azure-cosmos-rust

# Azure Cosmos DB library for Rust Client library for Azure Cosmos DB NoSQL API — document CRUD, containers, and globally distributed data. Use this skill when: - An app needs to store or query documents in Cosmos DB from Rust - You need CRUD operations on items with partition keys - You need key-based auth as an alternative to Entra ID > **IMPORTANT:** Only use the official `azure_data_cosmos` crate published by the [azure-sdk](https://crates.io/users/azure-sdk) crates.io user. Do NOT use the unofficial `azure_cosmos` or `azure_sdk_for_rust` community crates. Official crates use underscores in names and none have version 0.21.0. ## Installation ```sh cargo add azure_data_cosmos azure_identity serde serde_json tokio ``` > If your code uses `azure_core` types directly (for example, `azure_core::credentials::TokenCredential`), add `azure_core` to `Cargo.toml`. If you only use `azure_data_cosmos` re-exports, direct `azure_core` dependency is optional. ## Environment Variables ```bash COSMOS_ENDPOINT=https://<account>.documents.azure.com/ # Required for all operations ``` ## Authentication ```rust use azure_identity::DeveloperToolsCredential; use azure_data_cosmos::{ CosmosClient, AccountReference, AccountEndpoint, RoutingStrategy, }; #[tokio::main] async fn main() -> Result<(), Box<dyn std::error::Error>> { // Local dev: DeveloperToolsCredential. Production: use ManagedIdentityCredential. let credential = DeveloperToolsCredential::new(None)?; let endpoint: AccountEndpoint = "https://<account>.documents.azure.com/" .parse()?; let account = AccountReference::with_credential(endpoint, credential); let client = CosmosClient::builder() .build(account, RoutingStrategy::ProximityTo("East US".into())) .await?; Ok(()) } ``` ## Client Hierarchy | Client | Purpose | Access | | ----------------- | ------------------------- | --------------------------------------- | | `CosmosClient` | Account-level operations | `CosmosClient::builder().build(account).await?` | | `DatabaseClient` | Database operations | `client.database_client("db")` | | `ContainerClient` | Container/item operations | `database.container_client("c").await` | ## Core Workflow ```rust use serde::{Serialize, Deserialize}; use azure_data_cosmos::CosmosClient; #[derive(Serialize, Deserialize)] struct Item { pub id: String, pub partition_key: String, pub value: String, } async fn crud(client: CosmosClient) -> Result<(), Box<dyn std::error::Error>> { let container = client .database_client("myDatabase") .container_client("myContainer") .await; let item = Item { id: "1".into(), partition_key: "pk1".into(), value: "hello".into(), }; // Create container.create_item("pk1", "1", item, None).await?; // Read let resp = container.read_item("pk1", "1", None).await?; let mut item: Item = resp.into_model()?; // Update item.value = "updated".into(); container.replace_item("pk1", "1", item, None).await?; // Delete container.delete_item("pk1", "1", None).await?; Ok(()) } ``` ### Patch Item ```rust use azure_data_cosmos::{PatchInstructions, PatchOperation}; let patch = PatchInstructions::from(vec![ PatchOperation::set("/value", serde_json::json!("patched")), ]); let patched: Item = container .patch_item("pk1", "1", patch, None) .await? .into_model()?; println!("Patched value: {}", patched.value); ``` ## Key Auth (Optional) Enable account key authentication with the feature flag: ```sh cargo add azure_data_cosmos --features key_auth ``` ## RBAC Roles For Entra ID auth, assign one of these built-in Cosmos DB roles: | Role | Access | | ------------------------------------- | ---------- | | `Cosmos DB Built-in Data Reader` | Read-only | | `Cosmos DB Built-in Data Contributor` | Read/write | ## Best Practices 1. **Use `cargo add` to manage dependencies, never edit `Cargo.toml` directly.** Add and remove Rust SDK dependencies with cargo commands instead of manual manifest edits. 2. **Add `azure_core` only when importing `azure_core` types directly.** If your code imports `azure_core::http::Url`, `azure_core::http::RequestContent`, or `azure_core::error::ErrorKind`, include `azure_core`; otherwise a direct dependency is optional. 3. **Use `DeveloperToolsCredential`** for local dev, **`ManagedIdentityCredential`** for production — Rust does not provide a single `DefaultAzureCredential` type 4. **Never hardcode credentials** — use environment variables or managed identity 5. **Reuse `CosmosClient`** — clients are thread-safe; create once, share across tasks 6. **Use `RoutingStrategy::ProximityTo`** — route to the nearest region for lowest latency 7. **Always specify partition key** for item operations — Cosmos DB requires it for all CRUD ## Reference Links | Resource | Link | | ------------- | ---------------------------------------------------------------------------------- | | API Reference | https://docs.rs/azure_data_cosmos/latest/azure_data_cosmos | | crates.io | https://crates.io/crates/azure_data_cosmos | | Source Code | https://github.com/Azure/azure-sdk-for-rust/tree/main/sdk/cosmos/azure_data_cosmos |