Our example needs three functions. The first function, add_session, adds an association between the token and user ID:

fn add_session(conn: &Connection, token: &str, uid: &str) -> Result<(), RedisError> {
    conn.hset(SESSIONS, token, uid)
}

This function only calls the hset method of a Connection and sets the uid value by the token key in the SESSIONS map. It returns RedisError if something is wrong with a set operation.

The next function, remove_session, is also pretty simple and calls the hdel method of Connection:

fn remove_session(conn: &Connection, token: &str) -> Result<(), RedisError> {
    conn.hdel(SESSIONS, token)
}

This function deletes a record with the token key from the SESSIONS map.

The last function, list_sessions, returns all token-uid pairs as a HashMap instance from the SESSION map. It uses the hgetall method of Connection, which calls the HGETALL method in Redis:

fn list_sessions(conn: &Connection) -> Result<HashMap<String, String>, RedisError> {
     conn.hgetall(SESSIONS)
}

As you can see, all functions map to raw Redis commands, which looks pretty simple. But all functions do a good job in the background too, converting values to their corresponding Rust types.

Now, we can create an arguments parser for the session tool.