Module async_client 

HTTP storage backend using async reqwest + Tokio. HTTP storage backend with embedded Tokio runtime.

This module provides an HTTP storage backend that wraps the reqwest async client in an embedded Tokio runtime. This allows the backend to present a synchronous StorageBackend interface while leveraging async I/O internally for efficient concurrent operations.

Architecture

The HttpBackend embeds a Tokio runtime (Arc<Runtime>) and uses runtime.block_on() to execute async operations synchronously. This design:

• Maintains compatibility with the synchronous StorageBackend trait
• Enables efficient connection pooling and concurrent requests via reqwest
• Provides async benefits (low memory overhead per connection) without requiring callers to use async/await

Redirect Handling

reqwest’s built-in redirect policy drops certain headers (including Range) on cross-origin redirects. Since CDNs like GitHub Releases → Azure Blob require cross-origin redirects with range headers, this backend disables auto-redirects and follows them manually, re-sending all headers on each hop.

Thread Safety

The backend is fully thread-safe (Send + Sync):

• The reqwest::Client is designed for concurrent use
• The Arc<Runtime> is shared safely across threads
• Multiple threads can call read_exact() concurrently without coordination

Security

This backend validates URLs to prevent SSRF attacks:

• Blocks access to localhost and private networks by default
• Set allow_restricted: true only in trusted environments
• See validate_url for details

Examples

use hexz_core::store::http::HttpBackend;
use hexz_core::store::StorageBackend;

let backend = HttpBackend::new(
    "https://cdn.example.com/snapshots/data.hxz".to_string(),
    false // block restricted IPs
)?;

println!("Snapshot size: {} bytes", backend.len());

let header = backend.read_exact(0, 512)?;
assert_eq!(header.len(), 512);

Structs

HttpBackend

HTTP storage backend with embedded Tokio runtime.