Mongo.startSession()

Definition

  • Mongo.startSession()

New in version 3.6.

Starts a session for the connection. Themongo shell assigns the session id tocommands associated with the session.

The startSession() method can take a document withsession options. The options available are:

FieldDescriptioncausalConsistencyBoolean. Enables or disables causal consistency for the session.Mongo.startSession() enables causalConsistencyby default.

After starting a session, you cannot modify itscausalConsistency setting.

Note

The session may have causal consistency enabled eventhough the Mongo connection object may havecausal consistency disabled or vice versa. To set causalconsistency on the connection object, seeMongo.setCausalConsistency().

readConcernDocument. Specifies the read concern.

To modify the setting after starting a session, seeSessions.getOptions().setReadConcern().readPreferenceDocument. Specifies the read preference.

The readPreference document contains the mode field andthe optional tags field:

  1. { mode: <string>, tags: <array> }

To modify the setting after starting a session, seeSessions.getOptions().setReadPreference().retryWritesBoolean. Enables or disables the ability to retry writes uponencountering transient network errors.

If you start the mongo shell with the—retryWrites option, retryWrites is enabled bydefault for Mongo.startSession().

After starting a session, you cannot modify itsretryWrites setting.writeConcernDocument. Specifies the write concern.

To modify the setting after starting a session, seeSessions.getOptions().setWriteConcern().

Examples

The following starts a session with causal consistency and retryablewrites enabled on the Mongo connection object associated withthe mongo shell’s global db variable:

  1. db = db.getMongo().startSession({retryWrites: true, causalConsistency: true}).getDatabase(db.getName());