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Scalable Consistency Protocol
CONTENTS
1. INTRODUCTION
2. DESIGN PRINCIPLES & EXPLNTION
2.1. !ODULE DESCRIPTIOIN
". PRO#ECT DICTIONR$
".1. DT%LO DIGR!S
".2. USE CSE DIGR!
".". CLSS DIGR!
'. %OR!S & REPORTS
'.1. I(O S!PLES
). TESTING
*. +I+ILIOGRP,$
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1. INTRUDECTION
EXISTING SYSTEM
s co-/tin0 beco-es -ore erasie local area net3or4s are beco-in0
lar0er an5 better interconnecte5. it6 t6is 0ro3t6 o7 interconnecte5
co-/tin0 6i06ly interactie alications 3ill san -any local net3or4s.
E8a-les o7 s/c6 alications co-e 7ro- t6e 5o-ain o7 co-/ter s/orte5
cooeratie 3or4 as 3ell as irt/al reality base5 5istrib/te5 0a-es s6oin0
an5 ot6ers.
T6ese alications nee5 to be s/orte5 by 5istrib/te5 serices t6at roi5e
lo3 latency access to 5yna-ically c6an0in0 s6are5 state. T6e roble- o7
scalable an5 consistent access is also i-ortant 7or 5yna-ic content on t6e
3eb. +/t e8istin0 syste- 7ollo3s sync6roni9ation an5 Co--/nication in
5istrib/te5 eniron-ent 36ic6 lea5s to increase latency ti-e.
DRAWBACKS OF EXISTING SYSTEM
In interactie alications ti-ely 5isse-ination o7 an /5ate is re:/ire5. It
is obio/s rotocols t6at i-le-ent stron0 consistency are -ore e8ensie
an5 5o not er-it any ;la0< t6at -ay be accetable in 5isse-inatin0 t6e
e77ects o7 /5ate oerations. e no3 6ae e8lore5 a notion o7 stron0
consistency t6at 0/arantees seriali9ation o7 all ob=ect accesses as in
se:/ential consistency. ,o3eer it allo3s client no5es control oer 6o3
:/ic4ly t6ey 3ant to beco-e a3are o7 /5ates to cac6e5 ob=ects. O/r belie7
is t6at s/c6 7le8ible control oer /5ate 5isse-ination is necessary 7or
5eeloin0 scalable rotocols 7or stron0 consistency.
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PROPOSED SYSTEM
co--on 3ay to a55ress scalability re:/ire-ents o7 5istrib/te5 serices in
e8istin0 syste- is to e-loy serer relication an5 client cac6in0 o7 ob=ects
t6at encas/late t6e serice state. T6e er7or-ance o7 s/c6 syste- co/l5
5een5 ery -/c6 on t6e rotocol i-le-ente5 by t6e syste- to -aintain
consistency a-on0 ob=ect coies. e e8lore scalable consistency rotocols
t6at neer re:/ires sync6roni9ation an5
Co--/nication bet3een all no5es t6at 6ae coies o7 relate5 ob=ects.
e ac6iee t6is by 5eeloin0 a noel aroac6 calle5
local consistency>LC?.
T6e basic i5ea o7 LC -ec6anis- is as 7ollo3s. In tra5itional stron0 consistency
rotocols no5es t6at /5ate a s6are5 ob=ect 8 ta4e t6e resonsibility o7
noti7yin0 no5es t6at 6ae coies o7 8 abo/t t6e /5ates. 6en s/c6 no5es are
3i5ely 5istrib/te5 /5ate latencies can be ery lar0e. In LC base5 rotocols
6o3eer no5es t6at /5ate s6are5 state are not resonsible 7or in7or-in0
ot6er no5es abo/t /5ates@ instea5 a no5e nee5s to beco-e a3are o7 an
e8ternal /5ate t6e no5e e8ec/tes consistency actions to inali5ate local
ob=ect coies t6at -ay be oer3ritten 3it6 resect to t6e ne3ly arrie5 ob=ect.
ccess latencies can be lo3er in LC base5 rotocols beca/se t6ey allo3 bot6
rea5 an5 3rite accesses to co-lete 3it6o/t re:/irin0 co--/nication 3it6 all
no5es t6at 6ae coies o7 t6e accesse5 ob=ect. No5es can 7etc6 coies o7
ob=ects eit6er on 5e-an5 or ne3 coies can be sent to no5es 36ic6 can
intro5/ce t6e- into t6eir cac6es in a consistent -anner. T6/s bot6 /s6 an5
/ll style /5ate 5isse-ination is ossible in LC base5 rotocols.
