动态线程池 - 配置中心nacos

1. 依赖

        <!-- nacos做 配置中心 依赖 -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
        </dependency>

2.配置

spring.application.name=consumer-dome1
spring.jackson.date-format=yyyy-MM-dd HH:mm:ss
spring.jackson.time-zone=GMT+8

# 在spring cloud gateway中不起作用，必须配置在 spring boot web 中
#server.servlet.context-path=/demo

# 若nacos开启了鉴权功能 即 nacos.core.auth.enabled=true，需要配置账号和密码
# nacos用户名
spring.cloud.nacos.username=nacos
# nacos密码
spring.cloud.nacos.password=nacos

#nacos配置中心地址
spring.cloud.nacos.config.server-addr=127.0.0.1:8848
#配置文件类型
spring.cloud.nacos.config.file-extension=properties
#指定加载配置文件
spring.config.import=optional:nacos:${spring.application.name}.${spring.cloud.nacos.config.file-extension}

3.创建一个单例线程池

public class SingleThreadPoolExecutor {
    private static final int CORE_SIZE = Runtime.getRuntime().availableProcessors();
    private static final int MAX_SIZE = CORE_SIZE * 2;
 
    /**
     * 1.共享可见
     * 2.禁止指令重排
     */
    private static volatile ThreadPoolExecutor threadPoolExecutor;
 
    /**
     * 构造器私有化
     * */
    private SingleThreadPoolExecutor() {
        throw new RuntimeException("禁止反射调用！");
    }
 
    
 
    /**
     * 双重检测锁 
     * 1.防止高并发下线程争夺共享资源
     * 2.提高效率
     * */
    public static ThreadPoolExecutor getThreadPoolExecutor() {
        if (threadPoolExecutor == null) {
            synchronized(SingleThreadPoolExecutor.class) {
                if (threadPoolExecutor == null) {
                    threadPoolExecutor = new ThreadPoolExecutor(CORE_SIZE, MAX_SIZE, 0L, TimeUnit.SECONDS, new LinkedBlockingQueue<>());
                }
            }
        }
 
        return threadPoolExecutor;
    }
 
}

4.监听nocos配置变更：更新线程核心线程数及最大线程数

@Configuration
@RefreshScope
@Data
public class GlobalRefreshConfig {

    @Value("${datasource.change.switch}")
    private String datasourceChangeSwitch;

    @Value("${global.thread.pool.core}")
    private Integer threadPoolCore;

    @Value("${global.thread.pool.max}")
    private Integer threadPoolMax;
}

@Configuration
public class SingleThreadPoolConfig implements InitializingBean{


    static ThreadPoolExecutor threadPoolExecutor = SingleThreadPoolExecutor.getThreadPoolExecutor();

    @Autowired
    private GlobalRefreshConfig globalRefreshConfig;

    @Autowired
    private NacosConfigManager nacosConfigManager;

    @Autowired
    private NacosConfigProperties nacosConfigProperties;


    @Override
    public void afterPropertiesSet() throws Exception {
        nacosConfigManager.getConfigService().addListener("consumer-dome1.properties", nacosConfigProperties.getGroup(),
                new Listener() {
                    @Override
                    public Executor getExecutor() {
                        System.out.println("exe getExecutor");
                        return null;
                    }

                    @Override
                    public void receiveConfigInfo(String configInfo) {
                        System.out.println("exe receiveConfigInfo");

                        //该方法体在配置变更时就会立即执行，此时@RefreshScope注解还未加载完毕，配置不会立即生效，需要延时一段时间
                        try {
                            TimeUnit.SECONDS.sleep(5);
                        } catch (InterruptedException e) {
                            throw new RuntimeException(e);
                        }
                        threadPoolExecutor.setCorePoolSize(globalRefreshConfig.getThreadPoolCore());
                        threadPoolExecutor.setMaximumPoolSize(globalRefreshConfig.getThreadPoolMax());
                    }
                });
    }
}

注意：核心线程数不得大于最大线程数,