應用服務器連接mysql，有時候會出現以下異常：
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_95]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_95]
at java.lang.Thread.run(Thread.java:745) [na:1.7.0_95]
Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3161) ~[mysql-connector-java-5.1.31.jar:na]
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3615) ~[mysql-connector-java-5.1.31.jar:na]
... 43 common frames omitted
這個問題主要原因是應用服務器很長時間沒有連接mysql，超過了mysql設置的最大超時時間，再連接mysql就會出現這個問題。mysql默認設置是8小時，一般網站白天都有人訪問，從夜里到早上一般都會超過8小時，所以再來訪問就會這個問題。
簡單的解決辦法就是修改最大超時時間，比如改為12小時或10小時，這樣恰好避免了無人訪問的時段，這里修改為10小時，方法如下：
mysql> show variables like '%timeout';
+----------------------------+-------+
| Variable_name | Value |
+----------------------------+-------+
| connect_timeout | 10 |
| delayed_insert_timeout | 300 |
| innodb_lock_wait_timeout | 50 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 28800 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| table_lock_wait_timeout | 50 |
| wait_timeout | 28800 |
+----------------------------+-------+
10 rows in set (0.00 sec)
mysql> set wait_timeout = 36000;
Query OK, 0 rows affected (0.00 sec)
mysql> set interactive_timeout = 36000;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like '%timeout';
+----------------------------+-------+
| Variable_name | Value |
+----------------------------+-------+
| connect_timeout | 10 |
| delayed_insert_timeout | 300 |
| innodb_lock_wait_timeout | 50 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 36000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| table_lock_wait_timeout | 50 |
| wait_timeout | 36000 |
+----------------------------+-------+
10 rows in set (0.00 sec)
