randomization.
    
    Returns:
    
    an instance of ReadFromImpl.ReadFromRegex.
    
    Since:
    
    6.1
  - select
```
public abstract List<RedisNodeDescription> select(ReadFrom.Nodes nodes)
```
    Chooses the nodes from the matching Redis nodes that match this read selector.
    
    Parameters:
    
    nodes - set of nodes that are suitable for reading
    
    Returns:
    
    List of RedisNodeDescriptions that are selected for reading
  - isOrderSensitive
```
protected boolean isOrderSensitive()
```
    Returns whether this ReadFrom requires ordering of the resulting nodes.
    
    Returns:
    
    true if code using ReadFrom should retain ordering or false to allow reordering of nodes.
    
    Since:
    
    5.2
  - valueOf
```
public static ReadFrom valueOf(String name)
```
    Retrieve the ReadFrom preset by name. For complex types like subnet or regex, the following syntax could be used subnet:192.168.0.0/16,2001:db8:abcd:0000::/52 and regex:.*region-1.* respectively.
    
    Parameters:
    
    name - the case-insensitive name of the read from setting
    
    Returns:
    
    the ReadFrom preset
    
    Throws:
    
    IllegalArgumentException - if name is empty, null or the ReadFrom preset is unknown.

Class ReadFrom

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MASTER

MASTER_PREFERRED

UPSTREAM

UPSTREAM_PREFERRED

REPLICA_PREFERRED

SLAVE_PREFERRED

REPLICA

SLAVE

LOWEST_LATENCY

NEAREST

ANY

ANY_REPLICA

Constructor Detail

ReadFrom

Method Detail

subnet

regex

regex

select

isOrderSensitive

valueOf