mongo_client – Tools for connecting to MongoDB

Tools for connecting to MongoDB.

See also

High Availability and PyMongo for examples of connecting to replica sets or sets of mongos servers.

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(host=['localhost:27017'], document_class=dict, tz_aware=False, connect=True), u'test_database')
>>> c['test-database']
Database(MongoClient(host=['localhost:27017'], document_class=dict, tz_aware=False, connect=True), u'test-database')
class pymongo.mongo_client.MongoClient(host=’localhost’, port=27017, document_class=dict, tz_aware=False, connect=True, **kwargs)

Client for a MongoDB instance, a replica set, or a set of mongoses.

The client object is thread-safe and has connection-pooling built in. If an operation fails because of a network error, ConnectionFailure is raised and the client reconnects in the background. Application code should handle this exception (recognizing that the operation failed) and then continue to execute.

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 percent encoded following RFC 2396:

try:
    # Python 3.x
    from urllib.parse import quote_plus
except ImportError:
    # Python 2.x
    from urllib import quote_plus

uri = "mongodb://%s:%s@%s" % (
    quote_plus(user), quote_plus(password), host)
client = MongoClient(uri)

Unix domain sockets are also supported. The socket path must be percent encoded in the URI:

uri = "mongodb://%s:%s@%s" % (
    quote_plus(user), quote_plus(password), quote_plus(socket_path))
client = MongoClient(uri)

But not when passed as a simple hostname:

client = MongoClient('/tmp/mongodb-27017.sock')

Starting with version 3.6, PyMongo supports mongodb+srv:// URIs. The URI must include one, and only one, hostname. The hostname will be resolved to one or more DNS SRV records which will be used as the seed list for connecting to the MongoDB deployment. When using SRV URIs, the authSource and replicaSet configuration options can be specified using TXT records. See the Initial DNS Seedlist Discovery spec for more details. Note that the use of SRV URIs implicitly enables TLS support. Pass ssl=false in the URI to override.

Note

MongoClient creation will block waiting for answers from DNS when mongodb+srv:// URIs are used.

Note

Starting with version 3.0 the MongoClient constructor no longer blocks while connecting to the server or servers, and it no longer raises ConnectionFailure if they are unavailable, nor ConfigurationError if the user’s credentials are wrong. Instead, the constructor returns immediately and launches the connection process on background threads. You can check if the server is available like this:

from pymongo.errors import ConnectionFailure
client = MongoClient()
try:
    # The ismaster command is cheap and does not require auth.
    client.admin.command('ismaster')
except ConnectionFailure:
    print("Server not available")

Warning

When using PyMongo in a multiprocessing context, please read Using PyMongo with Multiprocessing first.

Parameters:
  • host (optional): hostname or IP address or Unix domain socket path of a single mongod or mongos 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). Multihomed and round robin DNS addresses are not supported.
  • port (optional): port number on which to connect
  • 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)
  • connect (optional): if True (the default), immediately begin connecting to MongoDB in the background. Otherwise connect on the first operation.
Other optional parameters can be passed as keyword arguments:
  • maxPoolSize (optional): 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.

  • minPoolSize (optional): The minimum required number of concurrent connections that the pool will maintain to each connected server. Default is 0.

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

  • socketTimeoutMS: (integer or None) Controls how long (in milliseconds) the driver will wait for a response after sending an ordinary (non-monitoring) database operation before concluding that a network error has occurred. Defaults to None (no timeout).

  • connectTimeoutMS: (integer or None) Controls how long (in milliseconds) the driver will wait during server monitoring when connecting a new socket to a server before concluding the server is unavailable. Defaults to 20000 (20 seconds).

  • serverSelectionTimeoutMS: (integer) Controls how long (in milliseconds) the driver will wait to find an available, appropriate server to carry out a database operation; while it is waiting, multiple server monitoring operations may be carried out, each controlled by connectTimeoutMS. Defaults to 30000 (30 seconds).

  • waitQueueTimeoutMS: (integer or None) 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 or None) Multiplied by maxPoolSize to give the number of threads allowed to wait for a socket at one time. Defaults to None (no limit).

  • heartbeatFrequencyMS: (optional) The number of milliseconds between periodic server checks, or None to accept the default frequency of 10 seconds.

  • appname: (string or None) The name of the application that created this MongoClient instance. MongoDB 3.4 and newer will print this value in the server log upon establishing each connection. It is also recorded in the slow query log and profile collections.

  • event_listeners: a list or tuple of event listeners. See monitoring for details.

