Lib.rs

Salvo is a web server framework written in Rust.

🎯 Features

• Base on hyper, tokio and async supported;
• Websocket supported;
• Middleware is handler and support executed before or after handle;
• Easy to use routing system, routers can be nested, and you can add middlewares on any routers;
• Multipart form supported, handle files upload is very simple;
• Serve a static virtual directory from many physical directories;

⚡️ Quick start

You can view samples here or read docs here.

Create a new rust project:

cargo new hello_salvo --bin

Add this to Cargo.toml

[dependencies]
salvo = { version = "0.11", features = ["full"] }
tokio = { version = "1.5", features = ["full"] }

Create a simple function handler in the main.rs file, we call it hello_world, this function just render plain text "Hello World".

use salvo::prelude::*;

#[fn_handler]
async fn hello_world(_req: &mut Request, _depot: &mut Depot, res: &mut Response) {
    res.render_plain_text("Hello World");
}

There are many ways to write function handler.

• You can omit function arguments if they do not used, like _req, _depot in this example:

  #[fn_handler]
  async fn hello_world(res: &mut Response) {
      res.render_plain_text("Hello World");
  }
  

• Any type can be function handler's return value if it implements Writer. For example &str implements Writer and it will render string as plain text:

  #[fn_handler]
  async fn hello_world(res: &mut Response) -> &'static str {// just return &str
      "Hello World"
  }
  

• The more common situation is we want to return a Result<T, E> to implify error handling. If T and E implements Writer, Result<T, E> can be function handler's return type:

  #[fn_handler]
  async fn hello_world(res: &mut Response) -> Result<&'static str, ()> {// return Result
      Ok("Hello World")
  }
  

In the main function, we need to create a root Router first, and then create a server and call it's bind function:

use salvo::prelude::*;

#[fn_handler]
async fn hello_world() -> &'static str {
    "Hello World"
}
#[tokio::main]
async fn main() {
    let router = Router::new().get(hello_world);
    let server = Server::new(router);
    server.bind(([0, 0, 0, 0], 7878)).await;
}

Middleware

There is no difference between Handler and Middleware, Middleware is just Handler.

Tree-like routing system

Normally we write routing like this：

Router::new().path("articles").get(list_articles).post(create_article);
Router::new()
    .path("articles/<id>")
    .get(show_article)
    .patch(edit_article)
    .delete(delete_article);

Often viewing articles and article lists does not require user login, but creating, editing, deleting articles, etc. require user login authentication permissions. The tree-like routing system in Salvo can meet this demand. We can write routers without user login together:

Router::new()
    .path("articles")
    .get(list_articles)
    .push(Router::new().path("<id>").get(show_article));

Then write the routers that require the user to login together, and use the corresponding middleware to verify whether the user is logged in:

Router::new()
    .path("articles")
    .before(auth_check)
    .post(list_articles)
    .push(Router::new().path("<id>").patch(edit_article).delete(delete_article));

Although these two routes have the same path("articles"), they can still be added to the same parent route at the same time, so the final route looks like this:

Router::new()
    .push(
        Router::new()
            .path("articles")
            .get(list_articles)
            .push(Router::new().path("<id>").get(show_article)),
    )
    .push(
        Router::new()
            .path("articles")
            .before(auth_check)
            .post(list_articles)
            .push(Router::new().path("<id>").patch(edit_article).delete(delete_article)),
    );

<id> matches a fragment in the path, under normal circumstances, the article id is just a number, which we can use regular expressions to restrict id matching rules, r"<id:/\d+/>".

For numeric characters there is an easier way to use <id:num>, the specific writing is:

• <id:num>, matches any number of numeric characters;
• <id:num[10]>, only matches a certain number of numeric characters, where 10 means that the match only matches 10 numeric characters;
• <id:num(..10)>, means matching 1 to 9 numeric characters;
• <id:num(3..10)>, means matching 3 to 9 numeric characters;
• <id:num(..=10)>, means matching 1 to 10 numeric characters;
• <id:num(3..=10)>, means match 3 to 10 numeric characters;
• <id:num(10..)>, means to match at least 10 numeric characters.

You can also use <*> or <**> to match all remaining path fragments. In order to make the code more readable, you can also add appropriate name to make the path semantics more clear, for example: <**file_path>.

It is allowed to combine multiple expressions to match the same path segment, such as /articles/article_<id:num>/.

File upload

We can get file async by the function get_file in Request:

#[fn_handler]
async fn upload(req: &mut Request, res: &mut Response) {
    let file = req.get_file("file").await;
    if let Some(file) = file {
        let dest = format!("temp/{}", file.filename().unwrap_or_else(|| "file".into()));
        if let Err(e) = tokio::fs::copy(&file.path, Path::new(&dest)).await {
            res.set_status_code(StatusCode::INTERNAL_SERVER_ERROR);
        } else {
            res.render_plain_text("Ok");
        }
    } else {
        res.set_status_code(StatusCode::BAD_REQUEST);
    }
}

Multiple files also very simple:

#[fn_handler]
async fn upload(req: &mut Request, res: &mut Response) {
    let files = req.get_files("files").await;
    if let Some(files) = files {
        let mut msgs = Vec::with_capacity(files.len());
        for file in files {
            let dest = format!("temp/{}", file.filename().unwrap_or_else(|| "file".into()));
            if let Err(e) = tokio::fs::copy(&file.path, Path::new(&dest)).await {
                res.set_status_code(StatusCode::INTERNAL_SERVER_ERROR);
                res.render_plain_text(&format!("file not found in request: {}", e.to_string()));
            } else {
                msgs.push(dest);
            }
        }
        res.render_plain_text(&format!("Files uploaded:\n\n{}", msgs.join("\n")));
    } else {
        res.set_status_code(StatusCode::BAD_REQUEST);
        res.render_plain_text("file not found in request");
    }
}

More Examples

Your can find more examples in examples folder:

• basic_auth.rs
• compression.rs
• custom_error_page.rs
• custom_filter.rs
• file_list.rs
• handle_error.rs
• proxy.rs
• remote_addr.rs
• routing.rs
• size_limiter.rs
• sse_chat.rs
• sse.rs
• tls.rs
• todos.rs
• unix_socket.rs
• ws_chat.rs
• ws.rs

You can run these examples with the following command:

cargo run --example basic_auth

You can use any example name you want to run instead of basic_auth here.

Some code and examples port from warp, multipart-async, mime-multipart and actix-web.

Performance

Benchmark testing result can be found from here:

https://web-frameworks-benchmark.netlify.app/result?l=rust

https://www.techempower.com/benchmarks/#section=test&runid=e81c66ad-1e37-4f2c-9e25-bcc79796fab8&hw=ph&test=plaintext&l=zik0zj-e6&a=2

Contributing

Contributions are absolutely, positively welcome and encouraged! Contributions come in many forms. You could:

• Submit a feature request or bug report as an issue;
• Comment on issues that require feedback;
• Contribute code via pull requests;
• Publish Salvo-related technical articles on blogs or technical platforms。

All pull requests are code reviewed and tested by the CI. Note that unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Salvo by you shall be dual licensed under the MIT License, without any additional terms or conditions.

☕ Supporters

Salvo is an open source project. If you want to support Salvo, you can ☕ buy a coffee here.

⚠️ License

Salvo is licensed under MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT).