[LOG4J2-2167] Memory leak in Apache Tomcat/8.5.24

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 2.10.0
• Component/s: Web/Servlet

Environment

OS (on AWS): ubuntu-xenial-16.04-amd64-server-20171121.1 (ami-fcc4db98)
Server version: Apache Tomcat/8.5.24
Server built: Nov 27 2017 13:05:30 UTC
Server number: 8.5.24.0
JVM Version: 1.8.0_151-b12
JVM Vendor: Oracle Corporation

• Assignee: Unassigned
• Reporter: Christian Salway
• Created: 30/Dec/17 04:51
• Updated: 30/Dec/17 11:22
• Resolved: 30/Dec/17 11:22

Description

I'm introducing log4j2 as the logger into my application and when I do that, on a reload, undeploy or stop of the Application, a memory leak is left, which only happens once I introduce the logger into the code.

The following web applications were stopped (reloaded, undeployed), but their
classes from previous runs are still loaded in memory, thus causing a memory
leak (use a profiler to confirm):
/myapp

My log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="trace">
    <Appenders>
        <Console name="Console">
            <PatternLayout pattern="%d %p [%c] %m%n" />
        </Console>
        <File name="File" bufferedIO="true" fileName="${env:CATALINA_BASE}/logs/app-${date:yyyy-mm-dd}.log">
            <PatternLayout pattern="%d %p %m%n" />
        </File>
    </Appenders>
    <Loggers>
        <Root level="all" includeLocation="false">
            <AppenderRef ref="Console" />
            <AppenderRef ref="File" />
        </Root>
    </Loggers>
</Configuration>

My dependencies in pom.xml:

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.10.0</version>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.10.0</version>
</dependency>

My WebServlet:

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "Servlet", urlPatterns = {"/servlet"}, loadOnStartup = 1)
public class Servlet extends HttpServlet {

    private final Logger logger = LogManager.getLogger(Servlet.class);

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        logger.info("doGet");

        PrintWriter out = response.getWriter();
        out.print("Servlet loaded");
        out.flush();
        out.close();
    }
}