Invalid logger usage in ThreadPool

[jflaland]

Jetty version(s) 12.1.4

Jetty Environment core

HTTP version Not relevant for this issue

Java version/vendor (use: java -version) openjdk version "25.0.1" 2025-10-21 LTS

OS type/version Windows 11 25H2

Description

There were a lot of invalid logger usages that were fixed in jetty 12.1.4 (see #13883 and #13884). However, I found a function that is still using invalid loggers in class org.eclipse.jetty.util.thread.ThreadPool:

    static boolean reject(Runnable task, Throwable cause)
    {
        Logger log = LoggerFactory.getLogger(ThreadPool.class);
        if (log.isDebugEnabled())
            log.debug("rejected {}", task, cause);
        if (task instanceof Closeable closeable)
        {
            try
            {
                closeable.close();
            }
            catch (Throwable t)
            {
                log.warn("Unable to close rejected job: {}", task, t);
                ExceptionUtil.addSuppressedIfNotAssociated(cause, t);
            }
            return true;
        }
        return false;
    }

Both loggers in this function have only one parameter in the message but two are provided (because the exception counts as a parameter).

It produces this warning when debug logs are enabled:

WARN found 1 argument placeholders, but provided 2 for pattern `rejected {}`

How to reproduce?

1. Use log4j-slf4j2-impl SLF4J backend
2. Enable debug logs for org.eclipse.jetty
3. Not sure exactly how to get into that method. In my application, it seems to happen most of the times when jetty is shutting down.

[jflaland]

Hi @lachlan-roberts, I saw the change you made in your pull request. I am not able to review it officially, but I just wanted to mention that there is still one logger that has not been corrected in the same function. At line 160:

log.warn("Unable to close rejected job: {}", task, t);

Thank you

[lachlan-roberts]

@jflaland this pattern is fine as long as the throwable is not null, and this is in a catch block so it is guaranteed not to be null. All the other warning logs in the Jetty code base are done in the same way.

In this debug log case the Throwable cause argument can sometimes be null, which is why you get this warning.