Re: How can I display number of requests over the past n seconds?
Mmmm, I think people is answering more than one question ;-)
If you need to be strict with respect to the timings, that is, you need
exactly the number of requests in the past five seconds counting from
the moment your request is done, you will need the solution proposed by
Tim. Just remember to synchronize the access to the list, to prevent
ConcurrentModification exceptions while you iterate over the list to get
the counter values :-)
If the time buckets idea works well for you, both Yoav and Justin
proposals are good. I just prefer Yoav one because I guess the cost
associated to the hash function, even if it is simple, is greater than
the associated to a thread that is sleeping most of the time (I mean, in
processing time terms).
I think Yoav idea could be implemented like this (with a variation on my
own ;-):
public class Historic extends Thread {
private static final int NUM_COUNTERS = 6;
private static final int INTERVAL = 5000;
private int[] counters = new int[NUM_COUNTERS];
private int pos = 0;
public Historic() {
super();
this.setDaemon(true);
}
public void run() {
try {
while (true) {
sleep(INTERVAL);
synchronized (this) {
pos = (pos + 1) % NUM_COUNTERS;
counters[pos] = 0;
}
}
}catch (InterruptedException e) {
}
}
public synchronized void addRequest() {
counters[pos] += 1;
}
public int[] getCounters() {
int[] copy;
int posCopy;
synchronized (this) {
System.arraycopy(counters, 0, copy, 0, NUM_COUNTERS);
posCopy = pos;
}
int[] values = new int[NUM_COUNTERS];
int count = 0;
int index = posCopy;
for (int i = 0; i NUM_COUNTERS; i++) {
count += copy[index];
values[i] = count;
index = (index == 0 ? NUM_COUNTERS : index) - 1;
}
return values;
}
}
Just instantiate the class and start it in your Filter initialization,
and call addRequest() on each received request. The getCounters() gives
you the number of requests in each time slice. Ah, and remember to
interrupt it on Filter finalization :-)
There is no guaranty that the pos variable will be changed exactly
each five seconds, as the sleep() method is not accurate by design. In a
highly loaded server with only one CPU, the time slicing will become
worse. If you detect the thread scheduling is too much biased, you can
raise its priority.
If this is not enough, you will have to calculate the cursor position in
each request, implementing the hashtable proposed by Justin:
public class Historic {
private static final int NUM_COUNTERS = 6;
private static final int INTERVAL = 5000;
private int[] counters = new int[NUM_COUNTERS];
private int pos = 0;
private long ts = System.currentTimeMillis();
public Historic() {
}
public synchronized void addRequest() {
adjust();
counters[pos] += 1;
}
public int[] getCounters() {
int[] copy;
int posCopy;
synchronized (this) {
adjust();
System.arraycopy(counters, 0, copy, 0, NUM_COUNTERS);
posCopy = pos;
}
int[] values = new int[NUM_COUNTERS];
int count = 0;
int index = posCopy;
for (int i = 0; i NUM_COUNTERS; i++) {
count += copy[index];
values[i] = count;
index = (index == 0 ? NUM_COUNTERS : index) - 1;
}
return values;
}
private void adjust() {
long now = System.currentTimeMillis();
while (now - ts = INTERVAL) {
pos = (pos + 1) % NUM_COUNTERS;
counters[pos] = 0;
ts += INTERVAL;
}
}
}
HTH,
Rodrigo Ruiz
I need to display on a .jsp page the number of requests for Tomcat in the past 5 / 10 / 15/ 30 / 45 / 60 seconds. I've already implement a Filter will count the total number of requests. I did this with a static int, which is incremented everytime a request comes in. But what should I do so that I can show number of request over past time intervals? Since the present time is always changing, the past n seconds is constantly changing also.
Thanks in advance,
Tom
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Re: How can I display number of requests over the past n seconds?
More academic exercise than recommendation, but... Write your own implementation of a Map/HashMap specific to java.util.Date objects. Identify your smallest time increment (5 seconds in your email). Identify largest time increment (60 seconds) Create (60/5)+1 buckets for your hash function Write your hash function such that each date object -- representing one request each -- gets placed in the right bucket. If the bucket contains aged dates, which you should know by simple counting (not comparison), empty it before placing a new one in. To display results, simply add up the content size of the appropriate buckets and return. This implementation is more lightweight than others suggested because the process of pruning is built into your implementation (instead of using external threads or comparisons each time you insert)... you're trading memory usage for decreased processing time. On the other hand, it doesn't *strictly* tell you how many requests came in the last X seconds -- only how many came since the last time unit started. It's also only reasonable for numbers like you suggested -- Tim or Yoav's suggestions would be better if your range is 5 seconds to 60 minutes, for example. justin At 07:10 AM 7/29/2004, you wrote: I need to display on a .jsp page the number of requests for Tomcat in the past 5 / 10 / 15/ 30 / 45 / 60 seconds. I've already implement a Filter will count the total number of requests. I did this with a static int, which is incremented everytime a request comes in. But what should I do so that I can show number of request over past time intervals? Since the present time is always changing, the past n seconds is constantly changing also. Thanks in advance, Tom __ Justin Ruthenbeck Software Engineer, NextEngine Inc. justinr - AT - nextengine DOT com Confidential. See: http://www.nextengine.com/confidentiality.php __ - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
How can I display number of requests over the past n seconds?
I need to display on a .jsp page the number of requests for Tomcat in the past 5 / 10 / 15/ 30 / 45 / 60 seconds. I've already implement a Filter will count the total number of requests. I did this with a static int, which is incremented everytime a request comes in. But what should I do so that I can show number of request over past time intervals? Since the present time is always changing, the past n seconds is constantly changing also. Thanks in advance, Tom __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Re: How can I display number of requests over the past n seconds?
You could use a list of java.util.Dates with the oldest date at the beginning of the list and the newest at the end of the List. Push new Dates onto the list and pull (expired) dates from the front of the list accoring to your threshold. The number of hits per unit time is the size of each list. -Tim tom ly wrote: I need to display on a .jsp page the number of requests for Tomcat in the past 5 / 10 / 15/ 30 / 45 / 60 seconds. I've already implement a Filter will count the total number of requests. I did this with a static int, which is incremented everytime a request comes in. But what should I do so that I can show number of request over past time intervals? Since the present time is always changing, the past n seconds is constantly changing also. - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: How can I display number of requests over the past n seconds?
Hi, You would need to modify your filter. One approach would be to have separate counters, one for each time period, with a monitor thread for each one. The monitor thread would sleep for the duration of the timer, then reset it. The Filter would initialize these counters and threads, then increment each timer by one every time a request comes in. The JSP would simply read the counter values. Yoav Shapira Millennium Research Informatics -Original Message- From: tom ly [mailto:[EMAIL PROTECTED] Sent: Thursday, July 29, 2004 10:11 AM To: [EMAIL PROTECTED] Subject: How can I display number of requests over the past n seconds? I need to display on a .jsp page the number of requests for Tomcat in the past 5 / 10 / 15/ 30 / 45 / 60 seconds. I've already implement a Filter will count the total number of requests. I did this with a static int, which is incremented everytime a request comes in. But what should I do so that I can show number of request over past time intervals? Since the present time is always changing, the past n seconds is constantly changing also. Thanks in advance, Tom __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
