Linking (Rust)

Link resources to Rust Lambda functions

Link resources to your Rust Lambda functions to access them at runtime.

Basic Linking

Link resources in your infrastructure code:

sst.config.ts

const bucket = new sst.aws.Bucket("MyBucket");
const table = new sst.aws.Dynamo("MyTable", {
  fields: { id: "string" },
  primaryIndex: { hashKey: "id" }
});

new sst.aws.Function("MyRustFunction", {
  handler: "bootstrap",
  runtime: "rust",
  link: [bucket, table]
});

Access them in your Rust code:

src/main.rs

use lambda_runtime::{service_fn, LambdaEvent, Error};
use serde_json::Value;

#[tokio::main]
async fn main() -> Result<(), Error> {
    lambda_runtime::run(service_fn(handler)).await
}

async fn handler(event: LambdaEvent<Value>) -> Result<Value, Error> {
    let bucket_name = std::env::var("SST_RESOURCE_MyBucket_name")
        .expect("MyBucket not linked");
    let table_name = std::env::var("SST_RESOURCE_MyTable_name")
        .expect("MyTable not linked");
    
    // Use the resources
    Ok(serde_json::json!({"statusCode": 200}))
}

Automatic Permissions

Linking automatically grants IAM permissions:

const bucket = new sst.aws.Bucket("MyBucket");

new sst.aws.Function("Upload", {
  handler: "bootstrap",
  runtime: "rust",
  link: [bucket]
  // Automatically gets s3:PutObject, s3:GetObject, etc.
});

Multiple Resources

Link multiple resources:

const bucket = new sst.aws.Bucket("MyBucket");
const table = new sst.aws.Dynamo("MyTable", { /* ... */ });
const queue = new sst.aws.Queue("MyQueue");

new sst.aws.Function("Worker", {
  handler: "bootstrap",
  runtime: "rust",
  link: [bucket, table, queue]
});

All accessible in your handler:

use lambda_runtime::{service_fn, LambdaEvent, Error};
use serde_json::Value;

#[tokio::main]
async fn main() -> Result<(), Error> {
    lambda_runtime::run(service_fn(handler)).await
}

async fn handler(event: LambdaEvent<Value>) -> Result<Value, Error> {
    let bucket = std::env::var("SST_RESOURCE_MyBucket_name")?;
    let table = std::env::var("SST_RESOURCE_MyTable_name")?;
    let queue_url = std::env::var("SST_RESOURCE_MyQueue_url")?;
    
    // Use all resources
    Ok(serde_json::json!({"statusCode": 200}))
}

Linking Secrets

sst.config.ts

const secret = new sst.Secret("ApiKey");

new sst.aws.Function("MyFunction", {
  handler: "bootstrap",
  runtime: "rust",
  link: [secret]
});

src/main.rs

use lambda_runtime::{service_fn, LambdaEvent, Error};
use serde_json::Value;

#[tokio::main]
async fn main() -> Result<(), Error> {
    lambda_runtime::run(service_fn(handler)).await
}

async fn handler(event: LambdaEvent<Value>) -> Result<Value, Error> {
    let api_key = std::env::var("SST_RESOURCE_ApiKey_value")?;
    // Use the secret
    Ok(serde_json::json!({"statusCode": 200}))
}

Building Rust Functions

SST automatically builds your Rust functions:

sst.config.ts

new sst.aws.Function("MyFunction", {
  handler: "bootstrap",
  runtime: "rust"
});

Project structure:

.
├── sst.config.ts
├── Cargo.toml
└── src/
    └── main.rs

Your Cargo.toml should include:

Cargo.toml

[package]
name = "my-function"
version = "0.1.0"
edition = "2021"

[dependencies]
lambda_runtime = "*"
tokio = { version = "1", features = ["full"] }
serde_json = "1"

Best Practices

Link Only What You Need

// ✓ Good - minimal permissions
new sst.aws.Function("GetUser", {
  runtime: "rust",
  handler: "bootstrap",
  link: [usersTable]
});

// ✗ Avoid - over-permissioned
new sst.aws.Function("GetUser", {
  runtime: "rust",
  handler: "bootstrap",
  link: [usersTable, ordersTable, productsTable]
});

Create Type-Safe Resource Structs

struct Resources {
    bucket_name: String,
    table_name: String,
    queue_url: String,
}

impl Resources {
    fn load() -> Result<Self, std::env::VarError> {
        Ok(Resources {
            bucket_name: std::env::var("SST_RESOURCE_MyBucket_name")?,
            table_name: std::env::var("SST_RESOURCE_MyTable_name")?,
            queue_url: std::env::var("SST_RESOURCE_MyQueue_url")?,
        })
    }
}

async fn handler(event: LambdaEvent<Value>) -> Result<Value, Error> {
    let resources = Resources::load()?;
    // Use resources.bucket_name, resources.table_name, etc.
    Ok(serde_json::json!({"statusCode": 200}))
}

Use Once Cell for Static Initialization

use once_cell::sync::Lazy;
use aws_sdk_s3::Client;

static RESOURCES: Lazy<Resources> = Lazy::new(|| {
    Resources::load().expect("Failed to load resources")
});

static S3_CLIENT: Lazy<Client> = Lazy::new(|| {
    let config = tokio::runtime::Runtime::new()
        .unwrap()
        .block_on(aws_config::load_from_env());
    Client::new(&config)
});

async fn handler(event: LambdaEvent<Value>) -> Result<Value, Error> {
    // Use RESOURCES and S3_CLIENT
    Ok(serde_json::json!({"statusCode": 200}))
}

Related

Resource Access

Learn more about the Resource API for Rust

Rust Functions

Deploy Rust Lambda functions