聊聊hikari连接池的leakDetectionThreshold

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本文主要研究一下hikari连接池的leakDetectionThreshold,也就是连接池泄露检测。

leakDetectionThreshold

用来设置连接被占用的超时时间,单位为毫秒,默认为0,表示禁用连接泄露检测。

如果大于0且不是单元测试,则进一步判断:(leakDetectionThreshold < SECONDS.toMillis(2) or (leakDetectionThreshold > maxLifetime && maxLifetime > 0),会被重置为0 .

即如果要生效则必须>0,同时满足:不能小于2秒,而且当maxLifetime > 0时不能大于maxLifetime,该值默认为1800000,即30分钟。

HikariPool.getConnection

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java

   /**
    * Get a connection from the pool, or timeout after the specified number of milliseconds.
    *
    * @param hardTimeout the maximum time to wait for a connection from the pool
    * @return a java.sql.Connection instance
    * @throws SQLException thrown if a timeout occurs trying to obtain a connection
    */
   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);
            if (poolEntry == null) {
               break; // We timed out... break and throw exception
            }

            final long now = currentTime();
            if (poolEntry.isMarkedEvicted() || (elapsedMillis(poolEntry.lastAccessed, now) > ALIVE_BYPASS_WINDOW_MS && !isConnectionAlive(poolEntry.connection))) {
               closeConnection(poolEntry, poolEntry.isMarkedEvicted() ? EVICTED_CONNECTION_MESSAGE : DEAD_CONNECTION_MESSAGE);
               timeout = hardTimeout - elapsedMillis(startTime);
            }
            else {
               metricsTracker.recordBorrowStats(poolEntry, startTime);
               return poolEntry.createProxyConnection(leakTaskFactory.schedule(poolEntry), now);
            }
         } while (timeout > 0L);

         metricsTracker.recordBorrowTimeoutStats(startTime);
         throw createTimeoutException(startTime);
      }
      catch (InterruptedException e) {
         Thread.currentThread().interrupt();
         throw new SQLException(poolName + " - Interrupted during connection acquisition", e);
      }
      finally {
         suspendResumeLock.release();
      }
   }
注意,getConnection返回的时候调用了poolEntry.createProxyConnection(leakTaskFactory.schedule(poolEntry), now)
注意,这里创建代理连接的时候关联了ProxyLeakTask

leakTaskFactory

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java

   /**
    * Construct a HikariPool with the specified configuration.
    *
    * @param config a HikariConfig instance
    */
   public HikariPool(final HikariConfig config)
   {
      super(config);

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

      this.houseKeepingExecutorService = initializeHouseKeepingExecutorService();

      checkFailFast();

      if (config.getMetricsTrackerFactory() != null) {
         setMetricsTrackerFactory(config.getMetricsTrackerFactory());
      }
      else {
         setMetricRegistry(config.getMetricRegistry());
      }

      setHealthCheckRegistry(config.getHealthCheckRegistry());

      registerMBeans(this);

      ThreadFactory threadFactory = config.getThreadFactory();

      LinkedBlockingQueue<Runnable> addConnectionQueue = new LinkedBlockingQueue<>(config.getMaximumPoolSize());
      this.addConnectionQueue = unmodifiableCollection(addConnectionQueue);
      this.addConnectionExecutor = createThreadPoolExecutor(addConnectionQueue, poolName + " connection adder", threadFactory, new ThreadPoolExecutor.DiscardPolicy());
      this.closeConnectionExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection closer", threadFactory, new ThreadPoolExecutor.CallerRunsPolicy());

      this.leakTaskFactory = new ProxyLeakTaskFactory(config.getLeakDetectionThreshold(), houseKeepingExecutorService);

      this.houseKeeperTask = houseKeepingExecutorService.scheduleWithFixedDelay(new HouseKeeper(), 100L, HOUSEKEEPING_PERIOD_MS, MILLISECONDS);
   }

   /**
    * Create/initialize the Housekeeping service {@link ScheduledExecutorService}.  If the user specified an Executor
    * to be used in the {@link HikariConfig}, then we use that.  If no Executor was specified (typical), then create
    * an Executor and configure it.
    *
    * @return either the user specified {@link ScheduledExecutorService}, or the one we created
    */
   private ScheduledExecutorService initializeHouseKeepingExecutorService()
   {
      if (config.getScheduledExecutor() == null) {
         final ThreadFactory threadFactory = Optional.ofNullable(config.getThreadFactory()).orElse(new DefaultThreadFactory(poolName + " housekeeper", true));
         final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, threadFactory, new ThreadPoolExecutor.DiscardPolicy());
         executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
         executor.setRemoveOnCancelPolicy(true);
         return executor;
      }
      else {
         return config.getScheduledExecutor();
      }
   }
注意,这里初始化了leakTaskFactory,以及houseKeepingExecutorService

ProxyLeakTaskFactory

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/ProxyLeakTaskFactory.java

/**
 * A factory for {@link ProxyLeakTask} Runnables that are scheduled in the future to report leaks.
 *
 * @author Brett Wooldridge
 * @author Andreas Brenk
 */
class ProxyLeakTaskFactory
{
   private ScheduledExecutorService executorService;
   private long leakDetectionThreshold;

