JDBC MySQL complains Too Many Connections

Question

When this happens, i check in my db(refer to table below), the connections has not reach the limit of 1000. This is weird... wonder if there's a hidden hard limit being hit.

mysql> show variables like 'max_connections';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 1000  |
+-----------------+-------+

mysql> SHOW STATUS WHERE `variable_name` = 'Max_used_connections';
+----------------------+-------+
| Variable_name        | Value |
+----------------------+-------+
| Max_used_connections | 510   |
+----------------------+-------+

FYI, my application is having an average of 300 connections to the database. So any idea? Thanks.

My setup: tomcat7, spring 3.1, tomcat7-dbcp, mysql5.5, java7

Answer 1

One possible explanation is that the MySQL server is hitting a limit on the number of open file descriptors imposed by the host OS.

For example, this blog posting describes a problem on Debian:

• https://codepoets.co.uk/2015/mysql-max_connections-stuck-on-214/

Here is a Q&A that talks about the same thing:

• The max_connections in MySQL 5.7