xitca-postgres 0.4.0

mod connect;
mod connection;
mod execute;

pub use self::connect::Connect;
pub use self::connection::{CachedStatement, PoolConnection};

use core::num::NonZeroUsize;

use std::{collections::VecDeque, sync::Mutex};

use tokio::sync::Semaphore;

use super::{config::Config, error::Error};

use self::{
    connect::{ConnectorDyn, DefaultConnector},
    connection::PoolClient,
};

/// builder type for connection pool
pub struct PoolBuilder {
    config: Result<Config, Error>,
    capacity: usize,
    cache_size: usize,
    connector: Box<dyn ConnectorDyn>,
}

impl PoolBuilder {
    /// set capacity. pool would spawn up to amount of capacity concurrent connections to database.
    ///
    /// # Default
    /// capacity default to 1
    pub fn capacity(mut self, cap: usize) -> Self {
        self.capacity = cap;
        self
    }

    /// set statment cache size. every connection in pool would keep a set of prepared statement cache to
    /// speed up repeated query
    ///
    /// # Default
    /// cache_size default to 16
    pub fn cache_size(mut self, size: usize) -> Self {
        self.cache_size = size;
        self
    }

    /// set connector type for establishing connection to database. C must impl [`Connect`] trait
    pub fn connector<C>(mut self, connector: C) -> Self
    where
        C: Connect + 'static,
    {
        self.connector = Box::new(connector) as _;
        self
    }

    /// try convert builder to a connection pool instance.
    pub fn build(self) -> Result<Pool, Error> {
        let cfg = self.config?;
        let cache_size = NonZeroUsize::new(self.cache_size).ok_or_else(Error::todo)?;

        Ok(Pool {
            conn: Mutex::new(VecDeque::with_capacity(self.capacity)),
            permits: Semaphore::new(self.capacity),
            config: Box::new(PoolConfig {
                connector: self.connector,
                cfg,
                cache_size,
            }),
        })
    }
}

/// connection pool for a set of connections to database. Can be used as entry point of query
///
/// # Examples
/// ```rust
/// # use xitca_postgres::{Error, Execute};
/// # async fn query() -> Result<(), Error> {
/// let pool = xitca_postgres::pool::Pool::builder("db_url").build()?;
/// xitca_postgres::Statement::named("SELECT 1", &[]).bind_none().execute(&pool).await?;
/// # Ok(())
/// # }
/// ```
///
/// # Caching
/// When connection pool is used as executor through [`Execute::query`] and [`Execute::execute`] methods
/// it would prepare and cache statement for reuse. For selective caching consider use [`PoolConnection`]
///
/// [`Execute::query`]: crate::Execute::query
/// [`Execute::execute`]: crate::Execute::execute
pub struct Pool {
    conn: Mutex<VecDeque<PoolClient>>,
    permits: Semaphore,
    config: Box<PoolConfig>,
}

struct PoolConfig {
    connector: Box<dyn ConnectorDyn>,
    cfg: Config,
    cache_size: NonZeroUsize,
}

impl Pool {
    /// start a builder of pool where it's behavior can be configured.
    pub fn builder<C>(cfg: C) -> PoolBuilder
    where
        Config: TryFrom<C>,
        Error: From<<Config as TryFrom<C>>::Error>,
    {
        PoolBuilder {
            config: cfg.try_into().map_err(Into::into),
            capacity: 1,
            cache_size: 16,
            connector: Box::new(DefaultConnector),
        }
    }

    /// try to get a connection from pool.
    /// when pool is empty it will try to spawn new connection to database and if the process failed the outcome will
    /// return as [`Error`]
    pub async fn get(&self) -> Result<PoolConnection<'_>, Error> {
        let _permit = self.permits.acquire().await.expect("Semaphore must not be closed");

        let conn = match self.try_get() {
            Some(conn) => conn,
            None => self.connect().await?,
        };

        Ok(PoolConnection {
            pool: self,
            conn: Some(conn),
            _permit,
        })
    }

    /// get configration of current connection pool.
    pub fn config(&self) -> &Config {
        &self.config.cfg
    }

    fn try_get(&self) -> Option<PoolClient> {
        let mut inner = self.conn.lock().unwrap();

        while let Some(conn) = inner.pop_front() {
            if !conn.closed() {
                return Some(conn);
            }
        }

        None
    }

    #[cold]
    #[inline(never)]
    async fn connect(&self) -> Result<PoolClient, Error> {
        self.config
            .connector
            .connect_dyn(self.config.cfg.clone())
            .await
            .map(|cli| PoolClient::new(cli, self.config.cache_size))
    }
}

#[cfg(not(feature = "io-uring"))]
#[cfg(test)]
mod test {
    use crate::{execute::Execute, iter::AsyncLendingIterator, statement::Statement};

    use super::*;

    #[tokio::test]
    async fn pool() {
        let pool = Pool::builder("postgres://postgres:postgres@localhost:5432")
            .build()
            .unwrap();

        {
            let mut conn = pool.get().await.unwrap();

            let stmt = Statement::named("SELECT 1", &[]).execute(&mut conn).await.unwrap();
            stmt.execute(&conn.consume()).await.unwrap();

            let num = Statement::named("SELECT 1", &[])
                .bind_none()
                .query(&pool)
                .await
                .unwrap()
                .try_next()
                .await
                .unwrap()
                .unwrap()
                .get::<i32>(0);

            assert_eq!(num, 1);
        }

        let res = [
            Statement::named("SELECT 1", &[]).bind_none(),
            Statement::named("SELECT 1", &[]).bind_none(),
        ]
        .query(&pool)
        .await
        .unwrap();

        for mut res in res {
            let num = res.try_next().await.unwrap().unwrap().get::<i32>(0);
            assert_eq!(num, 1);
        }

        let _ = vec![
            Statement::named("SELECT 1", &[]).bind_dyn(&[&1]),
            Statement::named("SELECT 1", &[]).bind_dyn(&[&"123"]),
            Statement::named("SELECT 1", &[]).bind_dyn(&[&String::new()]),
        ]
        .query(&pool)
        .await;
    }
}