Class MERGE2


  • public class MERGE2
    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 retrieve the initial membership (using the FIND_INITIAL_MBRS event provided e.g. by PING or TCPPING protocols. This list contains {coord,addr} pairs.
    • If there is more than 1 coordinator:
      1. Get all coordinators
      2. Create a MERGE event with the list of coordinators as argument
      3. Send the event up the stack

    Requires: FIND_INITIAL_MBRS event from below
    Provides: sends MERGE event with list of coordinators up the stack

    Author:
    Bela Ban, Oct 16 2001
    • Constructor Detail

      • MERGE2

        public MERGE2()
    • Method Detail

      • init

        public void init()
                  throws java.lang.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:
        java.lang.Exception - Thrown if protocol cannot be initialized successfully. This will cause the ProtocolStack to fail, so the channel constructor will throw an exception
      • getName

        public java.lang.String getName()
        Specified by:
        getName in class Protocol
      • getMinInterval

        public long getMinInterval()
      • setMinInterval

        public void setMinInterval​(long i)
      • getMaxInterval

        public long getMaxInterval()
      • setMaxInterval

        public void setMaxInterval​(long l)
      • getSuspended

        public boolean getSuspended()
      • setProperties

        public boolean setProperties​(java.util.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
      • requiredDownServices

        public java.util.Vector<java.lang.Integer> requiredDownServices()
        Description copied from class: Protocol
        List of events that are required to be answered by some layer below.
        Overrides:
        requiredDownServices in class Protocol
        Returns:
        Vector (of Integers)
      • 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
      • up

        public java.lang.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 java.lang.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
      • suspendMergeTask

        public void suspendMergeTask()
        Suspends the sending of merge multicasts (only if coord)
      • resumeMergeTask

        public void resumeMergeTask()
        Resumes the sending of merge multicast (only if coord)
      • sendMergeSolicitation

        public void sendMergeSolicitation()
        Discovers members and detects whether we have multiple coordinator. If so, kicks off a merge