COMP2017 9017 Assignment 3
This assignment is worth 5% + 10% + 30% of your final assessment
This assessment is CONFIDENTIAL. University of Sydney.
Due:
Milestone: 23:59 Wednesday 26 April 2023 local Sydney time.
Final: 23:59 Tuesday 9 May 2023 local Sydney time.
Task description
Introducing ProgExchange (PEX), a cutting-edge platform for computer programmers to buy and sell high-demand components in a virtual marketplace. The need for in-person trading has been replaced by a state-of-the-art digital marketplace, allowing for greater accessibility and faster transactions, while providing a safe and convenient way for seasoned programmers to connect and make transac- tions.
As part of this assignment, you will be tasked with developing two key components of ProgExchange: the exchange itself, which will handle all incoming orders, and an auto-trading program that executes trades based on predefined conditions. With your expertise in systems programming, you will play a crucial role in bringing this innovative platform to life and helping to drive the future of computer component trading.
You are encouraged to ask questions on Ed1. Make sure your question post is of "Question" post type and is under "Assignment" category → "A3" subcategory. As with any assignment, make sure that your work is your own2, and that you do not share your code or solutions with other students.
To complete this assignment, you should be familiar with:
Dynamic memory allocation: malloc(), realloc(), free(), etc ? open(), read(), write() system calls
Processes: fork(), exec(), waitpid(), etc
Signals: sigaction(), kill(), etc
Named Pipes (FIFOs): mkfifo()
1 https://edstem.org/au/courses/10466/discussion/ 2Not GPT-3/4’s, ChatGPT’s or copilot’s, etc.
Some implementation details are purposefully left ambiguous; you have the freedom to decide on the specifics yourself. Additionally this description does not define all possible behaviour that can be exhibited by the system; some error cases are not documented. You are expected to gracefully report and handle these errors yourself.
High Level Overview
Exchange
The purpose of the ProgExchange is to allow trading to happen in an efficient and orderly manner. It receives orders from traders and matches them, allowing the buying and selling of computer compo- nents.
The exchange also tracks the cash balance of each trader (which starts at $0 for each trading session).
For providing such trading avenue, ProgExchange collects a 1% transaction fee on all successful orders.
IPC
The exchange communicates with trader processes using a combination of named pipes (FIFOs) and signals. All messages are followed by the delimiter ; and signal SIGUSR1.
All messages sent through FIFOs are highlighted in this document:
EXAMPLE;
Traders
Traders carry out their buying and selling activities by placing orders on the exchange.
Commands
The following commands may be sent from traders to the exchange:
BUY: An order to buy a product at or below the specified price, up to the specified quantity. ? SELL: An order to sell a product at the specified price, up to the specified quantity.
AMEND: Update the quantity or price of an existing order, that has yet to be fully filled.
CANCEL: Cancel an existing order, that has yet to be fully filled.
Data Types and Ranges
ORDER_ID: integer, 0 - 999999 (incremental)
Order ID is unique per Trader (i.e. Trader 0 and 1 can both have their own Order ID 0). Order IDs are not reused (with the exception of Invalid orders, which can be fixed and re-sent with the same ID, given the next ID is not yet used).
PRODUCT: string, alphanumeric, case sensitive, up to 16 characters
QTY, PRICE: integer, 1 - 999999
Products
Products traded on the exchange are provided through a text file of the following structure:
n_items
Product 1
Product 2
...
Product N
For example:
2
GPU
Motherboard
BUY
;
SELL
;
AMEND
;
CANCEL ;
Page 3 of 17
COMP2017 9017 PEX
Basic Example
Trader 0 places a SELL order for 15 CPUs at $300 each
SELL 0 CPU 15 300;
Trader 1 places a BUY order for 10 CPUs at $300 each
BUY 0 CPU 10 300;
ProgExchangematchestheseorders,Trader1buys10CPUsfromTrader0for$3,000andpays $30 transaction fee.
