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
high_availability.rst.
MongoClients now close themselves cleanly when garbage-collected. Dropping the database at the end of TestMongosHighAvailability isn't needed since the whole cluster will be destroyed.
Rename the attributes of IsMaster, ServerDescription, TopologyDescription, and
TopologySettings from "set_name" to "replica_set_name" for greater clarity.
The Server Discovery And Monitoring Spec has replaced the term "cluster"
with "topology", since "cluster" in MongoDB terminology should be reserved
for sharded clusters. "Topology" describes a single server, replica set, or a
set of mongoses.
The previous commit replaced "cluster" with "topology" in file names. Here
I replace the term in class and variable names.
MongoClient now supports all MongoReplicaSetClient's features.
Fix bugs and add features in the new MongoClient to bring it up
to spec. MongoReplicaSetClient is now a deprecated stub that
subclasses MongoClient.
Introduce new errors, NetworkTimeout and NotMasterError, to
communicate events that MongoClient must handle specially.
A 2.6 primary may not be ready to step down immediately after the RS
is initialized: "no secondaries within 10 seconds of optime". Keep
trying for a while.
This commit does a few things:
- Adds tag_sets back (deprecated)
- Adds secondary_acceptable_latency_ms back (deprecated)
- Makes acceptable latency a per read preference setting
- Cleans up read preference instance generation
- Adds latencyThresholdMS as an alias for secondaryAcceptableLatencyMS.
The name may change before 3.0 is released.
This commit introduces the following changes:
- Each read preference is now a class.
- Read preferences other than Primary accept a tag_sets parameter.
- The tag_sets attribute of MongoClient, Database, and Collection has
been removed. Use the tag_sets parameter of the new classes instead.
- The read_preferences.ReadPreference constant still exists and should
continue to work as expected for most users.
- Renamed to acceptableLatencyMS since it is also used
in choosing a new mongos during mongos HA failover.
- Moved to a global immutable setting. The expectation is
that the value would be determined by a network/system
admin. Changing it per operation doesn't make a lot of
sense.
Note - it's possible the name of this option may change again
before 3.0 is released.
