Andre-John Mas wrote:
On 7-May-2009, at 17:28, Peter Crowther wrote:
From: David kerber [mailto:dcker...@verizon.net]
The tomcat application simply takes the post request,
does a checksum verification of it, decrypts the
lightly-encrypted data,
and writes it to a log file with the timestamps and site identifiers I
mentioned above. Pretty simple processing, and it is all inside a
synchronized{} construct:
protected synchronized void doPost(HttpServletRequest request,
HttpServletResponse response )
throws ServletException, IOException {
synchronized ( criticalProcess ) {
totalReqCount++;
dailyReqCount++;
processRequest( request, response, false );
}
}
Doesn't the "synchronized" in the above mean that you're essentially
single-threading Tomcat? So you have all this infrastructure... and
that sync may well be the bottleneck.
That would be my impression too. It is best to avoid making the
synchronized scope so large, unless there is a very good reason.
David, do you have any reason for this? Beyond the counter, what other
stuff do you synchronise? Also, it has generally been recommended to
me to avoid hitting the disk in every request, since you may result
with an I/O bottle neck, so if you can write the logs in batches you
will have better performance. If you know that you are only going to
have very few users at a time (say, less than 10), it may not be worth
the time optimising this, but if you know that you are going to get at
least several hundred, then this is something to watch out for.
Thanks for the comments, Andre-John and Peter. When I wrote that app, I
didn't know as much as I do now, but I'm still not very knowledgeable
about synchronized operations.
The synchronized section doesn't do a whole lot, so it doesn't take long
to process. My question is, what kinds of operations need to be
synchronized? All I do is decrypt the data from the POST, send a small
acknowledgement response back to the site, and write the line to the log
file. Does that sound like something that would need to be
synchronized? If not, pulling that out would be a really easy test to
see if it helps my performance issue.
Thanks!
D
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