How to use MongoDB with r2d2 and actix in rust

Question

I am trying to make a basic web application with the rust language, using the actix framework and r2d2 with mongodb as the database. I could not find any complete and working documentation on how to archive this. Maybe someone can help me out here.

The problem is, that i can't seem to get a mongodb connection from the r2d2 connection pool. Sadly this part isnt covered in any documentation i found.

Some links i found:

Using r2d2 with actix: https://github.com/actix/examples/blob/master/r2d2/src/main.rs
Using mongodb with r2d2: https://docs.rs/r2d2-mongodb/0.2.2/r2d2_mongodb/

This part creates the connection pool and hands it to actix.

fn main() {
    std::env::set_var("RUST_LOG", "actix_web=info");
    env_logger::init();

    let manager = MongodbConnectionManager::new(
        ConnectionOptions::builder()
            .with_host("localhost", 27017)
            .with_db("mydatabase")
            .build()
    );    

    let pool = Pool::builder()
        .max_size(16)
        .build(manager)
        .unwrap();

    HttpServer::new( move || {
        App::new()
            // enable logger
            .wrap(middleware::Logger::default())
            // store db pool in app state
            .data(pool.clone())
            // register simple handler, handle all methods
            .route("/view/{id}", web::get().to(view))
    })
    .bind("127.0.0.1:8080")
    .expect("Can not bind to port 8080")
    .run()
    .unwrap();
}

This is the handler function trying to access the connection pool

fn view(req: HttpRequest, 
        pool: web::Data<Pool<MongodbConnectionManager>>) -> impl Responder {

    let id = req.match_info().get("id").unwrap_or("unknown");
    let conn = pool.get().unwrap();
    let result = conn.collections("content").findOne(None, None).unwrap();

   // HERE BE CODE ...

    format!("Requested id: {}", &id)
}

This is the error showing my problem. The conn variable doesnt seem to be a propper mongodb connection.

error[E0599]: no method named `collections` found for type `std::result::Result<r2d2::PooledConnection<r2d2_mongodb::MongodbConnectionManager>, r2d2::Error>` in the current scope  --> src\main.rs:29:23
   |
29 |     let result = conn.collections("content").findOne(None, None).unwrap();
   |

Maybe you are just missing an `unwrap` (better: proper error handling)? `conn.unwrap().collections...` — hellow, Aug 06 '19 at 09:01
`No method named 'unwrap' found` Didnt help. Im pretty new to rust, i have to admit ;). Proper error handling and much more architecture would follow after this poc works. — ToBe, Aug 06 '19 at 09:04

score 2 · Accepted Answer · answered Aug 31 '19 at 16:31

2

10 |     let coll = conn.collection("simulations");
   |                     ^^^^^^^^^^
   |
   = help: items from traits can only be used if the trait is in scope
   = note: the following trait is implemented but not in scope, perhaps add a `use` for it:
           `use crate::mongodb::db::ThreadedDatabase;`

my compiler told me to add mongodb::db::ThreadedDatabase in scope.

answered Aug 31 '19 at 16:31

kuma

36
1

In my case, the compiler already seems to knopw what type `coll`is. Sadly it's not `ThreadedDatabase` but `r2d2::PooledConnection`. Adding the use didnt change that. – ToBe Sep 02 '19 at 09:38
1

Adding `use mongodb::db::ThreadedDatabase` worked fine for me :) My mongodb was newer and wanted `find_one` instead of `findOne`. @ToBe: it was also `collection` and not `collections` to get it working for me. – sigurdga Sep 06 '19 at 10:07
That was it, tnx! – ToBe Sep 09 '19 at 13:24

How to use MongoDB with r2d2 and actix in rust

1 Answers1