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).- Author:
- Bela Ban
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Nested Class Summary
Nested Classes Modifier and Type Class Description protected static class
FRAG2.FragEntry
Class represents an entry for a message.
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Field Summary
Fields Modifier and Type Field Description protected AverageMinMax
avg_size_down
protected AverageMinMax
avg_size_up
protected int
curr_id
Used to assign fragmentation-specific sequence IDs (monotonically increasing)protected int
frag_size
protected java.util.concurrent.ConcurrentMap<Address,java.util.concurrent.ConcurrentMap<java.lang.Long,FRAG2.FragEntry>>
fragment_list
protected Address
local_addr
protected java.util.List<Address>
members
protected java.util.concurrent.atomic.LongAdder
num_frags_received
protected java.util.concurrent.atomic.LongAdder
num_frags_sent
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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 FRAG2()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
clearAllFragments()
void
clearFragmentsFor(Address mbr)
java.lang.Object
down(Event evt)
Fragment a packet if larger than frag_size (add a header).java.lang.Object
down(Message msg)
A message is sent down the stack.protected void
fragment(Message msg)
Send all fragments as separate messages (with same ID !).int
fragSize()
FRAG2
fragSize(int size)
java.lang.String
getAvgSizeDown()
java.lang.String
getAvgSizeUp()
int
getFragSize()
long
getNumberOfReceivedFragments()
long
getNumberOfSentFragments()
protected void
handleViewChange(View view)
void
init()
Called after instance has been created (null constructor) and before protocol is started.void
resetStats()
void
setFragSize(int s)
protected Message
unfragment(Message msg, FragHeader hdr)
1.java.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.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, isErgonomics, level, parse, providedDownServices, providedUpServices, requiredDownServices, requiredUpServices, resetStatistics, setDownProtocol, setErgonomics, setId, setLevel, setProtocolStack, setSocketFactory, setUpProtocol, setValue, start, statsEnabled, stop
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Field Detail
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frag_size
protected int frag_size
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fragment_list
protected final java.util.concurrent.ConcurrentMap<Address,java.util.concurrent.ConcurrentMap<java.lang.Long,FRAG2.FragEntry>> fragment_list
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curr_id
protected int curr_id
Used to assign fragmentation-specific sequence IDs (monotonically increasing)
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members
protected final java.util.List<Address> members
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local_addr
protected Address local_addr
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num_frags_sent
protected java.util.concurrent.atomic.LongAdder num_frags_sent
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num_frags_received
protected java.util.concurrent.atomic.LongAdder num_frags_received
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avg_size_down
protected final AverageMinMax avg_size_down
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avg_size_up
protected final AverageMinMax avg_size_up
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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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getNumberOfSentFragments
public long getNumberOfSentFragments()
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getNumberOfReceivedFragments
public long getNumberOfReceivedFragments()
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fragSize
public int fragSize()
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fragSize
public FRAG2 fragSize(int size)
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getAvgSizeDown
public java.lang.String getAvgSizeDown()
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getAvgSizeUp
public java.lang.String getAvgSizeUp()
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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 fragmentation is needed !
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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)
If event is a message, if it is fragmented, re-assemble fragments into big message and pass up the stack.
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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 view)
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clearFragmentsFor
public void clearFragmentsFor(Address mbr)
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clearAllFragments
public void clearAllFragments()
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fragment
protected void fragment(Message msg)
Send all fragments as separate messages (with same ID !). Example:Given the generated ID is 2344, number of fragments=3, message {dst,src,buf} would be fragmented into: [2344,3,0]{dst,src,buf1}, [2344,3,1]{dst,src,buf2} and [2344,3,2]{dst,src,buf3}
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unfragment
protected Message unfragment(Message msg, FragHeader hdr)
1. Get all the fragment buffers 2. When all are received -> Assemble them into one big buffer 3. Read headers and byte buffer from big buffer 4. Set headers and buffer in msg 5. Return the message
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