Classe « ReadPreference »

Informations générales

Héritage

builtins.object
    ReadPreference

Définition

class ReadPreference(builtins.object):

help(ReadPreference)

An enum that defines some commonly used read preference modes.

Apps can also create a custom read preference, for example::

   Nearest(tag_sets=[{"node":"analytics"}])

See :doc:`/examples/high_availability` for code examples.

A read preference is used in three cases:

:class:`~pymongo.mongo_client.MongoClient` connected to a single mongod:

- ``PRIMARY``: Queries are allowed if the server is standalone or a replica
  set primary.
- All other modes allow queries to standalone servers, to a replica set
  primary, or to replica set secondaries.

:class:`~pymongo.mongo_client.MongoClient` initialized with the
``replicaSet`` option:

- ``PRIMARY``: Read from the primary. This is the default, and provides the
  strongest consistency. If no primary is available, raise
  :class:`~pymongo.errors.AutoReconnect`.

- ``PRIMARY_PREFERRED``: Read from the primary if available, or if there is
  none, read from a secondary.

- ``SECONDARY``: Read from a secondary. If no secondary is available,
  raise :class:`~pymongo.errors.AutoReconnect`.

- ``SECONDARY_PREFERRED``: Read from a secondary if available, otherwise
  from the primary.

- ``NEAREST``: Read from any member.

:class:`~pymongo.mongo_client.MongoClient` connected to a mongos, with a
sharded cluster of replica sets:

- ``PRIMARY``: Read from the primary of the shard, or raise
  :class:`~pymongo.errors.OperationFailure` if there is none.
  This is the default.

- ``PRIMARY_PREFERRED``: Read from the primary of the shard, or if there is
  none, read from a secondary of the shard.

- ``SECONDARY``: Read from a secondary of the shard, or raise
  :class:`~pymongo.errors.OperationFailure` if there is none.

- ``SECONDARY_PREFERRED``: Read from a secondary of the shard if available,
  otherwise from the shard primary.

- ``NEAREST``: Read from any shard member.

Constructeur(s)

Signature du constructeur	Description
__init__(self, /, args, *kwargs)	Initialize self. See help(type(self)) for accurate signature. _{[extrait de __init__.__doc__]}

Liste des opérateurs

Opérateurs hérités de la classe object

__eq__, __ge__, __gt__, __le__, __lt__, __ne__

Liste des méthodes

Toutes les méthodes Méthodes d'instance Méthodes statiques

Signature de la méthode	Description
NEAREST(selection: 'Selection') -> 'Selection'	Nearest read preference. _{[extrait de __doc__]}
PRIMARY(selection: 'Selection') -> 'Selection'	Primary read preference. _{[extrait de __doc__]}
PRIMARY_PREFERRED(selection: 'Selection') -> 'Selection'	PrimaryPreferred read preference. _{[extrait de __doc__]}
SECONDARY(selection: 'Selection') -> 'Selection'	Secondary read preference. _{[extrait de __doc__]}
SECONDARY_PREFERRED(selection: 'Selection') -> 'Selection'	SecondaryPreferred read preference. _{[extrait de __doc__]}