Trader 1’s order is now fulfilled. Trader 0 has 5 CPUs remaining on the market for sale.
Implementation details
Write programs in C that implement ProgExchange as shown in the examples.
You are guaranteed not to have NULL returned from malloc() or realloc() in this context.
Your submission must be contained in the following files and produce no errors when built and run on Ed C compiler.
pe_common.h: Common constants and structures
pe_exchange.c, pe_exchange.h: Part 1 (Exchange, compiles to pe_exchange) ? pe_trader.c, pe_trader.h: Part 2 (Trader, compiles to pe_trader)
Test cases in tests directory
README.md: Code Description
Read / write with FIFOs and/or write to stdout as instructed.
Your program output must match the exact output format shown in the examples and on Ed. You are encouraged to submit your assignment while you are working on it, so you can obtain feedback.
You may modify any of the existing scaffold files, or make your own.
No external code outside the standard C library functions should be required.
In order to obtain full marks, your program must free all of the dynamic memory it allocates.
COMP2017 9017 PEX
Milestone: Auto-Trader
To complete the milestone, you need to implement an auto-trader in pe_trader.c and pe_trader.h, which will be tested against a reference exchange server implementation.
The logic of the auto-trader is very simple: as soon as a SELL order is available in the exchange, it will place an opposite BUY order to attempt to buy the item.
As an example, as soon as the auto-trader receives the following message (and signal) from the ex- change:
MARKET SELL CPU 2 300;
It would place the following order:
BUY CPU 2 300;
The auto-trader should gracefully disconnect and shut down if there is a BUY order with quantity greater than or equal to 1000.
For the milestone, you may assume that for the purposes of this auto-trader, there are no other com- peting traders placing BUY orders.
However, signals are inherently unreliable, that is, multiple signals (perhaps from multiple auto- traders) may overwrite one another and cause a race condition. In the final version, you should design your auto-trader in such way that it is fault-tolerant, while conforming to the Exchange messaging protocol (first write to the pipe, then signal SIGUSR1), and does not place unreasonable load on the exchange.
Exchange: Start Up
The exchange accepts command line arguments as follows:
./pe_exchange [product file] [trader 0] [trader 1] ... [trader n]
The following example uses a product file named products.txt and trader binaries trader_a and trader_b:
./pe_exchange products.txt ./trader_a ./trader_b
Upon start up, the exchange should read the product file to find out about what it will trade. It should then create two named pipes for each trader:
/tmp/pe_exchange_
/tmp/pe_trader_
The pe_exchange_* named pipes are for the exchange write to each trader and pe_trader_* named pipes are for each trader to write to the exchange.
After both pipes are created for a trader, the exchange shall launch that trader binary as a new child process, assigning it a trader ID starting from 0, in the Command Line Argument order. The trader ID shall be passed to the trader binary as a command line argument.
For the example above, the trader binaries should be launched like so:
./trader_a 0
./trader_b 1
Upon launching each binary, the exchange and trader should attempt to connect to both named pipes.
After all binaries are launched and pipes are connected, the exchange should send each trader (lowest trader IDs first) the following message using the pe_exchange_* named pipes; afterwards, notify each trader using the SIGUSR1 signal.
MARKET OPEN;
Exchange: Placing Orders
Traders may place orders with the exchange by sending the appropriate commands through their pe_trader_
named pipe. Once the whole command is written to the pipe, it shall notify the exchange with the SIGUSR1 signal.
Once the exchange receives the SIGUSR1 signal from a trader, it would read the command from the pe_trader_
named pipe and process the order appropriately. Depending on whether the order was accepted (for new buy / sell orders), amended or cancelled, or if the command is invalid, it would write one of the following messages to the pe_exchange_
named pipe and notify the trader using the SIGUSR1 signal.
