hotaru 0.8.2

Small, sweet, easy framework for full-stack web application
Documentation

The Hotaru 0.8 era starts from 23/May/2026.

Hotaru Web Framework

Latest Version Crates.io MIT License

Small, sweet, easy framework for full-stack Rust web applications

Overview

Hotaru is a lightweight, intuitive web framework focused on simplicity and productivity. It supports regex-based routing, tree-structured URLs, and integrates seamlessly with the Akari templating system.

Official Website

Example Project

MSRV: 1.86

Key Features

  • Multi-Protocol Support: Handle HTTP/HTTPS, WebSocket, and custom TCP protocols
  • Simple API: Intuitive request/response handling with minimal boilerplate
  • Full-Stack: Built-in template rendering with Akari templates
  • Flexible Routing: Support for regex patterns, literal URLs, and nested routes
  • Asynchronous: Built with Tokio for efficient async handling
  • Form Handling: Easy processing of form data and file uploads
  • Middleware Support: Create reusable request processing chains

Quick Start

use hotaru::prelude::*;
use hotaru::http::*;

LServer!(
    APP = Server::new()
        .binding("127.0.0.1:3003")
        .single_protocol(ProtocolBuilder::new(HTTP::server(HttpSafety::default())))
        .build()
);

#[tokio::main]
async fn main() {
    APP.clone().run().await;
}

endpoint! {
    APP.url("/"),
    pub index<HTTP> {
        text_response("Hello, Hotaru!")
    }
}

Installation

Using the CLI Tool (Recommended)

Install the Hotaru CLI tool:

cargo install hotaru

Create a new project:

hotaru new my_app
cd my_app
cargo run

Manual Installation

Add to your Cargo.toml:

[dependencies]
hotaru = "0.8.2"
tokio = { version = "1", features = ["full"] }

Optional Features

Default features: trans, http. Cargo's additive feature unification means sub-features pull in their prerequisites automatically — you never have to enable a base feature by hand.

Protocol stack

  • http (default-on): HTTP/1.1 stack (hotaru_http + ahttpm). Opt out with default-features = false for protocol-only builds (e.g. gRPC-only deployments) — hotaru::http::*, HTTP, HttpContext, HttpRequest, HttpResponse, etc. then disappear from the crate surface.
  • https: TLS/HTTPS support — surfaces HTTPS, TlsTransport, TlsOutboundTarget, TlsClientConfig. Implies http.
  • http_compression: HTTP body codecs for Content-Encoding (gzip / deflate / brotli / zstd). Off by default because brotli + zstd together add ~7 s to a clean build. Implies http. Without this feature, ContentCoding::decode_compressed / encode_compressed return io::ErrorKind::Unsupported for compressed bodies.

Endpoint macro flavor — pick one (see Core Concepts):

  • trans (default) — bang macro with hotaru-blocks body
  • semi-trans — stacked attributes above an fn
  • attr — single attribute with args

Misc

  • debug: Enable debug logging for development and troubleshooting.
  • external-ctor: Use the external ctor crate instead of Hotaru's built-in constructor implementation. When enabling, you must also add ctor to your dependencies: 
    [dependencies]
hotaru = { version = "0.8.2", features = ["external-ctor"] }
ctor = "0.4.0"
tokio = { version = "1", features = ["full"] }

Example — HTTPS server with body compression:

[dependencies]
hotaru = { version = "0.8.2", features = ["https", "http_compression"] }
tokio = { version = "1", features = ["full"] }

Example — gRPC-only (no HTTP):

[dependencies]
hotaru = { version = "0.8.2", default-features = false, features = ["trans"] }
hotaru_grpc = "..."
tokio = { version = "1", features = ["full"] }

Binary Commands

Use the CLI to scaffold projects — it generates build.rs for asset copying and src/resource.rs for runtime template/static lookup, which are non-trivial to wire up by hand.

cargo install hotaru                   # install the CLI (see Installation above)
hotaru new my_app                      # scaffold a new project
hotaru init                            # or scaffold into the current Cargo crate
cd my_app && cargo run                 # serves http://127.0.0.1:3003

Project Structure

my_app/
├── Cargo.toml              # Dependencies and project metadata
├── build.rs                # Asset copying build script
├── src/
│   ├── main.rs            # Application entry point with LServer! + endpoint!
│   └── resource.rs        # Resource locator helpers
├── templates/             # Akari HTML templates
└── programfiles/          # Static assets (CSS, JS, images)

The build script copies templates/ and programfiles/ to the target directory at compile time so they're accessible at runtime.

