cursor.maxTimeMS()

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

Starting in MongoDB 3.6, MongoDB drivers and mongosh 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mongosh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 mongosh create an implicit session and associate 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mongosh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. 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。When the MongoDB server closes the session, it also kills any in-progress operations and open cursors associated with the session. 当MongoDB服务器关闭会话时，它还会终止与会话相关联的任何正在进行的操作和打开的游标。This includes cursors configured with noCursorTimeout() or a maxTimeMS() greater than 30 minutes.这包括配置了noCursorTimeout()或大于30分钟的maxTimeMS()的游标。

For example, consider a find() operation with the maxTimeMS() configured for a timeout of 31 minutes. 例如，考虑将maxTimeMS()配置为超时31分钟的find()操作。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一批文档的时间超过30分钟，则会话将标记为过期并关闭。When the server closes the session, it also kills the cursor despite the cursor being configured with maxTimeMS() greater than 30 minutes. 当服务器关闭会话时，它还会杀死游标，尽管游标被配置为大于30分钟的maxTimeMS()。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 Mongo.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Mongo.startSession()在显式会话中发出操作，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.maxTimeMS() to keep the cursor open for at least 31 minutes. 使用cursor.maxTimeMS()配置游标，使游标保持打开状态至少31分钟。The while loop includes a block that uses refreshSessions to refresh the session every 5 minutes. while循环包含一个块，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 up to the configured maxTimeMS().由于会话永远不会超过30分钟的空闲超时，因此游标可以一直打开到配置的maxTimeMS()。

For MongoDB drivers, defer to the driver documentation for instructions and syntax for creating sessions.对于MongoDB驱动程序，有关创建会话的说明和语法，请参阅驱动程序文档。