ejabberd_odbc:log:666 p1_mysql_conn: Connection closed

my ejabberd 15.09 work fine but it returns this error:
when check my sql connection it's ok. the time is regular and every 8 hours.

2015-11-11 16:39:30.205 [error] <0.1448.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.205 [info] <0.1448.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4036>: ok
2015-11-11 16:39:30.208 [error] <0.1454.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.208 [info] <0.1454.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4039>: ok
2015-11-11 16:39:30.209 [error] <0.1455.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.209 [info] <0.1455.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4037>: ok
2015-11-11 16:39:30.209 [error] <0.1450.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.209 [error] <0.1453.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.209 [info] <0.1450.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4041>: ok
2015-11-11 16:39:30.210 [info] <0.1453.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4040>: ok
2015-11-11 16:39:30.210 [error] <0.1451.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.210 [error] <0.1457.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.210 [info] <0.1451.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4042>: ok
2015-11-11 16:39:30.210 [info] <0.1457.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4038>: ok
2015-11-11 16:39:30.224 [error] <0.1462.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.224 [info] <0.1462.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4043>: ok
2015-11-11 16:39:30.248 [error] <0.1464.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.248 [error] <0.1466.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-11 16:39:30.248 [info] <0.1464.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4045>: ok
2015-11-11 16:39:30.248 [info] <0.1466.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4044>: ok
2015-11-12 00:39:30.209 [error] <0.1902.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.209 [info] <0.1902.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4073>: ok
2015-11-12 00:39:30.213 [error] <0.1906.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.214 [info] <0.1906.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4075>: ok
2015-11-12 00:39:30.214 [error] <0.1908.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.214 [info] <0.1908.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4074>: ok
2015-11-12 00:39:30.214 [error] <0.1912.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.214 [error] <0.1913.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.214 [info] <0.1912.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4078>: ok
2015-11-12 00:39:30.214 [info] <0.1913.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4079>: ok
2015-11-12 00:39:30.214 [error] <0.1910.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.214 [info] <0.1910.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4077>: ok
2015-11-12 00:39:30.214 [error] <0.1904.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.214 [info] <0.1904.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4076>: ok
2015-11-12 00:39:30.229 [error] <0.1916.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.229 [info] <0.1916.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4080>: ok
2015-11-12 00:39:30.249 [error] <0.1920.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.249 [info] <0.1920.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4081>: ok
2015-11-12 00:39:30.249 [error] <0.1918.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 00:39:30.249 [info] <0.1918.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4082>: ok
2015-11-12 08:39:30.213 [error] <0.2802.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.213 [info] <0.2802.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4084>: ok
2015-11-12 08:39:30.217 [error] <0.2811.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.217 [info] <0.2811.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4085>: ok
2015-11-12 08:39:30.218 [error] <0.2806.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.218 [info] <0.2806.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4089>: ok
2015-11-12 08:39:30.218 [error] <0.2813.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.218 [info] <0.2813.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4086>: ok
2015-11-12 08:39:30.218 [error] <0.2805.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.219 [info] <0.2805.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4090>: ok
2015-11-12 08:39:30.219 [error] <0.2808.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.219 [error] <0.2804.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.219 [info] <0.2808.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4088>: ok
2015-11-12 08:39:30.219 [info] <0.2804.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4087>: ok
2015-11-12 08:39:30.228 [error] <0.2816.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.228 [info] <0.2816.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4091>: ok
2015-11-12 08:39:30.249 [error] <0.2818.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.249 [info] <0.2818.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4092>: ok
2015-11-12 08:39:30.249 [error] <0.2820.0>@ejabberd_odbc:log:666 p1_mysql_conn: Connection closed, exiting.
2015-11-12 08:39:30.249 [info] <0.2820.0>@ejabberd_odbc:log:665 Closing connection #Port<0.4093>: ok