CSE Homework #8: Stock Market (Phase 1) Solution

Description

This homework assignment must be turned-in electronically via Canvas CODE plug-in. Ensure your C++ source code is named MUID_homework8.cpp, where MUID is your Miami University Unique ID (e.g., raodm_homework8.cpp). Ensure your program compiles without any warnings or style violations. Ensure you thoroughly test operations of your program as indicated. Once you have tested your implementation, upload the following onto Canvas:

1. The 1 C++ source file developed for this homework.

General Note: Upload each file associated with homework individually to Canvas. Do not upload archive file formats such as zip/tar/gz/7zip/rar etc.

Objective

The objective of this homework is to develop a custom “stock market” web-server to:

• Understand the use of multiple detached threads.

• Understand the use of critical sections created using a std::mutex and std::lock_guard.

• Understand the use of synchronization constructs with object-oriented design

• Continue to gain experience with HTTP protocol and working with sockets.

• Demonstrate expertise with straightforward string processing.

• Continue to gain familiarity with automated functional testing.

• Using shared variables with a namespace.

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 [8 points]: Correctly process transactions (as described below) by implementing clientThread method.

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Due before: Deadline posted on canvas

Due before: Deadline posted on canvas

Requirements

In this homework, you are expected to develop a simple multithreaded stock market web-server that operates using standard HTTP requests and responses. The stock market consists of a collection of stocks stored as an unordered_map, with the stock’s name as the key. You are supplied with a Stock.h file that contains the definition for a Stock class. Each stock is identified by a unique name (a std::string). Each stock has a balance field that indicates number of available stocks.

Your stock market web-server is expected operate as follows:

1. The server should be developed by implementing the supplied clientThread method (see starter code) as the top-level method. You may add helper methods as you see fit.

2. Each request will be a standard HTTP GET request in the form (with each line terminated with a “\r\n”):

	General structure	Eample request(s)
	GET /TransactionInfo HTTP/1.1\r\n	GET /trans=buy&stock=0x1&amount=5 HTTP/1.1\r\n
	Host: localhost:4000\r\n	Host: localhost:4000\r\n
	Connection: close\r\n	Connection: close\r\n
	// More headers may be here\r\n	// More headers not shown\r\n
	// They are not shown\r\n	\r\n
	// For brevity\r\n
		GET /trans=status&stock=msft HTTP/1.1\r\n
	\r\n	Host: localhost:4000\r\n
		Connection: close\r\n
		// More headers not shown\r\n
		\r\n

Where, TransactionInfo is a HTTP-query string in the form:

“trans=cmd&stock=StockName&amount=amt”. The cmd indicates type of operation to perform. The stock and amount information are optional. The expected operation and responses (or outputs) for each command is shown below.

Note: The commands below assume that stock name is 0x01. However, the name can be different/vary. So do not hardcode stock name to 0x01.

	TransactionInfo (all		Description of required operation				Expected msg from
	on 1 line)						server in HTTP response
	A request that is not		Browsers may make additional requests				Invalid request
	one of the 4 below		(e.g., for facicon.ico). You should
			handle those correctly.
	trans=reset		Clear out all stocks.			Stocks reset
			Note: Stock resetting requests will be
			performed in single-threaded mode only.
	trans=create&stock		Add stock (to unordered_map) with				Stock 0x01 created
	=0x01&amount=10		optional	balance=amount (default is 0)			with balance = 10 or
							Stock 0x01 already
			if stock with same name does not exist.
							exists
			Note: Stock creation requests will be
			performed in single-threaded mode only
			by stock_client.cpp.
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Due before: Deadline posted on canvas

	trans=buy&stock=0x		Subtract specified amount from stock’s		Stock 0x01’s balance
	01&amount=5		balance, if stock exists. If stock does		updated or
			not exist, generate error.
					Stock not found
	trans=sell&stock=0		Add specified amount to stock’s		Stock 0x01’s balance
	x01&amount=20		balance, if stock exists. Otherwise		updated or
			generate error.		Stock not found
	trans=status&stock		Return stock’s balance, if stock exists.		Balance for stock
	=0x01		Otherwise generate error.		0x01 = 24
					Stock not found

Note: The message “Stock not found” is returned if the specified stock name does not exist (in the unordered_map stockMap). The response is always in the format shown earlier but the specific message in the response will vary as shown above.

Important Notes & Implementation Tips:

• The starter code already does multithreading using detached threads for you.

• Processing HTTP requests in the clientThread method is more-or-less just a repeat from prior projects/exercises.

• Don’t forget to read (and ignore) request headers from the client. Otherwise, your server will not operate correctly with the web-browser or any standard web-clients.

• You will need to URL decode the request prior to processing it.

• Extracting the values from the request is relatively straightforward as suggested in the

example code fragment below:

std::string request = “trans=sell&stock=0x01&amount=20″; request = url_decode(request);

• Replace ‘&’ and ‘=’ characters in the request to make it

• easier to parse out the data. std::replace(request.begin(), request.end(), ‘&’, ‘ ‘); std::replace(request.begin(), request.end(), ‘=’, ‘ ‘);

• Create a string input stream to read words out.

std::string trans, stock;

unsigned int amount = 0;

std::istringstream(request) >> dummy >> trans >> dummy >> stock >> dummy >> amount;

• Note that, stock creation requests will be performed in single-threaded mode only (by stock_client.cpp). However, for non-base case functionality, rest of the operations will be performed in multithreaded mode.

• To add new stock entries, you can use the following simple approach: std::string stock = “msft”;

sm::stockMap[stock].name	=	stock;
sm::stockMap[stock].balance =		10;

• Ensure you appropriately lock & unlock the mutex for a Stock prior to sell/buy/status operations to avoid race conditions. Ensure you use a std::lock_guard to automatically lock & unlock a mutex.

• Do not perform I/O in the critical section. Keep critical sections as short as possible.

• All changes to a stock must be completed before sending response to client.

Page 4 of 6

Due before: Deadline posted on canvas

Due before: Deadline posted on canvas

The 1 C++ source file named with the convention you modified for this homework.

Ensure your source file is named with the convention MUID_homework8.cpp, where

MUID is your Miami University Unique ID (e.g., raodm_homework8.cpp).

Upload all the necessary C++ source files to onto Canvas independently. Do not submit zip/7zip/tar/gzip files. Upload each file independently.

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