SWE 622- Distributed Systems

Project Phase I

Eric Barnes, David Chang, David Nelson

Fisayo Oluwadiya, Xiang Shen

Architecture

Exchange

`

Trader

NetWork

Exchange

`

Trader

TCP Connection

TCP Connection

TCP Connection

TCP Connection

… ...

… ...

Message

Message

Message

Message

Message

Processor

ExchangeServerSqlite

DB

JFrameExchangeGUI

TraderOutput

TraderInput

initDB

start

start

start

quer

y, co

mm

it

query

SwingWorkerstart

update

input queue

TraderInput

TraderOutput

...

output queue

output queue

time msg

time msg

TraderClient

Trader

Monitor

JFrameTraderGUI

TraderWorker

Listener

SwingWorker

Exchange Trader

processed queue

TraderWorker

Listener

start

start

startstart

update

some other exchange some other trader

start

start,

business msg

business msg

sell, buy

start, sync time...

business msg

Exchange

new

one TCP connection

Exchange waits for new connections. Spawn new threads TraderOutput/

Input for each new connection. It also

creates all the queues.

sync time

Message Format I

For business transactions, the messages are line based and each field is separated by a colon. The format is:

Op:exchangeName:traderName:product:quantity:price:timeStamp:

For example:

Trader Messages:sell:Exchange1:Trader2:product_one:0:43.53:0:buy:Exchange2:Trader1:product_two:34:0:0:

Exchange Messages:sell:Exchange1:Trader2:product_one:0:123.45:1237237965973buy:Exchange1:Trader2:product_one:756:123.45:1237237970443

Message Format II

For clock synchronization , the messages are line based and each field is separated by a colon as well. The format is:

Time request from trader to exchange:

time:exchangeName:traderName:time

Time response from exchange to trader:

time:time

For example:Trader Messages:

time:E1:T2:1237237964619

Exchange Messages:

time:1237237964534

Synchronization

• Problem: Traders (clients) need to determine the age of a message from Exchanges (servers).– Clocks are not guaranteed to be synchronized.– There may be non-trivial latency in the network– A solution is needed to determine clock-skew and

network latency to compensate.

Synchronization• Clients will query Servers for timestamps.

1. Client will take a timestamp, and send a message to server for server time.

2. Server will take a timestamp upon receipt and immediately send it back to and the original client.

3. Client takes another timestamp upon receipt of the server response.

4. Client will calculate the network latency and clock skew.

1. Network latency will be one half of the difference between the two client timestamps.

2. Clock Skew will be the difference between the average of the two client timestamps and the server timestamp.

5. Client will maintain the clock skews for the Servers it receives messages from and use those values to determine message age.

Synchronization Mechanism

t1 t2 t3

•After acknowledgement message has been received from the server, client will have client timestamps for t1 and t3, and a server timestamp for t2.

•Client will assume that the network latency is approximately symmetrical, and that the server processing time is negligible.

•The clock offset will be calculated by t2-(t1+t3)/2.

•This value will be stored in the client and used to determine message age.

Server

Client

Implementation For Synchronization

• Assuming the server processing time is negligible.

• Samples are taken every 5 seconds.

• Each sample is averaged by three requests.

• Only the latest sample is saved.

Deployment For Evaluation

• More than one Exchange will be created

• More than one trader will be created

• Exchanges and traders will be deployed to team member’s laptops and/or GMU servers such as mason.gmu.edu or zeus.ite.gmu.edu

Test Cases For Exchange

1. Exchange comes online and is ready to accept sell requests2. Exchange receives first sell order3. Exchange receives first buy order4. Exchange is already selling a product and receives another

selling order and successfully processes it within set time limit5. Exchange is currently processing a buy order and receives

another and successfully processes it within set time limit6. Exchange is shutdown after processing all orders7. Exchange shuts down normally8. Exchange crashes

Test Cases For Trader

1. Trader comes online and is ready to send buy/sell orders

2. Trader sends buy order

3. Trader sends sell order

4. Trader receives confirmation for buy/sell order

5. Trader doesn’t receive confirmation for buy/sell order within expected time limit

6. Trader is unable to connect to Exchange

7. Trader shuts down normally

8. Trader crashes

Fault Simulation

• Simulate clock skew– Modify the system clocks for exchanges and traders

• Simulate Exchange/Trader failure– Use kill or task manager to terminate exchanges and traders

• Simulate Network failure– Unplug the network cable– Shutdown the NIC, Network switch etc.

• Simulate Network latency– Connect the trader and exchange via a SOCKS proxy server– Use open source server such as Simple SOCKS Server for Perl– Modify the code and randomly sleep a few seconds before forwarding

the packets

Methods For Verification

• Manually run the system and use our eye balls

• Check the log files for verification

• Possible automation via scripting, such as using Perl Win32::GuiTest etc.