Package org.jgroups.stack

Class Protocol

java.lang.Object
org.jgroups.stack.Protocol
Direct Known Subclasses:
AUTH, BARRIER, BSH, COMPRESS, DAISYCHAIN, DELAY, DELAY_JOIN_REQ, DISCARD, DISCARD_PAYLOAD, Discovery, DUPL, ENCRYPT, EXAMPLE, Executing, FC, FD, FD_ALL, FD_SIMPLE, FD_SOCK, FlowControl, FLUSH, FRAG, FRAG2, GMS, HDRS, HTOTAL, Locking, MERGE2, MERGE3, MERGEFAST, NAKACK, PERF_TP, PRIO, ProtocolStack, RATE_LIMITER, RELAY, SCOPE, SEQUENCER, SFC, SHUFFLE, SIZE, SMACK, STABLE, STATE_TRANSFER, STATS, STOMP, STREAMING_STATE_TRANSFER, TP, TP.ProtocolAdapter, TRACE, UNICAST, UNICAST2, VERIFY_SUSPECT, VIEW_SYNC
public abstract class Protocol extends Object
The Protocol class provides a set of common services for protocol layers. Each layer has to be a subclass of Protocol and override a number of methods (typically just up(), down() and getName(). Layers are stacked in a certain order to form a protocol stack. Events are passed from lower layers to upper ones and vice versa. E.g. a Message received by the UDP layer at the bottom will be passed to its higher layer as an Event. That layer will in turn pass the Event to its layer and so on, until a layer handles the Message and sends a response or discards it, the former resulting in another Event being passed down the stack.

The important thing to bear in mind is that Events have to passed on between layers in FIFO order which is guaranteed by the Protocol implementation and must be guranteed by subclasses implementing their on Event queuing.

Note that each class implementing interface Protocol MUST provide an empty, public constructor !

Author:
Bela Ban

  • Field Details

    • up_prot

      protected Protocol up_prot

    • down_prot

      protected Protocol down_prot

    • stack

      protected ProtocolStack stack

    • stats

      protected boolean stats

    • ergonomics

      protected boolean ergonomics

    • name

      @Deprecated protected String name
      Deprecated.
      The name of the protocol. Is by default set to the protocol's classname. This property should rarely need to be set, e.g. only in cases where we want to create more than 1 protocol of the same class in the same stack

    • id

      protected short id

    • log

      protected final Log log

  • Constructor Details

    • Protocol

      public Protocol()

  • Method Details

    • setLevel

      public void setLevel(String level)
      Sets the level of a logger. This method is used to dynamically change the logging level of a running system, e.g. via JMX. The appender of a level needs to exist.
      Parameters:
      level - The new level. Valid values are "fatal", "error", "warn", "info", "debug", "trace" (capitalization not relevant)

    • getLevel

      public String getLevel()

    • isErgonomics

      public boolean isErgonomics()

    • setErgonomics

      public void setErgonomics(boolean ergonomics)

    • setProperties

      protected boolean setProperties(Properties props)
      Deprecated.
      The properties are now set through the @Property annotation on the attribute or setter
      Configures the protocol initially. A configuration string consists of name=value items, separated by a ';' (semicolon), e.g.:
       "loopback=false;unicast_inport=4444"

    • setProperty

      public void setProperty(String key, String val)
      Deprecated.
      Use the corresponding setter instead
      Sets a property
      Parameters:
      key -
      val -

    • setPropertiesInternal

      public boolean setPropertiesInternal(Properties props)
      Deprecated.
      Use a setter instead
      Called by Configurator. Removes 2 properties which are used by the Protocol directly and then calls setProperties(), which might invoke the setProperties() method of the actual protocol instance.

    • getValue

      public Object getValue(String name)

    • setValues

      public Protocol setValues(Map<String,Object> values)

    • setValue

      public Protocol setValue(String name, Object value)

    • getProperties

      public Properties getProperties()
      Deprecated.
      Use a getter to get the actual instance variable
      Returns:

    • getProtocolStack

      public ProtocolStack getProtocolStack()

    • getConfigurableObjects

      protected List<Object> getConfigurableObjects()
      After configuring the protocol itself from the properties defined in the XML config, a protocol might have additional objects which need to be configured. This callback allows a protocol developer to configure those other objects. This call is guaranteed to be invoked after the protocol itself has been configured. See AUTH for an example.
      Returns:

    • getTransport

      protected TP getTransport()

    • getThreadFactory

      public ThreadFactory getThreadFactory()
      Supposed to be overwritten by subclasses. Usually the transport returns a valid non-null thread factory, but thread factories can also be created by individual protocols
      Returns:

    • getSocketFactory

      public SocketFactory getSocketFactory()
      Returns the SocketFactory associated with this protocol, if overridden in a subclass, or passes the call down
      Returns:
      SocketFactory

    • setSocketFactory

      public void setSocketFactory(SocketFactory factory)
      Sets a SocketFactory. Socket factories are typically provided by the transport (TP) or TP.ProtocolAdapter
      Parameters:
      factory -

    • upThreadEnabled

      public boolean upThreadEnabled()
      Deprecated.
      up_thread was removed
      Returns:
      false by default

    • downThreadEnabled

      public boolean downThreadEnabled()
      Deprecated.
      down thread was removed
      Returns:
      boolean False by default

    • statsEnabled

      public boolean statsEnabled()

    • enableStats

      public void enableStats(boolean flag)

    • resetStats

      public void resetStats()

    • printStats

      public String printStats()

    • dumpStats

      public Map<String,Object> dumpStats()

    • init

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

    • start

      public void start() throws Exception
      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.
      Throws:
      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()
      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

    • destroy

      public void destroy()
      This method is called on a Channel.close(). Does some cleanup; after the call the VM will terminate

    • requiredUpServices

      public Vector<Integer> requiredUpServices()
      List of events that are required to be answered by some layer above.
      Returns:
      Vector (of Integers)

    • requiredDownServices

      public Vector<Integer> requiredDownServices()
      List of events that are required to be answered by some layer below.
      Returns:
      Vector (of Integers)

    • providedUpServices

      public Vector<Integer> providedUpServices()
      List of events that are provided to layers above (they will be handled when sent down from above).
      Returns:
      Vector (of Integers)

    • providedDownServices

      public Vector<Integer> providedDownServices()
      List of events that are provided to layers below (they will be handled when sent down from below).
      Returns:
      Vectorinvalid input: '<'Integer (of Integers)

    • getName

      public String getName()
      All protocol names have to be unique !

    • getId

      public short getId()

    • setId

      public void setId(short id)

    • getUpProtocol

      public Protocol getUpProtocol()

    • getDownProtocol

      public Protocol getDownProtocol()

    • setUpProtocol

      public void setUpProtocol(Protocol up_prot)

    • setDownProtocol

      public void setDownProtocol(Protocol down_prot)

    • setProtocolStack

      public void setProtocolStack(ProtocolStack stack)

    • up

      public Object 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 down_prot.down() or c) the event (or another event) is sent up the stack using up_prot.up().

    • down

      public Object 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 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().