Description

The MongoDB Rust driver team is pleased to announce the v2.2.0 release of the mongodb crate.

Highlighted Changes

The following sections detail some of the more important changes included in this release. For a full list of changes, see the Full Release Notes section below.

Change Streams (RUST-521, RUST-74, RUST-522, RUST-1149, RUST-523, RUST-1104)

This release adds support for Change Streams, which allow applications to access real-time data changes without the complexity and risk of tailing the oplog. Applications can use change streams to subscribe to all data changes on a single collection, a database, or an entire deployment, and immediately react to them.

let mut change_stream = coll.watch(None, None).await?;
let coll_ref = coll.clone();
task::spawn(async move {
    coll_ref.insert_one(doc! { "x": 1 }, None).await;
});
while let Some(event) = change_stream.next().await.transpose()? {
    println!("operation performed: {:?}, document: {:?}", event.operation_type, event.full_document);
    // operation performed: Insert, document: Some(Document({"x": Int32(1)}))
}

Raw BSON Incorporation (RUST-1133, RUST-1175)

This release uses the new raw BSON types introduced in v2.2 of the bson crate for internal operations, boosting performance in certain circumstances. It also allows for zero-copy deserialization when working with cursors via the new Cursor::deserialize_current method:

use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct Cat<'a> {
    #[serde(borrow)]
    name: &'a str
}

let coll = db.collection::<Cat>("cat");
let mut cursor = coll.find(None, None).await?;
while cursor.advance().await? {
    println!("{:?}", cursor.deserialize_current()?);
}

MSRV and Dependency Update (RUST-1192, RUST-1220)

This release updates the version of all dependencies used by the Rust driver to their most recent, which required an update of the MSRV to 1.51.

OpenSSL Support (RUST-1083)

This release adds optional support for using OpenSSL for TLS streams via the new openssl-tls feature. Note that rustls is still required as a dependency in this case to avoid breaking backwards compatibility; this will be removed in a future major version release.

Full Release Notes

New Features

• RUST-521 Implement naive streaming and resume token caching for change streams (#531)
• RUST-1133 Update driver to use the raw BSON API (#546)
• RUST-74 Add cluster_time to ChangeStreamEvent (#548)
• RUST-522 Implement resume functionality for change streams (#547)
• RUST-1149 Prose tests for change streams. (#561)
• RUST-523 Support change streams in unified spec tests (#564)
• RUST-1104 sync wrapper for the change stream API (#566)
• RUST-1106 Make the change streams API visible (#571)
• RUST-43 Add change streams examples for documentation (#572)
• RUST-1138 Add bson-serde_with feature flag (#580)
• RUST-1175 Support zero-copy deserialization from cursors (#579)
• RUST-995 Add tokio-sync feature flag (#578)
• RUST-1083 Add openssl as an optional TLS provider (#590)

Bugfixes

• minor: derive TypedBuilder for TimeseriesOptions (#557)
• minor: fix external crate links (#552)
• RUST-1163 Fix load balancer tests (#576)
• RUST-812 Reduce flakiness of in_window::load_balancing_test (#568)
• RUST-1163 Fix load balancer auth tests (#581)
• RUST-1268 Use rustc_version_runtime for runtime metadata (#622)

Improvements

• RUST-1088 Always specify error labels at the top level (#553)
• RUST-894 Unskip write_error::details test on sharded clusters (#526)
• RUST-395 Log skipped tests (#523)
• RUST-1143 Bump max wire version to 15 (#573)
• RUST-1077 Update read/write concern document tests (#567)
• RUST-1173 Replace "Versioned API" references with "Stable API" (#585)
• RUST-1192 Bump MSRV to 1.49.0 (#584)
• RUST-1207 Bump zstd to v0.10 (#588) (thanks @moy2010!)
• RUST-1220 Bump outdated dependencies (#596)
• RUST-886 Use lossy UTF-8 decoding for responses to insert and update commands (#601)
• RUST-803 Conditionally use hello for monitoring (#600)
• RUST-1064 Retry on handshake failure (#598)