Package org.jgroups.protocols

Class FlowControl

java.lang.Object
org.jgroups.stack.Protocol
org.jgroups.protocols.FlowControl
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.
Author:
Bela Ban

  • Field Details

    • REPLENISH_HDR

      protected static final FcHeader REPLENISH_HDR

    • CREDIT_REQUEST_HDR

      protected static final FcHeader CREDIT_REQUEST_HDR

    • 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 invalid input: '<'= 0 means to wait forever.

    • max_block_times

      protected Map<Long,Long> max_block_times
      Defines the max number of milliseconds for a message to block before being sent, based on the length of the message. The property is defined as a comma-separated list of values (separated by ':'), where the key is the size in bytes and the value is the number of milliseconds to block. Example: max_block_times="50:1,500:3,1500:5,10000:10,100000:100". This means that messages up to 50 bytes wait 1 ms max until they get sent, messages up to 500 bytes 3 ms, and so on. If a message's length (size of the payload in bytes) is for example 15'000 bytes, FlowControl blocks it for a max of 100 ms.

    • 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 times min_theshold. If explicitly set, this will override the above computation

    • ignore_synchronous_response

      protected boolean ignore_synchronous_response
      Whether an up thread that comes back down should be allowed to bypass blocking if all credits are exhausted. Avoids JGRP-465. Set to false by default in 2.5 because we have OOB messages for credit replenishments - this flag should not be set to true if the concurrent stack is used

    • num_credit_requests_received

      protected int num_credit_requests_received

    • num_credit_requests_sent

      protected int num_credit_requests_sent

    • num_credit_responses_sent

      protected int num_credit_responses_sent

    • num_credit_responses_received

      protected int num_credit_responses_received

    • received

      protected final Map<Address,FlowControl.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_received

      protected boolean frag_size_received

    • ignore_thread

      protected final ThreadLocal<Boolean> ignore_thread
      Thread that carries messages through up() and shouldn't be blocked in down() if ignore_synchronous_response==true. JGRP-465.

  • Constructor Details

    • FlowControl

      public FlowControl()

  • Method Details

    • resetStats

      public void resetStats()
      Overrides:
      resetStats in class Protocol

    • getMaxCredits

      public long getMaxCredits()

    • setMaxCredits

      public void setMaxCredits(long max_credits)

    • getMinThreshold

      public double getMinThreshold()

    • setMinThreshold

      public void setMinThreshold(double min_threshold)

    • getMinCredits

      public long getMinCredits()

    • setMinCredits

      public void setMinCredits(long min_credits)

    • getNumberOfBlockings

      public abstract int getNumberOfBlockings()

    • getMaxBlockTime

      public long getMaxBlockTime()

    • setMaxBlockTime

      public void setMaxBlockTime(long t)

    • setMaxBlockTimes

      public void setMaxBlockTimes(String str)

    • getMaxBlockTimes

      public String getMaxBlockTimes()

    • getTotalTimeBlocked

      public abstract long getTotalTimeBlocked()

    • getAverageTimeBlocked

      public double getAverageTimeBlocked()

    • getNumberOfCreditRequestsReceived

      public int getNumberOfCreditRequestsReceived()

    • getNumberOfCreditRequestsSent

      public int getNumberOfCreditRequestsSent()

    • getNumberOfCreditResponsesReceived

      public int getNumberOfCreditResponsesReceived()

    • getNumberOfCreditResponsesSent

      public int getNumberOfCreditResponsesSent()

    • printSenderCredits

      public abstract String printSenderCredits()

    • printReceiverCredits

      public String printReceiverCredits()

    • printCredits

      public String printCredits()

    • dumpStats

      public Map<String,Object> dumpStats()
      Overrides:
      dumpStats in class Protocol

    • getMaxBlockTime

      protected long getMaxBlockTime(long length)

    • handleMulticastMessage

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

    • handleCredit

      protected abstract void handleCredit(Address sender, long increase)

    • 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 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

    • start

      public void start() throws 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:
      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

    • 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

    • 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

    • handleConfigEvent

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

    • handleDownMessage

      protected abstract Object handleDownMessage(Event evt, Message msg, Address dest, int length)

    • adjustCredit

      protected long adjustCredit(Map<Address,FlowControl.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,FlowControl.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 messages, 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(Vector<Address> mbrs)

    • printMap

      protected static String printMap(Map<Address,FlowControl.Credit> m)