Package org.jgroups.protocols

Class PING

java.lang.Object

org.jgroups.stack.Protocol

org.jgroups.protocols.Discovery

org.jgroups.protocols.PING

Direct Known Subclasses:

BPING, MPING

public class PING
extends Discovery

The PING protocol layer retrieves the initial membership (used by the GMS when started by sending event FIND_INITIAL_MBRS down the stack). We do this by mcasting PING requests to an IP MCAST address. The responses should allow us to determine the coordinator whom we have to contact, e.g. in case we want to join the group. When we are a server (after having received the BECOME_SERVER event), we'll respond to PING requests with a PING response.

Author:

Bela Ban

Nested Class Summary

Nested classes/interfaces inherited from class org.jgroups.protocols.Discovery

Discovery.Responses

Field Summary

Fields

Modifier and Type	Field	Description
protected final Promise<Boolean>	discovery_reception

Fields inherited from class org.jgroups.protocols.Discovery

group_addr, local_addr, members, ping_responses, rank, timer, view

Fields inherited from class org.jgroups.stack.Protocol

down_prot, ergonomics, id, log, name, stack, stats, up_prot

Constructor Summary

Constructors

Constructor	Description
PING()

Method Summary

Modifier and Type	Method	Description
void	sendGetMembersRequest(String cluster_name, Promise promise, boolean return_views_only)
void	stop()	This method is called on a Channel.disconnect().
Object	up(Event evt)	An event was received from the layer below.
protected void	waitForDiscoveryRequestReception()

Methods inherited from class org.jgroups.protocols.Discovery

discoveryRequestReceived, down, findAllMembers, findAllViews, findAllViewsAsString, findInitialMembers, findInitialMembers, findInitialMembersAsString, getNumberOfDiscoveryRequestsSent, getNumInitialMembers, getNumPingRequests, getTimeout, getView, handleConnect, handleDisconnect, init, makeView, providedUpServices, resetStats, setNumInitialMembers, setNumPingRequests, setTimeout, start

Methods inherited from class org.jgroups.stack.Protocol

destroy, downThreadEnabled, dumpStats, enableStats, getConfigurableObjects, getDownProtocol, getId, getLevel, getName, getProperties, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getValue, isErgonomics, printStats, providedDownServices, requiredDownServices, requiredUpServices, setDownProtocol, setErgonomics, setId, setLevel, setProperties, setPropertiesInternal, setProperty, setProtocolStack, setSocketFactory, setUpProtocol, setValue, setValues, statsEnabled, upThreadEnabled

Methods inherited from class java.lang.Object

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

Field Details

discovery_reception

protected final Promise<Boolean> discovery_reception

Constructor Details

PING

public PING()

Method Details

stop

public void stop()

Description copied from class: Protocol

This method is called on a Channel.disconnect(). Stops work (e.g. by closing multicast socket). Will be called from top to bottom. This means that at the time of the method invocation the neighbor protocol below is still working. This method will replace the STOP, STOP_OK, CLEANUP and CLEANUP_OK events. The ProtocolStack guarantees that when this method is called all messages in the down queue will have been flushed

Overrides:

stop in class Discovery

sendGetMembersRequest

public void sendGetMembersRequest(String cluster_name,
 Promise promise,
 boolean return_views_only)
                           throws Exception

Specified by:

sendGetMembersRequest in class Discovery

Throws:

Exception

up

public Object up(Event evt)

Description copied from class: Discovery

An event was received from the layer below. Usually the current layer will want to examine the event type and - depending on its type - perform some computation (e.g. removing headers from a MSG event type, or updating the internal membership list when receiving a VIEW_CHANGE event). Finally the event is either a) discarded, or b) an event is sent down the stack using PassDown or c) the event (or another event) is sent up the stack using PassUp.

For the PING protocol, the Up operation does the following things. 1. If the event is a Event.MSG then PING will inspect the message header. If the header is null, PING simply passes up the event If the header is PingHeader.GET_MBRS_REQ then the PING protocol will PassDown a PingRequest message If the header is PingHeader.GET_MBRS_RSP we will add the message to the initial members vector and wake up any waiting threads. 2. If the event is Event.SET_LOCAL_ADDR we will simple set the local address of this protocol 3. For all other messages we simple pass it up to the protocol above

Overrides:

up in class Discovery

Parameters:

evt - - the event that has been sent from the layer below

waitForDiscoveryRequestReception

protected void waitForDiscoveryRequestReception()