1、异常情况:

MySQL 的默认设置下,当一个连接的空闲时间超过8小时后,MySQL 就会断开该连接,而 hikari 连接池则以为该被断开的连接依然有效。在这种情况下,如果客户端代码向 hikari 连接池请求连接的话,连接池就会把已经失效的连接返回给客户端,客户端在使用该失效连接的时候即抛出异常

The last packet successfully received from the server was 36,012 milliseconds ago. The last packet sent successfully to the server was 36,013 milliseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.

2、背景1:springboot 2.3.4默认版本

-->>spring-boot-starter-batch-2.3.4
-->>spring-boot-starter-jdbc-2.3.4
-->引入hikari-3.4.5
<dependency>
  <groupId>com.zaxxer</groupId>
  <artifactId>HikariCP</artifactId>
  <version>3.4.5</version>
  <scope>compile</scope>
</dependency>

2、背景2:HikariCP

参数说明: 有参数connectionTestQuery ,没有keepalivetime时间设置机制

connectionTestQueryIf your driver supports JDBC4 we strongly recommend not setting this property. This is for “legacy” drivers that do not support the JDBC4 Connection.isValid() API. This is the query that will be executed just before a connection is given to you from the pool to validate that the connection to the database is still alive. Again, try running the pool without this property, HikariCP will log an error if your driver is not JDBC4 compliant to let you know. Default: none

翻译大概就是。只有第一次获取连接的时候才会有执行该sql

  • 解决方案1: mysql 超时相关配置

    show variables like "%time%"; 
    -- 相关参数 (8小时 60 *60*8) 单位秒 =28800
    wait_timeout =35          (等待时间)
    interactive_timeout  =35 (交互时间)
    
    解决方法8小时不够那就加长: (60 * 60 *24)
    set interactive_timeout=86400;
    set wait_timeout=86400;
    
  • 解决方案2:定期使用连接池内的连接,使得它们不会因为闲置超时而被 MySQL 断开。使用中的连接是不会被空闲执行的。

    也就是通过获取连接之后Thread.sleep 的方式是管不到的。验证druid的空闲连接方法也是同样的道理

    # 一个连接在池里闲置多久时会被抛弃
    # 当 minimumIdle < maximumPoolSize 才生效
    # 默认值 600000 ms,最小值为 10000 ms,0表示禁用该功能。支持 JMX 动态修改
    idleTimeout=600000
    
    # 多久检查一次连接的活性
    # 检查时会先把连接从池中拿出来(空闲的话),然后调用isValid()或执行connectionTestQuery来校验活性,如果通过校验,则放回池里。
    # 默认 0 (不启用),最小值为 30000 ms,必须小于 maxLifetime。支持 JMX 动态修改
    keepaliveTime=0
    
    # 当一个连接存活了足够久,HikariCP 将会在它空闲时把它抛弃
    # 默认 1800000  ms,最小值为 30000 ms,0 表示禁用该功能。支持 JMX 动态修改
    maxLifetime=1800000
    
    # 用来检查连接活性的 sql,要求是一个查询语句,常用select 'x'
    # 如果驱动支持 JDBC4.0,建议不设置,这时默认会调用  Connection.isValid() 来检查,该方式会更高效一些
    # 默认为空
    # connectionTestQuery=
    
    # 池中至少要有多少空闲连接。
    # 当空闲连接 < minimumIdle,总连接 < maximumPoolSize 时,将新增连接
    # 默认等于 maximumPoolSize。支持 JMX 动态修改
    minimumIdle=5
    

核心代码逻辑:

# 初始化连接池
public HikariPool(final HikariConfig config)
   {
      super(config);

      this.connectionBag = new ConcurrentBag<>(this);
      this.suspendResumeLock = config.isAllowPoolSuspension() ? new SuspendResumeLock() : SuspendResumeLock.FAUX_LOCK;

      this.houseKeepingExecutorService = initializeHouseKeepingExecutorService();
	  //在里面创建连接
      checkFailFast();
		/***省略其他逻辑 ***/
      this.houseKeeperTask = houseKeepingExecutorService.scheduleWithFixedDelay(new HouseKeeper(), 100L, housekeepingPeriodMs, MILLISECONDS);
		
