Package org.jgroups.protocols

Class FlowControl

java.lang.Object
org.jgroups.stack.Protocol
org.jgroups.protocols.FlowControl
All Implemented Interfaces:
Lifecycle
Direct Known Subclasses:
MFC, UFC
public abstract class FlowControl extends Protocol
Simple flow control protocol based on a credit system. Each sender has a number of credits (bytes to send). When the credits have been exhausted, the sender blocks. Each receiver also keeps track of how many credits it has received from a sender. When credits for a sender fall below a threshold, the receiver sends more credits to the sender.

  • Field Details

    • max_credits

      protected long max_credits
      Max number of bytes to send per receiver until an ack must be received before continuing sending

    • max_block_time

      protected long max_block_time
      Max time (in milliseconds) to block. If credit hasn't been received after max_block_time, we send a REPLENISHMENT request to the members from which we expect credits. A value <= 0 means to wait forever.

    • min_threshold

      protected double min_threshold
      If we're down to (min_threshold * max_credits) bytes for P, we send more credits to P. Example: if max_credits is 1'000'000, and min_threshold 0.25, then we send ca. 250'000 credits to P once we've got only 250'000 credits left for P (we've received 750'000 bytes from P).

    • min_credits

      protected long min_credits
      Computed as max_credits * min_theshold. If explicitly set, this will override the above computation

    • num_credit_requests_received

      protected long num_credit_requests_received

    • num_credit_requests_sent

      protected long num_credit_requests_sent

    • num_credit_responses_received

      protected long num_credit_responses_received

    • num_credit_responses_sent

      protected long num_credit_responses_sent

    • num_msgs_dropped

      protected long num_msgs_dropped

    • received

      protected final Map<Address,Credit> received
      Keeps track of credits per member at the receiver. For each message, the credits for the sender are decremented by the size of the received message. When the credits fall below the threshold, we refill and send a REPLENISH message to the sender.

    • running

      protected volatile boolean running
      Whether FlowControl is still running, this is set to false when the protocol terminates (on stop())

    • frag_size

      protected int frag_size

  • Constructor Details

    • FlowControl

      public FlowControl()

  • Method Details

    • resetStats

      public void resetStats()
      Overrides:
      resetStats in class Protocol

    • getNumberOfBlockings

      public abstract int getNumberOfBlockings()

    • getAverageTimeBlocked

      public abstract double getAverageTimeBlocked()

    • getMaxCredits

      public long getMaxCredits()

    • setMaxCredits

      public <T extends FlowControl> T setMaxCredits(long m)

    • getMinThreshold

      public double getMinThreshold()

    • setMinThreshold

      public <T extends FlowControl> T setMinThreshold(double m)

    • getMinCredits

      public long getMinCredits()

    • setMinCredits

      public <T extends FlowControl> T setMinCredits(long m)

    • getMaxBlockTime

      public long getMaxBlockTime()

    • setMaxBlockTime

      public <T extends FlowControl> T setMaxBlockTime(long t)

    • getNumberOfCreditRequestsReceived

      @Deprecated public long getNumberOfCreditRequestsReceived()
      Deprecated.
      Don't remove! https://issues.redhat.com/browse/JGRP-2814

    • getNumberOfCreditRequestsSent

      @Deprecated public long getNumberOfCreditRequestsSent()
      Deprecated.
      Don't remove! https://issues.redhat.com/browse/JGRP-2814

    • getNumberOfCreditResponsesReceived

      @Deprecated public long getNumberOfCreditResponsesReceived()
      Deprecated.
      Don't remove! https://issues.redhat.com/browse/JGRP-2814

    • getNumberOfCreditResponsesSent

      @Deprecated public long getNumberOfCreditResponsesSent()
      Deprecated.
      Don't remove! https://issues.redhat.com/browse/JGRP-2814

    • printSenderCredits

      public abstract String printSenderCredits()

    • printReceiverCredits

      public String printReceiverCredits()

    • getReceiverCreditsFor

      public long getReceiverCreditsFor(Address mbr)

    • printCredits

      public String printCredits()

    • handleMulticastMessage

      protected abstract boolean handleMulticastMessage()
      Whether the protocol handles message with dest == null || dest.isMulticastAddress()

    • handleCredit

      protected abstract void handleCredit(Address sender, long increase)

