mongo_client – Tools for connecting to MongoDB

Tools for connecting to MongoDB.

See also

Module master_slave_connection for connecting to master-slave clusters, and High Availability and PyMongo for an example of how to connect to a replica set, or specify a list of mongos instances for automatic failover.

To get a Database instance from a MongoClient use either dictionary-style or attribute-style access:

>>> from pymongo import MongoClient
>>> c = MongoClient()
>>> c.test_database
Database(MongoClient('localhost', 27017), u'test_database')
>>> c['test-database']
Database(MongoClient('localhost', 27017), u'test-database')
class pymongo.mongo_client.MongoClient([host='localhost'[, port=27017[, max_pool_size=100[, document_class=dict[, tz_aware=False[, **kwargs]]]]]])

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

The resultant client object has connection-pooling built in. It also performs auto-reconnection when necessary. If an operation fails because of a connection error, ConnectionFailure is raised. If auto-reconnection will be performed, AutoReconnect will be raised. Application code should handle this exception (recognizing that the operation failed) and then continue to execute.

Raises TypeError if port is not an instance of int. Raises ConnectionFailure if the connection cannot be made.

The host parameter can be a full mongodb URI, in addition to a simple hostname. It can also be a list of hostnames or URIs. Any port specified in the host string(s) will override the port parameter. If multiple mongodb URIs containing database or auth information are passed, the last database, username, and password present will be used. For username and passwords reserved characters like ‘:’, ‘/’, ‘+’ and ‘@’ must be escaped following RFC 2396.

Parameters :
  • host (optional): hostname or IP address of the instance to connect to, or a mongodb URI, or a list of hostnames / mongodb URIs. If host is an IPv6 literal it must be enclosed in ‘[‘ and ‘]’ characters following the RFC2732 URL syntax (e.g. ‘[::1]’ for localhost)
  • port (optional): port number on which to connect
  • max_pool_size (optional): The maximum number of connections that the pool will open simultaneously. If this is set, operations will block if there are max_pool_size outstanding connections from the pool. Defaults to 100.
  • document_class (optional): default class to use for documents returned from queries on this client
  • tz_aware (optional): if True, datetime instances returned as values in a document by this MongoClient will be timezone aware (otherwise they will be naive)
Other optional parameters can be passed as keyword arguments:
  • socketTimeoutMS: (integer) How long (in milliseconds) a send or receive on a socket can take before timing out. Defaults to None (no timeout).
  • connectTimeoutMS: (integer) How long (in milliseconds) a connection can take to be opened before timing out. Defaults to 20000.
  • waitQueueTimeoutMS: (integer) How long (in milliseconds) a thread will wait for a socket from the pool if the pool has no free sockets. Defaults to None (no timeout).
  • waitQueueMultiple: (integer) Multiplied by max_pool_size to give the number of threads allowed to wait for a socket at one time. Defaults to None (no waiters).
  • auto_start_request: If True, each thread that accesses this MongoClient has a socket allocated to it for the thread’s lifetime. This ensures consistent reads, even if you read after an unacknowledged write. Defaults to False
  • use_greenlets: If True, start_request() will ensure that the current greenlet uses the same socket for all operations until end_request()
Write Concern options:
  • w: (integer or string) If this is a replica set, write operations will block until they have been replicated to the specified number or tagged set of servers. w=<int> always includes the replica set primary (e.g. w=3 means write to the primary and wait until replicated to two secondaries). Passing w=0 disables write acknowledgement and all other write concern options.
  • wtimeout: (integer) Used in conjunction with w. Specify a value in milliseconds to control how long to wait for write propagation to complete. If replication does not complete in the given timeframe, a timeout exception is raised.
  • j: If True block until write operations have been committed to the journal. Cannot be used in combination with fsync. Prior to MongoDB 2.6 this option was ignored if the server was running without journaling. Starting with MongoDB 2.6 write operations will fail with an exception if this option is used when the server is running without journaling.
  • fsync: If True and the server is running without journaling, blocks until the server has synced all data files to disk. If the server is running with journaling, this acts the same as the j option, blocking until write operations have been committed to the journal. Cannot be used in combination with j.
Replica set keyword arguments for connecting with a replica set - either directly or via a mongos:
(ignored by standalone mongod instances)
  • replicaSet: (string) The name of the replica set to connect to. The driver will verify that the replica set it connects to matches this name. Implies that the hosts specified are a seed list and the driver should attempt to find all members of the set. Ignored by mongos.
  • read_preference: The read preference for this client. If connecting to a secondary then a read preference mode other than PRIMARY is required - otherwise all queries will throw AutoReconnect “not master”. See ReadPreference for all available read preference options.
  • tag_sets: Ignored unless connecting to a replica set via mongos. Specify a priority-order for tag sets, provide a list of tag sets: [{'dc': 'ny'}, {'dc': 'la'}, {}]. A final, empty tag set, {}, means “read from any member that matches the mode, ignoring tags.
SSL configuration:
  • ssl: If True, create the connection to the server using SSL.
  • ssl_keyfile: The private keyfile used to identify the local connection against mongod. If included with the certfile then only the ssl_certfile is needed. Implies ssl=True.
  • ssl_certfile: The certificate file used to identify the local connection against mongod. Implies ssl=True.
  • ssl_cert_reqs: Specifies whether a certificate is required from the other side of the connection, and whether it will be validated if provided. It must be one of the three values ssl.CERT_NONE (certificates ignored), ssl.CERT_OPTIONAL (not required, but validated if provided), or ssl.CERT_REQUIRED (required and validated). If the value of this parameter is not ssl.CERT_NONE, then the ssl_ca_certs parameter must point to a file of CA certificates. Implies ssl=True.
  • ssl_ca_certs: The ca_certs file contains a set of concatenated “certification authority” certificates, which are used to validate certificates passed from the other end of the connection. Implies ssl=True.