   }
#
private void checkFailFast()
   {
      final long initializationTimeout = config.getInitializationFailTimeout();
      if (initializationTimeout < 0) {
         return;
      }

      final long startTime = currentTime();
      do {
         final PoolEntry poolEntry = createPoolEntry();
         			/***省略其他逻辑 ***/
      	}
   }
# 创建池对象
private PoolEntry createPoolEntry()
   {
      try {
         final PoolEntry poolEntry = newPoolEntry();
			/***省略其他逻辑 ***/
		 final long keepaliveTime = config.getKeepaliveTime();
         if (keepaliveTime > 0) {
            // variance up to 10% of the heartbeat time
            final long variance = ThreadLocalRandom.current().nextLong(keepaliveTime / 10);
            final long heartbeatTime = keepaliveTime - variance;
            //定时执行
            poolEntry.setKeepalive(houseKeepingExecutorService.scheduleWithFixedDelay(new KeepaliveTask(poolEntry), heartbeatTime, heartbeatTime, MILLISECONDS));
         }

         return poolEntry;
      }
      catch (ConnectionSetupException e) {
         
      }
      return null;
   }
   
## 执行任务线程
private final class KeepaliveTask implements Runnable
   {
      private final PoolEntry poolEntry;

      KeepaliveTask(final PoolEntry poolEntry)
      {
         this.poolEntry = poolEntry;
      }

      public void run()
      {	
        
      	// 关键判断 只判断是连接池种空闲的连接,已经被标记为使用的连接 不做判断
      	// return poolEntry.compareAndSet(STATE_NOT_IN_USE, STATE_RESERVED);
      	// 总共四种状态 
      	//int STATE_NOT_IN_USE = 0;
        //int STATE_IN_USE = 1;
        //int STATE_REMOVED = -1;
        //int STATE_RESERVED = -2;
         if (connectionBag.reserve(poolEntry)) {
            if (!isConnectionAlive(poolEntry.connection)) {
               softEvictConnection(poolEntry, DEAD_CONNECTION_MESSAGE, true);
               addBagItem(connectionBag.getWaitingThreadCount());
            }
            else {
               connectionBag.unreserve(poolEntry);
               logger.debug("{} - keepalive: connection {} is alive", poolName, poolEntry.connection);
            }
         }
      }
   }

# 连接什么时候状态被置为 STATE_IN_USE
public Connection getConnection(final long hardTimeout) throws SQLException
   {
      suspendResumeLock.acquire();
      final long startTime = currentTime();

      try {
         long timeout = hardTimeout;
         do {
            PoolEntry poolEntry = connectionBag.borrow(timeout, MILLISECONDS);
}
# borrow 标记方法
public T borrow(long timeout, final TimeUnit timeUnit) throws InterruptedException
   {
      try {
         for (T bagEntry : sharedList) {
         	//获取连接 将连接标记为STATE_IN_USE
            if (bagEntry.compareAndSet(STATE_NOT_IN_USE, STATE_IN_USE)) {
               // If we may have stolen another waiter's connection, request another bag add.
               if (waiting > 1) {
                  listener.addBagItem(waiting - 1);
               }
               return bagEntry;
            }
         }
      }
   }
   

3测试代码:

  • 配置代码: 数据库mysql 35s 超时

    spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
    spring.datasource.url = jdbc:mysql://127.0.0.1:3306/uuid_task?autoReconnect=true&useUnicode=true&characterEncoding=utf-8&serverTimezone=GMT
    spring.datasource.username = root
    spring.datasource.password = root1234
    spring.datasource.hikari.minimum-idle = 1
    spring.datasource.hikari.maximum-pool-size=1
    spring.datasource.hikari.auto-commit=false
    spring.datasource.hikari.connection-timeout=10000
    spring.datasource.hikari.max-lifetime = 650000
    spring.datasource.hikari.idle-timeout = 650000
    spring.datasource.hikari.validation-timeout = 300000
    spring.datasource.hikari.connectionTestQuery = select 99 from dual
    spring.datasource.hikari.keepaliveTime = 40000
    
@Test
    void hikariDataSourceSingleTestOne() {
        try {
            System.out.println("===================sleep=60s::"+new Date());
            Thread.sleep(60000);
            Connection connection =dataSource.getConnection();
            System.out.println("======connection==="+connection);
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }
    }

hikari-4.0.1 keepalivetime=40s

===================sleep=36s::Tue May 10 16:11:49 CST 2022
2022-05-10 16:12:17.729 DEBUG 27580 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Pool stats (total=1, active=0, idle=1, waiting=0)
2022-05-10 16:12:17.730 DEBUG 27580 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Fill pool skipped, pool is at sufficient level.
2022-05-10 16:12:25.942 DEBUG 27580 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - keepalive: connection com.mysql.cj.jdbc.ConnectionImpl@28e19366 is alive
2022-05-10 16:12:47.741 DEBUG 27580 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Pool stats (total=1, active=0, idle=1, waiting=0)
2022-05-10 16:12:47.742 DEBUG 27580 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Fill pool skipped, pool is at sufficient level.
======connection===HikariProxyConnection@2079332573 wrapping com.mysql.cj.jdbc.ConnectionImpl@28e19366

