Package org.jgroups.protocols
Class FRAG2
- java.lang.Object
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- org.jgroups.stack.Protocol
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- org.jgroups.protocols.FRAG2
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public class FRAG2 extends Protocol
Fragmentation layer. Fragments messages larger than frag_size into smaller packets. Reassembles fragmented packets into bigger ones. The fragmentation number is prepended to the messages as a header (and removed at the receiving side).Each fragment is identified by (a) the sender (part of the message to which the header is appended), (b) the fragmentation ID (which is unique per FRAG2 layer (monotonically increasing) and (c) the fragement ID which ranges from 0 to number_of_fragments-1.
Requirement: lossless delivery (e.g. NAK, ACK). No requirement on ordering. Works for both unicast and multicast messages.
Compared to FRAG, this protocol does not need to serialize the message in order to break it into smaller fragments: it looks only at the message's buffer, which is a byte[] array anyway. We assume that the size addition for headers and src and dest address is minimal when the transport finally has to serialize the message, so we add a constant (200 bytes).- Version:
- $Id: FRAG2.java,v 1.36.2.1 2008/07/22 11:51:22 belaban Exp $
- Author:
- Bela Ban
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Constructor Summary
Constructors Constructor Description FRAG2()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
down(Event evt)
Fragment a packet if larger than frag_size (add a header).int
getFragSize()
java.lang.String
getName()
long
getNumberOfReceivedFragments()
long
getNumberOfReceivedMessages()
long
getNumberOfSentFragments()
long
getNumberOfSentMessages()
int
getOverhead()
void
init()
Called after instance has been created (null constructor) and before protocol is started.void
resetStats()
void
setFragSize(int s)
void
setOverhead(int o)
boolean
setProperties(java.util.Properties props)
Setup the Protocol instance acording to the configuration stringjava.lang.Object
up(Event evt)
If event is a message, if it is fragmented, re-assemble fragments into big message and pass up the stack.-
Methods inherited from class org.jgroups.stack.Protocol
destroy, downThreadEnabled, dumpStats, enableStats, getDownProtocol, getProperties, getProtocolStack, getThreadFactory, getTransport, getUpProtocol, printStats, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, setDownProtocol, setPropertiesInternal, setProtocolStack, setUpProtocol, start, statsEnabled, stop, upThreadEnabled
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Method Detail
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getFragSize
public int getFragSize()
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setFragSize
public void setFragSize(int s)
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getOverhead
public int getOverhead()
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setOverhead
public void setOverhead(int o)
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getNumberOfSentMessages
public long getNumberOfSentMessages()
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getNumberOfSentFragments
public long getNumberOfSentFragments()
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getNumberOfReceivedMessages
public long getNumberOfReceivedMessages()
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getNumberOfReceivedFragments
public long getNumberOfReceivedFragments()
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setProperties
public boolean setProperties(java.util.Properties props)
Setup the Protocol instance acording to the configuration string- Overrides:
setProperties
in classProtocol
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init
public void init() throws java.lang.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.
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resetStats
public void resetStats()
- Overrides:
resetStats
in classProtocol
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down
public java.lang.Object down(Event evt)
Fragment a packet if larger than frag_size (add a header). Otherwise just pass down. Only add a header if framentation is needed !
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