JMeter测试1万+用户遇OutOfMemoryError：根因排查与内存扩容咨询

测试流程 #

• 先发送1个POST请求
• 再发送N个PUT请求（N为用户数量）
• 所有响应保存至target目录

问题现象 #

当测试用户量达到10000+时，JMeter抛出内存溢出错误：

Uncaught Exception java.lang.OutOfMemoryError: Java heap space in thread Thread[MyCoolTest 1-3165,5,main]. See log file for details.

运行一段时间后出现内存耗尽，日志详情如下：

java.lang.OutOfMemoryError: Java heap space
    at java.nio.HeapByteBuffer.<init>(HeapByteBuffer.java:61) ~[?:?]
    at java.nio.ByteBuffer.allocate(ByteBuffer.java:348) ~[?:?]
    at org.apache.logging.log4j.core.layout.StringBuilderEncoder.getThreadLocalState(StringBuilderEncoder.java:82) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.layout.StringBuilderEncoder.encode(StringBuilderEncoder.java:64) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.layout.StringBuilderEncoder.encode(StringBuilderEncoder.java:32) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:231) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:59) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:197) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:190) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:181) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:543) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:502) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:485) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:460) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:82) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.core.Logger.log(Logger.java:161) ~[log4j-core-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.spi.AbstractLogger.tryLogMessage(AbstractLogger.java:2198) ~[log4j-api-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.spi.AbstractLogger.logMessageTrackRecursion(AbstractLogger.java:2152) ~[log4j-api-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.spi.AbstractLogger.logMessageSafely(AbstractLogger.java:2135) ~[log4j-api-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2028) ~[log4j-api-2.13.1.jar:2.13.1]
    at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1899) ~[log4j-api-2.13.1.jar:2.13.1]
    at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:184) ~[log4j-slf4j-impl-2.13.1.jar:2.13.1]
    at org.apache.jmeter.threads.JMeterThread.initRun(JMeterThread.java:712) ~[ApacheJMeter_core-5.3.jar:5.3]
    at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:252) ~[ApacheJMeter_core-5.3.jar:5.3]
    at java.lang.Thread.run(Thread.java:829) [?:?]

环境信息 #

• 运行环境：CircleCI的Linux机器，Ubuntu 20.04.5 LTS，x86_64架构
• Java版本：openjdk:11.0
• JMeter版本：5.5
• 依赖管理：通过Maven在Docker镜像中安装JMeter

咨询问题 #

1. 该问题的根本原因是什么？
2. 在CircleCI的Docker镜像中运行JMeter时，是否可以增加内存？（推测可找到jmeter.bat文件并调大Xmx参数）

解答 #

问题1：根本原因分析 #

从日志和测试场景来看，核心原因包括：

1. 默认堆内存不足：JMeter默认分配的Java堆内存（通常几百MB）无法支撑10000+并发线程，每个线程需要存储请求/响应数据、上下文状态等，线程数过载直接导致内存耗尽。
2. 响应保存加剧内存消耗：将所有响应保存到target目录的操作，如果未配置异步写入或批量处理，会在内存中暂存大量响应数据，进一步占用堆空间。
3. 日志系统内存压力：溢出发生在Log4j编码阶段，高并发下大量INFO级别日志输出会持续占用内存，频繁的日志生成和编码操作加速了内存耗尽。

问题2：CircleCI Docker镜像中调整JMeter内存的方法 #

可以增加内存，注意Linux环境下没有jmeter.bat，对应是jmeter shell脚本，常用调整方式如下：

• 修改启动脚本：找到Docker镜像中/opt/apache-jmeter/bin/jmeter脚本，修改JVM_ARGS参数，比如将-Xmx1g改为-Xmx4g（建议不超过物理内存的70%）。
• 环境变量传递：在CircleCI配置文件（.circleci/config.yml）中启动JMeter时设置环境变量：

  JVM_ARGS="-Xms2g -Xmx4g" jmeter -n -t testplan.jmx -l result.jtl
  

• Maven插件配置：如果通过Maven运行JMeter，在pom.xml中添加JVM参数配置：

  <plugin>
      <groupId>com.lazerycode.jmeter</groupId>
      <artifactId>jmeter-maven-plugin</artifactId>
      <version>3.5.0</version>
      <configuration>
          <jvmArgs>-Xms2g -Xmx4g</jvmArgs>
          <!-- 其他测试配置 -->
      </configuration>
  </plugin>
  

额外优化建议：

• 关闭不必要的监听器，仅保留核心结果收集组件
• 降低日志级别至WARN或ERROR，减少日志输出量
• 配置响应异步写入，避免内存堆积大量响应数据
• 采用分布式测试，将并发压力分散到多个JMeter节点

内容的提问来源于stack exchange，提问作者Zedd Demir