See also

end_request()

See general MongoDB documentation

connections

Changed in version 2.5: Added additional ssl options

New in version 2.4.

disconnect()

Disconnect from MongoDB.

Disconnecting will close all underlying sockets in the connection pool. If this instance is used again it will be automatically re-opened. Care should be taken to make sure that disconnect() is not called in the middle of a sequence of operations in which ordering is important. This could lead to unexpected results.

See also

end_request()

New in version 1.3.

close()

Alias for disconnect()

Disconnecting will close all underlying sockets in the connection pool. If this instance is used again it will be automatically re-opened. Care should be taken to make sure that disconnect() is not called in the middle of a sequence of operations in which ordering is important. This could lead to unexpected results.

See also

end_request()

New in version 2.1.

alive()

Return False if there has been an error communicating with the server, else True.

This method attempts to check the status of the server with minimal I/O. The current thread / greenlet retrieves a socket from the pool (its request socket if it’s in a request, or a random idle socket if it’s not in a request) and checks whether calling select on it raises an error. If there are currently no idle sockets, alive() will attempt to actually connect to the server.

A more certain way to determine server availability is:

client.admin.command('ping')
c[db_name] || c.db_name

Get the db_name Database on MongoClient c.

Raises InvalidName if an invalid database name is used.

host

Current connected host.

Changed in version 1.3: host is now a property rather than a method.

port

Current connected port.

Changed in version 1.3: port is now a property rather than a method.

is_primary

If this instance is connected to a standalone, a replica set primary, or the master of a master-slave set.

New in version 2.3.

is_mongos

If this instance is connected to mongos.

New in version 2.3.

max_pool_size

The maximum number of sockets the pool will open concurrently.

When the pool has reached max_pool_size, operations 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.

Warning

SIGNIFICANT BEHAVIOR CHANGE in 2.6. Previously, this parameter would limit only the idle sockets the pool would hold onto, not the number of open sockets. The default has also changed to 100.

Changed in version 2.6.

New in version 1.11.

nodes

List of all known nodes.

Nodes are either specified when this instance was created, or discovered through the replica set discovery mechanism.

New in version 1.8.

auto_start_request

Is auto_start_request enabled?

document_class

Default class to use for documents returned from this client.

New in version 1.7.

tz_aware

Does this client return timezone-aware datetimes?

New in version 1.8.

max_bson_size

Return the maximum size BSON object the connected server accepts in bytes. Defaults to 16MB if not connected to a server.

New in version 1.10.

max_message_size

Return the maximum message size the connected server accepts in bytes. Defaults to 32MB if not connected to a server.

New in version 2.6.

min_wire_version

The minWireVersion reported by the server.

Returns 0 when connected to server versions prior to MongoDB 2.6.

New in version 2.7.

max_wire_version

The maxWireVersion reported by the server.

Returns 0 when connected to server versions prior to MongoDB 2.6.

New in version 2.7.

read_preference

The read preference mode for this instance.

See ReadPreference for available options.

New in version 2.1.

tag_sets

Set tag_sets to a list of dictionaries like [{‘dc’: ‘ny’}] to read only from members whose dc tag has the value "ny". To specify a priority-order for tag sets, provide a list of tag sets: [{'dc': 'ny'}, {'dc': 'la'}, {}]. A final, empty tag set, {}, means “read from any member that matches the mode, ignoring tags.” ReplicaSetConnection tries each set of tags in turn until it finds a set of tags with at least one matching member.

New in version 2.3.

secondary_acceptable_latency_ms

Any replica-set member whose ping time is within secondary_acceptable_latency_ms of the nearest member may accept reads. Defaults to 15 milliseconds.

See ReadPreference.

New in version 2.3.

Note

secondary_acceptable_latency_ms is ignored when talking to a replica set through a mongos. The equivalent is the localThreshold command line option.

write_concern

The default write concern for this instance.

