rget (Resilient Get) 🛡️

A standalone, stateful, self-healing downloader for harsh environments.

面向受限与恶劣网络环境的无依赖、有状态、自愈系下载工具。

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📖 Overview (简介)

rget is designed for environments where dependencies like jq or python are missing (e.g., Kubernetes Init Containers, GKE COS, Alpine) and network reliability is not guaranteed.

It implements a Stateful Waterfall Strategy to ensure the file is downloaded, no matter what:

rget 专为缺乏 jq 或 python 等依赖的受限环境（如 Kubernetes Init Containers, GKE COS, Alpine）设计。针对不稳定的网络环境，它实现了一套有状态的瀑布流策略，以确保文件下载成功率最大化。

🌊 The Waterfall Logic (核心逻辑)

graph TD
    Start[Start] --> CheckState{State Exists?}
    CheckState -- Yes --> ReadHistory[Read Last Success URL]
    CheckState -- No --> Dynamic[Strategy A: Dynamic Resolution]
    
    ReadHistory --> Dynamic
    
    Dynamic -- Success --> DownloadA[Download & Verify]
    Dynamic -- Fail --> History[Strategy B: History Replay]
    
    History -- Success --> DownloadB[Download & Verify]
    History -- Fail --> Fallback[Strategy C: Hard Fallback]
    
    Fallback -- Success --> DownloadC[Download & Verify]
    Fallback -- Fail --> Fatal[Exit 1]
    
    DownloadA --> UpdateState[Update State File]
    DownloadB --> UpdateState
    DownloadC --> UpdateState

    UpdateState --> Exit[Exit 0]

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Dynamic Resolution (最新策略): Tries to fetch the latest version via a command pipeline. History Replay (历史回放): If dynamic fails, retries the URL that worked last time (from state file). Hard Fallback (硬兜底): If all else fails, uses a hardcoded stable URL.

✨ Key Features (特性)

Zero Dependency (零依赖): Pure Bash. Only needs curl OR wget, and standard text tools (grep, sed, awk). Stateful Persistence (状态持久化): Supports custom state file paths via CLI or Env Var, enabling persistence across Pod restarts. Idempotency (幂等性): If the file exists and matches the provided SHA256, it skips downloading to save bandwidth. Non-Interactive (静默模式): Designed for automation. Logs to stderr, exits 0 or 1.

🚀 Usage (使用方法)

Interface

Bash

./rget.sh [OPTIONS] <TARGET_PATH>

Option Description 说明 --name Required. Unique key for the state file. 必填。状态文件中的唯一标识键。 --dynamic-cmd Shell pipeline to fetch the latest URL. 用于获取最新 URL 的 Shell 命令管道。 --fallback-url Stable backup URL. 稳定的兜底 URL。 --manual-url Force download from this URL (Bypass all). 强制指定 URL（跳过所有策略）。 --hash Expected hash for verification. 期望的 SHA256 哈希值（用于校验）。 --state-file Custom path to state file (Default: ~/.rget.state). 自定义状态文件路径。

Environment Variables (环境变量)

You can also configure the state file location globally: 你也可以通过环境变量全局配置状态文件位置： RGET_STATE_FILE: Overrides the default location (Same effect as --state-file).

🔥 Examples (实战示例)

1. GKE/Kubernetes Scenario (GKE 场景)

Downloading a WasmEdge shim in a GKE Init Container. Crucial: Note the use of --state-file (or RGET_STATE_FILE) pointing to a host-mounted directory (/node/...). This ensures the tool "remembers" successful URLs even if the Pod is recreated. 在 GKE 初始化容器中下载 WasmEdge shim。 关键点： 注意使用了 --state-file 指向宿主机挂载目录 (/node/...)。这确保了即使 Pod 重建，工具依然能“记住”成功的 URL。

Bash

Using CLI Option

./rget.sh
--name "wasm-shim"
--state-file "/node/home/kubernetes/bin/rget.state"
--dynamic-cmd "curl -s https://api.github.com/repos/containerd/runwasi/releases/latest | grep browser_download_url | grep musl | cut -d '"' -f 4 | head -n1"
--fallback-url "https://github.com/containerd/runwasi/releases/download/containerd-shim-wasmedge/v0.6.0/containerd-shim-wasmedge-x86_64-linux-musl.tar.gz"
--hash "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
/home/kubernetes/bin/shim.tar.gz

2. Manual Override (手动强制模式)

Bash

./rget.sh
--name "wasm-shim"
--manual-url "https://example.com/stable/shim.tar.gz"
/tmp/shim.tar.gz

🛠️ Testing (测试)

The repository includes a mock test suite covering dynamic resolution, fallback logic, and custom state paths. 仓库包含一个模拟测试套件，覆盖了动态解析、兜底逻辑以及自定义状态路径测试。

Bash

bash ./test.sh

⚖️ License

MIT License. Order out of Chaos.