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https://issues.apache.org/jira/browse/LOG4J2-2118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16429556#comment-16429556
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ASF GitHub Bot commented on LOG4J2-2118:
----------------------------------------

Github user cakofony commented on the issue:

    https://github.com/apache/logging-log4j2/pull/131
  
    @uncleyo @zslayton This should be resolved as of 
[this](https://github.com/apache/logging-log4j2/commit/967bb0f71155aa00acadbd95362a90832bed69f6)
 commit (included in 2.11.0).
    
    
[LOG4J2-2307](https://github.com/apache/logging-log4j2/commit/0738cf970c111a07a7307549b8c16af4d44af8a4)
 may also be relevant for scenarios where a memento is created (AsyncAppender, 
for instance)


> MutableLogEvent does not retain the Message format string
> ---------------------------------------------------------
>
>                 Key: LOG4J2-2118
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-2118
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Layouts
>    Affects Versions: 2.8
>         Environment: Mac OS X 10.11.6
> Java 1.8.0_141
>            Reporter: Zack Slayton
>            Assignee: Remko Popma
>            Priority: Major
>              Labels: layout
>             Fix For: 2.11.0
>
>
> I'm attempting to create a custom binary Layout that stores the provided 
> format string separate from the parameters rather than eagerly formatting 
> them all into a single piece of text. However, when I went to implement 
> `Layout::toByteArray`, I discovered that the `Message::getFormat` method 
> always returns null.
> {code:java}
> import org.apache.logging.log4j.LogManager;
> import org.apache.logging.log4j.Logger;
> import org.apache.logging.log4j.core.LogEvent;
> import org.apache.logging.log4j.core.config.plugins.Plugin;
> import org.apache.logging.log4j.core.config.plugins.PluginFactory;
> import org.apache.logging.log4j.core.layout.AbstractLayout;
> import java.io.Serializable;
> import java.util.Arrays;
> @Plugin(name = "MyLayout", category = "Core", elementType = "layout", 
> printObject = true)
> public class MyLayout extends AbstractLayout {
>     public MyLayout() {
>         super(null, null, null);
>     }
>     @PluginFactory
>     public static MyLayout createLayout(){
>         return new MyLayout();
>     }
>     public static void main(String[] args) {
>         Logger log = LogManager.getLogger(MyLayout.class);
>         log.info("Here's a thing: {}. And another: {}", 75, "walrus");
>     }
>     @Override
>     public byte[] toByteArray(LogEvent event) {
>         System.out.println("Format: " + event.getMessage().getFormat());
>         System.out.println("Parameters: " + 
> Arrays.toString(event.getMessage().getParameters()));
>         return new byte[0];
>     }
>     @Override
>     public Serializable toSerializable(LogEvent event) {
>         return null;
>     }
>     @Override
>     public String getContentType() {
>         return null;
>     }
>     @Override
>     public byte[] getFooter() {
>         return new byte[0];
>     }
>     @Override
>     public byte[] getHeader() {
>         return new byte[0];
>     }
> }
> {code}
> If I run `main` (with an extra `PatternLayout`+`Console` appender in my 
> config), I see the following output:
> {code}
> 17:55:28.524 [main] INFO  com.example.logging.plugins.MyLayout - Here's a 
> thing: 75. And another: walrus
> Format: null
> Parameters: [75, walrus]
> {code}
> I had expected to be able to see the format string and the array of 
> parameters, but instead I can only see the parameters. The format string is 
> always null.
> This appears to be due to the implementation of `MutableLogEvent::setMessage` 
> highlighted [in 
> LOG4J2-1510|https://issues.apache.org/jira/browse/LOG4J2-1510]. Because the 
> messages are reusable, they appear to be eagerly formatted and the format 
> string itself is discarded. The `getFormat` method is hardcoded to return 
> `null`.
> Is this by design? If so, what is the prescribed approach to getting the 
> format string in my layout? (Preferably one that does not disable the 
> performance optimizations offered by enabling threadlocals.)
> Thanks!



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