cursor.noCursorTimeout()

Definition定义

cursor.noCursorTimeout()

mongo Shell Method

This page documents the mongo shell method, and does not refer to the MongoDB Node.js driver (or any other driver) method. 本页记录了mongo shell方法，未提及MongoDB Node.js驱动程序（或任何其他驱动程序）方法。For corresponding MongoDB driver API, refer to your specific MongoDB driver documentation instead.有关相应的MongoDB驱动程序API，请参阅特定的MongoDB驱动程序文档。

Instructs the server to avoid closing a cursor automatically after a period of inactivity.指示服务器避免在一段时间不活动后自动关闭游标。

The noCursorTimeout() method has the following prototype form:noCursorTimeout()方法的原型形式如下：

db.collection.find(<query>).noCursorTimeout()

Behavior行为

Session Idle Timeout Overrides 会话空闲超时覆盖noCursorTimeout

Starting in MongoDB 3.6, MongoDB drivers and the mongo shell associate all operations with a server session, with the exception of unacknowledged write operations. 从MongoDB 3.6开始，MongoDB驱动程序和mongo shell将所有操作与服务器会话相关联，但未确认的写入操作除外。For operations not explicitly associated with a session (i.e. using Mongo.startSession()), MongoDB drivers and the mongo shell creates an implicit session and associates it with the operation.对于未显式与会话关联的操作（即使用Mongo.startSession()），MongoDB驱动程序和mongo shell会创建一个隐式会话，并将其与操作关联。

If a session is idle for longer than 30 minutes, the MongoDB server marks that session as expired and may close it at any time. When the MongoDB server closes the session, it also kills any in-progress operations and open cursors associated with the session. 如果会话空闲时间超过30分钟，MongoDB服务器会将该会话标记为已过期，并可随时将其关闭。当MongoDB服务器关闭会话时，它还会终止任何正在进行的操作以及与会话相关的打开游标。This includes cursors configured with noCursorTimeout or a maxTimeMS greater than 30 minutes.这包括配置了noCursorTimeout或maxTimeMS（大于30分钟）的游标。

Consider an application that issues a db.collection.find() with cursor.noCursorTimeout. 考虑一个应用程序，它使用一个cursor.noCursorTimeout发出一个db.collection.find()。The server returns a cursor along with a batch of documents defined by the cursor.batchSize() of the find().服务器返回一个游标以及由find()的cursor.batchSize()定义的一批文档。 The session refreshes each time the application requests a new batch of documents from the server. 每次应用程序从服务器请求新的一批文档时，会话都会刷新。However, if the application takes longer than 30 minutes to process the current batch of documents, the session is marked as expired and closed. 但是，如果应用程序处理当前批文档的时间超过30分钟，则会话将被标记为过期并关闭。When the server closes the session, it also kills the cursor despite the cursor being configured with noCursorTimeout. 当服务器关闭会话时，它也会杀死游标，尽管游标配置为noCursorTimeout。When the application requests the next batch of documents, the server returns an error.当应用程序请求下一批文档时，服务器返回一个错误。

For operations that return a cursor, if the cursor may be idle for longer than 30 minutes, issue the operation within an explicit session using Session.startSession() and periodically refresh the session using the refreshSessions command. 对于返回游标的操作，如果游标空闲时间可能超过30分钟，请使用Session.startSession()在显式会话中发出该操作，并使用refreshSessions命令定期刷新会话。For example:例如：

var session = db.getMongo().startSession()
var sessionId = session.getSessionId().id

var cursor = session.getDatabase("examples").getCollection("data").find().noCursorTimeout()
var refreshTimestamp = new Date() // take note of time at operation start

while (cursor.hasNext()) {

  // Check if more than 5 minutes have passed since the last refresh
  if ( (new Date()-refreshTimestamp)/1000 > 300 ) {
    print("refreshing session")
    db.adminCommand({"refreshSessions" : [sessionId]})
    refreshTimestamp = new Date()
  }

  // process cursor normally

}

In the example operation, the db.collection.find() method is associated with an explicit session. 在示例操作中，db.collection.find()方法与显式会话相关联。The cursor is configured with cursor.noCursorTimeout() to prevent the server from closing the cursor if idle. 游标配置为cursor.noCursorTimeout()，以防止服务器在空闲时关闭游标。The while loop includes a block that uses refreshSessions to refresh the session every 5 minutes. while循环包括一个块，该块使用refreshSessions每5分钟刷新一次会话。Since the session will never exceed the 30 minute idle timeout, the cursor can remain open indefinitely.由于会话永远不会超过30分钟空闲超时，因此游标可以无限期地保持打开状态。

For MongoDB drivers, defer to the driver documentation for instructions and syntax for creating sessions.对于MongoDB驱动程序，请按照驱动程序文档获取创建会话的说明和语法。