remaining connection slots are reserved for non-replication superuser connections

使用客户端工具连接pg，连接失败，报错以下错误：

FATAL: remaining connection slots are reserved for non-replication superuser connections 

查看数据库连接状态和配置信息

select * from pg_stat_activity where pid<>pg_backend_pid() and state='idle';##pg_backend_pid()的结果是当前会话的pid
select datname,datconnlimit from pg_database ;
select current_setting('max_connections');
select current_setting('superuser_reserved_connections');

　　

发现参数max_connections设置太低。

因为是测试环境，就先把idle状态的连接先杀掉：

##把数据库中的所有的空闲会话全部kill掉
select pg_terminate_backend(pid) from pg_stat_activity where pid<>pg_backend_pid() and state='idle';

 然后修改参数max_connections的值。