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Root `make check` only ever ran the frontend, so the "main is always green" policy was satisfied vacuously: the Go backend could be entirely broken and the root gate stayed green. - The backend moves onto scripts-to-rule-them-all. Its test, lint, fmt, fmt-check, build, run and clean implementations now live in `backend/script/`, and `backend/Makefile` is thin shims. The backend is its own project (own module, README, LICENSE, linter config, Dockerfile stage), and `Dockerfile.backend` only copies `backend/` into its builder, so its scripts have to live under `backend/`. - The root `script/test`, `script/lint`, `script/fmt` and `script/fmt-check` now run the frontend step and then the matching `backend/script/*` step, so `script/check` — and therefore the pre-commit hook — gates both halves. The frontend-only steps moved into `script/frontend-*` so nothing is duplicated. - `script/bootstrap` now provisions the backend's toolchain as well, because widening the gate without widening bootstrap left the documented fresh-clone path (`make setup`) installing a pre-commit hook that rejected every commit with `golangci-lint: not found`. Go is reused when the installed version is new enough, otherwise it is installed from the official `go1.25.7` release archive; golangci-lint is installed at exactly `2.7.2`, the version `Dockerfile.backend` pins, so local findings match CI. Both come from a specific release archive whose sha256 is hardcoded here and verified before anything is unpacked — never an install script piped to a shell — and both are symlinked onto `PATH`, since nvm-style activation does not reach `make` or the git hook. - `script/frontend-check` is the frontend half of the gate, exposed as the `frontend-check` target, for the frontend Dockerfile: its build stage is a node image with no Go toolchain. The backend half is gated by `Dockerfile.backend`, and `script/cibuild` builds both images, so the two Dockerfiles together still gate the whole repo. The `backend-check` target is the mirror of it. Both targets are named after the script they shim, like every other target. - `script/cibuild` builds both images through one `build_image` helper, and the Gitea workflow's only build step is `script/cibuild`; the raw `docker build -f Dockerfile.backend .` is gone from the workflow. `script/docker` likewise builds and tags both images. - `backend/Makefile`'s `hooks` target is removed. It wrote the same `.git/hooks/pre-commit` as `script/install-precommit`, so the two clobbered each other and the developer silently ended up gating on only one half of the repo. `script/install-precommit` is now the only installer, and the hook it writes runs the repo-wide `script/check`. - `backend/Makefile`'s `docker` target is removed too: the backend image builds from the repo root with a root-level Dockerfile, so it belongs to the root `script/docker` and `script/cibuild` rather than to a backend script that would have to reach outside `backend/`. - `backend/script/lint` verifies that `.golangci.yml` still matches its pinned sha256 before running the linter. Offline hash comparison, no network. The pin is marked provisional in the file: it is the config currently on `main`, and the comment names PR #31 and the canonical hash that must replace it when #31 lands. - Every script locates the repo root with the mandated `$(cd "$(dirname "$0")/.." && pwd -P)` idiom, `cd`s there, and calls siblings as `"$ROOT/script/<name>"`; the `SCRIPT_DIR` variant is gone. READMEs at the root and in `backend/` document every script, the backend's Getting Started separates commands run from `backend/` from those run at the repo root, and `TODO.md` records the change.
213 lines
8.3 KiB
Markdown
213 lines
8.3 KiB
Markdown
NetWatch is an MIT-licensed JavaScript single-page application by
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[@sneak](https://sneak.berlin) that provides real-time network latency
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monitoring to common internet hosts, displayed with color-coded figures and
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sparkline graphs, served from a static bucket or Docker container.
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## Getting Started
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```bash
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# Install dependencies
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yarn install
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# Development server
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yarn dev
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# Production build
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yarn build
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# Preview production build
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yarn preview
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# Docker
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docker build -t netwatch .
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docker run -p 8080:8080 netwatch
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```
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## Entrypoints
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This repository adheres to the
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[Scripts to Rule Them All](https://github.com/github/scripts-to-rule-them-all)
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standard: normalized scripts in `script/` are the entrypoints for the
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development workflow, and the Makefile targets are thin shims that call them.