    • getReplenishHeader

      protected abstract Header getReplenishHeader()

    • getCreditRequestHeader

      protected abstract Header getCreditRequestHeader()

    • unblock

      public void unblock()
      Allows to unblock all blocked senders from an external program, e.g. JMX

    • init

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

    • start

      public void start() throws Exception
      Description copied from class: Protocol
      This method is called on a JChannel.connect(String); starts work. Protocols are connected ready to receive events. Will be called from bottom to top.
      Specified by:
      start in interface Lifecycle
      Overrides:
      start in class Protocol
      Throws:
      Exception - Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, so JChannel.connect(String) will throw an exception

    • stop

      public void stop()
      Description copied from class: Protocol
      Called on a JChannel.disconnect(); stops work (e.g. by closing multicast socket). Will be called from top to bottom.
      Specified by:
      stop in interface Lifecycle
      Overrides:
      stop in class Protocol

    • down

      public Object down(Event evt)
      Description copied from class: Protocol
      An event is to be sent down the stack. A protocol 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 protocol may need to add a header to it (or do nothing at all) before sending it down the stack using down_prot.down().
      Overrides:
      down in class Protocol

    • down

      public Object down(Message msg)
      Description copied from class: Protocol
      A message is sent down the stack. Protocols may examine the message and do something (e.g. add a header) with it, before passing it down.
      Overrides:
      down in class Protocol

    • up

      public Object up(Event evt)
      Description copied from class: Protocol
      An event was received from the protocol below. Usually the current protocol 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

    • up

      public Object up(Message msg)
      Description copied from class: Protocol
      A single message was received. Protocols may examine the message and do something (e.g. add a header) with it before passing it up.
      Overrides:
      up in class Protocol

    • handleUpEvent

      protected void handleUpEvent(Message msg, FcHeader hdr)

    • up

      public void up(MessageBatch batch)
      Description copied from class: Protocol
      Sends up a multiple messages in a MessageBatch. The sender of the batch is always the same, and so is the destination (null == multicast messages). Messages in a batch can be OOB messages, regular messages, or mixed messages, although the transport itself will create initial MessageBatches that contain only either OOB or regular messages.

      The default processing below sends messages up the stack individually, based on a matching criteria (calling Protocol.accept(Message)), and - if true - calls Protocol.up(org.jgroups.Event) for that message and removes the message. If the batch is not empty, it is passed up, or else it is dropped.

      Subclasses should check if there are any messages destined for them (e.g. using MessageBatch.iterator(Predicate)), then possibly remove and process them and finally pass the batch up to the next protocol. Protocols can also modify messages in place, e.g. ENCRYPT could decrypt all encrypted messages in the batch, not remove them, and pass the batch up when done.

      Overrides:
      up in class Protocol
      Parameters:
      batch - The message batch

    • handleConfigEvent

      protected void handleConfigEvent(Map<String,Object> info)

    • handleDownMessage

      protected abstract Object handleDownMessage(Message msg, int length)

    • adjustCredit

      protected long adjustCredit(Map<Address,Credit> map, Address sender, int length)
      Check whether sender has enough credits left. If not, send it some more
      Parameters:
      map - The hashmap to use
      sender - The address of the sender
      length - The number of bytes received by this message. We don't care about the size of the headers for the purpose of flow control
      Returns:
      long Number of credits to be sent. Greater than 0 if credits needs to be sent, 0 otherwise

    • handleCreditRequest

      protected void handleCreditRequest(Map<Address,Credit> map, Address sender, long requested_credits)
      Parameters:
      map - The map to modify
      sender - The sender who requests credits
      requested_credits - Number of bytes that the sender has left to send messages to us

    • sendCredit

      protected void sendCredit(Address dest, long credits)

    • sendCreditRequest

      protected void sendCreditRequest(Address dest, long credits_needed)
      We cannot send this request as OOB message, as the credit request needs to queue up behind the regular messages; if a receiver cannot process the regular messages, that is a sign that the sender should be throttled !
      Parameters:
      dest - The member to which we send the credit request
      credits_needed - The number of bytes (of credits) left for dest

    • handleViewChange

      protected void handleViewChange(List<Address> mbrs)

    • printMap

      protected static String printMap(Map<Address,? extends Credit> m)