Cannot start a runtime from within a runtime.

[sagarnayak]

Api call -

use rocket::serde::json::Json;
use rocket::State;

use crate::core::database::db_pool::DbPool;
use crate::model::status_message::StatusMessage;
use crate::model::user::User;

#[get("/getUsersFromDatabase")]
pub fn get_all_user(db_pool: &State<DbPool>) -> Result<Json<Vec<User>>, Json<StatusMessage>> {
	let mut db = db_pool.database.get().unwrap();

	let statement = db.prepare(
		"SELECT * FROM users"
	);

	match statement {
		Err(_) => {
			return Err(
				Json(
					StatusMessage {
						code: 400,
						message: "test error".to_string(),
					}
				)
			);
		}
		_ => {}
	}

	let result_for_users = db.query(&statement.unwrap(), &[]);

	match result_for_users {
		Err(_) => {
			return Err(
				Json(
					StatusMessage {
						code: 400,
						message: "test error".to_string(),
					}
				)
			);
		}
		_ => {}
	}

	Ok(
		Json(
			vec![
				User {
					name: "test user".to_string()
				}
			]
		)
	)
}

db pool creation code -

use postgres::NoTls;
use r2d2_postgres::PostgresConnectionManager;
use r2d2_postgres::r2d2::Pool;

use crate::config_controller::ConfigData;
use crate::core::database::db_pool::DbPool;

fn get_pool() -> Pool<PostgresConnectionManager<NoTls>> {
	let config = ConfigData::new().expect("Failed to get config data");
	let database = config.database;

	let host = database.host;
	let port = database.port;
	let user = database.user;
	let password = database.password;
	let pool_size = database.pool_size;

	let manager = PostgresConnectionManager::new(
		format!("host={} port={} user={} password={}", host, port, user, password).parse().unwrap(),
		NoTls,
	);

	println!("created database manager");

	Pool::builder().max_size(pool_size).build(manager).unwrap()
}

pub fn get_db_pools() -> DbPool {
	DbPool {
		database: get_pool()
	}
}

I am getting this error when i call the above end point -

   >> Matched: (get_all_user) GET /getUsersFromDatabase
thread 'rocket-worker-thread' panicked at 'Cannot start a runtime from within a runtime. This happens because a function (like `block_on`) attempted to block the current thread while the thread is being used to drive asynchronous tasks.', C:\Users\SAGAR\.cargo\registry\src\github.com-1ecc6299db9ec823\tokio-1.8.1\src\runtime\enter.rs:39:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'rocket-worker-thread' panicked at 'Cannot start a runtime from within a runtime. This happens because a function (like `block_on`) attempted to block the current thread while the thread is being used to drive asynchronous tasks.', C:\Users\SAGAR\.cargo\registry\src\github.com-1ecc6299db9ec823\tokio-1.8.1\src\runtime\enter.rs:39:9

Please do suggest what am I missing.

[jebrosen]

Since 0.5, Rocket uses Rust's async/await programming with Futures.

For postgres, you should prefer either the existing support for postgres via rocket_sync_db_pools, which makes the non-async postgres API usable from async code, or use an async-first database connection pool such as deadpool-postgres instead of r2d2. #1117 is the tracking issue for making an async equivalent for rocket_sync_db_pools.

[sagarnayak]

Hi, any recent example of using rocket with Postgres without any ORM. I am new to rust and unable to find any recent example.

[jebrosen]

We don't currently provide such an example in this repository, but it's fairly simple to do with deadpool-postgres or other crates. https://www.reddit.com/r/rust/comments/e9n6mx/creating_and_using_a_postgres_database_pool_is/ demonstrates the overall approach - initialize a connection Pool and put into managed state, and retrieve connections in routes or request guards as needed.

[sweihub]

Found a solution here
https://stackoverflow.com/a/62536772/2258077