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The repo holds two projects: the frontend at the repo root and the Go backend in
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`backend/`, which has its own `script/` directory and its own shim Makefile. The
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root scripts cover both, so `make check` at the root fails if either half is
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broken. We provide:
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- `script/bootstrap` — install all dependencies, assuming nothing is present:
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pinned node via nvm if needed, yarn via corepack,
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`yarn install --frozen-lockfile`, and the backend's toolchain — Go (reused if
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already new enough) and golangci-lint at the version `Dockerfile.backend`
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pins. Everything not installed by the system package manager comes from a
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hash-verified release archive and is symlinked onto `PATH`, so `make check`
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works in a plain shell afterwards
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- `script/setup` — make a fresh clone ready for development: bootstrap plus the
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git pre-commit hook
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- `script/projectname` — print the project name (used for the Docker image tags)
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- `script/test` — run the whole repo's tests: `script/frontend-test`, then
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`backend/script/test`
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- `script/lint` — lint the whole repo: `script/frontend-lint`, then
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`backend/script/lint`
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- `script/fmt` — format the whole repo (writes): `script/frontend-fmt`, then
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`backend/script/fmt`
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- `script/fmt-check` — check formatting across the whole repo (read-only)
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- `script/check` — run test, lint, and fmt-check; this is the repo-wide gate
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- `script/frontend-test` — the frontend's test: the production build (no unit
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tests yet)
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- `script/frontend-lint` — run prettier in check mode
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- `script/frontend-fmt` — format everything prettier understands (writes)
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- `script/frontend-fmt-check` — check prettier formatting (read-only)
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- `script/frontend-check` — the frontend half of `script/check`, shimmed by
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`make frontend-check` and used by `Dockerfile`, whose build stage is a node
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image with no Go toolchain. Its mirror `make backend-check` shims to
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`backend/script/check`
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- `script/docker` — build both images, tagged via `script/projectname`:
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`netwatch` from `Dockerfile` and `netwatch-server` from `Dockerfile.backend`
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- `script/cibuild` — CI entrypoint: builds both images; the only build step in
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the Gitea workflow
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- `script/precommit` — run by the git pre-commit hook; runs `script/check`, so a
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commit is gated on both halves of the repo
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- `script/install-precommit` — install the git pre-commit hook; this is the
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repo's only pre-commit hook installer
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The backend's scripts are shimmed by `backend/Makefile` and are also called by
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the root scripts above:
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- `backend/script/build` — compile `netwatch-server` with version and
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architecture stamped in
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- `backend/script/test` — run the Go tests under a 30-second timeout
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- `backend/script/lint` — assert `.golangci.yml` still matches its pinned
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sha256, then run golangci-lint
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- `backend/script/fmt` — format the Go sources (writes)
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- `backend/script/fmt-check` — check Go formatting (read-only)
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- `backend/script/check` — run the backend's test, lint, and fmt-check
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- `backend/script/run` — build and run the server locally
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- `backend/script/clean` — remove build artifacts
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## Rationale
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When debugging network issues, it's useful to have a persistent at-a-glance view
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of latency and reachability to multiple well-known internet endpoints. NetWatch
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provides this as a zero-dependency SPA that can be deployed anywhere static
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files are served, with no backend required.
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## Design
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The application is a single-page app built with Vite and Tailwind CSS v4. All
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code lives in `src/main.js` with a class-based architecture:
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- **`CONFIG`**: Frozen configuration object (update interval, timeouts, axis
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ticks, etc.)