   ProxyLeakTaskFactory(final long leakDetectionThreshold, final ScheduledExecutorService executorService)
   {
      this.executorService = executorService;
      this.leakDetectionThreshold = leakDetectionThreshold;
   }

   ProxyLeakTask schedule(final PoolEntry poolEntry)
   {
      return (leakDetectionThreshold == 0) ? ProxyLeakTask.NO_LEAK : scheduleNewTask(poolEntry);
   }

   void updateLeakDetectionThreshold(final long leakDetectionThreshold)
   {
      this.leakDetectionThreshold = leakDetectionThreshold;
   }

   private ProxyLeakTask scheduleNewTask(PoolEntry poolEntry) {
      ProxyLeakTask task = new ProxyLeakTask(poolEntry);
      task.schedule(executorService, leakDetectionThreshold);

      return task;
   }
}
注意,如果leakDetectionThreshold=0,即禁用连接泄露检测,schedule返回的是ProxyLeakTask.NO_LEAK,否则则新建一个ProxyLeakTask,在leakDetectionThreshold时间后触发

ProxyLeakTask

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/ProxyLeakTask.java

/**
 * A Runnable that is scheduled in the future to report leaks.  The ScheduledFuture is
 * cancelled if the connection is closed before the leak time expires.
 *
 * @author Brett Wooldridge
 */
class ProxyLeakTask implements Runnable
{
   private static final Logger LOGGER = LoggerFactory.getLogger(ProxyLeakTask.class);
   static final ProxyLeakTask NO_LEAK;

   private ScheduledFuture<?> scheduledFuture;
   private String connectionName;
   private Exception exception;
   private String threadName; 
   private boolean isLeaked;

   static
   {
      NO_LEAK = new ProxyLeakTask() {
         @Override
         void schedule(ScheduledExecutorService executorService, long leakDetectionThreshold) {}

         @Override
         public void run() {}

         @Override
         public void cancel() {}
      };
   }

   ProxyLeakTask(final PoolEntry poolEntry)
   {
      this.exception = new Exception("Apparent connection leak detected");
      this.threadName = Thread.currentThread().getName();
      this.connectionName = poolEntry.connection.toString();
   }

   private ProxyLeakTask()
   {
   }

   void schedule(ScheduledExecutorService executorService, long leakDetectionThreshold)
   {
      scheduledFuture = executorService.schedule(this, leakDetectionThreshold, TimeUnit.MILLISECONDS);
   }

   /** {@inheritDoc} */
   @Override
   public void run()
   {
      isLeaked = true;

      final StackTraceElement[] stackTrace = exception.getStackTrace(); 
      final StackTraceElement[] trace = new StackTraceElement[stackTrace.length - 5];
      System.arraycopy(stackTrace, 5, trace, 0, trace.length);

      exception.setStackTrace(trace);
      LOGGER.warn("Connection leak detection triggered for {} on thread {}, stack trace follows", connectionName, threadName, exception);
   }

   void cancel()
   {
      scheduledFuture.cancel(false);
      if (isLeaked) {
         LOGGER.info("Previously reported leaked connection {} on thread {} was returned to the pool (unleaked)", connectionName, threadName);
      }
   }
}
可以看到NO_LEAK类里头的方法都是空操作
一旦该task被触发,则抛出Exception("Apparent connection leak detected")

ProxyConnection.close

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/ProxyConnection.java

   /** {@inheritDoc} */
   @Override
   public final void close() throws SQLException
   {
      // Closing statements can cause connection eviction, so this must run before the conditional below
      closeStatements();

      if (delegate != ClosedConnection.CLOSED_CONNECTION) {
         leakTask.cancel();

         try {
            if (isCommitStateDirty && !isAutoCommit) {
               delegate.rollback();
               lastAccess = currentTime();
               LOGGER.debug("{} - Executed rollback on connection {} due to dirty commit state on close().", poolEntry.getPoolName(), delegate);
            }

            if (dirtyBits != 0) {
               poolEntry.resetConnectionState(this, dirtyBits);
               lastAccess = currentTime();
            }

            delegate.clearWarnings();
         }
         catch (SQLException e) {
            // when connections are aborted, exceptions are often thrown that should not reach the application
            if (!poolEntry.isMarkedEvicted()) {
               throw checkException(e);
            }
         }
         finally {
            delegate = ClosedConnection.CLOSED_CONNECTION;
            poolEntry.recycle(lastAccess);
         }
      }
   }

