MongoDB Rust Driver

This repository contains the officially supported MongoDB Rust driver, a client side library that can be used to interact with MongoDB deployments in Rust applications. It uses the bson crate for BSON support. The driver contains a fully async API that supports either tokio (default) or async-std, depending on the feature flags set. The driver also has a sync API that may be enabled via feature flag.

Index

• Installation
  • Requirements
  • Importing
    • Configuring the async runtime
    • Enabling the sync API
    • All feature flags
• Example Usage
  • Using the async API
    • Connecting to a MongoDB deployment
    • Getting a handle to a database
    • Inserting documents into a collection
    • Finding documents in a collection
  • Using the sync API
• Platforms
• Atlas note
• Windows DNS note
• Warning about timeouts / cancellation
• Bug Reporting / Feature Requests
• Contributing
• Running the tests
• Continuous Integration
• License

Installation

Requirements

• Rust 1.48+
• MongoDB 3.6+

Importing

The driver is available on crates.io. To use the driver in your application, simply add it to your project's Cargo.toml.

[dependencies]
mongodb = "2.0.0"

Configuring the async runtime

The driver supports both of the most popular async runtime crates, namely tokio and async-std. By default, the driver will use tokio, but you can explicitly choose a runtime by specifying one of "tokio-runtime" or "async-std-runtime" feature flags in your Cargo.toml.

For example, to instruct the driver to work with async-std, add the following to your Cargo.toml:

[dependencies.mongodb]
version = "2.0.0"
default-features = false
features = ["async-std-runtime"]

Enabling the sync API

The driver also provides a blocking sync API. To enable this, add the "sync" feature to your Cargo.toml:

[dependencies.mongodb]
version = "2.0.0"
default-features = false
features = ["sync"]

Note: if the sync API is enabled, the async-specific types will be privatized (e.g. mongodb::Client). The sync-specific types can be imported from mongodb::sync (e.g. mongodb::sync::Client).

All Feature Flags

Feature	Description	Extra dependencies	Default
tokio-runtime	Enable support for the tokio async runtime	tokio 1.0 with the full feature	yes
async-std-runtime	Enable support for the async-std runtime	async-std 1.0	no
sync	Expose the synchronous API (mongodb::sync). This flag cannot be used in conjunction with either of the async runtime feature flags.	async-std 1.0	no
aws-auth	Enable support for the MONGODB-AWS authentication mechanism.	reqwest 0.11	no
bson-uuid-0_8	Enable support for v0.8 of the uuid crate in the public API of the re-exported bson crate.	n/a	no
bson-chrono-0_4	Enable support for v0.4 of the chrono crate in the public API of the re-exported bson crate.	n/a	no
zlib-compression	Enable support for compressing messages with zlib	flate2 1.0	no
zstd-compression	Enable support for compressing messages with zstd. This flag requires Rust version 1.54.	zstd 0.9.0	no
snappy-compression	Enable support for compressing messages with snappy	snap 1.0.5	no

Example Usage

Below are simple examples of using the driver. For more specific examples and the API reference, see the driver's docs.rs page.

Using the async API

Connecting to a MongoDB deployment

use mongodb::{Client, options::ClientOptions};

// Parse a connection string into an options struct.
let mut client_options = ClientOptions::parse("mongodb://localhost:27017").await?;

// Manually set an option.
client_options.app_name = Some("My App".to_string());

// Get a handle to the deployment.
let client = Client::with_options(client_options)?;

// List the names of the databases in that deployment.
for db_name in client.list_database_names(None, None).await? {
    println!("{}", db_name);
}

Getting a handle to a database

// Get a handle to a database.
let db = client.database("mydb");

// List the names of the collections in that database.
for collection_name in db.list_collection_names(None).await? {
    println!("{}", collection_name);
}

Inserting documents into a collection

use mongodb::bson::{doc, Document};

// Get a handle to a collection in the database.
let collection = db.collection::<Document>("books");

let docs = vec![
    doc! { "title": "1984", "author": "George Orwell" },
    doc! { "title": "Animal Farm", "author": "George Orwell" },
    doc! { "title": "The Great Gatsby", "author": "F. Scott Fitzgerald" },
];

// Insert some documents into the "mydb.books" collection.
collection.insert_many(docs, None).await?;

