Monitoring a Queue.

Question

Hi Guys,
A bit of advise please.
I am working on a trading application, where the gui client, among other messages, sends trade requests to the server.
The server then responds back with either an accept or reject message.
I have been asked to add a layer of protection in case a trade is executed but the server fails to notify the client.
Here is what I am thinking of doing:
1. Create a Map (tradeId - Trade object) which will store all the trades that were executed.
2. Have the client ack every trade.
3. When the server receives the ack, it will look up that particular trade in the map.
3.1 If the trade is found, remove the trade from the map.
3.2 If the trade is not found, insert the trade into a list (unAckedList).
4. Have a thread that will periodically check the size of the unAckedList.
5. If the size if not 0, pop the trade and then again, check whether the trade exists in the map.
(To safe guard against cases when the receipt of the trade ack was slightly delayed).
6. If the trade is still in the map, raise an alert.
Just curious to know your thoughts on this design. Any tips, suggestions are welcome.
Cheers,
Hastings

Answer 1

Thanks Chuck and good suggestion about not removing trades.
To clarify a bit more, the purpose of this bit of work is to only guard against the possibility of communication failure between the client and my server. There is an another server, outside my domain with which my server interacts (where the trades are actually booked). That trade booking server is also implementing a similar mechanism.
(client - My server - booking server)
And while I agree that this approach doesn't guard against all undesirable events (like machine failure), I have been asked to to store trades in memory.
Cheers,
-Hastings