connection error

It is bit hard to figure out, which exceptions I should catch if I want to recover my application from connection errors.

So far

• OSError - when database is down
• CannotConnectNowError when PostgreSQL is starting
• ConnectionDoesNotExistError when connection is removed from connection pool
• InterfaceError when message contains one of
  • connection has been released back to the pool
  • the underlying connection is closed

It seems I should add one PostgresConnectionError deriving classes as well? Anything else?

首先检查现有的异常定义以及 issue 中描述的连接错误路径。比较 OSError、CannotConnectNowError、ConnectionDoesNotExistError 和 InterfaceError 的引发方式，然后确定统一的 PostgresConnectionError 层次结构是否涵盖所列出的恢复情况。完成的标准是就所需的异常 API 及其兼容性影响达成一致。