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2. DESIGN PRINCIPLES & EXPLANATION
2.1. MODULE DESCRIPTIOIN
Local Con!"#nc$ A%%oac'
In t6e syste- -o5el ass/-e5 6ere s6are5 ob=ects are store5 at serer no5es.
Client no5es can cac6e ob=ect coies an5 access t6e- locally. Ob=ects can be
relate5 an5 consistency re:/ire-ents can be 5e7ine5 across relate5 ob=ects. %or
e8a-le i7 8 an5 y are t3o relate5 5oc/-ent ob=ects >e.0.8 contains res/lts o7
an e8eri-ent an5 y contains a 5isc/ssion o7 t6ese res/lts?an5 a /ser 7irst
/5ates 8 an5 t6en y it is 5esirable t6at anot6er /ser t6at accesses t6e
/5ate5 coy o7 y 3ill also see t6e ne3 coy o7 8. since no5es 6ae coies o7
s/c6 ob=ects t6ey are intereste5 in /5ates to ob=ects accesse5 t6e-. 3e
5e7ine a syste- 0lobal ie3 an5 no5e ie3s to cat/re t6e al/es o7 ob=ects
t6at can be accesse5 by no5es.
LC Ba#( Po"ocol)
1. In LC base5 rotocols 36en a serer trans7ers 3rite access to a ne3
no5e e8istin0 rea5ers are not sent inali5ation -essa0es. in 7act
rea5ers o7 an ob=ect can coe8ist 3it6 a 3riter by rea5in0 al/es 7ro- ol5
b/t consistent no5e ie3s. T6/s not only inali5ation -essa0es are
aoi5e5 a no5e 5oes not nee5 to receie an5 rocess -essa0es eac6
ti-e an ob=ect cac6e5 by it is /5ate5 at anot6er no5e.
2. LC base5 rotocols or5er all accesses to relate5 ob=ects by a5ancin0
no5e ie3s in a consistent -anner. t t6e ti-e a ne3 ob=ect coy is
a55e5 to a no5e cac6e t6e no5e er7or-s local consistency actions to
ens/re t6at c/rrently store5 coies o7 s6are5 ob=ects are ali5 in t6e ne3
no5e ie3. S/c6 consistency actions re:/ire no co--/nication beca/se
t6ey only inali5ate5 beca/se t6ey only inali5ate local coies t6at
otentially oer3ritten in t6e ie3.
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". client no5e -/st co--/nicate 3it6 an ob=ectAs serer 36en it eit6er
5oes not 6ae t6e ob=ect in its or it 3ants to /5ate t6e ob=ect b/t 6as
only rea5 er-ission. S/c6 co--/nication 3it6 t6e serer can a5ance
t6e clients ie3.in a55ition client ie3s can be a5ance5 3it6 erio5ic
co--/nication t6at can be initiate5 by t6e serer or t6e client ie3s an5
t6e 0lobal ie3 is bo/n5e5. T6/s 36ile 0/aranteein0 t6at ob=ect accesses
can be seriali9e5 LC base5 rotocols o77ers t6e 7le8ibility to control t6e
c/rrency o7 cac6e5 ob=ect coies base5 on reso/rce aailability an5
alication nee5s.
O*+#c" L!,#"!-# Ba#( Po"ocol
In t6is rotocol 3e ass/-e t6at relate5 ob=ects are artitione5 a-on0
serers an5 t6e serer 7or an ob=ect re-ains 7i8e5.
