Module org.jgroups.raft

Package org.jgroups.raft.util

Class CounterStateMachine

java.lang.Object

org.jgroups.raft.util.CounterStateMachine

All Implemented Interfaces:

StateMachine

public class CounterStateMachine
extends Object
implements StateMachine

Sample state machine accepting additions and subtractions

Since:

1.0.5

Author:

Bela Ban

Field Summary

Fields

Modifier and Type	Field	Description
protected final AtomicInteger	additions
protected final AtomicInteger	counter
protected final AtomicInteger	subtractions

Constructor Summary

Constructors

Constructor	Description
CounterStateMachine()

Method Summary

Modifier and Type	Method	Description
int	additions()
byte[]	apply(byte[] data, int offset, int length, boolean serialize_response)	Applies a command to the state machine.
int	counter()
static String	readAndDumpSnapshot(DataInput in)
void	readContentFrom(DataInput in)	Reads the contents of the state machine from an input stream.
static String	reader(LogEntry le)
CounterStateMachine	reset()
int	subtractions()
String	toString()
void	writeContentTo(DataOutput out)	Writes the contents of the state machine to an output stream.

Methods inherited from class java.lang.Object

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

Field Details

counter

protected final AtomicInteger counter

additions

protected final AtomicInteger additions

subtractions

protected final AtomicInteger subtractions

Constructor Details

CounterStateMachine

public CounterStateMachine()

Method Details

counter

public int counter()

additions

public int additions()

subtractions

public int subtractions()

apply

public byte[] apply(byte[] data,
 int offset,
 int length,
 boolean serialize_response)
             throws Exception

Description copied from interface: StateMachine

Applies a command to the state machine. The contents of the byte[] buffer are interpreted by the state machine. The command could for example be a set(), remove() or clear() command.

Specified by:

apply in interface StateMachine

Parameters:

data - The byte[] buffer

offset - The offset at which the data starts

length - The length of the data

serialize_response - If true, serialize and return the response, else return null

Returns:

A serialized response value, or null (e.g. if the method returned void)

Throws:

Exception - Thrown on deserialization or other failure

readAndDumpSnapshot

public static String readAndDumpSnapshot(DataInput in)

reader

public static String reader(LogEntry le)

readContentFrom

public void readContentFrom(DataInput in)
                     throws Exception

Description copied from interface: StateMachine

Reads the contents of the state machine from an input stream.

This can be the case when an InstallSnapshot RPC is used to bootstrap a new node, or a node that's lagging far behind. The parsing depends on the concrete state machine implementation, but the idea is that the stream is a sequence of commands, each of which can be passed to StateMachine.apply(byte[], int, int, boolean).

The state machine may need to block modifications until the contents have been set (unless e.g. copy-on-write is used). The state machine implementation may need to remove all contents before populating itself from the stream.

Specified by:

readContentFrom in interface StateMachine

Parameters:

in - The input stream

Throws:

Exception

writeContentTo

public void writeContentTo(DataOutput out)
                    throws Exception

Description copied from interface: StateMachine

Writes the contents of the state machine to an output stream. This is typically called on the leader to provide state to a new node, or a node that's lagging far behind.

Updates to the state machine may need to be put on hold while the state is written to the output stream.

Specified by:

writeContentTo in interface StateMachine

Parameters:

out - The output stream

Throws:

Exception

reset

public CounterStateMachine reset()

toString

public String toString()

Overrides:

toString in class Object