org.jgroups.protocols
Class Discovery

java.lang.Object
  extended byorg.jgroups.stack.Protocol
      extended byorg.jgroups.protocols.Discovery
Direct Known Subclasses:
PING, TCPGOSSIP, TCPPING, WANPING

public abstract class Discovery
extends Protocol

The Discovery 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 specific subclasses, e.g. by mcasting PING requests to an IP MCAST address or, if gossiping is enabled, by contacting the GossipServer. 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.

The FIND_INITIAL_MBRS event will eventually be answered with a FIND_INITIAL_MBRS_OK event up the stack. The following properties are available

Version:
$Id: Discovery.java,v 1.14 2005/12/16 16:02:43 belaban Exp $
Author:
Bela Ban

Field Summary
 
Fields inherited from class org.jgroups.stack.Protocol
down_handler, down_prot, down_queue, down_thread, down_thread_prio, log, observer, props, stack, stats, trace, up_handler, up_prot, up_queue, up_thread, up_thread_prio, warn
 
Constructor Summary
Discovery()
           
 
Method Summary
 void down(Event evt)
          An event is to be sent down the stack.
 java.util.Vector findInitialMembers()
          Finds the initial membership
 java.lang.String findInitialMembersAsString()
           
 int getNumberOfDiscoveryRequestsSent()
           
 int getNumInitialMembers()
           
 int getNumPingRequests()
           
 long getTimeout()
           
 void handleConnect()
           
 void handleConnectOK()
          Called when CONNECT_OK has been received
 void handleDisconnect()
           
 void localAddressSet(Address addr)
          Called after local_addr was set
protected  View makeView(java.util.Vector mbrs)
           
 java.util.Vector providedUpServices()
          List of events that are provided to layers above (they will be handled when sent down from above).
 void resetStats()
           
abstract  void sendGetMembersRequest()
           
 void setNumInitialMembers(int num_initial_members)
           
 void setNumPingRequests(int num_ping_requests)
           
 boolean setProperties(java.util.Properties props)
          sets the properties of the PING protocol.
 void setTimeout(long timeout)
           
 void start()
          This method is called on a Channel.connect(String).
 void stop()
          This method is called on a Channel.disconnect().
 void up(Event evt)
          An event was received from the layer below.
 
Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getDownQueue, getName, getProperties, getUpProtocol, getUpQueue, handleSpecialDownEvent, init, isTrace, isWarn, passDown, passUp, printStats, providedDownServices, receiveDownEvent, receiveUpEvent, requiredDownServices, requiredUpServices, setDownProtocol, setObserver, setPropertiesInternal, setProtocolStack, setTrace, setUpProtocol, setWarn, startDownHandler, startUpHandler, statsEnabled, stopInternal, upThreadEnabled
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Discovery

public Discovery()
Method Detail

localAddressSet

public void localAddressSet(Address addr)
Called after local_addr was set


sendGetMembersRequest

public abstract void sendGetMembersRequest()

handleConnectOK

public void handleConnectOK()
Called when CONNECT_OK has been received


handleDisconnect

public void handleDisconnect()

handleConnect

public void handleConnect()

getTimeout

public long getTimeout()

setTimeout

public void setTimeout(long timeout)

getNumInitialMembers

public int getNumInitialMembers()

setNumInitialMembers

public void setNumInitialMembers(int num_initial_members)

getNumPingRequests

public int getNumPingRequests()

setNumPingRequests

public void setNumPingRequests(int num_ping_requests)

getNumberOfDiscoveryRequestsSent

public int getNumberOfDiscoveryRequestsSent()

providedUpServices

public java.util.Vector providedUpServices()
Description copied from class: Protocol
List of events that are provided to layers above (they will be handled when sent down from above).

Overrides:
providedUpServices in class Protocol
Returns:
Vector (of Integers)

setProperties

public boolean setProperties(java.util.Properties props)
sets the properties of the PING protocol. The following properties are available property: timeout - the timeout (ms) to wait for the initial members, default is 3000=3 secs property: num_initial_members - the minimum number of initial members for a FIND_INITAL_MBRS, default is 2

Overrides:
setProperties in class Protocol
Parameters:
props - - a property set
Returns:
returns true if all properties were parsed properly returns false if there are unrecnogized properties in the property set

resetStats

public void resetStats()
Overrides:
resetStats in class Protocol

start

public void start()
           throws java.lang.Exception
Description copied from class: Protocol
This method is called on a Channel.connect(String). Starts work. Protocols are connected and queues are ready to receive events. Will be called from bottom to top. This call will replace the START and START_OK events.

Overrides:
start in class Protocol
Throws:
java.lang.Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so Channel.connect(String) will throw an exception

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 Protocol

findInitialMembers

public java.util.Vector findInitialMembers()
Finds the initial membership

Returns:
Vector

findInitialMembersAsString

public java.lang.String findInitialMembersAsString()

up

public void up(Event evt)
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 Protocol
Parameters:
evt - - the event that has been sent from the layer below

down

public void down(Event evt)
An event is to be sent down the stack. The layer may want to examine its type and perform some action on it, depending on the event's type. If the event is a message MSG, then the layer may need to add a header to it (or do nothing at all) before sending it down the stack using PassDown. In case of a GET_ADDRESS event (which tries to retrieve the stack's address from one of the bottom layers), the layer may need to send a new response event back up the stack using passUp(). The PING protocol is interested in several different down events, Event.FIND_INITIAL_MBRS - sent by the GMS layer and expecting a GET_MBRS_OK Event.TMP_VIEW and Event.VIEW_CHANGE - a view change event Event.BECOME_SERVER - called after client has joined and is fully working group member Event.CONNECT, Event.DISCONNECT.

Overrides:
down in class Protocol

makeView

protected View makeView(java.util.Vector mbrs)


Copyright ? 1998-2005 Bela Ban. All Rights Reserved.