read_preferences – Utilities for choosing which member of a replica set to read from.
Utilities for choosing which member of a replica set to read from.
Primary
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class
pymongo.read_preferences.
Primary
Primary read preference.
When directly connected to one mongod queries are allowed if the server is standalone or a replica set primary.
When connected to a mongos queries are sent to the primary of a shard.
When connected to a replica set queries are sent to the primary of the replica set.
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document
Read preference as a document.
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mode
The mode of this read preference instance.
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name
The name of this read preference.
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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.” MongoReplicaSetClient tries each set of tags in turn until it finds a set of tags with at least one matching member.
PrimaryPreferred
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class
pymongo.read_preferences.
PrimaryPreferred
(tag_sets=None)
PrimaryPreferred read preference.
When directly connected to one mongod queries are allowed to standalone servers, to a replica set primary, or to replica set secondaries.
When connected to a mongos queries are sent to the primary of a shard if available, otherwise a shard secondary.
When connected to a replica set queries are sent to the primary if available, otherwise a secondary.
tag_sets - The tag_sets to use if the primary is not available.
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document
Read preference as a document.
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mode
The mode of this read preference instance.
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name
The name of this read preference.
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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.” MongoReplicaSetClient tries each set of tags in turn until it finds a set of tags with at least one matching member.
Secondary
-
class
pymongo.read_preferences.
Secondary
(tag_sets=None)
Secondary read preference.
When directly connected to one mongod queries are allowed to standalone servers, to a replica set primary, or to replica set secondaries.
When connected to a mongos queries are distributed among shard secondaries. An error is raised if no secondaries are available.
When connected to a replica set queries are distributed among secondaries. An error is raised if no secondaries are available.
tag_sets - The tag_sets to use with this read_preference
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document
Read preference as a document.
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mode
The mode of this read preference instance.
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name
The name of this read preference.
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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.” MongoReplicaSetClient tries each set of tags in turn until it finds a set of tags with at least one matching member.
SecondaryPreferred
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class
pymongo.read_preferences.
SecondaryPreferred
(tag_sets=None)
SecondaryPreferred read preference.
When directly connected to one mongod queries are allowed to standalone servers, to a replica set primary, or to replica set secondaries.
When connected to a mongos queries are distributed among shard secondaries, or the shard primary if no secondary is available.
When connected to a replica set queries are distributed among secondaries, or the primary if no secondary is available.
tag_sets - The tag_sets to use with this read_preference
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document
Read preference as a document.
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mode
The mode of this read preference instance.
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name
The name of this read preference.
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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.” MongoReplicaSetClient tries each set of tags in turn until it finds a set of tags with at least one matching member.
Nearest
-
class
pymongo.read_preferences.
Nearest
(tag_sets=None)
Nearest read preference.
When directly connected to one mongod queries are allowed to standalone servers, to a replica set primary, or to replica set secondaries.
When connected to a mongos queries are distributed among all members of a shard.
When connected to a replica set queries are distributed among all members.
tag_sets - The tag_sets to use with this read_preference
-
document
Read preference as a document.
-
mode
The mode of this read preference instance.
-
name
The name of this read preference.
-
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.” MongoReplicaSetClient tries each set of tags in turn until it finds a set of tags with at least one matching member.
ReadPreference
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class
pymongo.read_preferences.
ReadPreference
An enum that defines the read preference modes supported by PyMongo.
A read preference is used in three cases:
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.
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 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 AutoReconnect.
SECONDARY_PREFERRED - Read from a secondary if available, otherwise from the primary.
NEAREST - Read from any member.
MongoClient connected to a mongos, with a sharded cluster of replica sets:
PRIMARY - Read from the primary of the shard, or raise 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 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.
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PRIMARY = Primary()
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PRIMARY_PREFERRED = PrimaryPreferred(tag_sets=None)
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SECONDARY = Secondary(tag_sets=None)
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SECONDARY_PREFERRED = SecondaryPreferred(tag_sets=None)
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NEAREST = Nearest(tag_sets=None)