Characteristics of the Architecture

1. Project PresentationCS 775/875Distributed SystemsRetail store chain ArchitectureTeam MembersJia ZhuRufeng LiuKajuluri SreeKalyana C

2. Characteristics of the Architecture • Availability:System works with at least one available server. • Redundancy:Exists by having replicas for the Retail store nodes. • Centralized authority held by a central server which provides the various remote methods for running the system. • Openness:New nodes can be added on the fly. • Response:Standard response time. • Failure detection:Methods are provided to detect the crashed nodes and report to the central server.

3. Level 1 Level i(i=2..n-1) EMPLOYEE DATABASE John Marshall 25 Mgr 58 12.5 Rose Mary Ann 34 Clerk 23 42 Level n MERCHANDISE 100 Shoes 156.99 45 200 Monitors 225.88 22 Architecture EMPLOYEE DATABASE John Marshall 25 Mgr 58 12.5 Rose Mary Ann 34 Clerk 23 42

4. Level 1(Central Server) • Central Server is responsible for maintaining the global tree structure for the sales network . • Handles new node registration with callRegister(node) method. • A newly registered intermediate/retail store node claims itself as somebody’s direct child using callConnect (child, parent). • An intermediate/retail store node to ask for its direct children uses method callRequestDirectChildren(father)

5. Level 1(Continued) • An intermediate/retail store node ,to ask for all its children and grandchildren uses methodcallRequestAllChildren(superParent). • To find out all the retail stores below it a node uses the method callRequestRetailStores(superParent). • An intermediate/retailstore node calls this method to move one child node to another parent node.(callChangeOwnership(newParent, oldParent, child) . • After checking the connectivity of the network, an intermediate/retailstore node calls this method to report the crashed nodecallClaimLostNode(node) • An intermediate/retailstore node calls to inquire the network structure of the sales network uses the method (callShowNetwork())

6. Level 2(Intermediate nodes/regional branch servers) • At any given point of time 3 threads run in each of the intermediate nodes. • The following tasks are accomplished by each thread. • Thread 1:In this thread, the interface which enables users to issue the queries and commands runs.If a user issues a query requesting the products information, it first calls callRequestRetailStores() at Central Server and retrieves all retail store’s addresses. Secondly, it calls every retail store and collects all products information from there and displays them to the users. • Thread 2:Runs the service methods pertaining to the employee database and handles all the queries on the employee database. • Thread 3:Checks the connectivity of the network.The checking process works as follows:Every intermediate/retail store node will periodically (say 1 minute) check its children and find out whether they are alive, if some of them crashed, it will report the crashed node to the center server.

7. Level 3(Retail Store Server) • Two threads run in the retail store nodes at any given point in time. • The following tasks are accomplished by the two threads: • Thread 1:Runs the interface which enables the user to enter queries regarding the store items. • Thread 2:Runs the service methods (maintaining product databases and employee database). • Replicas/Back up:Each retail store in the architecture has a replica which gets the same sort of updates as the main node.when the main node crashes the replica acts as the main node and handles all the updates.when the main node comes to life it will inform the central server that it is up.At this point it has to update itself with the back ups database and carry on with its normal duties.

8. Database handling/File handling • Nodes at each of the levels are responsible for their files. • Updations as a result of queries are stored in a linked list structure,and then written on to the text file. • Simultaneously the sale information is written into another text file . • This text file is used for total sales,and other such details. • Employee database is handled separately at each node. • The administrator is responsible for entering the details of the employee pay hours. • Based upon which the employee monthly salary is calculated.

9. References: • George Coulouris,Jean Dollimore,Tim Kinderberg,”Distributed Systems Concepts and Design”ISBN 81-7808-462-7,Person Education Ltd,Second Indian reprint 2002. • Harvey M.Deitel,Paul J.Deitel “Java How to Program”ISBN 0-13-101621-0,Prentice Hall,4th Edition.