This is a preview release for the upcoming 2.15 version.

Major new features of the 2.15 driver version are:

• RUBY-2429 Versioned MongoDB API
• RUBY-1682 Support for Zstandard compression
• RUBY-2439 Support for Snappy compression
• RUBY-2411 Query cache middleware moved from Mongoid to the driver and is usable in applications that do not use Mongoid

The following minor improvements have been made:

• RUBY-2509 Expose server error code name in OperationFailure exception message
• RUBY-1387 Applications can tweak SSLContext used by the driver
• RUBY-2458 Link heartbeat succeeded/failed to started events
• RUBY-2463 Enforce timeout on socket closes
• RUBY-2520 estimated_document_count uses the $collStats aggregation pipeline stage Instead of count command on 5.0+ servers
• RUBY-2444 Remove generic SSL messaging w.r.t. server configuration
• RUBY-2459 Include connection purpose in platform metadata