[jboss-jira] [JBoss JIRA] Commented: (JGRP-484) Dynamically configure logging at runtime

[Bela Ban (JIRA)]

    [ http://jira.jboss.com/jira/browse/JGRP-484?page=comments#action_12360673 ] 
            
Bela Ban commented on JGRP-484:
-------------------------------


The program below measured that for 1 million log statements (with tracing turned OFF for 'bla'), the overhead of if(log.isTraceEnabled()) compared to if(trace) was 16 ms, so that's negligible.


--------------------------- code ------------------
package org.jgroups.tests;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * @author Bela Ban
 * @version $Id$
 */
public class bla {
    final static int NUM=1000 * 1000;


    public static void main(String[] args) throws Exception {
        Log log=LogFactory.getLog(bla.class);
        testWithCaching(log);
        testWithoutCaching(log);
        testWithCaching(log);
        testWithoutCaching(log);
    }

    private static void testWithCaching(Log log) {
        long start, stop, diff;
        boolean trace=log.isTraceEnabled();

        start=System.nanoTime();
        for(int i=0; i < NUM; i++) {
            if(trace) {
                log.trace("testing");
            }
        }
        stop=System.nanoTime();
        diff=stop - start;
        System.out.println(NUM + " with caching: " + diff + " ns (" + diff / 1000000 + " ms)");
    }


    private static void testWithoutCaching(Log log) {
        long start, stop, diff;

        start=System.nanoTime();
        for(int i=0; i < NUM; i++) {
            if(log.isTraceEnabled()) {
                log.trace("testing");
            }
        }
        stop=System.nanoTime();
        diff=stop - start;
        System.out.println(NUM + " without caching: " + diff + " ns (" + diff / 1000000 + " ms)");
    }

}


---------------- output -----------------

1000000 with caching: 4803404 ns (4 ms)
1000000 without caching: 24840308 ns (24 ms)
1000000 with caching: 377981 ns (0 ms)
1000000 without caching: 19888841 ns (19 ms)


> Dynamically configure logging at runtime
> ----------------------------------------
>
>                 Key: JGRP-484
>                 URL: http://jira.jboss.com/jira/browse/JGRP-484
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>            Priority: Minor
>             Fix For: 2.6
>
>
> For performance reasons, JGroups caches log levels as follows:
> boolean trace=log.isTraceEnabled();
> // later:
> if(trace) {
>      log.trace(...);
> }
> While caching created a measurable performance increase, it also disabled the ability to change the log levels at runtime (example: JBoss' log4j.xml, which is re-read every 60 secs).
> Investigate how to have both good performance and dynamic runtime configuration of log levels. E.g. signal to enable logging ?

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