Page 6 of 17
COMP2017 9017 PEX
ACCEPTED ;
AMENDED ;
CANCELLED ;
INVALID;
The exchange should also message all other traders (lowest trader IDs first) using the pe_exchange_* named pipes, and notify them using the SIGUSR1 signal, with the following message:
MARKET
;
N.B.: In case of a cancelled order, QTY = 0 and PRICE = 0.
Sample order flow
1. Trader 0 writes to pe_trader_0:
SELL 20 CPU 2 300;
2. Trader 0 sends SIGUSR1 signal to the Exchange
3. Exchange reads pe_trader_0 and adds the order to the order book
4. Exchange writes to pe_exchange_0:
ACCEPTED 20;
5. Exchange sends SIGUSR1 signal to Trader 0
6. Exchange writes to all other pe_exchange_* pipes:
MARKET SELL CPU 2 300;
7. Exchange sends SIGUSR1 signal to all other Traders.
8. All traders can read their own pe_exchange_* and places further orders if desired
Exchange: Matching Orders
The exchange should attempt to match orders once there is at least one BUY and one SELL order for any particular product. Orders match if the price of the BUY order is larger than or equal to the price of the SELL order. The matching price is the price of the older order. Of the two matched traders, the exchange charges 1% transaction fee to the trader who placed the order last, rounded to the nearest dollar (eg: $4.50 -> $5.00).
When there are multiple orders in the exchange, order matching should follow price-time priority: ? Match the highest-priced BUY order against lowest-priced SELL order
If there are multiple orders at the same price level, match the earliest order first
As the order matches, the exchange shall write the following message to the appropriate pe_exchange_*
pipes belonging to the matched traders, then send the SIGUSR1 signal: FILL ;
It is possible for a single order with sufficient quantity to match against multiple existing orders in the market. Similarly, an order could be partially filled and remain in the market if there isn’t sufficient quantity available. Orders are removed from the market once their quantity reaches zero.
Example Scenarios
COMP2017 9017 PEX
Example
Orderbook Before (type, qty, price)
New Order
Orderbook After (type, qty, price)
Explanation
0
SELL 2 $500 BUY 2 $450
BUY 2 $500
BUY 2 $450
The new buy order matched against the SELL order. Both orders are fully filled.
1
SELL 2 $501 SELL 2 $500
BUY 5 $505
BUY 1 $505
The new BUY order matched against both SELL orders. The SELL orders are fully filled. The BUY order is par- tially filled (qty 4) and re- mains on the market (qty 1).
Exchange: Reporting
In addition to reading and writing to the named pipes, the exchange also needs to print a range of messages to standard out (stdout), as per the examples later in this document. Please follow the examples for the outputs required.
Specifically, the order book and trader positions need to be printed after each successful order, for example:
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] --POSITIONS--
--ORDERBOOK--
Product: GPU; Buy levels: 3; Sell levels: 1
SELL 99 @ $511 (1 order)
BUY 30 @ $502 (1 order)
BUY 60 @ $501 (2 orders)
BUY 30 @ $500 (1 order)
[PEX] Trader 0: GPU 0 ($0), Router 0 ($0)
Page 8 of 17
Here, all orders in the market are sorted from the highest to lowest price. Each unique price is called a level, and there may be multiple orders in the same level. Positions refer to the quantity of products owned (or owed) by each trader, which may be positive or negative after each order.
Note: Tabs (\t) are used for indentation. Exchange: Teardown
As soon as a trader disconnects (closing their end of the pipes or process exits), your exchange should print out the following message:
[PEX] Trader
disconnected
It shall reject any pending or further orders from the trader but keep existing orders in the orderbook (if any).
After all traders disconnect, the exchange should print out the following message:
[PEX] Trading completed
[PEX] Exchange fees collected: $
Make sure to clean up any remaining child processes, close and delete FIFOs, and free memory before exiting.
Code Description
To support your implementation, you need to provide a succinct answer to each of the questions in the file README.md. The word limit is 150 for each question.
1. Describe how your exchange works, using diagram(s) if necessary.
2. Describe your design decisions for the trader and how it’s fault-tolerant and efficient. 3. Describe your tests and how to run them.
