Package org.jgroups.protocols
Class SEQUENCER
- java.lang.Object
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- org.jgroups.stack.Protocol
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- org.jgroups.protocols.SEQUENCER
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public class SEQUENCER extends Protocol
Implementation of total order protocol using a sequencer. Consult SEQUENCER.txt for details- Author:
- Bela Ban
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected class
SEQUENCER.Flusher
static class
SEQUENCER.SequencerHeader
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Field Summary
Fields Modifier and Type Field Description protected boolean
ack_mode
When ack_mode is set, we need to wait for an ack for each forwarded message until we can send the next oneprotected Promise<java.lang.Long>
ack_promise
Used for each resent message to wait until the message has been receivedprotected long
bcast_msgs
protected Address
coord
protected long
delivered_bcasts
protected java.util.concurrent.ConcurrentMap<Address,BoundedHashMap<java.lang.Long,java.lang.Long>>
delivery_table
protected int
delivery_table_max_size
protected boolean
flush_forward_table
protected SEQUENCER.Flusher
flusher
protected boolean
flushing
Set when we block all sending threads to resend all messages from forward_tableprotected java.util.NavigableMap<java.lang.Long,Message>
forward_table
Maintains messages forwarded to the coord which which no ack has been received yet.protected long
forwarded_msgs
protected java.util.concurrent.atomic.AtomicInteger
in_flight_sends
Keeps track of the threads sending messagesprotected boolean
is_coord
protected Address
local_addr
protected int
num_acks
protected long
received_bcasts
protected long
received_forwards
protected boolean
running
protected java.util.concurrent.locks.Condition
send_cond
protected java.util.concurrent.locks.Lock
send_lock
protected java.util.concurrent.atomic.AtomicLong
seqno
protected int
threshold
protected View
view
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Fields inherited from class org.jgroups.stack.Protocol
after_creation_hook, down_prot, ergonomics, id, log, stack, stats, up_prot
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Constructor Summary
Constructors Constructor Description SEQUENCER()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected void
block()
protected void
broadcast(Message msg, boolean copy, Address original_sender, long seqno, boolean resend)
protected boolean
canDeliver(Address sender, long seqno)
Checks if seqno has already been received from sender.protected void
deliver(Message msg, SEQUENCER.SequencerHeader hdr)
java.lang.Object
down(Event evt)
An event is to be sent down the stack.java.lang.Object
down(Message msg)
A message is sent down the stack.protected void
flush(Address new_coord)
protected void
flushMessagesInForwardTable()
Sends all messages currently in forward_table to the new coordinator (changing the dest field).protected void
forward(Message msg, long seqno, boolean flush)
protected void
forwardToCoord(long seqno, Message msg)
Address
getCoordinator()
int
getForwardTableSize()
Address
getLocalAddress()
protected void
handleViewChange(View v)
boolean
isCoordinator()
void
resetStats()
void
setDeliveryTableMaxSize(int size)
void
setThreshold(int new_threshold)
void
start()
This method is called on aJChannel.connect(String)
.protected void
startFlusher(Address new_coord)
void
stop()
This method is called on aJChannel.disconnect()
.protected void
stopFlusher()
protected void
unblockAll()
protected void
unwrapAndDeliver(Message msg, boolean flush_ack)
Unmarshal the original message (in the payload) and then pass it up (unless already delivered)java.lang.Object
up(Event evt)
An event was received from the protocol below.java.lang.Object
up(Message msg)
A single message was received.void
up(MessageBatch batch)
Sends up a multiple messages in aMessageBatch
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Methods inherited from class org.jgroups.stack.Protocol
accept, afterCreationHook, destroy, enableStats, getConfigurableObjects, getDownProtocol, getDownServices, getId, getIdsAbove, getLevel, getLog, getName, getProtocolStack, getSocketFactory, getThreadFactory, getTransport, getUpProtocol, getUpServices, getValue, init, isErgonomics, level, parse, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, resetStatistics, setDownProtocol, setErgonomics, setId, setLevel, setProtocolStack, setSocketFactory, setUpProtocol, setValue, statsEnabled
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Field Detail
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local_addr
protected Address local_addr
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coord
protected volatile Address coord
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view
protected volatile View view
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is_coord
protected volatile boolean is_coord
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seqno
protected final java.util.concurrent.atomic.AtomicLong seqno
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forward_table
protected final java.util.NavigableMap<java.lang.Long,Message> forward_table
Maintains messages forwarded to the coord which which no ack has been received yet. Needs to be sorted so we resend them in the right order
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send_lock
protected final java.util.concurrent.locks.Lock send_lock
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send_cond
protected final java.util.concurrent.locks.Condition send_cond
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ack_mode
protected volatile boolean ack_mode
When ack_mode is set, we need to wait for an ack for each forwarded message until we can send the next one
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flushing
protected volatile boolean flushing
Set when we block all sending threads to resend all messages from forward_table
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running
protected volatile boolean running
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in_flight_sends
protected final java.util.concurrent.atomic.AtomicInteger in_flight_sends
Keeps track of the threads sending messages
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delivery_table
