Description
In this assignment, you are going to design and implement a Distributed Library
Management System (DLMS) for a group of libraries: a distributed system used by library
managers to manage the information about the items available in the libraries and library
users to borrow or return items across the libraries.
Consider three libraries: Concordia (CON), McGill (MCG) and Montreal (MON) for your
implementation. The users of the system are library managers and library users identified
by a unique managerID and userID respectively, which is constructed from the acronym of
their library and a 4-digit number (e.g. CONM1111 for a manager and CONU1111 for a
user).
Whenever the user performs an operation, the system must identify the server that
user belongs to by looking at the ID prefix (i.e. CONM or CONU) and perform the
operation on that server. The user should also maintain a log (text file) of the actions they
performed on the system and the response from the system when available. For example, if
you have 10 users using your system, you should have a folder containing 10 logs.
In this DLMS, there are different managers for the three libraries/servers. They create
availability of items in their library along with the quantity of the items. A user can
borrow an item offered by any library, if it is still available (if the item quantity is not yet
zero).
You should ensure that if the quantity of an item is zero, no more users cannot
borrow that item. Also, a user can borrow multiple items in their own library, but only 1
item from each of the other libraries. Each item in a library has an associated itemID
(a 4-digit number appended to the library acronym, like CON1012, MCG1023, MON1034,
etc.) and an itemName (a string describing the item). Note that different libraries can
have the item with the same itemName under different itemIDs.
Each server also maintains a log file containing the history of all the operations that have
been performed on that server. This should be an external text file (one per server) and
shall provide as much information as possible about what operations are performed, at
what time and who performed the operation.
These are some details that a single log file
record must contain:
• Date and time the request was sent.
• Request type (borrow an item, return an item, etc.).
• Request parameters (userID, itemID, etc.).
• Request successfully completed/failed.
• Server response for the particular request.
The information in a library are maintained in a hashmap as shown in Figure 1. All
information must be kept only in the library servers, not in the clients.
Fig. 1 Hashmap of a single library
Manager Role:
The operations that can be performed by a manager are the following:
• addItem (managerID, itemID, itemName, quantity):
When a manager invokes this method on the associated server (determined by the
unique managerID prefix), it attempts to add an item with the information passed,
and inserts the record at the appropriate location in the hash map. The server
returns information to the manager whether the operation was successful or not
and both the server and the client store this information in their logs. If an item
already exists, the new quantity entered should be added to the current quantity of
the item. If an item does not exist in the database, then simply add it. Log the
information into the manager log file.
• removeItem (managerID, itemID, quantity)
When invoked by a manager, the server associated with this manager (determined
by the unique managerID) searches in the hashmap to find and delete the item.
There can be two cases of deletion, first, if the manager wants to decrease the
quantity of that item, second, if the manager wants to completely remove the item
from the library. Upon success or failure it returns a message to the manager and
the logs are updated with this information.
If an item does not exist, then obviously
there is no deletion performed. Just in case that, if an item exists and a user has
borrowed it, then, delete the item and take the necessary actions. Log the
information into the log file.
• listItemAvailability (managerID):
When a manager invokes this method from his/her library through the associated
server, that library server finds out the names and quantities of each item available
in the library. Eg: CON6231 Distributed Systems 5, CON6441 Advanced
Programming 4, CON6491 Systems Software 0.
CON1012
CON1023
CON1034
Name, 10
Name, 1
Name, 6
CON1012
CON1023
CON1034
CONU1111,
MCGU2345
MONU1111,
CONU1233
MCGU1111,
CONU2345,
CONU1234
User Role:
The operations that can be performed by a user are the following:
• borrowItem (userID, itemID, numberOfDays) :
When a user invokes this method from his/her library through the server associated
with this user (determined by the unique userId prefix), it attempts to borrow the
specified item.
If the item is from a different library, then the user’s library sends a
UDP/IP request to the item’s library to borrow. If the operation was successful,
borrow the item and decrement the quantity for that item. Also, display an
appropriate message to the user and both the server, the client stores this
information in their logs.
If the borrow operation is unsuccessful, ask the user if
he/she wants to be added in the waiting queue. If prompted no, method ends,
otherwise add the userID to the queue corresponding to the requested item and
whenever the item is available again, automatically lend the item to the first user in
that queue.
• findItem (userID, itemName):
When a user invokes this method from his/her library through the server associated
with this user, that library server gets all the itemIDs with the specified itemName
and the number of such items available in each of the libraries and display them on
the console. This requires inter server communication that will be done using
UDP/IP sockets and the result will be returned to the user. Eg: MON6231 5,
CON6441 4, CON6497 1, MCG6132 5.
• returnItem (userID, itemID):
When a user invokes this method from his/her library through the server associated
with this user (determined by the unique userID prefix) searches the hash map to
find the itemID and returns the item to its library. Upon success or failure it
returns a message to the user and the logs are updated with this information. It is
required to check that an item can only be returned if it was borrowed by the same
user who sends the return request.
Thus, this application has a number of servers (one per library) each implementing the
above operations for that library, userClient invoking the user’s operations at the
associated server as necessary and managerClient invoking the manager’s operations at
the associated server. When a server is started, it registers its address and
related/necessary information with a central repository.
For each operation, the
userClient/managerClient finds the required information about the associated server from
the central repository and invokes the corresponding operation. Your servers should
ensure that a user can only perform a user operation and cannot perform a
manager operation and vice-versa.
In this assignment, you are going to develop this application using Java RMI. Specifically,
do the following:
• Write the Java RMI interface definition for the server with the specified operations.
• Implement the server.
• Design and implement a userClient, which invokes the server system to test the correct
operation of the DLMS invoking multiple servers (each of the servers initially has a few
records) and multiple users.
• Design and implement a managerClient, which invokes the server system to test the
correct operation of the DLMS invoking multiple server (each of the servers initially
has a few records) and multiple managers.
You should design the server maximizing concurrency. In other words, use proper
synchronization that allows multiple users to perform operations for the same or different
records at the same time.
Marking Scheme
[30%] Design Documentation: Describe the techniques you use and your architecture,
including the data structures. Design proper and sufficient test scenarios and
explain what you want to test. Describe the most important/difficult part in this
assignment. You can use UML and text description, but limit the document to 10
pages. Submit the documentation and code electronically by the due date; print the
documentation and bring it to your DEMO.
[70%] DEMO in the Lab: You have to register for a 5–10 minutes demo. Please come to
the lab session and choose your preferred demo time in advance. You cannot demo
without registering, so if you did not register before the demo week, you will lose
40% of the marks. Your demo should focus on the following.
[50%] Correctness of code: Demo your designed test scenarios to illustrate the
correctness of your design. If your test scenarios do not cover all possible
issues, you will lose part of marks up to 40%.
[20%] Questions: You need to answer some simple questions (like what we have
discussed during lab tutorials) during the demo. They can be theoretical
related directly to your implementation of the assignment.
