Fw: [mongodb-user] MongoDB 4.2.0-rc0 is released

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Satoshi OKANO

Jun 7, 2019, 12:34:19 AM6/7/19
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> In addition, new driver-side helpers make it easier for you to develop transaction retry logic in your app.


Forwarded by Satoshi OKANO <s-o...@nri.co.jp>
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From: "'Kelsey Schubert' via mongodb-user" <mongod...@googlegroups.com>
To: mongodb-...@googlegroups.com, mongod...@googlegroups.com, mongodb-dev <mongo...@googlegroups.com>
Date: Wed, 5 Jun 2019 12:33:24 -0400
Subject: [mongodb-user] MongoDB 4.2.0-rc0 is released

MongoDB 4.2.0-rc0, the first release candidate of MongoDB 4.2, is out and
is ready for testing. This is the culmination of the 4.1.x development
series, and includes many exciting new features. Here are some of the
Transactional Data Integrity

Distributed Transactions: Support for multi-document ACID transactions
is now extended to sharded clusters.

Global Point In Time Reads: Snapshot read isolation in 4.2 guarantees your
apps are always returned a consistent view of data, even when the data is
distributed across a sharded cluster, and as it is being modified by other

Large Transactions: By representing transactions across multiple oplog
entries, you can now write more than 16MB of data in a single ACID

Transaction Diagnostics and Error Handling: Transactions metrics are now
written to system logs, helping you optimize application performance. In
addition, new driver-side helpers make it easier for you to develop
transaction retry logic in your app.

Mutable Shard Key Values: You can now update one or more shard key values
to modify the placement of a document in a cluster using a single,
all-or-nothing ACID transaction (subject to the existing 60 second default
execution time).
Complex Queries & Real-Time Analytics

On-Demand Materialized Views: Outputs from aggregation pipeline queries can
now be merged with existing persisted result sets whenever you run the
pipeline, giving you materialized views that are refreshed on-demand.

Wildcard indexes: You can now define a filter that automatically indexes
matching fields, sub-documents, and arrays in a document
providing much simpler schema design for polymorphic document structures.

More Expressive Update Language: You can now use the aggregation pipeline
to construct update operations based on values in other fields, with all
updates performed in a single atomic operation.

New Mathematical Operators: New aggregation operators and expressions:
MongoDB 4.2 adds support for new regex aggregation operators, a dozen new
mathematical expressions for rounding
and trigonometry
as well as current time expressions like $$NOW to reduce the amount of code
you need to implement back in your app tier.
Resilience and Scalability

New Online Index Builds: As fast as foreground builds, they don’t block
service to the app

10x Faster stepDown and Keepalive Connections: As soon as you issue a
stepDown command, the MongoDB primary now immediately initiates an election
rather than wait on the secondaries to call it. After the stepDown,
existing read connections on the former primary are kept open, and are only
re-established on the new primary once reads have completed and their
associated cursors closed.

Storage Node Watchdog: Adding to existing network heartbeats
the Storage Node Watchdog
can be used to monitor MongoDB’s underlying filesystems and initiate an
automated failover if any of them becomes unresponsive. This allows the
cluster to automatically self-heal in the face of a wider range of failure

Faster Initial Sync: You can now add new nodes to a replica set 15%
faster, while also reducing load on the source replica.

Zstandard Compression: MongoDB 4.2 adds support for Zstandard compression
providing up to 55% storage savings compared to snappy, with lower CPU
overhead than Zlib.
Enterprise Security

Improved Auditing Performance: We’ve refactored internal locking within the
Auditing plugin, resulting in a 3x performance improvement.

Multi-Certificate Authority and Forward Secrecy TLS Encryption: Separate
Certificate Authorities can now be configured for inbound and outbound
encrypted connections to a MongoDB Atlas cluster. In-flight encryption also
now supports the latest TLS cipher suites offering Forward Secrecy.

Zero Downtime Certificate and Keyfile Rotation: You can now change your
keyfiles and X.509 certificates without having to take down your cluster.

MongoDB 4.2 Release Notes <http://docs.mongodb.org/master/release-notes/4.2>
| Changelog
| Downloads <https://www.mongodb.com/download-center>

-- The MongoDB Team

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