Memory serve

memory-serve enables fast static file serving for axum web applications, by keeping all assets in memory.

It loads static web assets like HTML, stylesheets, images and scripts into the rust binary at compile time and exposes them as an axum Router. It automatically adds cache headers and handles file compression.

During development (debug builds) files are served dynamically, they are read and compressed at request time.

Text-based files like HTML or javascript are compressed using brotli at compile time and decompressed at startup, to minimize the binary size.

All files are served with an etag header and If-None-Match requests are handled accordingly.

Text-based files are served in plain or with gzip or brotli compression based on the abilities and preferences of the client.

Routing can be configured in a flexible manner, for instance to accommodate an SPA.

Compatibility

memory-serve is designed to work with axum

Usage

There are two mechanisms to include assets at compile time.

1. Specify the path using a enviroment variable ASSET_DIR and call: MemoryServe::from_env() (best-practice)
2. Call the load_assets! macro, and pass this to the constructor: MemoryServe::new(load_assets!("/foo/bar"))

The environment variable is handled by a build script and instructs cargo to re-evaluate when an asset in the directory changes. The output of the macro might be cached between build.

Both options try to be smart in resolving absolute and relative paths.

When an instance of MemoryServe is created, we can bind these to your axum instance. Calling [MemoryServe::into_router()] on the MemoryServe instance produces an axum Router that can either be merged in another Router or used directly in a server by calling Router::into_make_service().

Named directories

Multiple directories can be included using different environment variables, all prefixed by ASSET_DIR_. For example: if you specify ASSET_DIR_FOO and ASSET_DIR_BAR the memory serve instances can be loaded using MemoryServe::from_env_name("FOO") and MemoryServe::from_env_name("BAR") respectively.

Features

Use the force-embed feature flag to always include assets in the binary - also in debug builds.

Environment variables

Use MEMORY_SERVE_ROOT to specify a root directory for relative paths provided to the load_assets! macro (or th ASSET_DIR variable).

Uee MEMORY_SERVE_QUIET=1 to not print log messages at compile time.

Example

use axum::{response::Html, routing::get, Router};
use memory_serve::{MemoryServe, load_assets};
use std::net::SocketAddr;

#[tokio::main]
async fn main() {
    let memory_router = MemoryServe::new(load_assets!("../static"))
        .index_file(Some("/index.html"))
        .into_router();

    // possible other routes can be added at this point, like API routes
    let app = Router::new()
        .merge(memory_router);

    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
    axum::serve(listener, app).await.unwrap();
}

Configuration options

An instance of the MemoryServe struct can be configured by calling the following configuration methods:

method	Default value	Description
[MemoryServe::index_file]	Some("/index.html")	Which file to serve on the route "/"
[MemoryServe::index_on_subdirectories]	false	Whether to serve the corresponding index in subdirectories
[MemoryServe::fallback]	None	Which file to serve if no routed matched the request
[MemoryServe::fallback_status]	StatusCode::NOT_FOUND	The HTTP status code to routes that did not match
[MemoryServe::enable_gzip]	true	Allow to serve gzip encoded files
[MemoryServe::enable_brotli]	true	Allow to serve brotli encoded files
[MemoryServe::html_cache_control]	CacheControl::Short	Cache control header to serve on HTML files
[MemoryServe::cache_control]	CacheControl::Medium	Cache control header to serve on other files
[MemoryServe::add_alias]	[]	Create a route / file alias
[MemoryServe::enable_clean_url]	false	Enable clean URLs

See Cache control for the cache control options.

Logging

During compilation, problems that occur with the inclusion or compression of assets are logged to stdout, for instance:

WARN skipping file "static/empty.txt": file empty

When running the resulting executable, all registered routes and asset sizes are logged using the tracing crate. To print or log them, use tracing-subscriber. Example output:

 INFO memory_serve: serving /assets/icon.jpg 1366 bytes
 INFO memory_serve: serving /assets/index.css 1552 bytes
 INFO memory_serve: serving /assets/index.css (brotli compressed) 509 bytes
 INFO memory_serve: serving /assets/index.css (gzip compressed) 624 bytes
 INFO memory_serve: serving /assets/index.js 20 bytes
 INFO memory_serve: serving /assets/stars.svg 2255 bytes
 INFO memory_serve: serving /assets/stars.svg (brotli compressed) 907 bytes
 INFO memory_serve: serving /assets/stars.svg (gzip compressed) 1048 bytes
 INFO memory_serve: serving /index.html 437 bytes
 INFO memory_serve: serving /index.html (brotli compressed) 178 bytes
 INFO memory_serve: serving /index.html (gzip compressed) 274 bytes
 INFO memory_serve: serving /index.html as index on /

Cache control

There are 5 different values to choose from for the cache-control settings:

Option	Description	Value
[CacheControl::Long]	clients can keep assets that have cache busting for a year	max-age=31536000, immutable
[CacheControl::Medium]	assets without cache busting are revalidated after a day and can be kept for a week	max-age=604800, stale-while-revalidate=86400
[CacheControl::Short]	cache kept for max 5 minutes, only at the client (not in a proxy)	max-age:300, private
[CacheControl::NoCache]	do not cache if freshness is really vital	no-cache
[CacheControl::Custom]	Custom value	user defined