>>> Wai Mun <[EMAIL PROTECTED]> 02-Jun-01 3:26:00 PM >>>
>i'm thinking of writing every count for every servlet
>visit to a counter file. this file would record the datetime,
>name of servlet visited, and this file will be read easily
>(txt format) by means from browser or whatsoever.
>question is: how do i update the counter file efficiently?
>and also considering concurrent access. i thought of one:
>that is to open & close the file everytime the servlet is
>called. is this a good method, a preferred one? or anyone
>can suggest a better solution to this?
File i/o can be costly. Opening and closing files can be even more
costly.
I would design a log class that has a method:
void log()
The log method would be used by your servlets, eg:
Logger logger=null;
public void init()
{
logger=new Logger(getServletName());
}
public void doGet(...
{
...
logger.log();
}
The design of the log class is the clever part:
The constructor:
- opens a file for writing
- creates a seperate thread for managing the file
The log method:
- gets the current time (System.currentTimeMillis)
- enters the current time into an array of 1000 longs
- when the long array is full passes it to the file management thread
and creates a new array
The file management thread
- when it recieves the long array it writes out a line for each long,
converting the long to a date first and adding the servlet name
- every now and then closes the file and opens another one (eg:
daily)
I have a GPLed class called TimedLogWriter which can do the part of
swapping log files on a daily basis. If you want to see that you
should go to:
http://savannah.gnu.org/cgi-bin/
viewcvs/paperclips/paperclips/source/
gnu/paperclips/utils/TimedLogWriter.java
?rev=1.2&content-type=text/vnd.viewcvs-markup
(note that is one whole URL but I've broken it into lines to make
things difficult for you /8-)
The TimedLogWriter can also write a logstamp on every log message,
but that's not what you want given the above scenario.
If you write such a class it would be great if you licenced it uthe
LGPL and contribed it to the Paperclips project.
Note that a variation on the scheme I outline above is to simply
count accesses for a particular resource and then write the count out
somewhere... possibly a database. That is an extreemly efficient way
of doing counting, much more efficient even than the scheme above (but
the scheme above has the advantage of time stamps).
Nic Ferrier
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