In LC base5 rotocol 36en a no5eAs ie3 a5ances beca/se o7 a ne3ly
cac6e5 ob=ect coy it nee5s to 4no3 36at e8istin0 ob=ect coies 6ae been
oer3ritten in t6e ne3 no5e ie3. e ta4e an aroac6 in 36ic6 -eta5ata
associate5 3it6 ob=ect coies are /se5 to 5eter-ine 36at e8istin0 ob=ect
coies are still ali5 36en a no5e -oes to a ne3er ie3.
Denote t6e coy o7 ob=ect 8 t6at stores al/e be 8>?. T6e -etaB5ata
associate5 3it6 8>? is calle5 its li7eti-e. Int/itiely t6e li7e ti-e o7 an
ob=ect coy is t6e ti-e interal 5/rin0 36ic6 t6e coy can be accesse5
3it6o/t iolatin0 consistency. T6is is 5one by associatin0 a ali5 ti-e. I7
eac6 ob=ect coy cac6e5 at a no5e 6as a li7e ti-e associate5 3it6 it a
strai06t 7or3ar5 test can be 5eeloe5 to 5eter-ine i7 a set o7 cac6e5
coies belon0 to a consistent 0lobal ie3.
In lar0eBscale 5istrib/te5 syste-s it is not reasonable to ass/-e t6e
e8istence o7 a sync6roni9e5 0lobal cloc4 to 5e7ine t6e ob=ect li7e ti-es. So
3e 7ollo3e5 a rotocol t6at 5oes not re:/ire sync6roni9e5 cloc4s. Instea5
lo0ical cloc4s are /se5 to recor5 ob=ect li7e ti-es.
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. PRO/ECT DICTIONARY
.1. DATAFLOW DIAGRAMS
Conte8t leel 5i0s leelB
Login user Process Distributor
Customer
Data base
Distributor Process
Add books
Delete books
Edit books
Issue books
ProcessCustomer Distributed
system
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Adding books Process
Data base
Deleting books Process
Data base
Editing books Process
Data base
Issuing books Process
Data base
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Conte8t leel 5i0s leelB
Multiplerequests from
customer Process
Data base
ProcessCustomer Distributed
system
Login user Process Distributor
Data base
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User
RequestsDistributo
r
Local
serer
!it"database
Connected serer #
Connected serer $
Connected serer %
Connected serer n
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User
Requests
Localserer
Local Data base
Distributor
&erer#&erer# ' ' ' &erer#Multiple requests
from clients
Local serer
Data base
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user
Recive the Response
Read-hit
send a request
Write Hit Write-Fault
Write-Miss
USE0CASE DIAGRAM
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Remote<<Interface>>
NameServerIntf
NameServerImpl
Runnable
nicastRemote!b"ect
Hash#able
CLASS DIAGRAM
(ote) t"is diagram represents t"e relations"ip among arious classes used to build t"e
system'
NameServerIntf
boolean re$ister%&void 'ithdra'%&Strin$ $et(ddress%&
NameServerImpl
ht ) Hashtable
NameServerImpl%&boolean re$ister%&void 'ithdra'%&
Strin$ $et(ddress%&
NameServer
static void main%&
e
s 5ia0ra- reresents t6e ario/s -et6o5s i-le-ente5 in eac6 o7
classes reresente5 aboe. ,ere t6e UnicastRe-oteOb=ect class
i5es t6e re-ote ob=ect re:/ire5 to rocess t6e serice in case
ob=ect is not resent in t6e 6as6table>collection? on t6e local
er
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) user
)NameServerIntf )NameServer Impl
)Hash#able )nicastRemote!b"ect
send request
identif* server I+address
connect to server search forrequested
ob"ect
for'ard result ifob"ect available
return messa$e ifob"ect not available
request readpermission ofob"ect from
remote server
return resultfrom ob"ect ofremote server
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) user
)NameServerIntf
)NameServerImpl
)Hash
#able
)nicastRemote!b"ect
,) identif* server I+ address
-) send request
.) connect to server
/) return messa$e ifob"ect not available
0) search forrequested ob"ect
1) for'ardresult if
ob"ectavailable
2) request read permission ofob"ect from remote server
3) return result from ob"ectof remote server
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. FORMS & REPORTS
.1. IO SAMPLES
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