```mermaid
classDiagram
    class LogLevel {
        <<enumeration>>
        DEBUG
        INFO
        WARNING
        ERROR
        FATAL
    }

    class LogRecord {
        +DateTime timestamp
        +LogLevel level
        +String message
        +String target
    }

    class LogOutput {
        <<interface>>
        +write(record: LogRecord) Future
    }

    class ConsoleOutput {
        +write(record: LogRecord)
    }

    class PostgresOutput {
        -PgPool pool
        +new(pool: PgPool)
        +write(record: LogRecord)
    }

    class FileOutput {
        -File file
        +write(record: LogRecord)
    }

    class LoggerConfig {
        +LogLevel min_level
        +Vec~Box~LogOutput~~ outputs
    }

    class Logger {
        -Sender~LogRecord~ tx
        -LogLevel min_level
        +init(config: LoggerConfig) Arc~Logger~
        +log(level, message, target)
        -run_background_task(rx, outputs)
    }

    %% Relationships
    LogOutput <|.. ConsoleOutput : Implements
    LogOutput <|.. PostgresOutput : Implements
    LogOutput <|.. FileOutput : Implements
    
    Logger ..> LogRecord : Creates
    Logger o-- LoggerConfig : Uses
    LoggerConfig o-- LogOutput : Aggregates (0..*)
    LogRecord -- LogLevel : Has
```

```mermaid
classDiagram
    %% 接口定义：强调 Send + Sync 约束
    class LogOutput {
        <<interface>>
        <<Send + Sync>>
        +write(record: LogRecord) Future
    }

    %% 具体实现
    class PostgresOutput {
        -PgPool pool
        +write(record)
    }
    class ConsoleOutput {
        +write(record)
    }

    %% 业务线程持有的 Logger (Producer)
    class Logger {
        <<Thread-Safe>>
        <<Shared via Arc>>
        -mpsc::Sender~LogRecord~ tx
        -LogLevel min_level
        +log(level, msg)
    }

    %% 后台异步任务 (Consumer)
    class BackgroundWorker {
        <<Active Object>>
        <<Running in tokio::spawn>>
        -mpsc::Receiver~LogRecord~ rx
        -Vec~Box~LogOutput~~ outputs
        +run()
    }

    %% 数据包
    class LogRecord {
        <<Immutable>>
        +timestamp
        +level
        +message
    }

    %% 关系描述
    LogOutput <|.. PostgresOutput
    LogOutput <|.. ConsoleOutput
    
    %% 关键的线程安全机制：MPSC Channel
    Logger "1" o-- "1" `mpsc::Sender` : Owns
    BackgroundWorker "1" o-- "1" `mpsc::Receiver` : Owns
    
    %% 逻辑流
    ClientThread ..> Logger : 1. Calls log() (Non-blocking)
    Logger ..> `mpsc::Sender` : 2. Sends Record
    `mpsc::Sender` ..> `mpsc::Receiver` : 3. Channel Transfer (Thread-Safe)
    `mpsc::Receiver` ..> BackgroundWorker : 4. Receives Record
    BackgroundWorker --> LogOutput : 5. Serialized Writes
```

```text
my-logger/
├── Cargo.toml
├── .env                # 数据库配置
├── src/
│   ├── lib.rs          # 库入口，定义宏
│   ├── model.rs        # 定义 LogLevel, LogRecord
│   ├── outputs/        # 输出模块
│   │   ├── mod.rs      # Trait 定义
│   │   ├── console.rs  # 控制台输出实现
│   │   └── postgres.rs # 数据库输出实现
│   ├── core.rs         # Logger 核心逻辑 (Channel, Spawn)
│   └── main.rs         # 模拟业务服务使用
```