Mysql：报错message from server: "Too many connections"(连接太多)

报错信息

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected establishment of connection,  message from server: "Too many connections"
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
    at com.mysql.jdbc.Util.getInstance(Util.java:408)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:918)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:897)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:886)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1040)
    at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2194)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2225)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2024)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:779)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
    at sun.reflect.GeneratedConstructorAccessor4.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:389)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330)
    at org.apache.commons.dbcp2.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:39)
    at org.apache.commons.dbcp2.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:256)
    at org.apache.commons.pool2.impl.GenericObjectPool.create(GenericObjectPool.java:868)
    at org.apache.commons.pool2.impl.GenericObjectPool.addObject(GenericObjectPool.java:961)
    at org.apache.commons.dbcp2.BasicDataSource.createDataSource(BasicDataSource.java:2081)
    ... 21 more

原因

MySQL的连接数超出其允许的最大值

解决

修改/etc/my.cnf配置文件内容，max_connections默认值是100，可以把值修改大一些，这个值对分布式流处理系统中很容易不够。

#修改文件
vi /etc/my.cnf
#修改连接数
max_connections=2000

修改后需要重启下Mysql服务。

文章转载至：https://blog.csdn.net/yitian_z/article/details/84768293