org.javagroups.protocols.pbcast
Class Digest
java.lang.Object
|
+--org.javagroups.protocols.pbcast.Digest
- All Implemented Interfaces:
- java.io.Externalizable, java.io.Serializable
- public class Digest
- extends java.lang.Object
- implements java.io.Externalizable
A message digest, which is used e.g. by the PBCAST layer for gossiping (also used by NAKACK for
keeping track of current seqnos for all members). It contains pairs of senders and a range of seqnos
(low and high), where each sender is associated with its highest and lowest seqnos seen so far. That
is, the lowest seqno which was not yet garbage-collected and the highest that was seen so far and is
deliverable (or was already delivered) to the application. A range of [0 - 0] means no messages have
been received yet.
April 3 2001 (bela): Added high_seqnos_seen member. It is used to disseminate
information about the last (highest) message M received from a sender P. Since we might be using a
negative acknowledgment message numbering scheme, we would never know if the last message was
lost. Therefore we periodically gossip and include the last message seqno. Members who haven't seen
it (e.g. because msg was dropped) will request a retransmission. See DESIGN for details.
- Author:
- Bela Ban
- See Also:
- Serialized Form
Method Summary |
void |
add(Address sender,
long low_seqno,
long high_seqno)
|
void |
add(Address sender,
long low_seqno,
long high_seqno,
long high_seqno_seen)
|
void |
add(Digest d)
|
boolean |
contains(Address sender)
|
Digest |
copy()
|
int |
getIndex(Address sender)
|
long |
highSeqnoAt(Address sender)
|
long |
highSeqnoAt(int index)
|
long |
highSeqnoSeenAt(Address sender)
|
long |
highSeqnoSeenAt(int index)
|
void |
incrementHighSeqno(Address sender)
Increment the sender's high_seqno by 1 |
long |
lowSeqnoAt(int index)
|
void |
merge(Address sender,
long low_seqno,
long high_seqno,
long high_seqno_seen)
Similar to add(), but if the sender already exists, its seqnos will be modified (no new entry) as follows:
this.low_seqno=min(this.low_seqno, low_seqno)
this.high_seqno=max(this.high_seqno, high_seqno)
this.high_seqno_seen=max(this.high_seqno_seen, high_seqno_seen)
If the sender doesn not exist, a new entry will be added (provided there is enough space) |
void |
merge(Digest d)
Adds a digest to this digest. |
java.lang.String |
printHighSeqnos()
|
java.lang.String |
printHighSeqnosSeen()
|
void |
readExternal(java.io.ObjectInput in)
|
void |
reset(int size)
|
void |
resetAt(int index)
Resets the seqnos for the sender at 'index' to 0. |
Address |
senderAt(int index)
|
void |
setHighSeqnoAt(Address sender,
long high_seqno)
|
void |
setHighSeqnoAt(int index,
long high_seqno)
|
void |
setHighSeqnoSeenAt(Address sender,
long high_seqno_seen)
|
void |
setHighSeqnoSeenAt(int index,
long high_seqno_seen)
|
void |
setLowSeqnoAt(int index,
long low_seqno)
|
int |
size()
|
java.lang.String |
toString()
|
void |
writeExternal(java.io.ObjectOutput out)
|
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Digest
public Digest()
Digest
public Digest(int size)
add
public void add(Address sender,
long low_seqno,
long high_seqno)
add
public void add(Address sender,
long low_seqno,
long high_seqno,
long high_seqno_seen)
add
public void add(Digest d)
merge
public void merge(Digest d)
- Adds a digest to this digest. This digest must have enough space to add the other digest; otherwise an error
message will be written. For each sender in the other digest, the merge() method will be called.
merge
public void merge(Address sender,
long low_seqno,
long high_seqno,
long high_seqno_seen)
- Similar to add(), but if the sender already exists, its seqnos will be modified (no new entry) as follows:
- this.low_seqno=min(this.low_seqno, low_seqno)
- this.high_seqno=max(this.high_seqno, high_seqno)
- this.high_seqno_seen=max(this.high_seqno_seen, high_seqno_seen)
If the sender doesn not exist, a new entry will be added (provided there is enough space)
getIndex
public int getIndex(Address sender)
contains
public boolean contains(Address sender)
incrementHighSeqno
public void incrementHighSeqno(Address sender)
- Increment the sender's high_seqno by 1
size
public int size()
senderAt
public Address senderAt(int index)
resetAt
public void resetAt(int index)
- Resets the seqnos for the sender at 'index' to 0. This happens when a member has left the group,
but it is still in the digest. Resetting its seqnos ensures that no-one will request a message
retransmission from the dead member.
reset
public void reset(int size)
lowSeqnoAt
public long lowSeqnoAt(int index)
highSeqnoAt
public long highSeqnoAt(int index)
highSeqnoSeenAt
public long highSeqnoSeenAt(int index)
highSeqnoAt
public long highSeqnoAt(Address sender)
highSeqnoSeenAt
public long highSeqnoSeenAt(Address sender)
setLowSeqnoAt
public void setLowSeqnoAt(int index,
long low_seqno)
setHighSeqnoAt
public void setHighSeqnoAt(int index,
long high_seqno)
setHighSeqnoSeenAt
public void setHighSeqnoSeenAt(int index,
long high_seqno_seen)
setHighSeqnoAt
public void setHighSeqnoAt(Address sender,
long high_seqno)
setHighSeqnoSeenAt
public void setHighSeqnoSeenAt(Address sender,
long high_seqno_seen)
copy
public Digest copy()
toString
public java.lang.String toString()
- Overrides:
toString
in class java.lang.Object
printHighSeqnos
public java.lang.String printHighSeqnos()
printHighSeqnosSeen
public java.lang.String printHighSeqnosSeen()
writeExternal
public void writeExternal(java.io.ObjectOutput out)
throws java.io.IOException
- Specified by:
writeExternal
in interface java.io.Externalizable
readExternal
public void readExternal(java.io.ObjectInput in)
throws java.io.IOException,
java.lang.ClassNotFoundException
- Specified by:
readExternal
in interface java.io.Externalizable
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