MotorClient – Connection to MongoDB

class motor.motor_tornado.MotorClient(*args, **kwargs)

Create a new connection to a single MongoDB instance at host:port.

Takes the same constructor arguments as MongoClient, as well as:

Parameters:
  • io_loop (optional): Special event loop instance to use instead of default
client[db_name] || client.db_name

Get the db_name MotorDatabase on MotorClient client.

Raises InvalidName if an invalid database name is used.

coroutine drop_database(name_or_database, session=None)

Drop a database.

Raises TypeError if name_or_database is not an instance of basestring (str in python 3) or Database.

Parameters:
  • name_or_database: the name of a database to drop, or a Database instance representing the database to drop
  • session (optional): a ClientSession.

Note

The write_concern of this client is automatically applied to this operation when using MongoDB >= 3.4.

coroutine fsync(**kwargs)

Flush all pending writes to datafiles.

Optional parameters can be passed as keyword arguments:
  • lock: If True lock the server to disallow writes.
  • async: If True don’t block while synchronizing.
  • session (optional): a ClientSession, created with start_session().

Note

Starting with Python 3.7 async is a reserved keyword. The async option to the fsync command can be passed using a dictionary instead:

options = {'async': True}
await client.fsync(**options)

Changed in version 1.2: Added session parameter.

Warning

async and lock can not be used together.

Warning

MongoDB does not support the async option on Windows and will raise an exception on that platform.

get_database(name=None, codec_options=None, read_preference=None, write_concern=None, read_concern=None)

Get a MotorDatabase with the given name and options.

Useful for creating a MotorDatabase with different codec options, read preference, and/or write concern from this MotorClient.

>>> from pymongo import ReadPreference
>>> client.read_preference == ReadPreference.PRIMARY
True
>>> db1 = client.test
>>> db1.read_preference == ReadPreference.PRIMARY
True
>>> db2 = client.get_database(
...     'test', read_preference=ReadPreference.SECONDARY)
>>> db2.read_preference == ReadPreference.SECONDARY
True
Parameters:
get_default_database(default=None, codec_options=None, read_preference=None, write_concern=None, read_concern=None)

Get the database named in the MongoDB connection URI.

>>> uri = 'mongodb://host/my_database'
>>> client = MotorClient(uri)
>>> db = client.get_default_database()
>>> assert db.name == 'my_database'
>>> db = client.get_default_database('fallback_db_name')
>>> assert db.name == 'my_database'
>>> uri_without_database = 'mongodb://host/'
>>> client = MotorClient(uri_without_database)
>>> db = client.get_default_database('fallback_db_name')
>>> assert db.name == 'fallback_db_name'

Useful in scripts where you want to choose which database to use based only on the URI in a configuration file.

Parameters:

New in version 2.1: Revived this method. Added the default, codec_options, read_preference, write_concern and read_concern parameters.

Changed in version 2.0: Removed this method.

coroutine list_database_names(session=None)

Get a list of the names of all databases on the connected server.

Parameters:
coroutine list_databases(session=None, **kwargs)

Get a cursor over the databases of the connected server.

Parameters:
  • session (optional): a ClientSession.
  • **kwargs (optional): Optional parameters of the listDatabases command can be passed as keyword arguments to this method. The supported options differ by server version.
Returns:

An instance of CommandCursor.

coroutine server_info(session=None)

Get information about the MongoDB server we’re connected to.

Parameters:
coroutine start_session(causal_consistency=True, default_transaction_options=None)

Start a logical session.

This method takes the same parameters as PyMongo’s SessionOptions. See the client_session module for details.