A Collection can be parameterized with any type that implements the Serialize and Deserialize traits from the serde crate, not just Document:

# In Cargo.toml, add the following dependency.
serde = { version = "1.0", features = ["derive"] }

use serde::{Deserialize, Serialize};

#[derive(Debug, Serialize, Deserialize)]
struct Book {
    title: String,
    author: String,
}

// Get a handle to a collection of `Book`.
let typed_collection = db.collection::<Book>("books");

let books = vec![
    Book {
        title: "The Grapes of Wrath".to_string(),
        author: "John Steinbeck".to_string(),
    },
    Book {
        title: "To Kill a Mockingbird".to_string(),
        author: "Harper Lee".to_string(),
    },
];

// Insert the books into "mydb.books" collection, no manual conversion to BSON necessary.
typed_collection.insert_many(books, None).await?;

Finding documents in a collection

Results from queries are generally returned via Cursor, a struct which streams the results back from the server as requested. The Cursor type implements the Stream trait from the futures crate, and in order to access its streaming functionality you need to import at least one of the StreamExt or TryStreamExt traits.

# In Cargo.toml, add the following dependency.
futures = "0.3"

// This trait is required to use `try_next()` on the cursor
use futures::stream::TryStreamExt;
use mongodb::{bson::doc, options::FindOptions};

// Query the books in the collection with a filter and an option.
let filter = doc! { "author": "George Orwell" };
let find_options = FindOptions::builder().sort(doc! { "title": 1 }).build();
let mut cursor = typed_collection.find(filter, find_options).await?;

// Iterate over the results of the cursor.
while let Some(book) = cursor.try_next().await? {
    println!("title: {}", book.title);
}

Using the sync API

The driver also provides a blocking sync API. See the Installation section for instructions on how to enable it.

The various sync-specific types are found in the mongodb::sync submodule rather than in the crate's top level like in the async API. The sync API calls through to the async API internally though, so it looks and behaves similarly to it.

use mongodb::{
    bson::doc,
    sync::Client,
};
use serde::{Deserialize, Serialize};

#[derive(Debug, Serialize, Deserialize)]
struct Book {
    title: String,
    author: String,
}

let client = Client::with_uri_str("mongodb://localhost:27017")?;
let database = client.database("mydb");
let collection = database.collection::<Book>("books");

let docs = vec![
    Book {
        title: "1984".to_string(),
        author: "George Orwell".to_string(),
    },
    Book {
        title: "Animal Farm".to_string(),
        author: "George Orwell".to_string(),
    },
    Book {
        title: "The Great Gatsby".to_string(),
        author: "F. Scott Fitzgerald".to_string(),
    },
];

// Insert some books into the "mydb.books" collection.
collection.insert_many(docs, None)?;

let cursor = collection.find(doc! { "author": "George Orwell" }, None)?;
for result in cursor {
    println!("title: {}", result?.title);
}

Platforms

The driver tests against Linux, MacOS, and Windows in CI.

Atlas note

Currently, the driver has issues connecting to Atlas tiers above M2 unless the server version is at least 4.2. We're working on fixing this, but in the meantime, a workaround is to upgrade your cluster to 4.2. The driver has no known issues with either M0 or M2 instances.

Windows DNS note

On Windows, there is a known issue in the trust-dns-resolver crate, which the driver uses to perform DNS lookups, that causes severe performance degradation in resolvers that use the system configuration. Since the driver uses the system configuration by default, users are recommended to specify an alternate resolver configuration on Windows until that issue is resolved. This only has an effect when connecting to deployments using a mongodb+srv connection string.

e.g.

use mongodb::{
    options::{ClientOptions, ResolverConfig},
    Client,
};

let options = ClientOptions::parse_with_resolver_config(
    "mongodb+srv://my.host.com",
    ResolverConfig::cloudflare(),
)
.await?;
let client = Client::with_options(options)?;

Warning about timeouts / cancellation

In async Rust, it is common to implement cancellation and timeouts by dropping a future after a certain period of time instead of polling it to completion. This is how tokio::time::timeout works, for example. However, doing this with futures returned by the driver can leave the driver's internals in an inconsistent state, which may lead to unpredictable or incorrect behavior (see RUST-937 for more details). As such, it is highly recommended to poll all futures returned from the driver to completion. In order to still use timeout mechanisms like tokio::time::timeout with the driver, one option is to spawn tasks and time out on their JoinHandle futures instead of on the driver's futures directly. This will ensure the driver's futures will always be completely polled while also allowing the application to continue in the event of a timeout.

