pub trait Poolable:
Send
+ Sized
+ 'static {
type Manager: ManageConnection<Connection = Self>;
type Error;
// Required method
fn pool(
config: DatabaseConfig<'_>,
) -> Result<Pool<Self::Manager>, Self::Error>;
}Expand description
Trait implemented by r2d2-based database adapters.
§Provided Implementations
Implementations of Poolable are provided for the following types:
diesel::MysqlConnectiondiesel::PgConnectiondiesel::SqliteConnectionpostgres::Connectionmysql::Connrusqlite::Connectionrusted_cypher::GraphClientredis::Connection
§Implementation Guide
As a r2d2-compatible database (or other resource) adapter provider,
implementing Poolable in your own library will enable Rocket users to
consume your adapter with its built-in connection pooling support.
§Example
Consider a library foo with the following types:
foo::ConnectionManager, which implementsr2d2::ManageConnectionfoo::Connection, theConnectionassociated type offoo::ConnectionManagerfoo::Error, errors resulting from manager instantiation
In order for Rocket to generate the required code to automatically provision
a r2d2 connection pool into application state, the Poolable trait needs to
be implemented for the connection type. The following example implements
Poolable for foo::Connection:
use rocket_contrib::databases::{r2d2, DbError, DatabaseConfig, Poolable};
impl Poolable for foo::Connection {
type Manager = foo::ConnectionManager;
type Error = DbError<foo::Error>;
fn pool(config: DatabaseConfig) -> Result<r2d2::Pool<Self::Manager>, Self::Error> {
let manager = foo::ConnectionManager::new(config.url)
.map_err(DbError::Custom)?;
r2d2::Pool::builder()
.max_size(config.pool_size)
.build(manager)
.map_err(DbError::PoolError)
}
}In this example, ConnectionManager::new() method returns a foo::Error on
failure. For convenience, the DbError enum is used to consolidate this
error type and the r2d2::Error type that can result from
r2d2::Pool::builder().
In the event that a connection manager isn’t fallible (as is the case with
Diesel’s r2d2 connection manager, for instance), the associated error type
for the Poolable implementation can simply be r2d2::Error as this is the
only error that can be result. For more concrete example, consult Rocket’s
existing implementations of Poolable.
Required Associated Types§
Sourcetype Manager: ManageConnection<Connection = Self>
type Manager: ManageConnection<Connection = Self>
The associated connection manager for the given connection type.
Required Methods§
Dyn Compatibility§
This trait is not dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.