This session is created uninitialized, use it in an await expression to initialize it, or an async with statement.

async def coro():
    collection = client.db.collection

    # End the session after using it.
    s = await client.start_session()
    await s.end_session()

    # Or, use an "async with" statement to end the session
    # automatically.
    async with await client.start_session() as s:
        doc = {'_id': ObjectId(), 'x': 1}
        await collection.insert_one(doc, session=s)

        secondary = collection.with_options(
            read_preference=ReadPreference.SECONDARY)

        # Sessions are causally consistent by default, so we can read
        # the doc we just inserted, even reading from a secondary.
        async for doc in secondary.find(session=s):
            print(doc)
            
    # Run a multi-document transaction:
    async with await client.start_session() as s:
        # Note, start_transaction doesn't require "await".
        async with s.start_transaction():
            await collection.delete_one({'x': 1}, session=s)
            await collection.insert_one({'x': 2}, session=s)
        
        # Exiting the "with s.start_transaction()" block while throwing an
        # exception automatically aborts the transaction, exiting the block
        # normally automatically commits it.

        # You can run additional transactions in the same session, so long as 
        # you run them one at a time.
        async with s.start_transaction():
            await collection.insert_one({'x': 3}, session=s)
            await collection.insert_many({'x': {'$gte': 2}},
                                         {'$inc': {'x': 1}}, 
                                         session=s)

Requires MongoDB 3.6. Do not use the same session for multiple operations concurrently. A MotorClientSession may only be used with the MotorClient that started it.

Returns:An instance of MotorClientSession.

Changed in version 2.0: Returns a MotorClientSession. Before, this method returned a PyMongo ClientSession.

New in version 1.2.

coroutine unlock(session=None)

Unlock a previously locked server.

Parameters:
watch(pipeline=None, full_document=None, resume_after=None, max_await_time_ms=None, batch_size=None, collation=None, start_at_operation_time=None, session=None, start_after=None)

Watch changes on this cluster.

Returns a MotorChangeStream cursor which iterates over changes on all databases in this cluster. Introduced in MongoDB 4.0.

See the documentation for MotorCollection.watch() for more details and examples.

Parameters:
  • pipeline (optional): A list of aggregation pipeline stages to append to an initial $changeStream stage. Not all pipeline stages are valid after a $changeStream stage, see the MongoDB documentation on change streams for the supported stages.
  • full_document (optional): The fullDocument option to pass to the $changeStream stage. Allowed values: ‘updateLookup’. When set to ‘updateLookup’, the change notification for partial updates will include both a delta describing the changes to the document, as well as a copy of the entire document that was changed from some time after the change occurred.
  • resume_after (optional): A resume token. If provided, the change stream will start returning changes that occur directly after the operation specified in the resume token. A resume token is the _id value of a change document.
  • max_await_time_ms (optional): The maximum time in milliseconds for the server to wait for changes before responding to a getMore operation.
  • batch_size (optional): The maximum number of documents to return per batch.
  • collation (optional): The Collation to use for the aggregation.
  • start_at_operation_time (optional): If provided, the resulting change stream will only return changes that occurred at or after the specified Timestamp. Requires MongoDB >= 4.0.
  • session (optional): a ClientSession.
  • start_after (optional): The same as resume_after except that start_after can resume notifications after an invalidate event. This option and resume_after are mutually exclusive.
Returns:

A MotorChangeStream.

Changed in version 2.1: Added the start_after parameter.

New in version 2.0.

See also

The MongoDB documentation on

changeStreams

HOST

str(object=’‘) -> str str(bytes_or_buffer[, encoding[, errors]]) -> str

Create a new string object from the given object. If encoding or errors is specified, then the object must expose a data buffer that will be decoded using the given encoding and error handler. Otherwise, returns the result of object.__str__() (if defined) or repr(object). encoding defaults to sys.getdefaultencoding(). errors defaults to ‘strict’.

PORT

int([x]) -> integer int(x, base=10) -> integer

Convert a number or string to an integer, or return 0 if no arguments are given. If x is a number, return x.__int__(). For floating point numbers, this truncates towards zero.

If x is not a number or if base is given, then x must be a string, bytes, or bytearray instance representing an integer literal in the given base. The literal can be preceded by ‘+’ or ‘-‘ and be surrounded by whitespace. The base defaults to 10. Valid bases are 0 and 2-36. Base 0 means to interpret the base from the string as an integer literal. >>> int(‘0b100’, base=0) 4

address

(host, port) of the current standalone, primary, or mongos, or None.

