实战 | 生产环境中如何动态调整线程池大小？

<properties>
  <nacos.version>2.1.2</nacos.version>
  <yaml.version>1.33</yaml.version>
  <java.version>17</java.version>
</properties>
<dependency>
  <groupId>com.alibaba.nacos</groupId>
  <artifactId>nacos-client</artifactId>
  <version>${nacos.version}</version>
  <!-- 指定纯净版SDK -->
  <classifier>pure</classifier>
</dependency>
<dependency>
  <groupId>com.alibaba.nacos</groupId>
  <artifactId>nacos-common</artifactId>
  <version>${nacos.version}</version>
</dependency>
<dependency>
  <groupId>com.alibaba.nacos</groupId>
  <artifactId>nacos-api</artifactId>
  <version>${nacos.version}</version>
</dependency>
<dependency>
  <groupId>org.yaml</groupId>
  <artifactId>snakeyaml</artifactId>
  <version>${yaml.version}</version>
</dependency>

public class NacosConfigListener {


  public void start() throws Exception {
    String serverAddr = "localhost:8848";
    String dataId = "dy-thread.yaml";
    String group = "dy";
    Properties properties = new Properties();
    properties.put("serverAddr", serverAddr);
    properties.put("username", "nacos") ;
    properties.put("password", "nacos") ;
    ConfigService configService = NacosFactory.createConfigService(properties);
    String content = configService.getConfig(dataId, group, 5000);
    System.out.println("初始配置：\n" + content) ;
    Yaml yaml = new Yaml() ;
    configService.addListener(dataId, group, new Listener() {
      public void receiveConfigInfo(String configInfo) {
        try {
          LinkedHashMap<String, Object> content = (LinkedHashMap<String, Object>) yaml.load(configInfo) ;
          System.out.println("监听线程池修改：" + content) ;
          // 当内容发生变化后，修改线程池的配置信息
          LinkedHashMap<String, Object> dy = (LinkedHashMap<String, Object>) content.get("dy") ;
          Integer coreSize = (Integer) dy.get("coreSize") ;
          Integer maximumPoolSize = (Integer) dy.get("maximumPoolSize") ;
          DynamicThreadPoolConfig.pool.setMaximumPoolSize(maximumPoolSize) ;
          DynamicThreadPoolConfig.pool.setCorePoolSize(coreSize) ;
        } catch (Exception e) {
          e.printStackTrace() ;
        }
      }
      @Override
      public Executor getExecutor() {
        return null ;
      }
    });
  }


}

public class DynamicThreadPoolConfig {


  public static final ThreadPoolExecutor pool = new ThreadPoolExecutor(2, 3, 60, TimeUnit.SECONDS, new ArrayBlockingQueue<>(100)) ;


  public static void main(String[] args) throws Exception {


    // 启动监听器
    new NacosConfigListener().start() ;


    var schedule = new ScheduledThreadPoolExecutor(1) ;
    // 以固定的周期打印线程池线程信息
    schedule.scheduleAtFixedRate(() -> {
      System.out.println( 
          "核心线程数: " + pool.getCorePoolSize() 
        + ", 最大线程数: " + pool.getMaximumPoolSize() 
        + ", 当前活动任务数: " + pool.getActiveCount()
      ) ;
    }, 0, 3, TimeUnit.SECONDS) ;


    // 动态添加任务
    for (var i = 0; i < 100; i++) {
      pool.execute(() -> {
        try {
          System.out.println(Thread.currentThread().getName()) ;
          TimeUnit.SECONDS.sleep(10) ;
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
      }) ;
    } 
  }
}