Re: Concurrent file read approaches?

From:
"Karl Uppiano" <karl.uppiano@verizon.net>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 08 Oct 2006 19:40:22 GMT
Message-ID:
<GucWg.403$HP.53@trndny08>
"Chris" <spam_me_not@goaway.com> wrote in message
news:45295186$0$5919$9a6e19ea@news.newshosting.com...

What's the best approach for heavily concurrent read access to a file?

I have a file that needs to be read by many threads. The file is much too
big to fit in memory. I'll do some caching, but access is mostly random so
there will be a large number of cache misses.

Unfortunately, RandomAccessFile is single threaded. To read data, you much
call seek() and then read(), and this can only be done one thread at a
time.

I see three possible approaches to the problem:
1. Wrap the calls to seek() and read() in a synchronized method. This will
be slow.
2. Have a pool of RandomAccessFile objects all pointing to the same file.
Have each thread grab and release objects from the pool as needed. The
downside here is that many file handles will be required.
3. Do something fancy with NIO and selectors. I haven't looked into this
deep enough to know if it's an option.

What's the best approach?


I don't know the "best" approach, but NIO is very powerful and scalable. It
is about as close as you can get to overlapped I/O in the OS.

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