Accessing address raises InvalidOperation if the client is load-balancing among mongoses, since there is no single address. Use nodes instead.

If the client is not connected, this will block until a connection is established or raise ServerSelectionTimeoutError if no server is available.

New in version 3.0.

arbiters

Arbiters in the replica set.

A sequence of (host, port) pairs. Empty if this client is not connected to a replica set, there are no arbiters, or this client was created without the replicaSet option.

close

Cleanup client resources and disconnect from MongoDB.

On MongoDB >= 3.6, end all server sessions created by this client by sending one or more endSessions commands.

Close all sockets in the connection pools and stop the monitor threads. If this instance is used again it will be automatically re-opened and the threads restarted unless auto encryption is enabled. A client enabled with auto encryption cannot be used again after being closed; any attempt will raise InvalidOperation.

Changed in version 3.6: End all server sessions created by this client.

codec_options

Read only access to the CodecOptions of this instance.

event_listeners

The event listeners registered for this client.

See monitoring for details.

is_mongos

If this client is connected to mongos. If the client is not connected, this will block until a connection is established or raise ServerSelectionTimeoutError if no server is available..

is_primary

If this client is connected to a server that can accept writes.

True if the current server is a standalone, mongos, or the primary of a replica set. If the client is not connected, this will block until a connection is established or raise ServerSelectionTimeoutError if no server is available.

local_threshold_ms

The local threshold for this instance.

max_bson_size

The largest BSON object the connected server accepts in bytes.

If the client is not connected, this will block until a connection is established or raise ServerSelectionTimeoutError if no server is available.

max_idle_time_ms

The maximum number of milliseconds that a connection can remain idle in the pool before being removed and replaced. Defaults to None (no limit).

max_message_size

The largest message the connected server accepts in bytes.

If the client is not connected, this will block until a connection is established or raise ServerSelectionTimeoutError if no server is available.

max_pool_size

The maximum allowable number of concurrent connections to each connected server. Requests to a server will block if there are maxPoolSize outstanding connections to the requested server. Defaults to 100. Cannot be 0.

When a server’s pool has reached max_pool_size, operations for that server block waiting for a socket to be returned to the pool. If waitQueueTimeoutMS is set, a blocked operation will raise ConnectionFailure after a timeout. By default waitQueueTimeoutMS is not set.

max_write_batch_size

The maxWriteBatchSize reported by the server.

If the client is not connected, this will block until a connection is established or raise ServerSelectionTimeoutError if no server is available.

Returns a default value when connected to server versions prior to MongoDB 2.6.

min_pool_size

The minimum required number of concurrent connections that the pool will maintain to each connected server. Default is 0.

nodes

Set of all currently connected servers.

Warning

When connected to a replica set the value of nodes can change over time as MongoClient’s view of the replica set changes. nodes can also be an empty set when MongoClient is first instantiated and hasn’t yet connected to any servers, or a network partition causes it to lose connection to all servers.

primary

The (host, port) of the current primary of the replica set.

Returns None if this client is not connected to a replica set, there is no primary, or this client was created without the replicaSet option.

New in version 3.0: MongoClient gained this property in version 3.0 when MongoReplicaSetClient’s functionality was merged in.

read_concern

Read only access to the ReadConcern of this instance.

New in version 3.2.

read_preference

Read only access to the read preference of this instance.

Changed in version 3.0: The read_preference attribute is now read only.

retry_reads

If this instance should retry supported write operations.

retry_writes

If this instance should retry supported write operations.

secondaries

The secondary members known to this client.

A sequence of (host, port) pairs. Empty if this client is not connected to a replica set, there are no visible secondaries, or this client was created without the replicaSet option.

New in version 3.0: MongoClient gained this property in version 3.0 when MongoReplicaSetClient’s functionality was merged in.

server_selection_timeout

The server selection timeout for this instance in seconds.

write_concern

Read only access to the WriteConcern of this instance.

Changed in version 3.0: The write_concern attribute is now read only.