e.g.

let collection = client.database("ok").collection("ok");
let handle = tokio::task::spawn(async move {
    collection.insert_one(doc! { "x": 1 }, None).await
});

tokio::time::timeout(Duration::from_secs(5), handle).await???;

Bug Reporting / Feature Requests

To file a bug report or submit a feature request, please open a ticket on our Jira project:

• Create an account and login at jira.mongodb.org
• Navigate to the RUST project at jira.mongodb.org/browse/RUST
• Click Create Issue - If the ticket you are filing is a bug report, please include as much detail as possible about the issue and how to reproduce it.

Before filing a ticket, please use the search functionality of Jira to see if a similar issue has already been filed.

Contributing

We encourage and would happily accept contributions in the form of GitHub pull requests. Before opening one, be sure to run the tests locally; check out the testing section for information on how to do that. Once you open a pull request, your branch will be run against the same testing matrix that we use for our continuous integration system, so it is usually sufficient to only run the integration tests locally against a standalone. Remember to always run the linter tests before opening a pull request.

Running the tests

Integration and unit tests

In order to run the tests (which are mostly integration tests), you must have access to a MongoDB deployment. You may specify a MongoDB connection string in the MONGODB_URI environment variable, and the tests will use it to connect to the deployment. If MONGODB_URI is unset, the tests will attempt to connect to a local deployment on port 27017.

Note: The integration tests will clear out the databases/collections they need to use, but they do not clean up after themselves.

To actually run the tests, you can use cargo like you would in any other crate:

cargo test --verbose # runs against localhost:27017
export MONGODB_URI="mongodb://localhost:123"
cargo test --verbose # runs against localhost:123

Auth tests

The authentication tests will only be included in the test run if certain requirements are met:

• The deployment must have --auth enabled
• Credentials must be specified in MONGODB_URI
• The credentials specified in MONGODB_URI must be valid and have root privileges on the deployment

export MONGODB_URI="mongodb://user:pass@localhost:27017"
cargo test --verbose # auth tests included

Topology-specific tests

Certain tests will only be run against certain topologies. To ensure that the entire test suite is run, make sure to run the tests separately against standalone, replicated, and sharded deployments.

export MONGODB_URI="mongodb://my-standalone-host:27017" # mongod running on 27017
cargo test --verbose
export MONGODB_URI="mongodb://localhost:27018,localhost:27019,localhost:27020/?replicaSet=repl" # replicaset running on ports 27018, 27019, 27020 with name repl
cargo test --verbose
export MONGODB_URI="mongodb://localhost:27021" # mongos running on 27021
cargo test --verbose

Run the tests with TLS/SSL

To run the tests with TLS/SSL enabled, you must enable it on the deployment and in MONGODB_URI.

export MONGODB_URI="mongodb://localhost:27017/?tls=true&tlsCertificateKeyFile=cert.pem&tlsCAFile=ca.pem"
cargo test --verbose

Note: When you open a pull request, your code will be run against a comprehensive testing matrix, so it is usually not necessary to run the integration tests against all combinations of topology/auth/TLS locally.

Linter Tests

Our linter tests use the nightly version of rustfmt to verify that the source is formatted properly and the stable version of clippy to statically detect any common mistakes. You can use rustup to install them both:

rustup component add clippy --toolchain stable
rustup component add rustfmt --toolchain nightly

Our linter tests also use rustdoc to verify that all necessary documentation is present and properly formatted. rustdoc is included in the standard Rust distribution.

To run the linter tests, run the check-clippy.sh, check-rustfmt.sh, and check-rustdoc.sh scripts in the .evergreen directory. To run all three, use the check-all.sh script.

bash .evergreen/check-all.sh

Continuous Integration

Commits to master are run automatically on evergreen.

Minimum supported Rust version (MSRV)

The MSRV for this crate is currently 1.48.0. This will be rarely be increased, and if it ever is, it will only happen in a minor or major version release.

License

This project is licensed under the Apache License 2.0.