[
https://issues.apache.org/jira/browse/LOG4J2-763?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Remko Popma updated LOG4J2-763:
-------------------------------
Description:
http://javaadventure.blogspot.com/2014/07/log4j-20-async-loggers-and-immutability.html
When using parameterized messages, the toString() method of the log messages is
not called when the log message is enqueued, rather after the log message has
been dequeued for writing. If any of the message parameters are mutable, they
can thus have changed state before the log message is written, thus resulting
in the logged message content being incorrect.
>From the blog post, code that demonstrates the problem:
{code}
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.util.concurrent.atomic.AtomicLong;
public class App {
private static final AtomicLong value = new AtomicLong();
public String toString() {
return Long.toString(value.get());
}
public long next() {
return value.incrementAndGet();
}
public static void main(String[] args) {
for (int i = 0; i < 32; i++) {
new Thread() {
final Logger logger = LogManager.getLogger(App.class);
final App instance = new App();
@Override
public void run() {
for (int i = 0; i < 100000; i++) {
logger.warn("{} == {}", instance.next(), instance);
}
}
}.start();
}
}
}
{code}
Here is the first few lines of logging output
{code}
2014-07-28 15:59:45,729 WARN t.App [Thread-13] 13 == 13
2014-07-28 15:59:45,730 WARN t.App [Thread-29] 29 == 29
2014-07-28 15:59:45,729 WARN t.App [Thread-15] 15 == 15
2014-07-28 15:59:45,729 WARN t.App [Thread-6] 6 == 6
2014-07-28 15:59:45,730 WARN t.App [Thread-30] 30 == 30
2014-07-28 15:59:45,729 WARN t.App [Thread-20] 20 == 20
2014-07-28 15:59:45,729 WARN t.App [Thread-8] 8 == 8
2014-07-28 15:59:45,730 WARN t.App [Thread-28] 28 == 28
2014-07-28 15:59:45,729 WARN t.App [Thread-19] 19 == 19
2014-07-28 15:59:45,729 WARN t.App [Thread-18] 18 == 18
2014-07-28 15:59:45,729 WARN t.App [Thread-5] 5 == 6
2014-07-28 15:59:45,731 WARN t.App [Thread-13] 33 == 37
2014-07-28 15:59:45,731 WARN t.App [Thread-8] 39 == 39
2014-07-28 15:59:45,731 WARN t.App [Thread-28] 40 == 41
2014-07-28 15:59:45,731 WARN t.App [Thread-18] 42 == 43
2014-07-28 15:59:45,731 WARN t.App [Thread-5] 43 == 43
{code}
To make my previous code work with Asynchronous loggers (other than by fixing
the mutable state) I would need to log like this:
{code}
if (logger.isWarnEnabled()) {
logger.warn("{} == {}", instance.next(), instance.toString());
}
{code}
was:
http://javaadventure.blogspot.com/2014/07/log4j-20-async-loggers-and-immutability.html
TL;DR When using parameterized messages, the toString() method of the log
messages is not called when the log message is enqueued, rather after the log
message has been dequeued for writing. If any of the message parameters are
mutable, they can thus have changed state before the log message is written,
thus resulting in the logged message content being incorrect.
> Async loggers convert message parameters toString at log record writing not
> at log statement execution
> ------------------------------------------------------------------------------------------------------
>
> Key: LOG4J2-763
> URL: https://issues.apache.org/jira/browse/LOG4J2-763
> Project: Log4j 2
> Issue Type: Bug
> Affects Versions: 2.0
> Reporter: Stephen Connolly
>
> http://javaadventure.blogspot.com/2014/07/log4j-20-async-loggers-and-immutability.html
> When using parameterized messages, the toString() method of the log messages
> is not called when the log message is enqueued, rather after the log message
> has been dequeued for writing. If any of the message parameters are mutable,
> they can thus have changed state before the log message is written, thus
> resulting in the logged message content being incorrect.
> From the blog post, code that demonstrates the problem:
> {code}
> import org.apache.logging.log4j.LogManager;
> import org.apache.logging.log4j.Logger;
> import java.util.concurrent.atomic.AtomicLong;
> public class App {
> private static final AtomicLong value = new AtomicLong();
> public String toString() {
> return Long.toString(value.get());
> }
> public long next() {
> return value.incrementAndGet();
> }
> public static void main(String[] args) {
> for (int i = 0; i < 32; i++) {
> new Thread() {
> final Logger logger = LogManager.getLogger(App.class);
> final App instance = new App();
> @Override
> public void run() {
> for (int i = 0; i < 100000; i++) {
> logger.warn("{} == {}", instance.next(), instance);
> }
> }
> }.start();
> }
> }
> }
> {code}
> Here is the first few lines of logging output
> {code}
> 2014-07-28 15:59:45,729 WARN t.App [Thread-13] 13 == 13
> 2014-07-28 15:59:45,730 WARN t.App [Thread-29] 29 == 29
> 2014-07-28 15:59:45,729 WARN t.App [Thread-15] 15 == 15
> 2014-07-28 15:59:45,729 WARN t.App [Thread-6] 6 == 6
> 2014-07-28 15:59:45,730 WARN t.App [Thread-30] 30 == 30
> 2014-07-28 15:59:45,729 WARN t.App [Thread-20] 20 == 20
> 2014-07-28 15:59:45,729 WARN t.App [Thread-8] 8 == 8
> 2014-07-28 15:59:45,730 WARN t.App [Thread-28] 28 == 28
> 2014-07-28 15:59:45,729 WARN t.App [Thread-19] 19 == 19
> 2014-07-28 15:59:45,729 WARN t.App [Thread-18] 18 == 18
> 2014-07-28 15:59:45,729 WARN t.App [Thread-5] 5 == 6
> 2014-07-28 15:59:45,731 WARN t.App [Thread-13] 33 == 37
> 2014-07-28 15:59:45,731 WARN t.App [Thread-8] 39 == 39
> 2014-07-28 15:59:45,731 WARN t.App [Thread-28] 40 == 41
> 2014-07-28 15:59:45,731 WARN t.App [Thread-18] 42 == 43
> 2014-07-28 15:59:45,731 WARN t.App [Thread-5] 43 == 43
> {code}
> To make my previous code work with Asynchronous loggers (other than by fixing
> the mutable state) I would need to log like this:
> {code}
> if (logger.isWarnEnabled()) {
> logger.warn("{} == {}", instance.next(), instance.toString());
> }
> {code}
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