Supports dict style access for getting/setting write concern options. Valid options include:

  • w: (integer or string) If this is a replica set, write operations will block until they have been replicated to the specified number or tagged set of servers. w=<int> always includes the replica set primary (e.g. w=3 means write to the primary and wait until replicated to two secondaries). Setting w=0 disables write acknowledgement and all other write concern options.
  • wtimeout: (integer) Used in conjunction with w. Specify a value in milliseconds to control how long to wait for write propagation to complete. If replication does not complete in the given timeframe, a timeout exception is raised.
  • j: If True block until write operations have been committed to the journal. Cannot be used in combination with fsync. Prior to MongoDB 2.6 this option was ignored if the server was running without journaling. Starting with MongoDB 2.6 write operations will fail with an exception if this option is used when the server is running without journaling.
  • fsync: If True and the server is running without journaling, blocks until the server has synced all data files to disk. If the server is running with journaling, this acts the same as the j option, blocking until write operations have been committed to the journal. Cannot be used in combination with j.
>>> m = pymongo.MongoClient()
>>> m.write_concern
{}
>>> m.write_concern = {'w': 2, 'wtimeout': 1000}
>>> m.write_concern
{'wtimeout': 1000, 'w': 2}
>>> m.write_concern['j'] = True
>>> m.write_concern
{'wtimeout': 1000, 'j': True, 'w': 2}
>>> m.write_concern = {'j': True}
>>> m.write_concern
{'j': True}
>>> # Disable write acknowledgement and write concern
...
>>> m.write_concern['w'] = 0

Note

Accessing write_concern returns its value (a subclass of dict), not a copy.

Warning

If you are using Connection or ReplicaSetConnection make sure you explicitly set w to 1 (or a greater value) or safe to True. Unlike calling set_lasterror_options(), setting an option in write_concern does not implicitly set safe to True.

uuid_subtype

This attribute specifies which BSON Binary subtype is used when storing UUIDs. Historically UUIDs have been stored as BSON Binary subtype 3. This attribute is used to switch to the newer BSON Binary subtype 4. It can also be used to force legacy byte order and subtype compatibility with the Java and C# drivers. See the bson.binary module for all options.

is_locked

Is this server locked? While locked, all write operations are blocked, although read operations may still be allowed. Use unlock() to unlock.

New in version 2.0.

database_names()

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

drop_database(name_or_database)

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
copy_database(from_name, to_name[, from_host=None[, username=None[, password=None]]])

Copy a database, potentially from another host.

Raises TypeError if from_name or to_name is not an instance of basestring (str in python 3). Raises InvalidName if to_name is not a valid database name.

If from_host is None the current host is used as the source. Otherwise the database is copied from from_host.

If the source database requires authentication, username and password must be specified.

Parameters :
  • from_name: the name of the source database
  • to_name: the name of the target database
  • from_host (optional): host name to copy from
  • username (optional): username for source database
  • password (optional): password for source database

Note

Specifying username and password requires server version >= 1.3.3+.

New in version 1.5.

get_default_database()

Get the database named in the MongoDB connection URI.

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

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

server_info()

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

start_request()

Ensure the current thread or greenlet always uses the same socket until it calls end_request(). This ensures consistent reads, even if you read after an unacknowledged write.

In Python 2.6 and above, or in Python 2.5 with “from __future__ import with_statement”, start_request() can be used as a context manager:

>>> client = pymongo.MongoClient(auto_start_request=False)
>>> db = client.test
>>> _id = db.test_collection.insert({})
>>> with client.start_request():
...     for i in range(100):
...         db.test_collection.update({'_id': _id}, {'$set': {'i':i}})
...
...     # Definitely read the document after the final update completes
...     print db.test_collection.find({'_id': _id})

If a thread or greenlet calls start_request multiple times, an equal number of calls to end_request() is required to end the request.

Changed in version 2.4: Now counts the number of calls to start_request and doesn’t end request until an equal number of calls to end_request.

New in version 2.2: The Request return value. start_request() previously returned None

end_request()

Undo start_request(). If end_request() is called as many times as start_request(), the request is over and this thread’s connection returns to the pool. Extra calls to end_request() have no effect.

Ending a request allows the socket that has been reserved for this thread by start_request() to be returned to the pool. Other threads will then be able to re-use that socket. If your application uses many threads, or has long-running threads that infrequently perform MongoDB operations, then judicious use of this method can lead to performance gains. Care should be taken, however, to make sure that end_request() is not called in the middle of a sequence of operations in which ordering is important. This could lead to unexpected results.

close_cursor(cursor_id)

Close a single database cursor.

Raises TypeError if cursor_id is not an instance of (int, long). What closing the cursor actually means depends on this client’s cursor manager.

Parameters :
  • cursor_id: id of cursor to close
kill_cursors(cursor_ids)

Send a kill cursors message with the given ids.

Raises TypeError if cursor_ids is not an instance of list.

Parameters :
  • cursor_ids: list of cursor ids to kill
set_cursor_manager(manager_class)

Set this client’s cursor manager.

Raises TypeError if manager_class is not a subclass of CursorManager. A cursor manager handles closing cursors. Different managers can implement different policies in terms of when to actually kill a cursor that has been closed.

Parameters :
  • manager_class: cursor manager to use

Changed in version 2.1+: Deprecated support for external cursor managers.

fsync(**kwargs)

Flush all pending writes to datafiles.

Parameters :

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.

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.

New in version 2.0.

unlock()

Unlock a previously locked server.

New in version 2.0.

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