   @SuppressWarnings("EmptyTryBlock")
   private synchronized void closeStatements()
   {
      final int size = openStatements.size();
      if (size > 0) {
         for (int i = 0; i < size && delegate != ClosedConnection.CLOSED_CONNECTION; i++) {
            try (Statement ignored = openStatements.get(i)) {
               // automatic resource cleanup
            }
            catch (SQLException e) {
               LOGGER.warn("{} - Connection {} marked as broken because of an exception closing open statements during Connection.close()",
                           poolEntry.getPoolName(), delegate);
               leakTask.cancel();
               poolEntry.evict("(exception closing Statements during Connection.close())");
               delegate = ClosedConnection.CLOSED_CONNECTION;
            }
         }

         openStatements.clear();
      }
   }

   final SQLException checkException(SQLException sqle)
   {
      SQLException nse = sqle;
      for (int depth = 0; delegate != ClosedConnection.CLOSED_CONNECTION && nse != null && depth < 10; depth++) {
         final String sqlState = nse.getSQLState();
         if (sqlState != null && sqlState.startsWith("08") || ERROR_STATES.contains(sqlState) || ERROR_CODES.contains(nse.getErrorCode())) {
            // broken connection
            LOGGER.warn("{} - Connection {} marked as broken because of SQLSTATE({}), ErrorCode({})",
                        poolEntry.getPoolName(), delegate, sqlState, nse.getErrorCode(), nse);
            leakTask.cancel();
            poolEntry.evict("(connection is broken)");
            delegate = ClosedConnection.CLOSED_CONNECTION;
         }
         else {
            nse = nse.getNextException();
         }
      }

      return sqle;
   }
连接有借有还,在connection的close的时候,closeStatements,checkException会调用leakTask.cancel();取消检测连接泄露的task。另外在delegate != ClosedConnection.CLOSED_CONNECTION的时候会显示调用leakTask.cancel();

HikariPool.evictConnection

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java

   /**
    * Evict a Connection from the pool.
    *
    * @param connection the Connection to evict (actually a {@link ProxyConnection})
    */
   public void evictConnection(Connection connection)
   {
      ProxyConnection proxyConnection = (ProxyConnection) connection;
      proxyConnection.cancelLeakTask();

      try {
         softEvictConnection(proxyConnection.getPoolEntry(), "(connection evicted by user)", !connection.isClosed() /* owner */);
      }
      catch (SQLException e) {
         // unreachable in HikariCP, but we're still forced to catch it
      }
   }
如果用户手工调用evictConnection的话,也会cancelLeakTask

实例

    /**
     * leak-detection-threshold: 5000
     * @throws SQLException
     * @throws InterruptedException
     */
    @Test
    public void testConnLeak() throws SQLException, InterruptedException {
        Connection conn = dataSource.getConnection();
        TimeUnit.SECONDS.sleep(10);
        String sql = "select 1";
        PreparedStatement pstmt = null;
        try {
            pstmt = (PreparedStatement)conn.prepareStatement(sql);
            ResultSet rs = pstmt.executeQuery();
            int col = rs.getMetaData().getColumnCount();
            while (rs.next()) {
                for (int i = 1; i <= col; i++) {
                    System.out.print(rs.getObject(i));
                }
                System.out.println("");
            }
            System.out.println("============================");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //close resources
            DbUtils.closeQuietly(pstmt);
            DbUtils.closeQuietly(conn);
        }
    }

输出

2018-01-29 22:46:31.028  WARN 1454 --- [l-1 housekeeper] com.zaxxer.hikari.pool.ProxyLeakTask     : Connection leak detection triggered for org.postgresql.jdbc.PgConnection@3abd581e on thread main, stack trace follows

java.lang.Exception: Apparent connection leak detected
    at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:123) ~[HikariCP-2.7.6.jar:na]
    at com.example.demo.HikariDemoApplicationTests.testConnLeak(HikariDemoApplicationTests.java:48) ~[test-classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) ~[junit-4.12.jar:4.12]
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) ~[junit-4.12.jar:4.12]
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) ~[junit-4.12.jar:4.12]
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) ~[junit-4.12.jar:4.12]
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) ~[junit-4.12.jar:4.12]
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) ~[junit-4.12.jar:4.12]
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) ~[junit-4.12.jar:4.12]
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) ~[junit-4.12.jar:4.12]
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) ~[junit-4.12.jar:4.12]
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) ~[junit-4.12.jar:4.12]
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363) ~[junit-4.12.jar:4.12]
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137) ~[junit-4.12.jar:4.12]
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) ~[junit-rt.jar:na]
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234) ~[junit-rt.jar:na]
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74) ~[junit-rt.jar:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) ~[idea_rt.jar:na]

1
可以看到ProxyLeakTask抛出java.lang.Exception: Apparent connection leak detected,但是这个是在Runnable中抛出的,并不影响主线程,主线程在超时过后,仍旧继续执行,最后输出结果。

小结

hikari连接池的leakDetectionThreshold用来设置连接被占用的超时时间,单位毫秒,默认为0,即禁用连接泄露检测。这个功能相当于tomcat jdbc pool的poolCleaner里头的checkAbandoned。

不同的如下:

  • tomcat jdbc pool是采用一个timerTask,间隔timeBetweenEvictionRunsMillis时间允许一次;而hikari是每借用一个connection则会创建一个延时的定时任务,在归还或者出异常的时候cancel掉这个task
  • tomcat jdbc pool是直接abandon连接即close掉,然后该connection在后续的收发数据时会抛出异常;而hikari则是在ProxyLeakTask中主动抛出Exception("Apparent connection leak detected")。因此前者是暴力的,后者只是在Runnable抛出异常,并不影响连接的后续操作。

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