postgresql - 如何防止BB8连接在多次重复后断开

Question

我有一个应将共享连接池用于所有请求的应用程序。我观察到，在看似随机的时间，请求失败，错误类型为“已关闭”。我已将此行为隔离到以下示例中:

use lazy_static::lazy_static;

use bb8_postgres::bb8::Pool;
use bb8_postgres::PostgresConnectionManager;
use bb8_postgres::tokio_postgres::{NoTls, Client};

lazy_static! {
    static ref CONNECTION_POOL: Pool<PostgresConnectionManager<NoTls>> = {
        let manager = PostgresConnectionManager::new_from_stringlike("dbname=demodb host=localhost user=postgres", NoTls).unwrap();

        Pool::builder().build_unchecked(manager)
    };
}

fn main() {
    println!("Hello, world!");
}


#[cfg(test)]
mod test {
    use super::*;

    #[tokio::test]
    async fn much_insert_traffic() {
        much_traffic("INSERT INTO foo(a,b) VALUES (1, 2) RETURNING id").await
    }

    #[tokio::test]
    async fn much_select_traffic() {
        much_traffic("SELECT MAX(id) FROM foo").await
    }

    #[tokio::test]
    async fn much_update_traffic() {
        much_traffic("UPDATE foo SET a = 81 WHERE id = 1919 RETURNING b").await;
    }

    async fn much_traffic(stmt: &str) {
        let c = CONNECTION_POOL.get().await.expect("Get a connection");
        let client = &*c;

        for i in 0..10000i32 {
            let res = client.query_opt(stmt, &[]).await.expect(&format!("Perform repeat {} of {} ok", i, stmt));
        }
    }

}

执行测试时，> 50％的测试之一将在以后的迭代中失败，并且输出类似于以下内容:

Perform repeat 8782 of UPDATE foo SET a = 81 WHERE id = 1919 RETURNING b ok: Error { kind: Closed, cause: None } thread 'test::much_update_traffic' panicked at 'Perform repeat 8782 of UPDATE foo SET a = 81 WHERE id = 1919 RETURNING b ok: Error { kind: Closed, cause: None }', src\main.rs:44:23

Answer 1

事实证明，问题完全取决于[tokio::test]批注，每当执行测试时，批注就启动一个独特的运行时。使用这些运行时之一来初始化惰性静态，并且一旦该运行时关闭，池就会被销毁。只要生成测试仍在运行，其他测试(具有不同的运行时)就可以使用该值，但是一旦关闭，它就会处于无效状态。