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lifecycle.md

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Lifecycle Design

There are mainly many types of resources involved in the project that need to be managed, including loop, request, and handle.

Besides the objects related to libuv, the relevant resources also contain objects for C++ features, and the relevant data is stored in the member data.

Loop

Following is the life states of loop.

stateDiagram-v2
    direction LR

    [*] --> Suspend
    Suspend --> Running: run
    Suspend --> [*]: close
    Running --> Suspend
    Running --> [*]: close

    classDef attached color:#67C23A;
    classDef detached stroke:red,color:#F56C6C;

    class Suspend attached
    class Running attached
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  • Suspend[attached]: Context data allocated. uv_loop_init applied.

  • Running[attached]: Loop running.

  • run: Run the loop.

  • close: Close the loop.

The context data will be allocated and released with uv_loop_t.

Note: object cannot be used after close.

Request

Following is the life states of request.

stateDiagram-v2
    direction LR

    [*] --> Hanging
    Hanging --> Waiting: request
    Waiting --> Dealing: response
    Dealing --> Waiting: request
    Dealing --> Hanging

    classDef attached color:#67C23A;
    classDef detached stroke:red,color:#F56C6C;

    class Hanging attached
    class Waiting attached
    class Dealing attached
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  • Hanging[attached]: Request object initialized.

  • Waiting[attached]: Context data allocated. Request method applied, waiting callback in loop event.

  • Dealing[attached]: Previous context data is about to be released. The request callback is being processed.

  • request: New context data. Call request method, such as fs::open, random and tcp::connect.

  • response: Release previous context data. resolve the request's promise.

Resources will be properly recycled in all states.
However, it should be noted that request operations can only be performed in the Hanging and Dealing states.

Handle

Following is the life states of handle.

stateDiagram-v2
    direction LR

    [*] --> Allocated: set_data
    Allocated --> Suspend: init
    Suspend --> Running: start
    Suspend --> [*]: close
    Running --> Suspend: stop
    Running --> [*]: close
    Running --> Detached: detach
    Detached --> [*]: close

    classDef attached color:#67C23A;
    classDef detached stroke:red,color:#F56C6C;

    class Allocated attached
    class Suspend attached
    class Running attached
    class Detached detached
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  • Allocated[attached]: Context data allocated but libuv's handle no initialized yet.

  • Suspend[attached]: Handle initialized but not running.

  • Running[attached]: Handle is running.

  • Detached[detached]: Handle detached. It must be explicitly closed manually.

  • set_data: New context data and set handle->data.

  • init: Initialize handle with uv_<handle>_init.

  • start: Start callback operations, such as start for timer, listen for tcp, and read_start for stream.

  • stop: Stop callback operations, but not close handle. such as stop for timer.

  • close: Close handle. Release context data and reset handle->data.

  • detach: Detach handle. It must be explicitly closed manually.

If the handle is in the attached state, resources will be automatically recycled when the handle is no longer referenced.

If the handle is in the detached state, resources will not be automatically recycled. Users need to explicitly call close or throw uvcxx::close_handle in the handle callback.

Note: object cannot be used after close.