Impala use Hive UDF with Mysql , there are to many Abandoned connection cleanup thread in Impalad

[arthas@93773]$ thread | grep Abandoned connection cleanup | wc -l 

there is 2K+ threads (Abandoned connection cleanup thread)  which thread state is timed_wating  in impalad

for example：

[arthas@93773]$ thread 262
"Abandoned connection cleanup thread" Id=262 TIMED_WAITING on java.lang.ref.ReferenceQueue$Lock@17b40f38
at java.lang.Object.wait(Native Method)

• waiting on java.lang.ref.ReferenceQueue$Lock@17b40f38
  at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
  at com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:64)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
  at java.lang.Thread.run(Thread.java:748)

Number of locked synchronizers = 1

• java.util.concurrent.ThreadPoolExecutor$Worker@2edcbdc4

Affect(row-cnt:0) cost in 87 ms.