我有一个与远程服务器通信的Tokio客户端，并且应该永久保持连接活动状态。我已经实现了初始身份验证握手，发现当我的测试终止时，我得到了一个奇怪的恐慌：
---- test_connect_without_database stdout ----
thread 'test_connect_without_database' panicked at 'Cannot drop a runtime in a context where blocking is not allowed. This happens when a runtime is dropped from within an asynchronous context.', /playground/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.3.5/src/runtime/blocking/shutdown.rs:51:21
我对可能导致这种情况的原因感到绝对不知所措，所以我不知道要为上下文添加哪些其他代码。
这是我的最小可重现示例(游乐场)：
use std::cell::RefCell;
use std::net::{IpAddr, SocketAddr};
use tokio::net::TcpStream;
use tokio::prelude::*;
use tokio::runtime;
#[derive(PartialEq, Debug)]
pub struct Configuration {
/// Database username.
username: String,
/// Database password.
password: String,
/// Database name.
db_name: String,
/// IP address for the remove server.
address: IpAddr,
/// Remote server port.
port: u16,
/// Number of connections to open.
connections: u16,
}
impl Configuration {
pub fn new(
username: &str,
password: &str,
db_name: &str,
address: &str,
port: u16,
connections: u16,
) -> Result<Configuration, Box<dyn std::error::Error>> {
let address = address.to_string().parse()?;
let configuration = Configuration {
username: username.to_string(),
password: password.to_string(),
db_name: db_name.to_string(),
address,
port,
connections,
};
Ok(configuration)
}
pub fn socket(&self) -> SocketAddr {
SocketAddr::new(self.address, self.port)
}
}
#[derive(Debug)]
pub struct Session {
configuration: Configuration,
runtime: RefCell<runtime::Runtime>,
}
impl Session {
fn new(config: Configuration) -> Result<Session, io::Error> {
let runtime = runtime::Builder::new_multi_thread()
.worker_threads(6)
.enable_all()
.build()?;
let session = Session {
configuration: config,
runtime: RefCell::new(runtime),
};
Ok(session)
}
fn configuration(&self) -> &Configuration {
&self.configuration
}
}
#[derive(Debug)]
pub(crate) struct Connection<'a> {
/// Socket uses to read and write from.
session: &'a Session,
/// Connection to the remote server.
stream: TcpStream,
/// Flag that indicates whether the connection is live.
live: bool,
}
impl<'a> Connection<'a> {
async fn new(session: &Session) -> Result<Connection<'_>, Box<dyn std::error::Error>> {
let mut stream = TcpStream::connect(session.configuration().socket()).await?;
let conn = Connection {
session,
stream,
live: true,
};
Ok(conn)
}
fn live(&self) -> bool {
self.live
}
}
#[tokio::test]
async fn test_connect_without_database() -> Result<(), Box<dyn std::error::Error>> {
let config = Configuration::new("rust", "", "", "127.0.0.1", 2345, 2).unwrap();
let session = Session::new(config).unwrap();
let conn = Connection::new(&session).await?;
assert!(conn.live());
Ok(())
}
fn main() {
println!("{}", 65u8 as char)
}
正如错误消息所述：
当从异步上下文中删除运行时时，会发生这种情况
您已经创建了嵌套运行时：
- 从
tokio::test - 从
runtime::Builder::new_multi_thread
第二个运行时由Session拥有，该运行时在异步测试结束时被删除。您可以通过使用以下mem::forget跳过析构函数来观察这一点：
#[tokio::test]
async fn test_connect_without_database() -> Result<(), Box<dyn std::error::Error>> {
let config = Configuration::new("rust", "", "", "127.0.0.1", 2345, 2).unwrap();
let session = Session::new(config).unwrap();
// Note that the assert was removed!
std::mem::forget(session);
Ok(())
}
不要生成嵌套运行时，也不要从一个运行时中删除另一个运行时。
另请参阅：
- 如何在另一个 Tokio 运行时内创建 Tokio 运行时而不会收到错误"无法从运行时内启动运行时"？
- "尝试使用 Tokio 实现嵌套并发时无法递归调用'核心'">
- 如何在稳定的 Rust 中同步返回在异步 Future 中计算的值？
尝试：cargo run --release而不是cargo run
https://dev.to/scyart/comment/1f88p