Core Concepts

Endpoints

Three macro flavors, enabled by the trans / semi-trans / attr cargo features. Pick one per project; trans is the default. All three register the same route at startup; they only differ in syntax.

trans (default) — bang macro with hotaru-blocks body:

endpoint! {
    APP.url("/users/<int:id>"),
    pub get_user<HTTP> {
        let user_id = req.param("id").unwrap_or_default();
        akari_json!({ id: user_id })
    }
}

semi-trans — stacked attributes above an fn:

#[endpoint]
#[url("/users/<int:id>")]
pub fn get_user<HTTP>() {
    let user_id = req.param("id").unwrap_or_default();
    akari_json!({ id: user_id })
}

attr — single attribute with args:

#[endpoint("/users/<int:id>")]
pub fn get_user<HTTP>() {
    let user_id = req.param("id").unwrap_or_default();
    akari_json!({ id: user_id })
}

akari_json! is the JSON-response macro re-exported via hotaru::prelude; it already wraps json_response(...) so callers don't compose the two. Keys are bare idents (not "..."). req.param(...) returns Option<String>.

Macro Notes

  • Endpoints and middleware auto-register at startup — no manual router.register().
  • trans form: brace syntax {} with doc comments inside the block; angle-bracket body defaults to req. Optional fn-style pub fn name(req: HTTP) { ... } is also accepted.
  • Remaining readme examples use trans. To switch, set default-features = false on the hotaru dependency and turn on the flavor you want, e.g. hotaru = { version = "0.8.2", default-features = false, features = ["semi-trans", "http"] }. Cargo feature unification would otherwise keep trans on alongside it; remember to re-add http since default-features = false also drops the default HTTP stack.
  • See macro_ra.md for syntax details. Analyzer support is planned.

Middleware

Attach a middleware to a protocol via the ProtocolBuilder. Add htmstd = "0.8" to your Cargo.toml for the bundled middleware library:

use htmstd::session::CookieSession;

LServer!(
    APP = Server::new()
        .binding("127.0.0.1:3003")
        .single_protocol(
            ProtocolBuilder::new(HTTP::server(HttpSafety::default()))
                .append_middleware::<CookieSession>(),
        )
        .build()
);

Middleware can also be attached per-endpoint via middleware = [...] inside the endpoint! block — see example_hotaru for the pattern.

Templates

Render HTML with Akari via akari_render! — the macro looks up the template file and substitutes the named bindings:

endpoint! {
    APP.url("/profile"),
    pub profile<HTTP> {
        akari_render!("profile.html", name = "Alice")
    }
}

HTTP Safety Configuration

Configure request validation per endpoint:

endpoint! {
    APP.url("/upload"),
    config = [HttpSafety::new()
        .with_max_body_size(50 * 1024 * 1024)  // 50MB
        .with_allowed_methods(vec![HttpMethod::POST])
    ],
    pub upload<HTTP> {
        // Handle file upload
    }
}

Examples

Check out the example repository for:

  • Basic routing and handlers
  • Form processing and file uploads
  • Session management with cookies
  • CORS configuration
  • Multi-protocol applications

Crate Ecosystem

Hotaru is built on a modular architecture:

  • hotaru - Main framework with convenient API
  • hotaru_core - Core protocol and routing engine
  • hotaru_trans - Procedural macros for endpoint! and middleware!
  • hotaru_http - HTTP implementation for Hotaru
  • hotaru_tls - TLS/HTTPS implementation for Hotaru
  • hotaru_lib - Utility functions (compression, encoding, etc.)
  • htmstd - Standard middleware library (CORS, sessions)