COMP2017 9017 PEX
Page 9 of 17
Exchange: Example Outputs
# cat products.txt
2
GPU
Router
1 trader, 1 order
Command:
./pe_exchange products.txt ./trader_a
Orders:
Trader 0: BUY 0 GPU 30 500
Standard out:
[PEX] Starting
[PEX] Trading 2 products: GPU Router
[PEX] Created FIFO /tmp/pe_exchange_0
[PEX] Created FIFO /tmp/pe_trader_0
[PEX] Starting trader 0 (./trader_a)
[PEX] Connected to /tmp/pe_exchange_0
[PEX] Connected to /tmp/pe_trader_0
[PEX] [T0] Parsing command:
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] Trader 0 disconnected
[PEX] Trading completed
[PEX] Exchange fees collected: $0
2 traders, 6 orders
Command:
./pe_exchange products.txt ./trader_a ./trader_b
Orders:
--ORDERBOOK--
Product: GPU; Buy levels: 1; Sell levels: 0
BUY 30 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 0 ($0), Router 0 ($0)
COMP2017 9017 PEX
Page 10 of 17
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] [T0] Parsing command:
--ORDERBOOK--
Product: GPU; Buy levels: 1; Sell levels: 0
BUY 30 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 0 ($0), Router 0 ($0)
Trader 1: GPU 0 ($0), Router 0 ($0)
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] [T0] Parsing command:
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
--ORDERBOOK--
Product: GPU; Buy levels: 2; Sell levels: 0
BUY 60 @ $501 (2 orders)
BUY 30 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 0 ($0), Router 0 ($0)
Trader 1: GPU 0 ($0), Router 0 ($0)
--ORDERBOOK--
Product: GPU; Buy levels: 2; Sell levels: 0
BUY 30 @ $501 (1 order)
BUY 30 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 0 ($0), Router 0 ($0)
Trader 1: GPU 0 ($0), Router 0 ($0)
COMP2017 9017 PEX
Trader 0: BUY 0 GPU 30 500
Trader 0: BUY 1 GPU 30 501
Trader 0: BUY 2 GPU 30 501
Trader 0: BUY 3 GPU 30 502
Trader 1: SELL 0 GPU 99 511
Trader 1: SELL 1 GPU 99 402
Standard out:
[PEX] Starting
[PEX] Trading 2 products: GPU Router
[PEX] Created FIFO /tmp/pe_exchange_0
[PEX] Created FIFO /tmp/pe_trader_0
[PEX] Starting trader 0 (./trader_a)
[PEX] Connected to /tmp/pe_exchange_0
[PEX] Connected to /tmp/pe_trader_0
[PEX] Created FIFO /tmp/pe_exchange_1
[PEX] Created FIFO /tmp/pe_trader_1
[PEX] Starting trader 1 (./trader_b)
[PEX] Connected to /tmp/pe_exchange_1
[PEX] Connected to /tmp/pe_trader_1
[PEX] [T0] Parsing command:
Page 11 of 17
[PEX] [T0] Parsing command:
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] [T1] Parsing command:
--ORDERBOOK--
Product: GPU; Buy levels: 3; Sell levels: 0
BUY 30 @ $502 (1 order)
BUY 60 @ $501 (2 orders)
BUY 30 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 0 ($0), Router 0 ($0)
Trader 1: GPU 0 ($0), Router 0 ($0)
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] [T1] Parsing command:
[PEX] Match: Order 3 [T0], New Order 1 [T1], value: $15060, fee: $151.
[PEX] Match: Order 1 [T0], New Order 1 [T1], value: $15030, fee: $150.
[PEX] Match: Order 2 [T0], New Order 1 [T1], value: $15030, fee: $150.
[PEX] Match: Order 0 [T0], New Order 1 [T1], value: $4500, fee: $45.