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- **`HostState`**: Per-host state management — history buffer, latency tracking,
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status transitions
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- **`AppState`**: Top-level state container — WAN hosts, local hosts, pause
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state, aggregate stats
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- **`SparklineRenderer`**: Canvas 2D sparkline drawing with fixed axes,
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color-coded line segments, error regions, and DPR-aware scaling
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- **UI functions**: `buildUI()` constructs the DOM, `updateHostRow()` /
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`updateSummary()` / `updateHealthBox()` handle incremental updates
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- **`tick()`**: Main loop — measures all hosts in parallel via `Promise.all`,
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pushes samples, redraws UI. When paused, pushes blank markers (no probes, no
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false outage)
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### Monitoring targets
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- **22 WAN hosts**: datavi.be, Anthropic API, OpenAI API, AWS Console, GCP
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Console, Azure, Cloudflare, Fastly, Akamai, GitHub, B2, 7 S3 regional
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endpoints (Cape Town, London, Bahrain, Tokyo, Sydney, Oregon, São Paulo), 4
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GCS locational endpoints (Iowa, Belgium, Singapore, Sydney)
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- **Local CPE**: Cable modem at 192.168.100.1 (always monitored)
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- **Local Gateway**: Auto-detected on startup by probing common default gateway
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addresses (192.168.1.1, 192.168.0.1, 192.168.8.1, 10.0.0.1); first responder
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wins. Note: modern browsers enforce Private Network Access restrictions that
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block public-origin pages from reaching RFC1918 addresses, so local targets
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only work when NetWatch is served from localhost or a private address.
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Local hosts are tracked separately from WAN stats.
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### Latency measurement
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HEAD requests with `mode: 'no-cors'` and `cache: 'no-store'`, timed with
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`performance.now()`. 1-second timeout; anything over 1000ms is clamped to
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unreachable. IPv4 only.
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### Color coding
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| Latency | Color |
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| ----------- | ------ |
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| < 50ms | Green |
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| < 100ms | Lime |
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| < 200ms | Yellow |
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| < 500ms | Orange |
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| >= 500ms | Red |
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| Unreachable | Gray |
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### Output structure
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```
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dist/
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├── index.html
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└── assets/
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├── index-*.css
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└── index-*.js
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```
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## Features
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- Real-time monitoring with 2s update interval and 300s history sparklines
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- Health indicator: green (HEALTHY) or red (DEGRADED) based on WAN reachability
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- Summary stats: reachable count, min/max/avg latency across WAN hosts only
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- Fixed chart axes: Y-axis 0–1000ms, X-axis 0–300s
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- Color-coded latency figures and sparkline line segments
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- Play/pause: pause stops probes but history keeps scrolling (blank gaps, no
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false outage)
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- Clickable service URLs
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- Canvas-based sparkline rendering with devicePixelRatio scaling
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- Zero runtime dependencies: all resources bundled into build artifacts
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## Deployment
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After running `yarn build`, deploy the contents of the `dist/` directory to any
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static file host (S3, GCS, Cloudflare Pages, Vercel, Netlify, GitHub Pages) or
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use the Docker image behind a reverse proxy.
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The Docker image:
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- Listens on port 8080 by default (override with `PORT` env var)
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- Trusts `X-Forwarded-For` from RFC1918 reverse proxies (10/8, 172.16/12,
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192.168/16)
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- Sends access logs to stdout
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- Caches static assets with immutable headers
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## Browser Compatibility
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Requires a modern browser with ES modules, Fetch API, Canvas API, and CSS custom
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properties.
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## Limitations
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- **CORS**: Some hosts may block cross-origin HEAD requests. The app uses
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`no-cors` mode which allows the request but provides opaque responses. Latency
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is still measurable based on request timing.
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- **Local gateway**: The 192.168.100.1 endpoint requires the host to be
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accessible from your network.
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- **Network conditions**: Measurements reflect browser-to-endpoint latency,
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which includes your local network, ISP, and internet routing.
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## TODO
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- Add unit tests
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- Add eslint for JS linting (currently lint target runs prettier only)
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- Add configurable host list (environment variable or config file)
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- Add latency history export (CSV/JSON)
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- Add notification/alert when status changes to DEGRADED
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## License
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MIT. See [LICENSE](LICENSE).
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## Author
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[@sneak](https://sneak.berlin)
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