  • retryWrites: (boolean) Whether supported write operations executed within this MongoClient will be retried once after a network error on MongoDB 3.6+. Defaults to False. The supported write operations are:

    Unsupported write operations include, but are not limited to, aggregate() using the $out pipeline operator and any operation with an unacknowledged write concern (e.g. {w: 0})). See https://github.com/mongodb/specifications/blob/master/source/retryable-writes/retryable-writes.rst

  • socketKeepAlive: (boolean) DEPRECATED Whether to send periodic keep-alive packets on connected sockets. Defaults to True. Disabling it is not recommended, see https://docs.mongodb.com/manual/faq/diagnostics/#does-tcp-keepalive-time-affect-mongodb-deployments”,

Write Concern options:
(Only set if passed. No default values.)
  • 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:
  • replicaSet: (string or None) The name of the replica set to connect to. The driver will verify that all servers it connects to match this name. Implies that the hosts specified are a seed list and the driver should attempt to find all members of the set. Defaults to None.
Read Preference:
  • readPreference: The replica set read preference for this client. One of primary, primaryPreferred, secondary, secondaryPreferred, or nearest. Defaults to primary.
  • readPreferenceTags: Specifies a tag set as a comma-separated list of colon-separated key-value pairs. For example dc:ny,rack:1. Defaults to None.
  • maxStalenessSeconds: (integer) The maximum estimated length of time a replica set secondary can fall behind the primary in replication before it will no longer be selected for operations. Defaults to -1, meaning no maximum. If maxStalenessSeconds is set, it must be a positive integer greater than or equal to 90 seconds.
Authentication:
  • username: A string.

  • password: A string.

    Although username and password must be percent-escaped in a MongoDB URI, they must not be percent-escaped when passed as parameters. In this example, both the space and slash special characters are passed as-is:

    MongoClient(username="user name", password="pass/word")
    
  • authSource: The database to authenticate on. Defaults to the database specified in the URI, if provided, or to “admin”.

  • authMechanism: See MECHANISMS for options. By default, use SCRAM-SHA-1 with MongoDB 3.0 and later, MONGODB-CR (MongoDB Challenge Response protocol) for older servers.

  • authMechanismProperties: Used to specify authentication mechanism specific options. To specify the service name for GSSAPI authentication pass authMechanismProperties=’SERVICE_NAME:<service name>’

SSL configuration:
  • ssl: If True, create the connection to the server using SSL. Defaults to False.
  • ssl_certfile: The certificate file used to identify the local connection against mongod. Implies ssl=True. Defaults to None.
  • 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. Defaults to None.
  • ssl_pem_passphrase: The password or passphrase for decrypting the private key in ssl_certfile or ssl_keyfile. Only necessary if the private key is encrypted. Only supported by python 2.7.9+ (pypy 2.5.1+) and 3.3+. Defaults to None.
  • 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_REQUIRED (certificates required and validated), or ssl.CERT_OPTIONAL (the same as CERT_REQUIRED, unless the server was configured to use anonymous ciphers). If the value of this parameter is not ssl.CERT_NONE and a value is not provided for ssl_ca_certs PyMongo will attempt to load system provided CA certificates. If the python version in use does not support loading system CA certificates then the ssl_ca_certs parameter must point to a file of CA certificates. Implies ssl=True. Defaults to ssl.CERT_REQUIRED if not provided and 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. Defaults to None.
  • ssl_crlfile: The path to a PEM or DER formatted certificate revocation list. Only supported by python 2.7.9+ (pypy 2.5.1+) and 3.4+. Defaults to None.
  • ssl_match_hostname: If True (the default), and ssl_cert_reqs is not ssl.CERT_NONE, enables hostname verification using the match_hostname() function from python’s ssl module. Think very carefully before setting this to False as that could make your application vulnerable to man-in-the-middle attacks.
Read Concern options:
(If not set explicitly, this will use the server default)
  • readConcernLevel: (string) The read concern level specifies the level of isolation for read operations. For example, a read operation using a read concern level of majority will only return data that has been written to a majority of nodes. If the level is left unspecified, the server default will be used.

See also

The MongoDB documentation on

connections

Changed in version 3.6: Added support for mongodb+srv:// URIs. Added the retryWrites keyword argument and URI option.

Changed in version 3.5: Add username and password options. Document the authSource, authMechanism, and authMechanismProperties `` options. Deprecated the `socketKeepAlive` keyword argument and URI option. `socketKeepAlive` now defaults to ``True.

Changed in version 3.0: MongoClient is now the one and only client class for a standalone server, mongos, or replica set. It includes the functionality that had been split into MongoReplicaSetClient: it can connect to a replica set, discover all its members, and monitor the set for stepdowns, elections, and reconfigs.

The MongoClient constructor no longer blocks while connecting to the server or servers, and it no longer raises ConnectionFailure if they are unavailable, nor ConfigurationError if the user’s credentials are wrong. Instead, the constructor returns immediately and launches the connection process on background threads.

