Skip to content

Bindings for writing a server that can act as MySQL/MariaDB

License

Notifications You must be signed in to change notification settings

databendlabs/msql-srv

 
 

Repository files navigation

msql-srv-rs

Crates.io Documentation Codecov Dependency status Maintenance

Bindings for emulating a MySQL/MariaDB server.

When developing new databases or caching layers, it can be immensely useful to test your system using existing applications. However, this often requires significant work modifying applications to use your database over the existing ones. This crate solves that problem by acting as a MySQL server, and delegating operations such as querying and query execution to user-defined logic.

To start, implement MysqlShim for your backend, and create a MysqlIntermediary over an instance of your backend and a connection stream. The appropriate methods will be called on your backend whenever a client issues a QUERY, PREPARE, or EXECUTE command, and you will have a chance to respond appropriately. For example, to write a shim that always responds to all commands with a "no results" reply:

extern crate mysql;
use msql_srv::*;
use mysql::prelude::*;

struct Backend;
impl<W: io::Write> MysqlShim<W> for Backend {
    type Error = io::Error;

    fn on_prepare(&mut self, _: &str, info: StatementMetaWriter<W>) -> io::Result<()> {
        info.reply(42, &[], &[])
    }
    fn on_execute(
        &mut self,
        _: u32,
        _: ParamParser,
        results: QueryResultWriter<W>,
    ) -> io::Result<()> {
        results.completed(0, 0)
    }
    fn on_close(&mut self, _: u32) {}

    fn on_init(&mut self, _: &str, writer: InitWriter<W>) -> io::Result<()> { Ok(()) }

    fn on_query(&mut self, _: &str, results: QueryResultWriter<W>) -> io::Result<()> {
        let cols = [
            Column {
                table: "foo".to_string(),
                column: "a".to_string(),
                coltype: ColumnType::MYSQL_TYPE_LONGLONG,
                colflags: ColumnFlags::empty(),
            },
            Column {
                table: "foo".to_string(),
                column: "b".to_string(),
                coltype: ColumnType::MYSQL_TYPE_STRING,
                colflags: ColumnFlags::empty(),
            },
        ];

        let mut rw = results.start(&cols)?;
        rw.write_col(42)?;
        rw.write_col("b's value")?;
        rw.finish()
    }
}

fn main() {
    let listener = net::TcpListener::bind("127.0.0.1:0").unwrap();
    let port = listener.local_addr().unwrap().port();

    let jh = thread::spawn(move || {
        if let Ok((s, _)) = listener.accept() {
            MysqlIntermediary::run_on_tcp(Backend, s).unwrap();
        }
    });

    let mut db = mysql::Conn::new(&format!("mysql://127.0.0.1:{}", port)).unwrap();
    assert_eq!(db.ping(), true);
    assert_eq!(db.query_iter("SELECT a, b FROM foo").unwrap().count(), 1);
    drop(db);
    jh.join().unwrap();
}

About

Bindings for writing a server that can act as MySQL/MariaDB

Resources

License

Code of conduct

Security policy

Stars

Watchers

Forks

Releases

No releases published

Packages

No packages published

Languages

  • Rust 100.0%