io.atomix.protocols.raft.service

Class AbstractRaftService

java.lang.Object

io.atomix.protocols.raft.service.AbstractRaftService

All Implemented Interfaces:

RaftService, RaftSessionListener, Snapshottable

public abstract class AbstractRaftService
extends Object
implements RaftService

Raft service.

Constructor Summary

Constructors

Constructor and Description
AbstractRaftService()

Method Summary

Modifier and Type	Method and Description
byte[]	apply(Commit<byte[]> commit) Applies a commit to the state machine.
void	init(ServiceContext context) Initializes the state machine.
void	onClose(RaftSession session) Called when a session was closed by the client.
void	onExpire(RaftSession session) Called when a session is expired by the system.
void	onOpen(RaftSession session) Called when a new session is registered.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.atomix.protocols.raft.service.RaftService

close

Methods inherited from interface io.atomix.protocols.raft.storage.snapshot.Snapshottable

install, snapshot

Constructor Detail

AbstractRaftService

public AbstractRaftService()

Method Detail

init

public void init(ServiceContext context)

Description copied from interface: RaftService

Initializes the state machine.

Specified by:

init in interface RaftService

Parameters:

context - The state machine context.

apply

public byte[] apply(Commit<byte[]> commit)

Description copied from interface: RaftService

Applies a commit to the state machine.

Specified by:

apply in interface RaftService

Parameters:

commit - the commit to apply

Returns:

the commit result

onOpen

public void onOpen(RaftSession session)

Description copied from interface: RaftSessionListener

Called when a new session is registered.

A session is registered when a new client connects to the cluster or an existing client recovers its session after being partitioned from the cluster. It's important to note that when this method is called, the RaftSession is not yet open and so events cannot be published to the registered session. This is because clients cannot reliably track messages pushed from server state machines to the client until the session has been fully registered. Session event messages may still be published to other already-registered sessions in reaction to a session being registered.

To push session event messages to a client through its session upon registration, state machines can use an asynchronous callback or schedule a callback to send a message.

   
   public void onOpen(RaftSession session) {
     executor.execute(() -> session.publish("foo", "Hello world!"));
   }
   
 

Sending a session event message in an asynchronous callback allows the server time to register the session and notify the client before the event message is sent. Published event messages sent via this method will be sent the next time an operation is applied to the state machine.

Specified by:

onOpen in interface RaftSessionListener

Parameters:

session - The session that was registered. State machines cannot RaftSession.publish(io.atomix.protocols.raft.event.RaftEvent) session events to this session.

onExpire

public void onExpire(RaftSession session)

Description copied from interface: RaftSessionListener

Called when a session is expired by the system.

This method is called when a client fails to keep its session alive with the cluster. If the leader hasn't heard from a client for a configurable time interval, the leader will expire the session to free the related memory. This method will always be called for a given session before RaftSessionListener.onClose(RaftSession), and RaftSessionListener.onClose(RaftSession) will always be called following this method.

State machines are free to RaftSession.publish(io.atomix.protocols.raft.event.RaftEvent) session event messages to any session except the one that expired. Session event messages sent to the session that expired will be lost since the session is closed once this method call completes.

Specified by:

onExpire in interface RaftSessionListener

Parameters:

session - The session that was expired. State machines cannot RaftSession.publish(io.atomix.protocols.raft.event.RaftEvent) session events to this session.

onClose

public void onClose(RaftSession session)

Description copied from interface: RaftSessionListener

Called when a session was closed by the client.

This method is called when a client explicitly closes a session.

State machines are free to RaftSession.publish(io.atomix.protocols.raft.event.RaftEvent) session event messages to any session except the one that was closed. Session event messages sent to the session that was closed will be lost since the session is closed once this method call completes.

Specified by:

onClose in interface RaftSessionListener

Parameters:

session - The session that was closed. State machines cannot RaftSession.publish(io.atomix.protocols.raft.event.RaftEvent) session events to this session.