Description
Objective
The objective of this homework is to:
• Understand the use of multiple threads
• Develop a custom multithreaded web server.
• Understand the use of critical sections created using a std::mutex and
std::lock_guard.
Grading Rubric:
The program submitted for this homework must pass necessary base
case test(s) in order to qualify for earning any score at all.
Programs that do not meet base case requirements will be assigned
zero score!
Program that do not compile, have a method longer than 25 lines, or
just some skeleton code will be assigned zero score.
• Base case [10 points]: No multithreading needed
• Extra function [10 points]: Multithreading and using std::lock_guard
• Documentation & Conciseness [5 points]: Overall structure, organization, conciseness,
documentation, variable-names, etc. If your methods are not concise points will be
deducted.
NOTE: Violating CSE programming style guidelines is a compiler error! Your program should
not have any style violations.
Due before: 11:59 PM (before Midnight) on Wed Oct 21 2020
Page 2 of 5
Starter code
A short starter code is supplied in homework7.cpp to streamline testing. You may reuse code
from previous homework and labs as you see fit.
However, for testing a custom multithreaded test client is supplied in bank_client.cpp
along with input files. You should not be modifying the supplied input text files. You should
not add bank_client.cpp to your NetBeans project. You are expected to separately
compile and run the supplied bank_client.cpp for testing your custom web-server as
shown further below.
F
Despite all the testing, it still takes a human to review a program to decide if a program is
correctly multithreaded. Hence, the even if your program passes all the tests in the CODE
plug-in it could still be incorrectly multithreaded. Consequently, double-check your
solution to ensure you are correctly multithreading your program in order to earn full
points for this homework.
Responses
The responses from your server should be in the following standard HTTP format, with each
HTTP header lines only terminated with a “\r\n”. The message at the end of the headers does
not have any newline characters.
HTTP/1.1 200 OK\r\n
Server: BankServer\r\n
Content-Length: 19\r\n
Connection: Close\r\n
Content-Type: text/plain\r\n
\r\n
Account 0x01 created
Note: The Content-Length corresponds to the length of the message (e.g., – “Account 0x01
created” has 19 characters) in the HTTP response. This message should not have any newline
characters in it.
Requirements
In this homework, you are expected to develop a simple multithreaded banking application that
operates using standard HTTP requests and responses. The bank consists of a collection of
accounts. Each account is identified by a unique account ID (a std::string) and its
associated balance (double). This information must be stored as a
std::unordered_map, with the account ID serving as the key.
The bank web-server is expected operate as follows:
1. The bank server should be developed by suitably implemented the supplied runServer
as the top-level method. Similar to other web-servers, this method should loop forever
and accept connections from web-clients.
2. For each connection, it should use a separate detached thread for processing the request
from the user. Each request will be a standard HTTP GET request in the form (with each
line terminated with a “\r\n”):
Due before: 11:59 PM (before Midnight) on Wed Oct 21 2020
Page 3 of 5
GET /TransactionInfo HTTP/1.1
Host: localhost:4000
Connection: close
Where, TransactionInfo is a standard query string in the form:
“trans=cmd&acct=AccountID&amount=amt”. The cmd indicates type of
operation to perform. The account and amount information are optional. The expected
operation for and output for each command is shown below.
Note: The commands below assume that account name is 0x01. However, the account
ID can be different/vary. So do not hardcode account ID to 0x01.
TransactionInfo (all in 1 line) Description of required
operation
Expected msg from
server in HTTP response
trans=reset Clear out all accounts All accounts reset
trans=create&acct=0x01 Create account only if account
does not exist.
Account 0x01 created
or
Account 0x01 already
exists
trans=credit&acct=0x01&am
ount=20.25 Add specified amount to account,
if account exists
Account balance
updated or
Account not found
trans=debit&acct=0x01&amo
unt=20.25 Subtract specified amount to
account, if account exists
Account balance
updated or
Account not found
trans=status&acct=0x01 Return account balance with
exactly 2 decimal places via:
ss << std::fixed <<
std::precision(2) << 20.25;
Account 0x01: $0.00
Account not found
Note: The message “Account not found” is returned if the specified account ID does not
exist. The response is always in the format shown earlier but the specific message in the response
will vary as shown above.
Notes & Suggestions
• Use the Bank class in starter code to encapsulate all of the data. You can pass a reference
to a shared bank object to various methods in your program.
• Processing requests is straightforward. But don’t forget to read request headers from
the client. Otherwise your server will not operate correctly with the web-browser or any
standard web-clients.
• It may be easier to use a std::istringstream to extract information after replacing
‘&’ and ‘=’ with a space. Of course, you already did something this in Homework #2.
• The web-server must use 1 detached thread per client connection.
• You may suitably use a std::mutex variable inside the Bank class (see starter code)
to avoid race conditions.
• Ensure checking for bank account and operating on accounts is performed within the
same critical section. Otherwise you will experience a race condition.
• Do not perform I/O in the critical section. Keep critical sections as short as possible.
• All changes to the bank account must be completed before sending response to client.
Due before: 11:59 PM (before Midnight) on Wed Oct 21 2020
Page 4 of 5
Basic Testing
Run your web-browser, in the debugger to help troubleshoot issues. Next, you can test your webserver using the following URLs, after changing the port number:
• http://os1.csi.miamioh.edu:12345/trans=reset
• http://os1.csi.miamioh.edu:12345/trans=create&acct=test1
• http://os1.csi.miamioh.edu:12345/trans=credit&acct=test1&amount=10.50
• http://os1.csi.miamioh.edu:12345/trans=debit&acct=test1&amount=1.25
• http://os1.csi.miamioh.edu:12345/trans=status&acct=test1
Functional testing
A custom multithreaded test client is supplied along with this homework for testing your server.
You will need to compile the tester program from a terminal once as shown below:
$ g++ -g -Wall -std=c++14 bank_client.cpp -o bank_client -lboost_system -lpthread
Base case [10 points] — Will be strictly enforced
The base case tests require the server to operate correctly in single threaded mode. The base case
is essentially just simple string processing. The base case testing should be conducted as shown
below, assuming your server is listening on port 6000.
$ ./bank_client base_case_req.txt 6000
Note: On correct operation, the client generates the following output:
Finished block #0 testing phase.
Finished block #1 testing phase.
Testing completed.
Multithreading case [10 points]
Once the base case is operating correctly, multithreading is relatively straightforward using
detached threads. However, ensure you use critical sections (using std::lock_guard will
make your life easier) when performing various operations. The multithreading testing should be
conducted as shown below, assuming your server is listening on port 6000.
$ ./bank_client mt_test_req.txt 6000
Note: On correct operation, the client will generate the following output:
Finished block #0 testing phase.
Finished block #1 testing phase.
Finished block #2 testing phase.
Finished block #3 testing phase.
Finished block #4 testing phase.
Testing completed.
Due before: 11:59 PM (before Midnight) on Wed Oct 21 2020
Page 5 of 5
Submit to Canvas
This homework assignment must be turned-in electronically via Canvas. Ensure your C++ source
files are named appropriately. Ensure your program compiles (without any warnings or style
errors) successfully. Ensure you have tested operations of your program as indicated. Once you
have tested your implementation, upload the following onto Canvas:
Ø The 1 C++ source file you developed for this homework
Upload all the necessary C++ source files to onto Canvas independently. Do not submit
zip/7zip/tar/gzip files. Upload each file independently.
