Sin t

1
A Distributed Web Information System Platform
for High Responsiveness and Fault
Tolerance Jordi Bataller, Hendrik Decker,
Luis Irún, Francesc Muñoz Instituto
Tecnológico de Informática Universidad
Politécnica Valencia, Spain
2
Replicated !
Development Operation also
OO, graphics
dissemination Master Mind
new protocols . private non-profit
on campus
A Distributed Web Information System Platform
for High Responsiveness Fault Tolerance High
Availability Consistency Jordi Bataller,
Hendrik Decker, Luis Irún, Francesc
Muñoz Instituto Tecnológico de
Informática Universidad Politécnica Valencia
3

• DIWISA
• Middleware to develop and run a distributed o-o
• web information system based on off-the-shelve
  DBMS

Application
Application
Application
Application
D I W I S A
IS
DBMS
DBMS
DBMS
DBMS
DB
DB
DB
DB
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Concurrent Users, Distributed Servers, High Data
Locality
Application
Application
Application
Application
Application
Application
W I S
W I S
W I S
DB
DB
DB
No replication
Partial replication
Total replication
5
Developers and Users transparent view
Application
Distributed WIS
DWIS
WIS
WIS
WIS
Distributed DBMS
DDB
Replicated Data
DB
DB
DB
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Is Distribution Replication worth the
Effort ?
Complex Distributed Concurrency Protocols
High Responsiveness
Fast Access to Local Data
Limited Network Capacities, Recovery needs to be
solved
Fault Tolerance
High Availability
Ease of Development
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• Centralized, Object-Relational
• Some support for different isolation levels
• Industry standard integrity checking
• Open Source

• Centralized, Relational
• No good transaction support (patches...)
• Almost no integrity support (patches...)
• Very fast reads (updating not recommended...)
• Open Source

• Distributed Relational DBMS
• Standard support of transactions and integrity
• Commercial

• Distributed Object-Relacional DBMS
• Industry standard support for Transactions
  and Integrity
• Commercial

DB2
INGRES
INFORMIX
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• Results of market analysis
• scant DBMS support distribution (consistency,
  recovery)
• little DBMS support for distributed object
  orientation
• Application development is difficult, costly
• and possibly not backward- nor
  upward-compatible
• Conclusion DIWISA

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DIWISA
API for application development
LIBRARY
Provides object-oriented data access
provides API
Core Component of DIWISA
Communication with other DIWISA Managers
Consistency Protocols Recovery Protocols
MANAGER
supports distribution
communicates with only one UDS
UDS
Translation of Managers function calls to
native underlying database
provides Object Orientation
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D I W I S A
LIBRARY
CORBA
MANAGER
JDBC
CORBA
UDS
JDBC
DBMS
DB
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Summary of highlights

• Transform off-the-shelve DBMS into full-fledged
  WAN-based
• distributed (o-o) DB system underlying WISs
• Flexible Replication, optimizes tradeoff
  Availability/Consistency
• Innovative Architecture, open for different
• networks, interfaces, libraries, protocols
• Pluggable protocols for message passing,
  transaction processing, replication, recovery
• Innovative concept of fault tolerance and error
  recovery
• Fully operational prototype (Java) is up and
  running
• still needed performance improvements,
  theoretical foundation