Distributed Systemsand users are able to access their systems remotely remote clients • For load balancing • Performance sources Consistency is all about timing!... state when a user
Trang 1System Integration
Mini Case Studies © 2010
Shawn A Butler, Ph.D.
Senior Lecturer, Executive Education Program
Institute for Software Research
Carnegie Mellon University
Concurrency and Case Study 2
Trang 2important to a system integrator
Trang 3Distributed Systems
and users are able to access their systems
remotely
remote clients
• For load balancing
• Performance
sources
Consistency is all about timing!
Trang 4Replicated Data and Services
services
Trang 5state when a user can access data at any source
and it will be the same
be in a consistent state?
few minutes, hours, or next day?
distributed systems based on user requirements!
more expensive the system
Trang 6Maintaining Consistency
Client
Naming Service
Foo(x) While i = ….
Application ABC
Naming Service
Trang 7Information Consistency - ACID
are completed or no task is completed
„legitimate‟ state at the end of a
transaction
to other transactions
finished, it will persist
Trang 8Why Do We Care?
ensure information consistency
requirements to improve performance
problems
Different transaction processing products
Different assumptions about consistency
Trang 9DB Middleware Presentation
DB
Middleware
Presentation
Middleware Presentation
Transaction
Trang 10DB Middleware Presentation
DB
Middleware
Presentation
Middleware Presentation
Transaction
Trang 11DB Middleware Presentation
DB
Middleware
Presentation
Middleware
Presentation
Transaction Bad Transaction
Trang 12DB Middleware Presentation
DB Middleware Presentation
Transaction Bad Transaction
10 10
10 10
10
10
10 10 +3 =13 +5 =15
Trang 13DB Middleware Presentation
DB Middleware Presentation
Transaction Bad Transaction
10 13
13 13
15
15
15
15 +3 =13 +5 =15
15
Trang 14DB Middleware Presentation
DB
Middleware
Presentation
Middleware Presentation
Transaction
Trang 15Heuristic 2
Build and maintain options as long as possible
in the design and implementation of complex systems
You will need them.
Trang 16concurrency issues
between performance and global
consistency
with databases and transaction processing,
but they are important when integrating
different types of systems
Trang 17Case Study 2: Integration
ACME Executive Management would like to see a
„dashboard‟ of important information that will help them
make informed decisions about ACME‟s employees.
ACME provided a list of key requirements for the
„dashboard‟, however, the design of the GUI is the
responsibility of the team.
The Executive Management team will not update the data,
the data is for information purposes only.
The Executive Management team will want to “drill down”
into the data presented.
The payroll and HR applications must remain unchanged!
The application should be thoroughly tested since it would
not look good for the development team to have buggy
Trang 18presentation model
limitations of this model and data
consistency
show that the system meets the CEO‟s
requirements