如何使用C ++驱动程序重新连接到MongoDB？ [英] How to re-connect to MongoDB using C++ driver?

问题描述

我有一个C ++函数，使用C ++驱动程序将文档保存到MongoDB。以连接引用为参数：

http://pastebin.com / jwRDhNWQ

当我重新启动MongoDB时，我可以看到正在进行新的连接。
然而，conn.isFailed（）仍然为真。

这可能是因为当我重新连接时，我使用 conn 而不是& conn
当我使用& conn 如& conn.connect（ localhost）; ，我收到错误消息 -

 错误：lvalue需要一元' ;'操作数
  

如何解决这个问题？即修改底层连接，以便在建立新的连接时conn.isFailed（）变为false？

解决方案

您应该在mongo :: DBClientConnection :: DBClientConnection构造函数中启用_autoReconnect。

http://api.mongodb.org/cplusplus/current/classmongo_1_1_d_b_client_connection.html#a6a1a348024dd302572504b7bfb6e74a2

在调用_check Connection之前，方法isfailed（）返回的变量_failed不会设置。直到发送到数据库之前，才调用_checkConnection，所以作为一种替代方法，可以在调用_isFailed之前调用ping命令。但是，建议的修复是启用_autoReconnect。

I've a C++ function which saves a document to MongoDB using C++ driver. It takes connection reference as argument:

http://pastebin.com/jwRDhNWQ

When I restart MongoDB, I can see that new connection is being made. However, conn.isFailed() remains true.

This maybe happening due to the fact that when I reconnect, I am using conn and not &conn When I do use &conn as in &conn.connect("localhost");, I get error message-

error: lvalue required as unary ‘&’ operand

How do I fix this? i.e. modify the underlying connection so that conn.isFailed() becomes false when a new connection has been established?

解决方案

You should enable _autoReconnect in the mongo::DBClientConnection::DBClientConnection constructor.
http://api.mongodb.org/cplusplus/current/classmongo_1_1_d_b_client_connection.html#a6a1a348024dd302572504b7bfb6e74a2

The variable _failed returned by the method isfailed() is not set until _check Connection is called. _checkConnection is not called until something is sent to the database, so as an alternative, you could call the ping command before calling _isFailed. However, the recommended fix is to enable _autoReconnect.

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