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Java Forum / General / June 2007Fastest hashing algorithm?
conside an example like... you have 5 Servers, one user queue, and you want to distribute the users to these 5 servers, users come at different time, assume truely random a simple algorithm is to use Random to generate index 0..4 and assign the server. but think about it, if user come at random, why you need to use radnom i don't know the implementation of Random, but seems a little bit overkill the requirements... a simple approach is to `mod` the current time and assign the server, what do you abt this suitation? thanks. | conside an example like... | [quoted text clipped - 12 lines] | a simple approach is to `mod` the current time and assign the server, | what do you abt this suitation? I would assign each incoming user to the least busy server. > I would assign each incoming user to the least busy server. I'm with Matt. I'm sure there's a simple way to get the load from a server, depending on your OS. A simpler interim solution might just be to keep track of how many user connections you have currently to each server. (This assumes users leave their connection "open" I guess.) Assign new users to the server with the least number of users connected. > I would assign each incoming user to the least busy server. I agree, but sometime checking the server status introduce some overheads. e.g. the JSP page need to store all the servers status into a persistent storage and check for every requests. So that's why many people still using DNS round-robin kind of for load balacing.. > you have 5 Servers, one user queue, and you want to distribute the > users to these 5 servers, users come at different time, assume truely [quoted text clipped - 7 lines] > i don't know the implementation of Random, but seems a little bit > overkill the requirements... Handling a user request is a relatively *HUGE* operation. Think how many cycles that will cost you, and guess how much creating a psuedo-random number costs. You can easily look at the implementation of Random. It's in the src.zip file in your JDK. Notice that (in recent versions) it doesn't so much as use a lock. Indeed, you could allocate round-robin. Just use a java.util.concurrent.atomic.AtomicInteger, and no need for locks. Tom Hawtin >you have 5 Servers, one user queue, and you want to distribute the >users to these 5 servers, users come at different time, assume truely >random Before you waste effort optimising, you must measure the time taken to make sure you are chewing at the bottleneck. Almost certainly optimising this will have no noticeable effect unless you were doing task scheduling inside the OS. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com >>you have 5 Servers, one user queue, and you want to distribute the >>users to these 5 servers, users come at different time, assume truely [quoted text clipped - 5 lines] >Almost certainly optimising this will have no noticeable effect unless >you were doing task scheduling inside the OS. I missed the original post but I do agree with Roedy. Are all the user tasks similar in resource usage and run time? Eric > I missed the original post but I do agree with Roedy. Are all the user tasks > similar in resource usage and run time? And are all the servers comparable in capacity (similar RAM, similar CPU, similar bandwidth...)? >you have 5 Servers, one user queue, and you want to distribute the >users to these 5 servers, users come at different time, assume truely >random why would random do better than round robin? If you want to get clever, I think you need a measure of who is most lightly loaded and give the new user to that server. On Vista there is a measure of disk and CPU time utilisation that even desk gadgets can get hold of. You would need a little JNI to gather those stats for your servers. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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