Amazon RDS多库连接异常：PHP(CakePHP3.9)二次连接报1045错误

背景 #

在Amazon RDS实例中创建了多个数据库，Elastic Beanstalk环境下通过PHP（CakePHP 3.9）访问这些数据库原本均无问题。实例拥有一个可访问所有数据库的主用户，同时每个数据库也配置了独立用户。

问题表现 #

最初误以为是新创建的数据库在PHP连接时返回1045权限错误，但使用相同凭据可通过SequelPro等数据库管理工具正常连接，且主用户与该数据库独立用户均出现此错误。同一实例下其他数据库均可正常访问，仅该新库（后续排查排除特定库因素）出现异常，错误日志如下：

default-log-channel: ERROR: 2022-09-15 04:19:57 Error: [PDOException] SQLSTATE[HY000] [1045] Access denied for user 'myuser'@'172.61.15.102' (using password: YES)

配置对比 #

报错的数据库连接配置 #

DSN：mysql:host=project-testing-1.xxxxx.eu-west-2.rds.amazonaws.com;port=3306;dbname=my_db;charset=utf8

array (size=15)
  'driver' => string 'Cake\Database\Driver\Mysql' (length=26)
  'persistent' => boolean false
  'host' => string 'project-testing-1.xxxxx.eu-west-2.rds.amazonaws.com' (length=55)
  'port' => string '3306' (length=4)
  'username' => string 'root' (length=13)
  'password' => string 'xxxx^sdsdsdsd@j&sdsd&' (length=30)
  'database' => string 'my_db' (length=17)
  'encoding' => string 'utf8' (length=4)
  'timezone' => string '+0:00' (length=5)
  'cacheMetadata' => boolean true
  'log' => boolean false
  'quoteIdentifiers' => boolean false
  'name' => string 'my_db' (length=17)
  'flags' => 
    array (size=3)
      12 => boolean false
      1000 => boolean true
      3 => int 2
  'init' => 
    array (size=2)
      0 => string 'SET time_zone = '+0:00'' (length=23)
      1 => string 'SET NAMES utf8' (length=14)

可正常连接的数据库配置 #

DSN：mysql:host=project-testing-1.xxxxx.eu-west-2.rds.amazonaws.com;port=3306;dbname=testing-db;charset=utf8

array (size=15)
  'driver' => string 'Cake\Database\Driver\Mysql' (length=26)
  'persistent' => boolean false
  'host' => string 'project-testing-1.xxxxx.eu-west-2.rds.amazonaws.com' (length=55)
  'port' => string '3306' (length=4)
  'username' => string 'root' (length=15)
  'password' => string 'xxxx^sdsdsdsd@j&sdsd&' (length=40)
  'database' => string 'testing-db' (length=24)
  'encoding' => string 'utf8' (length=4)
  'timezone' => string '+0:00' (length=5)
  'cacheMetadata' => boolean true
  'log' => boolean false
  'quoteIdentifiers' => boolean false
  'name' => string 'testing-db' (length=7)
  'flags' => 
    array (size=3)
      12 => boolean false
      1000 => boolean true
      3 => int 2
  'init' => 
    array (size=2)
      0 => string 'SET time_zone = '+0:00'' (length=23)
      1 => string 'SET NAMES utf8' (length=14)

排查更新 #

经进一步排查，问题并非特定数据库导致，而是第二次数据库连接时必现1045权限错误，首次连接始终正常，即使使用root用户也会报错。相关DSN示例：

mysql://root:xxxxxxx@project-testing-1.xxxxx.eu-west-2.rds.amazonaws.com/testing-db

请求协助 #

请帮忙排查此问题。

内容的提问来源于stack exchange，提问作者R0bertinski