Ktron

A Kotlin web framework to break benchmarks.

Ktron is an HTTP/1.1 framework on the Kotlin port of ioxide, a shared-nothing io_uring runtime: one reactor per core, each with its own ring and its share of the SO_REUSEPORT listeners, the syscalls made straight through the JVM's Foreign Function & Memory API. Handlers run on the reactor thread that took the request; a suspending one resumes there too. There is no thread pool.

fun main() {
    Ktron(KtronOptions(port = 8080))
        .use(Compression())
        .get("/hello/{name}") { ctx -> ctx.response.text("hello " + ctx.request.param("name")) }
        .get("/items/{id}") { ctx -> ctx.response.json(Item(ctx.request.paramInt("id"), "widget")) }
        .getAsync("/later") { ctx ->
            ctx.delay(10)   // an IORING_OP_TIMEOUT on the reactor's ring
            ctx.response.text("later")
        }
        .run()
}

@GhostSerialization
data class Item(val id: Int, val name: String)

How it works

• Parsing: Glyph11, the hardened HTTP/1.1 parser (request smuggling, limits, RFC 9112 strictness), from genhttp-kt's Kotlin port, rewritten to parse a byte array in one pass and hand back offsets: about 25 ns for a GET and 130 ns for a 12-header browser request, allocating nothing. That is 2 to 3 times faster than Glyph11's C core called through FFM, whose downcall costs only about 5 ns; the C parse itself is the slower part. See glyph11/.
• Routing: a trie over path segments - literals, {param} (or :param), {*rest} - with handlers by method, 405 with an Allow line, HEAD from GET. A match allocates nothing: parameters are offsets into the request.
• Middleware: before/after hooks, in order, that can short-circuit. They are synchronous, so the sync path runs no coroutine at all; handlers between them may suspend.
• Responses: status, headers and body in one call (text, bytes, json), staged in the connection's io_uring write slab and sent with one flush per batch of pipelined requests.
• JSON: Ghost's KSP-generated serializers, writing into a buffer of the connection's own: no array per response.
• Compression: the Compression middleware, gzip on libdeflate and brotli on libbrotlienc, both over FFM. It defaults to gzip level 1: measured on dynamic JSON of a few KB against every gzip, zlib and brotli setting, it scores best under HttpArena's json-comp formula, where speed outweighs the bytes a slower level saves. Without libdeflate it falls back to java.util.zip.
• TLS: ioxide's, on BoringSSL with optional kernel TLS (KtronTls).

Layout

• ktron/ the framework
• glyph11/ the parser
• examples/arena/ HttpArena's HTTP/1.1 profiles on Ktron

The runtime is ioxide's Kotlin port: check out the ioxide repo's kotlin branch next to this one, or point -PioxideKt=<dir> at its kotlin/ioxide elsewhere. Build with ./gradlew build; JDK 25.

MIT.