reactor线程阻塞引起故障

• 大致线程模型：
  

• jstack打印JVM堆栈，可以看到reactor线程阻塞了，导致它对应的前端连接无法使用。阻塞在了oracle驱动rollback动作，这里其实是因为oracle驱动为了保证串行请求响应而在底层加了锁，而这个通道被慢语句塞住了，所以reactor线程都塞了。

"$_NIOREACTOR-7-RW" prio=10 tid=0x00007f069856f000 nid=0xde1 waiting for monitor entry [0x00007f0677011000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at oracle.jdbc.driver.PhysicalConnection.rollback(PhysicalConnection.java:1167)
    - waiting to lock <0x000000068086fbc0> (a oracle.jdbc.driver.T4CConnection)


"$_NIOREACTOR-4-RW" prio=10 tid=0x00007f069851e000 nid=0xddd waiting for monitor entry [0x00007f0677415000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at oracle.jdbc.driver.PhysicalConnection.rollback(PhysicalConnection.java:1167)
    - waiting to lock <0x000000068083cf80> (a oracle.jdbc.driver.T4CConnection)


"$_NIOREACTOR-0-RW" prio=10 tid=0x00007f06984b2000 nid=0xdd9 waiting for monitor entry [0x00007f0677819000]
   java.lang.Thread.State: BLOCKED (on object monitor)
    at oracle.jdbc.driver.PhysicalConnection.rollback(PhysicalConnection.java:1167)
    - waiting to lock <0x000000068081c5f0> (a oracle.jdbc.driver.T4CConnection)

• 解决方案，异步化