COMP2017 9017 PEX
--ORDERBOOK--
Product: GPU; Buy levels: 3; Sell levels: 1
SELL 99 @ $511 (1 order)
BUY 30 @ $502 (1 order)
BUY 60 @ $501 (2 orders)
BUY 30 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 0 ($0), Router 0 ($0)
Trader 1: GPU 0 ($0), Router 0 ($0)
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX]
[PEX] Trader 0 disconnected
[PEX] Trader 1 disconnected
[PEX] Trading completed
[PEX] Exchange fees collected: $496
--ORDERBOOK--
Product: GPU; Buy levels: 1; Sell levels: 1
SELL 99 @ $511 (1 order)
BUY 21 @ $500 (1 order)
Product: Router; Buy levels: 0; Sell levels: 0
--POSITIONS--
Trader 0: GPU 99 ($-49620), Router 0 ($0)
Trader 1: GPU -99 ($49124), Router 0 ($0)
Page 12 of 17
Working on your assignment
Staff may make announcements on Ed (https://edstem.org/) regarding any updates or clarifications to the assignment. The Ed resources section will contain a PDF outlining any notes/changes/corrections to the assignment. You can ask questions on Ed using the assignments category. Please read this assignment description carefully before asking questions. Please ensure that your work is your own and you do not share any code or solutions with other students.
You can work on this assignment using your own computers or lab machines. You will need to submit to Ed via Git, which is covered elsewhere in this course. When you make a submission, your submission will be automatically compiled and run and you will receive feedback as to whether you passed the public test cases as well as a link that will enable you to inspect the output of your submission.
It is important that you continually back up your assignment files. You are encouraged to submit your assignment while you are in the process of completing it to receive feedback and to check for correctness of your solution.
Compilation and Execution
Your program will be compiled by running the default rule of a make file. Upon compiling your program should produce a two binaries: pe_exchange, pe_trader
make
./pe_exchange products.txt ./trader_a ./trader_b
Please make sure the above commands will compile and run your program. An example Makefile has been provided in the Scaffold, but you’re encouraged to customize it to your needs. Additionally, consider implementing the project using multiple C source files and utilizing header files.
Testswillbecompiledandrunusingtwomakerules;make testsandmake run_tests. make tests
make run_tests
These rules should build any tests you need, then execute each test and report back on your correct- ness.
Failing to adhere to these conventions will prevent your markers from running your code and tests. In this circumstance you will be awarded a mark of 0 for this assignment.
You are encouraged to submit multiple times, but only your last submission will be marked.
Writing your own test cases
We have provided you with some test cases but these do not test all the functionality described in the assignment. It is important that you thoroughly test your code by writing your own test cases, including both end-to-end (input / output) tests and unit tests using cmocka.
COMP2017 9017 PEX
Page 13 of 17
You should place all of your end-to-end test cases in the tests/E2E directory. Ensure that each test case has a .out output file and optionally an .in file. We recommend that the names of your test cases are descriptive so that you know what each is testing, e.g. buy-order.out and amend-order.out.
You should place all of your unit tests in the tests directory, under unit-tests.c (and more files, if necessary). All unit tests must be constructed with the cmocka unit testing framework.
You should have a brief description of your tests, and how they can be run, in README.md. Error handling
Your code should have appropriate mechanisms in place to detect and handle errors, including but not limited to:
NULL pointers
Buffer overflows and underflows ? Unable to open FIFOs
Unable to launch child processes ? Invalid or malformed commands
Restrictions
If your program does not adhere to these restrictions, your submission will receive 0. No Variable Length Arrays (VLAs)
No threads (processes only)
No excessive / 100% CPU usage when idling (eg: busy-waiting loops, active polling) ? Traders must be launched as child processes of the exchange process.
Marking
A grade for this assignment is made where there is a submission that compiles and the oral examina- tion has been completed.
Milestone Automated Test Cases - 5 - Passing automatic test cases.
Final Automated Test Cases - 10 - Passing automatic test cases, a number of tests will not be released or run until after your final submission.
