vkarpov15 has created PR #3889: fix: make findOne() close implicit session to avoid memory leak in node-mongodb-native

Issue

When constructing a find command for the findOne API, the limit is set to -1 and batchSize is set to 1. The driver's command construction logic builds a find command that includes batchSize:1,limit:1,singleBatch:true whereas pymongo builds a find command that includes only limit:1,singleBatch:true. The inclusion of batchSize:1 only when running a find against a timeseries collection will cause the reply to have a non-zero value for cursor.id. Since the value is non-zero the driver treats the cursor as still alive and the session created is never ended.

Acceptance Criteria

Implementation Requirements

• store the cursor and call close on it after receiving the initial response (document or null)

Testing Requirements

• Run findOne against a time series collection, assert activeSessions does not grow before and after.

Documentation Requirements

• none

Follow Up Requirements

• File a server ticket about the behavior difference.