Therefore the alive method is removed since it no longer provides meaningful information; even if the client is disconnected, it may discover a server in time to fulfill the next operation.

In PyMongo 2.x, MongoClient accepted a list of standalone MongoDB servers and used the first it could connect to:

MongoClient(['host1.com:27017', 'host2.com:27017'])

A list of multiple standalones is no longer supported; if multiple servers are listed they must be members of the same replica set, or mongoses in the same sharded cluster.

The behavior for a list of mongoses is changed from “high availability” to “load balancing”. Before, the client connected to the lowest-latency mongos in the list, and used it until a network error prompted it to re-evaluate all mongoses’ latencies and reconnect to one of them. In PyMongo 3, the client monitors its network latency to all the mongoses continuously, and distributes operations evenly among those with the lowest latency. See mongos Load Balancing for more information.

The connect option is added.

The start_request, in_request, and end_request methods are removed, as well as the auto_start_request option.

The copy_database method is removed, see the copy_database examples for alternatives.

The MongoClient.disconnect() method is removed; it was a synonym for close().

MongoClient no longer returns an instance of Database for attribute names with leading underscores. You must use dict-style lookups instead:

client['__my_database__']

Not:

client.__my_database__
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.

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

c[db_name] || c.db_name

Get the db_name Database on MongoClient c.

Raises InvalidName if an invalid database name is used.

event_listeners

The event listeners registered for this client.

See monitoring for details.

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.

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.

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.

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.

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.

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..

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.

min_pool_size

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

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).

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.

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_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_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.

local_threshold_ms

The local threshold for this instance.

server_selection_timeout

The server selection timeout for this instance in seconds.

codec_options

Read only access to the CodecOptions of this instance.

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.

write_concern

Read only access to the WriteConcern of this instance.

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

read_concern

Read only access to the ReadConcern of this instance.

New in version 3.2.

is_locked

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

start_session(causal_consistency=True)

Start a logical session.

This method takes the same parameters as SessionOptions. See the client_session module for details and examples.

Requires MongoDB 3.6. It is an error to call start_session() if this client has been authenticated to multiple databases using the deprecated method authenticate().

A ClientSession may only be used with the MongoClient that started it.

Returns:An instance of ClientSession.

New in version 3.6.

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.

New in version 3.6.

list_database_names(session=None)

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

Parameters:

Changed in version 3.6: Added session parameter.

database_names(session=None)

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

Parameters:

Changed in version 3.6: Added session parameter.

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.

Changed in version 3.6: Added session parameter.

Note

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

Changed in version 3.4: Apply this client’s write concern automatically to this operation when connected to MongoDB >= 3.4.

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

Get a Database with the given name and options.

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

>>> client.read_preference
Primary()
>>> db1 = client.test
>>> db1.read_preference
Primary()
>>> from pymongo import ReadPreference
>>> db2 = client.get_database(
...     'test', read_preference=ReadPreference.SECONDARY)
>>> db2.read_preference
Secondary(tag_sets=None)
Parameters:

Changed in version 3.5: The name parameter is now optional, defaulting to the database named in the MongoDB connection URI.

server_info(session=None)

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

Parameters:

Changed in version 3.6: Added session parameter.

close_cursor(cursor_id, address=None)

Send a kill cursors message soon with the given id.

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.

This method may be called from a Cursor destructor during garbage collection, so it isn’t safe to take a lock or do network I/O. Instead, we schedule the cursor to be closed soon on a background thread.

Parameters:
  • cursor_id: id of cursor to close
  • address (optional): (host, port) pair of the cursor’s server. If it is not provided, the client attempts to close the cursor on the primary or standalone, or a mongos server.

Changed in version 3.0: Added address parameter.

kill_cursors(cursor_ids, address=None)

DEPRECATED - Send a kill cursors message soon with the given ids.

Raises TypeError if cursor_ids is not an instance of list.

Parameters:
  • cursor_ids: list of cursor ids to kill
  • address (optional): (host, port) pair of the cursor’s server. If it is not provided, the client attempts to close the cursor on the primary or standalone, or a mongos server.

Changed in version 3.3: Deprecated.

Changed in version 3.0: Now accepts an address argument. Schedules the cursors to be closed on a background thread instead of sending the message immediately.

set_cursor_manager(manager_class)

DEPRECATED - 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 3.3: Deprecated, for real this time.

Changed in version 3.0: Undeprecated.

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.

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}
client.fsync(**options)

Changed in version 3.6: 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.

unlock(session=None)

Unlock a previously locked server.

Parameters:

Changed in version 3.6: Added session parameter.

get_default_database()

DEPRECATED - 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'
>>> db = client.get_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.

Changed in version 3.5: Deprecated, use get_database() instead.