hikari-4.0.1 keepalivetime=65s

===================sleep=36s::Tue May 10 16:18:42 CST 2022
2022-05-10 16:19:09.819 DEBUG 25464 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Pool stats (total=1, active=0, idle=1, waiting=0)
2022-05-10 16:19:09.819 DEBUG 25464 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Fill pool skipped, pool is at sufficient level.
2022-05-10 16:19:39.820 DEBUG 25464 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Pool stats (total=1, active=0, idle=1, waiting=0)
2022-05-10 16:19:39.821 DEBUG 25464 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Fill pool skipped, pool is at sufficient level.
2022-05-10 16:19:42.560  WARN 25464 --- [           main] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Failed to validate connection com.mysql.cj.jdbc.ConnectionImpl@5cb042da (Communications link failure

The last packet successfully received from the server was 60,704 milliseconds ago. The last packet sent successfully to the server was 60,715 milliseconds ago.). Possibly consider using a shorter maxLifetime value.
2022-05-10 16:19:42.561 DEBUG 25464 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@5cb042da: (connection is dead)
2022-05-10 16:19:42.588 DEBUG 25464 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@5cb042da failed

java.sql.SQLNonTransientConnectionException: Communications link failure during rollback(). Transaction resolution unknown.
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:110) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.ConnectionImpl.rollback(ConnectionImpl.java:1848) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:1705) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.ConnectionImpl.close(ConnectionImpl.java:721) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.zaxxer.hikari.pool.PoolBase.quietlyCloseConnection(PoolBase.java:143) ~[HikariCP-4.0.1.jar:na]
	at com.zaxxer.hikari.pool.HikariPool.lambda$closeConnection$1(HikariPool.java:451) [HikariCP-4.0.1.jar:na]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_301]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_301]
	at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_301]

2022-05-10 16:19:42.656 DEBUG 25464 --- [onnection adder] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Added connection com.mysql.cj.jdbc.ConnectionImpl@175fb217
Tue May 10 16:19:42 CST 2022======connection===HikariProxyConnection@718781734 wrapping com.mysql.cj.jdbc.ConnectionImpl@175fb217


hikari-3.4.5

===================sleep=36s::Tue May 10 16:08:02 CST 2022
2022-05-10 16:08:30.769 DEBUG 4024 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Pool stats (total=1, active=0, idle=1, waiting=0)
2022-05-10 16:08:30.769 DEBUG 4024 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Fill pool skipped, pool is at sufficient level.
2022-05-10 16:09:00.776 DEBUG 4024 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Pool stats (total=1, active=0, idle=1, waiting=0)
2022-05-10 16:09:00.776 DEBUG 4024 --- [l-1 housekeeper] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Fill pool skipped, pool is at sufficient level.
2022-05-10 16:09:02.662  WARN 4024 --- [           main] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Failed to validate connection com.mysql.cj.jdbc.ConnectionImpl@4726927c (Communications link failure

The last packet successfully received from the server was 60,303 milliseconds ago. The last packet sent successfully to the server was 60,305 milliseconds ago.). Possibly consider using a shorter maxLifetime value.
2022-05-10 16:09:02.664 DEBUG 4024 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@4726927c: (connection is dead)
2022-05-10 16:09:02.674 DEBUG 4024 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@4726927c failed

java.sql.SQLNonTransientConnectionException: Communications link failure during rollback(). Transaction resolution unknown.
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:110) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.ConnectionImpl.rollback(ConnectionImpl.java:1848) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:1705) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.mysql.cj.jdbc.ConnectionImpl.close(ConnectionImpl.java:721) ~[mysql-connector-java-8.0.21.jar:8.0.21]
	at com.zaxxer.hikari.pool.PoolBase.quietlyCloseConnection(PoolBase.java:143) ~[HikariCP-3.4.5.jar:na]
	at com.zaxxer.hikari.pool.HikariPool.lambda$closeConnection$1(HikariPool.java:451) [HikariCP-3.4.5.jar:na]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_301]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_301]
	at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_301]

======connection===HikariProxyConnection@2079332573 wrapping com.mysql.cj.jdbc.ConnectionImpl@77812b64
2022-05-10 16:09:02.717 DEBUG 4024 --- [onnection adder] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Added connection com.mysql.cj.jdbc.ConnectionImpl@77812b64

4、结论

  1. hikar连接池也是需要开启keepalivetime参数的。 需要在4.0.1版本以上
  2. hikari如果不开的且未超过最大maxlifetime时间。
  3. hikari如果不开的且超过最大maxlifetime时间。连接是可以被关闭且会主动重新连接的
作者:|jackssybin|,原文链接: http://www.imooc.com/article/325400

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