azure-cosmos-rust

Azure Cosmos DB SDK for Rust

Client library for Azure Cosmos DB NoSQL API — globally distributed, multi-model database.

The examples below require a reviewed compatible crate set and replacement of every resource placeholder. Do not use production data for demonstration writes.

Installation

cargo add azure_data_cosmos@=0.37.1 azure_identity@=1.0.0 azure_core@=1.1.0

Environment Variables

export COSMOS_ENDPOINT="https://<account>.documents.azure.com:443/"
export COSMOS_DATABASE="mydb"
export COSMOS_CONTAINER="mycontainer"

Authentication

use azure_identity::DeveloperToolsCredential;
use azure_data_cosmos::{AccountEndpoint, AccountReference, CosmosClient, RoutingStrategy};

let credential = DeveloperToolsCredential::new(None)?;
let endpoint: AccountEndpoint = "https://<account>.documents.azure.com/".parse()?;
let account = AccountReference::with_credential(endpoint, credential.clone());
let client = CosmosClient::builder()
    .build(account, RoutingStrategy::ProximityTo("East US".into()))
    .await?;

Client Hierarchy

Client	Purpose	Get From
CosmosClient	Account-level operations	Direct instantiation
DatabaseClient	Database operations	client.database_client()
ContainerClient	Container/item operations	database.container_client()

Core Workflow

Get Database and Container Clients

let database = client.database_client("myDatabase");
let container = database.container_client("myContainer", None).await?;

Create Item

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize)]
struct Item {
    pub id: String,
    pub partition_key: String,
    pub value: String,
}

let item = Item {
    id: "1".into(),
    partition_key: "partition1".into(),
    value: "hello".into(),
};

container.create_item("partition1", "1", item, None).await?;

Read Item

let response = container.read_item("partition1", "1", None).await?;
let item: Item = response.into_model()?;

Replace Item

let mut item: Item = container.read_item("partition1", "1", None).await?.into_model()?;
item.value = "updated".into();

container.replace_item("partition1", "1", item, None).await?;

Patch Item

// Explicit preview opt-in: cargo add azure_data_cosmos@=0.37.1 --features preview_patch
use azure_data_cosmos::models::{PatchInstructions, PatchOperation};

let patch = PatchInstructions::from(vec![
    PatchOperation::set("/value", serde_json::json!("newValue")),
]);
let patched: Item = container.patch_item("partition1", "1", patch, None)
    .await?.into_model()?;

Delete Item

container.delete_item("partition1", "1", None).await?;

The reviewed current API uses an async builder/container initialization and a separate explicit item ID. Preview PATCH is not a production-ready guarantee; review its selected strategy, conflict/retry behavior and request-unit cost. Official crate reference.

Key Auth (Optional)

Enable key-based authentication with feature flag:

cargo add azure_data_cosmos@=0.37.1 --features key_auth

Best Practices

1. Always specify partition key — required for point reads and writes
2. Use into_model()? — to deserialize responses into your types
3. Derive Serialize and Deserialize — for all document types
4. Use Entra ID auth — prefer DeveloperToolsCredential over key auth
5. Reuse client instances — clients are thread-safe and reusable

The reviewed example set uses azure_data_cosmos 0.37.1 and compatible Azure core/credential crates. Record and commit Cargo.lock; source/API review is not a compiler or live-service test.

Reference Links

Resource	Link
API Reference	https://docs.rs/azure_data_cosmos
Source Code	https://github.com/Azure/azure-sdk-for-rust/tree/main/sdk/cosmos/azure_data_cosmos
crates.io	https://crates.io/crates/azure_data_cosmos

When to Use

Use when a Rust application needs Cosmos DB NoSQL item CRUD, partition-key point reads, container access or explicitly opted-in preview patching.

Limitations

• Examples are fragments inside async application code, with compatible pinned Azure crates and the required Tokio/Serde/Futures dependencies; verify the selected version’s API before use. They were reviewed against official source/reference, not compiled or run against a cloud account here.
• Use an authorized tenant, resource and identity with least privilege. Writes, overwrites, deletes, backup retrieval and account changes require the corresponding scope; cleanup may remove only explicitly identified disposable resources. Bound requests, retries and downloaded bytes, and do not log payloads, credentials or secret values.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.