Write Concern for Replica Sets复制集的写入关注

Write concern for replica sets describe the number of data-bearing members (i.e. the primary and secondaries, but not arbiters) that must acknowledge a write operation before the operation returns as successful. 副本集的写入关注点描述了在操作返回成功之前必须确认写入操作的数据承载成员（即主成员和辅助成员，但不是仲裁器）的数量。A member can only acknowledge a write operation after it has received and applied the write successfully.成员只有在成功接收并应用写入操作后才能确认写入操作。

For replica sets, the write concern of w: "majority" requires acknowledgement that the write operations have propagated to a calculated majority of the data-bearing voting members. 对于副本集，w: "majority"的写入问题需要确认写入操作已传播到计算出的大多数数据承载投票成员。For most replica set configurations, w: "majority" is the default write concern. 对于大多数副本集配置，w: "majority"是默认的写入问题。To learn how MongoDB determines the default write concern, see Implicit Default Write Concern.要了解MongoDB如何确定默认写问题，请参阅隐式默认写问题。

For clusters where members have journaling enabled, combining "majority" write concern with j : true can prevent rollback of write concern acknowledged data.对于成员已启用日志记录的集群，将"majority"写关注点与j : true组合可以防止写关注点确认数据的回滚。

Write operations with a write concern of w: 1 require that only the primary replica set member acknowledge the write before returning write concern acknowledgment. 写问题为w: 1的写操作要求只有主副本集成员在返回写问题确认之前确认写。You can specify an integer value greater than 1 to require acknowledgment from the primary and as many secondaries as needed to meet the specified value, up to the total number of data-bearing members in the replica set.您可以指定一个大于1的整数值，以要求主服务器和所需数量的辅助服务器进行确认，以满足指定的值，最大值为副本集中数据承载成员的总数。

For complete documentation on write acknowledgment behavior, see Acknowledgment Behavior.有关写入确认行为的完整文档，请参阅确认行为。

An application that issues a write operation that requires write concern acknowledgment waits until the primary receives acknowledgment from the required number of members for the specified write concern. 发出需要写问题确认的写操作的应用程序将等待，直到主应用程序收到指定写问题所需成员数的确认。For write concern of w greater than 1 or w : "majority", the primary waits until the required number of secondaries acknowledge the write before returning write concern acknowledgment. 对于w大于1或w : "majority"的写入问题，主系统等待直到所需数量的辅助系统确认写入，然后返回写入问题确认。For write concern of w: 1, the primary can return write concern acknowledgment as soon as it locally applies the write since it is eligible for contributing to the requested write concern.对于w: 1的写入关注点，主服务器可以在本地应用写入时立即返回写入关注点确认，因为它有资格参与请求的写入关注。

The more members that acknowledge a write, the less likely the written data could roll back if the primary fails. 确认写入的成员越多，如果primary失败，写入的数据回滚的可能性就越小。However, specifying a high write concern can increase latency as the client must wait until it receives the requested level of write concern acknowledgment.但是，指定高写问题可能会增加延迟，因为客户端必须等待，直到收到请求的写问题确认级别。

Selecting the ideal write concern for any given write operation depends on your application's performance goals and data durability requirements. 为任何给定的写入操作选择理想的写入关注点取决于应用程序的性能目标和数据持久性要求。For more guidance on configuring write concern to prevent rollbacks, see Avoid Replica Set Rollbacks.有关配置写问题以防止回滚的更多指导，请参阅避免副本集回滚。

db.products.insertOne(
   { item: "envelopes", qty : 100, type: "Clasp" },
   { writeConcern: { w: "majority" , wtimeout: 5000 } }
)