protected final java.util.concurrent.ConcurrentMap<Address,BoundedHashMap<java.lang.Long,java.lang.Long>> delivery_table
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flusher
protected volatile SEQUENCER.Flusher flusher
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ack_promise
protected final Promise<java.lang.Long> ack_promise
Used for each resent message to wait until the message has been received
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delivery_table_max_size
protected int delivery_table_max_size
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threshold
protected int threshold
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flush_forward_table
protected boolean flush_forward_table
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num_acks
protected int num_acks
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forwarded_msgs
protected long forwarded_msgs
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bcast_msgs
protected long bcast_msgs
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received_forwards
protected long received_forwards
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received_bcasts
protected long received_bcasts
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delivered_bcasts
protected long delivered_bcasts
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Method Detail
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isCoordinator
public boolean isCoordinator()
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getCoordinator
public Address getCoordinator()
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getLocalAddress
public Address getLocalAddress()
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getForwardTableSize
public int getForwardTableSize()
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setThreshold
public void setThreshold(int new_threshold)
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setDeliveryTableMaxSize
public void setDeliveryTableMaxSize(int size)
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resetStats
public void resetStats()
- Overrides:
resetStats
in classProtocol
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start
public void start() throws java.lang.Exception
Description copied from class:Protocol
This method is called on aJChannel.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 classProtocol
- Throws:
java.lang.Exception
- Thrown if protocol cannot be started successfully. This will cause the ProtocolStack to fail, soJChannel.connect(String)
will throw an exception
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stop
public void stop()
Description copied from class:Protocol
This method is called on aJChannel.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
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down
public java.lang.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 usingdown_prot.down()
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down
public java.lang.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.
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up
public java.lang.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 usingdown_prot.down()
or c) the event (or another event) is sent up the stack usingup_prot.up()
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up
public java.lang.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.
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up
public void up(MessageBatch batch)
Description copied from class:Protocol
Sends up a multiple messages in aMessageBatch
. 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 (callingProtocol.accept(org.jgroups.Message)
), and - if true - callsProtocol.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. usingMessageBatch.getMatchingMessages(short,boolean)
), 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.
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handleViewChange
protected void handleViewChange(View v)
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flush
protected void flush(Address new_coord) throws java.lang.InterruptedException
- Throws:
java.lang.InterruptedException
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flushMessagesInForwardTable
protected void flushMessagesInForwardTable()
Sends all messages currently in forward_table to the new coordinator (changing the dest field). This needs to be done, so the underlying reliable unicast protocol (e.g. UNICAST) adds these messages to its retransmission mechanism
Note that we need to resend the messages in order of their seqnos! We also need to prevent other message from being inserted until we're done, that's why there's synchronization.
Access to the forward_table doesn't need to be synchronized as there won't be any insertions during flushing (all down-threads are blocked)
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forwardToCoord
protected void forwardToCoord(long seqno, Message msg)
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forward
protected void forward(Message msg, long seqno, boolean flush)
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broadcast
protected void broadcast(Message msg, boolean copy, Address original_sender, long seqno, boolean resend)
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unwrapAndDeliver
protected void unwrapAndDeliver(Message msg, boolean flush_ack)
Unmarshal the original message (in the payload) and then pass it up (unless already delivered)- Parameters:
msg
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deliver
protected void deliver(Message msg, SEQUENCER.SequencerHeader hdr)
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canDeliver
protected boolean canDeliver(Address sender, long seqno)
Checks if seqno has already been received from sender. This weeds out duplicates. Note that this method is never called concurrently for the same sender, as the sender in NAKACK will always be the coordinator.
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block
protected void block()
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unblockAll
protected void unblockAll()
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startFlusher
protected void startFlusher(Address new_coord)
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stopFlusher
protected void stopFlusher()
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