This can be done in Java, but like everything in Java the solution is kind of lengthy and perhaps requires several classes.

I've attached a simple skeleton program that spawns threads to search but then processes only those results returned in the first 10 seconds.  The code for performing the searches is obviously missing as is the consolidation code, but the concurrency issue is addressed.  In this example the search threads aren't killed, but instead left running to finish naturally though their results would be ignored if they weren't done in 10 seconds.  It might be better to kill them depending on the circumstances.


-----Original Message-----
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of Eric Lease Morgan
Sent: Monday, February 18, 2008 1:43 PM
To: [log in to unmask]
Subject: [CODE4LIB] many processes, one resultCode for Libraries [[log in to unmask]]

How do I write a computer program that spawns many processes but
returns one result?

I suppose the classic example of my query is the federated search. Get
user input. Send it to many remote indexes. Wait. Combine results.
Return. In this scenario when one of the remote indexes is slow things
grind to a halt.

I have a more modern example. Suppose I want to take advantage of many
Web Services. One might be spell checker. Another might be a
thesaurus. Another might be an index. Another might be a user lookup
function. Given this environment, where each Web Service will return
different sets of streams, how do I query each of them simultaneously
and then aggregate the result? I don't want to so this sequentially. I
want to fork them all at once and wait for their return before a
specific time out. In Perl I can use the system command to fork a
process, but I must wait for it to return. There is another Perl
command allowing me to fork a process and keep going but I don't
remember what it is. Neither one of these solutions seem feasible. Is
the idea of threading in Java suppose to be able to address this

Eric Lease Morgan
University Libraries of Notre Dame

(574) 631-8604