COMP2017 9017 PEX
Viva - 30 - You will need to answer questions from a COMP2017 teaching staff member re- garding your implementation. You will be required to attend a zoom session with COMP2017 teaching staff member after the code submission deadline. A reasonable attempt will need to be made, otherwise you will receive zero for the assessment.
To be eligible for Viva, you need to complete all test cases, whose name contains the key- word VIVA, before the final due date. These cases may be found in both milestone and final assignment.
In this session, you will be asked to explain:
– General questions about your understanding of the concepts needed for this assignment, – How you have arranged your memory, data structures and types
– How you managed IPC (Inter Process Communication)
– How you handle errors / make your code fault-tolerant
– Answer further questions Additionally marks will be deducted if:
your program has memory leaks.
excessive memory is used, e.g preallocation or over allocation of what is required.
your program avoids malloc family of C functions to instantiate memory dynamically.
your program does not use named pipes or signals for IPC.
uses unjustifiable magic numbers.
uses files, or mapped memory.
all documentation parts of your submission, including code comments, README files, and so on, are not written in English.
poor code readability will result in the deduction of marks. Your code and test cases should be neatly divided between header and source files in appropriate directories, should be commented, contain meaningful variable names, useful indentation, white space and functions should be used appropriately. Please refer to this course’s style guide for more details.
Warning: Any attempts to deceive the automatic marking will result in an immediate zero for the entire assignment. Negative marks can be assigned if you do not properly follow the assignment description, or your code is unnecessarily or deliberately obfuscated.
Working on your assignment
You can work on this assignment on your own computer or the lab machines. It is important that you continually back up your assignment files onto your own machine, external drives, and in the cloud. You are responsible for your assignment files to remain private to you, and not accessible by others.
You are encouraged to submit your assignment on Ed while you are in the process of completing it. By submitting you will obtain some feedback of your progress on the sample test cases provided.
If you have any questions about any C functions, then refer to the corresponding man pages. You can ask questions about this assignment on Ed. As with any assignment, make sure that your work is your own, and that you do not share your code or solutions with other students.
Where to start
Begin with implementing the auto-trader (Milestone):
read the full specification and make sure you understand the communication protocol. ? confirm you can open FIFOs setup by the exchange process.
create a trader with basic functionality.
Exchange.
confirm you can setup FIFOs and launch child processes
confirm your processes can communicate through FIFOs and signals
implement a simple order book for BUY / SELL orders
check that it can handle multiple orders, identical orders and overlapping orders
Next, implement AMEND / CANCEL commands and the ability to handle multiple traders. Next, implement the auto-trader, paying special attention to fault-tolerance and error recovery.
Academic declaration
By submitting this assignment you declare the following:
I declare that I have read and understood the University of Sydney Student Plagiarism: Coursework Policy and Procedure, and except where specifically acknowledged, the work contained in this assignment/project is my own work, and has not been copied from other sources or been previously submitted for award or assessment.
I understand that failure to comply with the Student Plagiarism: Coursework Policy and Procedure can lead to severe penalties as outlined under Chapter 8 of the University of Sydney By-Law 1999 (as amended). These penalties may be imposed in cases where any significant portion of my submitted work has been copied without proper acknowledgment from other sources, including published works, the Internet, existing programs, the work of other students, or work previously submitted for other awards or assessments.
I realise that I may be asked to identify those portions of the work contributed by me and required to demonstrate my knowledge of the relevant material by answering oral questions or by undertaking supplementary work, either written or in the laboratory, in order to arrive at the final assessment mark.
I acknowledge that the School of Computer Science, in assessing this assignment, may reproduce it entirely, may provide a copy to another member of faculty, and/or communicate a copy of this assignment to a plagiarism checking service or in-house computer program, and that a copy of the assignment may be maintained by the service or the School of Computer Science for the purpose of future plagiarism checking.
COMP2017 9017 PEX