ferro-blob-store

Foundation crate for content-addressed blob storage in the Ferro ecosystem. A deliberately tiny async fn trait (5 methods) plus two reference backends (in-memory + filesystem) plus a Digest newtype with SHA-256 / SHA-512 support.

⚠️ Alpha (v0.0.1). API may change. The trait surface is minimal on purpose so it stays stable as we add streaming variants in v0.1.

Part of the Ferro ecosystem. Used as the storage abstraction under ferro-oci-server, ferro-maven-layout, and ferro-cargo-registry-server.

What this crate does

• Digest — an <algo>:<hex> content identifier (SHA-256 or SHA-512). Validates hex length and character set on construction. Computes from bytes via Digest::sha256_of(&[u8]).
• BlobStore — five-method async trait: put, get, contains, delete, list. Writers verify the SHA-256 of the input matches the supplied digest. Implementations are expected to be Send + Sync.
• InMemoryBlobStore — Arc<RwLock<HashMap<Digest, Bytes>>> reference implementation. Useful for tests and ephemeral caches.
• FsBlobStore (default feature fs) — local-filesystem backend that lays out blobs at <root>/<algo>/<2-char-prefix>/<rest-of-hex>. Atomic writes via temp-file + rename.

What this crate does not do

• Streaming (put_stream / get_stream). Coming in v0.1.
• Cloud backends (S3, GCS, Azure). Use the object_store crate family and write a 50-line adapter; the trait is small enough.
• Tiered storage (Hot/Warm/Cold). The Ferro internal repo has a router for this; it is not in the public crate.
• Replication / dedupe / compression. Layer it under your own BlobStore impl that wraps an inner one.

Quick start

use ferro_blob_store::{BlobStore, Digest, InMemoryBlobStore};
use bytes::Bytes;

# async fn run() -> Result<(), Box<dyn std::error::Error>> {
let store = InMemoryBlobStore::new();
let body = Bytes::from_static(b"hello world");
let digest = Digest::sha256_of(&body);

store.put(&digest, body.clone()).await?;
assert!(store.contains(&digest).await?);
assert_eq!(store.get(&digest).await?, body);
assert_eq!(store.list().await?.len(), 1);
# Ok(()) }

Filesystem variant:

use ferro_blob_store::{BlobStore, Digest, FsBlobStore};
use bytes::Bytes;

# async fn run() -> Result<(), Box<dyn std::error::Error>> {
let store = FsBlobStore::new("/var/lib/my-registry/blobs")?;
let body = Bytes::from_static(b"layer bytes");
let digest = Digest::sha256_of(&body);
store.put(&digest, body).await?;
# Ok(()) }

Status

Used in production by

• ferro-oci-server — OCI Distribution v1.1 server primitives.
• ferro-maven-layout — Maven Repository Layout 2.0 + HTTP handlers.
• ferro-cargo-registry-server — Cargo Alternative Registry sparse-index server.

License

Apache-2.0. See LICENSE.