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Posted to log4j-dev@logging.apache.org by "Remko Popma (JIRA)" <ji...@apache.org> on 2014/08/10 08:44:11 UTC
[jira] [Resolved] (LOG4J2-763) Async loggers convert message
parameters toString at log record writing not at log statement execution
[ https://issues.apache.org/jira/browse/LOG4J2-763?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Remko Popma resolved LOG4J2-763.
--------------------------------
Resolution: Fixed
Improved FormattedMessage, StringFormattedMessage, LocalizedMessage, MessageFormatMessage and ObjectMessage for asynchronous logging to ensure the formatted message does not change even if parameters are modified by the application. Added JUnit tests.
ParameterizedMessage and ThreadDumpMessage were already safe.
Improved docs for MapMessage and StructuredDataMessage: these are mutable by design and users should take care when logging these messages asynchronously. Improved site docs.
Fixed in revision 1617051. Please verify and close.
> 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
> Assignee: Remko Popma
> Fix For: 2.0.2
>
> Attachments: LOG4J2-763.patch
>
>
> 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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