Changelog

0.8.2 (Current)

  • http (default-on) + http_compression (default-off) features: HTTP and codecs are now optional; default-features = false drops HTTP entirely, https/http_compression imply http.
  • HTTP re-exports moved to hotaru::http (use hotaru::http::*;); clean builds ~35 % faster (20.5 s → 13.3 s) from dropping tracing and gating heavy codecs.
  • Workspace + dep alignment: five core crates pinned to 0.8.2; regex bumped 1.5.6 → 1.12.
  • hotaru_core access-point table no longer poisons: AccessPointTable switched to parking_lot::RwLock via the existing PRwLock alias.
  • hotaru_trans .. middleware inheritance honors the URL's app ident: was hardcoded to APP, breaking multi-app setups.
  • hotaru_trans anonymous-fn _ form actually works: _ was matched as Punct (it's an Ident), so the auto-name branch never fired.

0.8.x

  • Client / outpoint runtime: new Client<TS> for outbound traffic, mirroring Server<TS>. Paired with the outpoint! macro (client-side counterpart to endpoint!) and run! / call! invocation-style sugar for one-shot and persistent outbound calls.
  • Protocol trait reshape: channel-based open_channel / handle / send, plus per-protocol install_channel bridge. type Context: RequestContext<Channel = Self::Channel> pins channel-type alignment. New Channel trait + ProtocolFlow give per-exchange close semantics (HTTP/1 closes the connection; multiplexed protocols may close only the stream).
  • RequestContext rework: Default supertrait; type Channel as a type anchor; inject_request / into_response added. type Error: ProtocolError is the single source of truth for chain errors, and now also requires From<std::io::Error> (since the client path surfaces transport-level I/O). Use the new EmptyError for prototypes / no-payload protocols.
  • Result-typed execution chain: middleware, final handlers, ExecutionChain::run, and UrlNode::run all return Result<C, <C as RequestContext>::Error> — no boxing at the chain boundary.
  • Named access points: every registered endpoint/outpoint has an explicit name. ProtocolEntry::register(name, path, step_names, binding, config) is the single canonical funnel; Server::url(url, name, ...) / Client::url(url, name, ...) are URL-first.
  • Instance-based transports: TransportSpec::Inbound / Outbound replace the old Accepter / Connector shape. TcpInbound::bind(target) and TcpOutbound::build(target) materialize once per Server / Client.
  • HTTPS feature: new https cargo feature on the umbrella hotaru crate forwards to hotaru_http/tls, surfacing HTTPS, TlsTransport, TlsOutboundTarget, TlsClientConfig. HTTPS = Http1Protocol<TlsStream, TlsTransport>.
  • LServer! / LClient! / LUrl! / LPattern! macros: replace the old LApp! for simplified lazy-static declarations. Default to TcpTransport.

0.7.x

  • Multi-protocol support (HTTP, WebSocket, custom TCP)
  • Enhanced security controls with HttpSafety
  • Improved middleware system with protocol inheritance
  • Performance optimizations in URL routing
  • Comprehensive security testing
  • .worker() method now properly configures dedicated worker threads per Server instance
  • Fixed hotaru new and hotaru init to generate correct endpoint! macro syntax
  • Built-in constructor implementation (no external ctor dependency required)
  • Fn-style blocks: New syntax pub fn name(req: HTTP) { ... } for endpoint! and middleware! macros (original hotaru blocks syntax preserved)
  • Bug fix for URL routing

0.6.x

  • Protocol abstraction layer
  • Request context improvements
  • Standard middleware library (htmstd)
  • Cookie-based session management

0.4.x and earlier

  • Async/await support with Tokio
  • Akari templating integration
  • Cookie manipulation APIs
  • File upload handling
  • Form data processing improvements

Learn More

Video Resources URL
Quick Tutorial Youtube: https://www.youtube.com/watch?v=8pV-o04GuKk&t=6s Bilibili: https://www.bilibili.com/video/BV1BamFB7E8n/

AI Declaration of each Mod

We believe in transparency about AI-assisted development. The framework is governed jointly by two maintainer groups using a shared four-tier system that prioritizes understanding over line counts.

