cloud-metadata

Minimal Rust crate for fetching custom instance metadata from AWS, GCP, and Azure VMs.

Features

• Auto-detect cloud provider
• Fetch custom metadata as bytes, string, or JSON
• Support for AWS IMDSv2, GCP Metadata Server, and Azure IMDS
• Automatic base64 decoding for Azure customData
• No OpenSSL dependency (uses rustls)

Installation

Add to your Cargo.toml:

[dependencies]
cloud-metadata = "0.1"

Or install the CLI:

cargo install cloud-metadata

Library Usage

use cloud_metadata::{CloudMetadata, MetadataError};
use serde::Deserialize;

#[derive(Deserialize)]
struct MyConfig {
    db_host: String,
    feature_flags: Vec<String>,
}

#[tokio::main]
async fn main() -> Result<(), MetadataError> {
    // Auto-detect cloud provider
    let metadata = CloudMetadata::detect().await?;

    // Fetch and deserialize JSON config
    let config: MyConfig = metadata.custom_json("user-data-json").await?;

    // Or fetch as raw bytes
    let raw: Vec<u8> = metadata.custom_data("user-data-json").await?;

    // Or fetch as string
    let text: String = metadata.custom_text("user-data-json").await?;

    Ok(())
}

Explicit Provider

// Skip auto-detection if you know the provider
let metadata = CloudMetadata::aws();
let metadata = CloudMetadata::gcp();
let metadata = CloudMetadata::azure();

GCP Project Attributes

let metadata = CloudMetadata::gcp();
let value = metadata.project_attribute("my-project-key").await?;

CLI Usage

# Auto-detect provider and fetch metadata
cloud-metadata fetch

# Fetch with explicit provider
cloud-metadata fetch --provider gcp

# Fetch specific key (for GCP)
cloud-metadata fetch my-custom-key

# Output as JSON
cloud-metadata fetch --format json

# Detect provider only
cloud-metadata detect

Provider-Specific Behavior

Instance Configuration Examples

AWS (Terraform)

resource "aws_instance" "example" {
  user_data = jsonencode({
    db_host       = "postgres.internal"
    feature_flags = ["new_ui"]
  })
}

GCP (Terraform)

resource "google_compute_instance" "example" {
  metadata = {
    user-data-json = jsonencode({
      db_host       = "postgres.internal"
      feature_flags = ["new_ui"]
    })
  }
}

Azure (Terraform)

resource "azurerm_linux_virtual_machine" "example" {
  custom_data = base64encode(jsonencode({
    db_host       = "postgres.internal"
    feature_flags = ["new_ui"]
  }))
}

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.