排错经历：openstack搭建dashboard进入输入帐号密码登录后报错
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查看error日志：
cat /var/log/httpd/error.log
[Thu Oct 13 13:37:00 2016] [error] raise exceptions.ConnectionFailed(reason=_("Maximum attempts reached"))
[Thu Oct 13 13:37:00 2016] [error] ConnectionFailed: Connection to neutron failed: Maximum attempts reached
neutron日志显示neutron的用户密码：
cat /var/log/neutron/server.log
perationalError: (OperationalError) (1045, "Access denied for user 'neutron'@'controller' (using password: YES)") None None
进入mysql查看果然：
[root@controller images]# mysql -uroot -p123456
mysql> SELECT user,host,password FROM mysql.user;
+----------+------------+-------------------------------------------+
| user | host | password |
+----------+------------+-------------------------------------------+
| root | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| root | controller | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| root | 127.0.0.1 | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| keystone | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| keystone | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| glance | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| glance | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| nova | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| nova | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| neutron | localhost | |
| neutron | % | |
| cinder | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| cinder | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| heat | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| heat | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| sahara | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| sahara | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+----------+------------+-------------------------------------------+
17 rows in set (0.06 sec)
解决：（重新建立用户，并授权）
mysql> drop database neutron;
mysql> create database neutron;
mysql> GRANT ALL PRIVILEGES ON neutron.* TO 'neutron'@'localhost' IDENTIFIED BY '123456';
mysql> GRANT ALL PRIVILEGES ON neutron.* TO 'neutron'@'%' IDENTIFIED BY '123456';
mysql> SELECT user,host,password FROM mysql.user;
+----------+------------+-------------------------------------------+
| user | host | password |
+----------+------------+-------------------------------------------+
| root | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| root | controller | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| root | 127.0.0.1 | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| keystone | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| keystone | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| glance | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| glance | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| nova | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| nova | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| neutron | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| neutron | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| cinder | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| cinder | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| heat | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| heat | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| sahara | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| sahara | % | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+----------+------------+-------------------------------------------+
重启mysqld 、memcached 、httpd、neutron-server 服务
成功解决，登录正常进入dashboard界面。