A key requirement is that all the servers must print out the trades in the same order. Brokers will get upset if it seems that they are not being given the same information as everyone else, because they make decisions about what to buy and sell based both on the latest prices and on price trends.
The larger purpose of this assignment is to learn about protocols for maintaining replicated data. If you have some data (a file system, for example) with identical replicas on a number of servers, you might want to perform updates on that data in a way that keeps the replicas identical. If you can arrange to perform the updates in the same order on all the replicas (and the updates are deterministic), then the data will remain identical. An important part of this is making sure all the replicas process the updates in the same order. That's what you'll do for this assignment, though with an unrealistically optimistic set of assumptions about network and failure behavior.
We supply you with a client program that submits new trades to the local server, using RPC. Each trade has a text tag. When a server sees a new trade submitted by a local client, it should tell all the other servers in the system about the trade. How this happens is up to you. We supply you with a prototype server that uses RPC (over UDP) to talk to the other servers; we suggest you start by modifying this server.
A server will receive notifications about trades from time to time from other servers. It should print each trade's tag on the standard output. All the servers should print the trade tags in the same order. The servers need not print the tags immediately when they arrive.
Here are some other rules you must follow:
Here are some slightly unusual things you are allowed to assume about the system:
$ tar xvfz /home/6824/labs/ticker.tgz $ cd ticker $ gmake
The server expects you to give it a unique numeric ID, a local port number on which to receive RPC/UDP packets, and (for each other server) a host name and port number. To test the server, run this on pain.lcs.mit.edu in one window:
$ ./ticker-server 1 2001 suffering.lcs.mit.edu 2001You may have to modify the port numbers in case someone else is running this test at the same time. Run this on suffering.lcs.mit.edu in another window:
$ ./ticker-server 2 2001 pain.lcs.mit.edu 2001In a third window (on either pain or suffering), submit a few trades:
$ ./ticker-client localhost 2001 IBM-90 $ ./ticker-client localhost 2001 DELL-16
Ideally, both servers would print either
IBM-90 DELL-16or else they would both print
DELL-16 IBM-90Either is acceptable, unless 7 or more seconds passed between submitting the two trades, in which case they must appear in order of submission. In fact you'll notice that the server we supply you with doesn't work; only one of the servers prints each trade.
A reasonable first step would be to modify the server code to forward a copy of each submission to each of the other servers. You can use RPC to do this, borrowing code from ticker-client.C. You'll probably need to add a new procedure to ticker.x.
$ ./ticker-client -r 5 suffering.lcs.mit.edu 2001 pain.lcs.mit.edu 2001This generates 5 submissions to each of the servers indicated, in rapid succession. (This isn't quite correct, since the client is only allowed to submit to the local server, but it's just for testing.) If your servers always agree on the order of outputs when you run the client this way, you're well on your way to finishing the lab.
We will use the test-ticker.pl program to decide whether your server works. You can run it as follows:
$ /home/6824/labs/ticker/test-ticker.pl ./ticker-server ./ticker-client One server, one transaction: passed Two servers, one transaction: passed Two servers, two transactions: passed Two servers, ten concurrent transactions: passed Five servers, continuous transactions: passed One of two servers fail: passed Three of six servers fail: passedYour server should pass all the tests.