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Files, uploads & media

Almost every app stores user files — avatars, attachments, exported reports, images. Rustango gives you a Storage trait with swappable backends (local disk, S3-compatible object storage, in-memory for tests), a safe multipart upload helper with size/type guards, and — when you need a tracked media library — a database-backed MediaManager with presigned URLs. Write your code once against the trait; switch from local disk to S3 with a one-line change.

Files in rustango: a multipart upload is size- and extension-checked then written through the Storage trait; the same trait backs local disk, S3, and in-memory, and url() returns a public address

New to a term here? storage backend, multipart, object storage, presigned URL — see the glossary.

Source: rustango::storage (Storage, LocalStorage, InMemoryStorage, s3::S3Storage, BoxedStorage), rustango::uploads (save_uploads, UploadConfig, sanitize_filename), and rustango::media (Media, MediaManager) — behind the storage / uploads / storage-s3 / media features (all on by default).

Runnable version: the Storage + upload-guard snippets are copied from files_doc.rs (cargo test -p rustango --test files_doc); the end-to-end multipart save_uploads flow is dogfooded by the in-file tests in crates/rustango/src/uploads.rs, and the media library by media_sqlite_live.rs.

Table of contents

Step 1 — Pick a storage backend

Every backend implements the same Storage trait, so your code never names the concrete type — it holds a BoxedStorage (Arc<dyn Storage>):

use rustango::storage::{BoxedStorage, LocalStorage};
use std::path::PathBuf;
use std::sync::Arc;

let storage: BoxedStorage = Arc::new(LocalStorage::new(PathBuf::from("./uploads")));
BackendFeatureUse for
LocalStoragestoragesingle-server deployments — files on local disk
S3Storagestorage-s3production — S3 / R2 / B2 / MinIO object storage
InMemoryStoragestoragetests — a HashMap, never touches disk

Step 2 — Save, load, and serve files

The trait is four async methods, keyed by a string path. save writes bytes, load reads them back, plus exists / delete:

use rustango::storage::{Storage, InMemoryStorage};

let store = InMemoryStorage::new();
store.save("avatars/7.png", &png_bytes).await?;
assert!(store.exists("avatars/7.png").await?);
let bytes = store.load("avatars/7.png").await?;
store.delete("avatars/7.png").await?;

Serving the file. Attach a base URL (your CDN or static host) and url(key) builds the public address you store on the model and hand to the browser:

let store = LocalStorage::new("./uploads".into())
    .with_base_url("https://cdn.example.com/uploads");

store.url("docs/report.pdf");   // Some("https://cdn.example.com/uploads/docs/report.pdf")

Without a base URL, url() returns None — you'd stream the bytes through a handler instead. LocalStorage also guards against path traversal in keys.

Step 3 — Accept an upload

save_uploads consumes an axum Multipart body, validates each file against an UploadConfig, and writes the survivors to your Storage — streaming, so an oversize file is rejected mid-transfer instead of buffering into memory first.

use rustango::uploads::{save_uploads, UploadConfig};
use axum::extract::Multipart;

async fn upload(mp: Multipart) -> Result<impl IntoResponse, UploadError> {
    let cfg = UploadConfig::new("avatars/")          // key prefix
        .max_bytes(2 * 1024 * 1024)                  // reject files over 2 MiB
        .allowed_extensions(&["png", "jpg", "jpeg", "webp"])
        .randomize_filename(true);                   // avoid collisions

    let saved = save_uploads(mp, &cfg, &storage).await?;   // Vec<SavedUpload>
    Ok(Json(saved))
}

The guards are enforced (and verified): allowed_extensions is case-insensitive ("PNG" and "png" are the same), and max_bytes aborts the stream as soon as the size is exceeded. The in-file uploads tests drive real multipart bodies and assert files land in storage, oversize files are rejected, and disallowed extensions are refused.

let cfg = UploadConfig::new("avatars/").allowed_extensions(&["PNG", "Jpg"]);
assert!(cfg.allowed_extensions.contains("png"));   // normalized to lowercase
assert!(cfg.allowed_extensions.contains("jpg"));

Safe filenames

Never trust a client-supplied filename. sanitize_filename reduces it to a safe basename — stripping directory components (path traversal) and replacing unsafe characters:

use rustango::uploads::sanitize_filename;

sanitize_filename("../../etc/passwd");   // "passwd"   — no traversal
sanitize_filename("my photo!.png");      // "my_photo_.png"
sanitize_filename("");                    // "upload"   — never empty

save_uploads applies this for you; call it directly only if you build keys by hand.

Production: S3-compatible storage

For multi-server deployments, swap LocalStorage for S3Storage (behind the storage-s3 feature). It speaks the S3 API with a hand-rolled SigV4 signer, so it works with AWS S3, Cloudflare R2, Backblaze B2, and MinIO. The trait is identical — only the constructor changes:

use rustango::storage::s3::S3Storage;   // needs the `storage-s3` feature

let storage: BoxedStorage = Arc::new(
    S3Storage::new(/* bucket, region, endpoint, credentials */)
);
// save / load / delete / url — exactly the same calls as LocalStorage

Your handlers and models don't change; only the wiring at startup does.

The media library

When files are first-class records — tracked in the database, browsable in the admin, with thumbnails and CDN/presigned delivery — reach for rustango::media instead of raw Storage. MediaManager persists a Media row per file and supports two upload flows:

  • Server-side: manager.save_bytes(...) stores the bytes and the row in one call.
  • Direct-to-storage: manager.begin_upload(...) returns a presigned PUT URL the browser uploads to directly (your server never proxies the bytes), then you confirm the row.
use rustango::media::{Media, MediaManager};

let manager = MediaManager::new_pool(pool.clone(), registry);
// Hand the browser a short-lived download link:
let url = manager.presigned_get(&media, Duration::from_secs(3600)).await?;

It also handles soft-delete and orphan purging. The full flow is dogfooded in media_sqlite_live.rs; the manager's presigned/direct-upload methods are PostgreSQL-oriented.

Reference

Storage trait: save(key, &bytes) · load(key) · delete(key) · exists(key) · url(key) -> Option<String>.

UploadConfig: new(prefix) · .max_bytes(n) · .allowed_extensions(&[..]) (case-insensitive) · .randomize_filename(bool). Used by save_uploads(multipart, &cfg, &storage).

Backends: LocalStorage (disk) · S3Storage (object storage, storage-s3) · InMemoryStorage (tests). All return a BoxedStorage.

See also

  • The admin — media and FK widgets surface uploaded files in the UI.
  • Background jobs — resize/transcode an upload off the request.
  • Caching — the same swap-the-backend trait pattern.
  • Security guide — validating untrusted upload input.
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