Maintained by: PMINE/Research

Name Tier Comments
hotaru_core/app Author-Owned
hotaru_core/connection Author-Owned
hotaru_core/executable Author-Owned
hotaru_core/url Author-Owned
hotaru_core/protocol Author-Owned
hotaru_http/trails Co-Authored
hotaru_http/* Human-Led
hotaru_mqtt/broker Co-Authored
hotaru_mqtt/traits Co-Authored
hotaru_mqtt/* Human-Led
hotaru_lib Human-Led Basic API Access
h2per Co-Authored Integration of Hyper - Not stable yet
htmstd/cors Human-Led
htmstd/session Human-Led

Maintained by: Project-StarFall

Name Tier Comments
hotaru_trans/endpoint Author-Owned Proof and language design must be fully understood by humans
hotaru_trans/outpoint Author-Owned Proof and language design must be fully understood by humans
hotaru_trans/middleware Author-Owned Proof and language design must be fully understood by humans
hotaru_trans/cors Co-Authored Trivial user-level abstraction
ahttpm Co-Authored Imports akari_macro plus improvements
SFX Co-Authored Trivial user-level abstraction
akari External https://crates.io/crates/akari
akari_lang External (TBD)
akari_macro External https://crates.io/crates/akari

Shared term meanings

Term Meaning
Forbidden The intelligence work in this module — design decisions, proof obligations, language semantics, novel logic — is authored by humans. AI is not used for this content (the mechanical/test/doc carve-out in operating rule 2 still applies). Reserved for modules where the work is the thinking, not the typing.
Author-Owned AI may assist with drafts and completion, but the committed code reads as the author's own throughout. A reviewer should not be able to tell where AI helped. The module signals "a human owns the design and the prose."
Human-Led The human authored the structure and the load-bearing pieces; AI filled in helpers, repetitive sections, or boilerplate. Some sections may visibly bear AI's hand, but the design choices and non-trivial logic are clearly human. The author can defend every part without re-consulting AI.
Co-Authored AI participated substantively in both design exploration and implementation. The human author has internalized the result and can defend, modify, and debug without re-prompting. Appropriate for well-understood patterns and third-party integrations.

The understanding requirement is uniform across Author-Owned, Human-Led, and Co-Authored: the author can explain any line, modify surrounding code without AI help, and walk a reviewer through the code on request. The tiers differ only in where AI's voice is allowed to show through, not in what the author owes the team.

Operating rules

  1. No quantification. Tiers describe the kind of collaboration, not the amount of AI-authored code. Counting lines is brittle and incentivizes the wrong behavior.
  2. Tests, documentation, and mechanical typing are permitted in every tier — including Forbidden. AI assistance is allowed across all modules for: unit tests; doc comments and inline prose; and mechanical typing where the design decision has already been made by a human and AI is only writing it out (e.g., applying a settled pattern across similar cases, expanding hand-authored pseudocode, regenerating a table from a spec). The defining criterion is that no intelligence work is delegated to AI — design, proof, and semantics decisions remain with the human. The author remains responsible for understanding what was generated.
  3. Reviewer-driven understanding check. Any reviewer may flag a PR with "this doesn't feel author-owned" — regardless of the module's tier. The author clears the flag by demonstrating understanding in PR comments or a short walkthrough. Flags are requests for evidence, not accusations.
  4. Smell-test threshold scales with tier. Author-Owned code is flagged if any section visibly reads as AI-generated. Human-Led is flagged if the structural code reads as AI-generated or AI's hand pervades rather than appearing locally. Co-Authored is flagged only if the author cannot defend the code in review.
  5. Tier reflects the work, not preferences. Maintainers set tiers based on the nature of the module. If the character of a module changes, the tier is re-set rather than stretched.
  6. External code is outside this policy. AI-authored code arriving through a third-party crate is governed by that crate's own conventions, transparently linked.

📄 License

MIT License — see LICENSE.txt.

Copyright (c) 2024-2026 @ Field of Dreams Studio (FDS) & Project-StarFall & PMINE-FDS