Class MERGE3

java.lang.Object
org.jgroups.stack.Protocol
org.jgroups.protocols.MERGE3

public class MERGE3 extends Protocol
Protocol to discover subgroups; e.g., existing due to a network partition (that healed). Example: group {p,q,r,s,t,u,v,w} is split into 3 subgroups {p,q}, {r,s,t,u} and {v,w}. This protocol will eventually send a MERGE event with the coordinators of each subgroup up the stack: {p,r,v}. Note that - depending on the time of subgroup discovery - there could also be 2 MERGE events, which first join 2 of the subgroups, and then the resulting group to the last subgroup. The real work of merging the subgroups into one larger group is done somewhere above this protocol (typically in the GMS protocol).

This protocol works as follows:

  • If coordinator: periodically broadcast a "I'm the coordinator" message. If a coordinator receives such a message, it immediately initiates a merge by sending up a MERGE event

    Provides: sends MERGE event with list of coordinators up the stack

Author:
Bela Ban, Oct 16 2001
  • Constructor Details

    • MERGE3

      public MERGE3()
  • Method Details

    • getName

      public String getName()
      Specified by:
      getName in class Protocol
    • setProperties

      public boolean setProperties(Properties props)
      Description copied from class: Protocol
      Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
       "loopback=false;unicast_inport=4444"
       
      Overrides:
      setProperties in class Protocol
    • init

      public void init() throws Exception
      Description copied from class: Protocol
      Called after instance has been created (null constructor) and before protocol is started. Properties are already set. Other protocols are not yet connected and events cannot yet be sent.
      Overrides:
      init in class Protocol
      Throws:
      Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception
    • up

      public Object up(Event evt)
      Description copied from class: Protocol
      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 down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().
      Overrides:
      up in class Protocol
    • down

      public Object down(Event evt)
      Description copied from class: Protocol
      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 down_prot.down(). 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 up_prot.up().
      Overrides:
      down in class Protocol