Add Vert.x: reactive JVM toolkit on Netty (~15k ⭐)

[BennyFranciscus]

Vert.x — Eclipse Vert.x 4.5.14

Adds Eclipse Vert.x (~15k ⭐) to HttpArena — the reactive toolkit for building high-performance JVM applications.

Why Vert.x?

Vert.x is the event-driven engine underneath Quarkus. HttpArena already has Spring (Tomcat), Spring (Jetty), and Quarkus (Vert.x/Netty) — but not raw Vert.x itself. This is the "framework vs engine" comparison:

• Quarkus = CDI + annotations + Vert.x under the hood
• Vert.x = event loops + handlers + Netty directly

How much overhead does Quarkus's abstraction add on top of raw Vert.x? Now we can find out.

Implementation

• Vert.x 4.5.14 (latest stable) with vertx-web for routing
• One verticle instance per CPU core, each on its own Netty event loop
• JDK 21 with ParallelGC + Netty performance tuning (same flags as quarkus-jvm)
• Pre-computed JSON + gzip responses at startup
• SQLite queries offloaded to worker threads via executeBlocking() (event loops never block)
• HTTP/2 + TLS on port 8443 via ALPN

All tests

baseline, pipelined, limited-conn, json, upload, compression, noisy, mixed, baseline-h2, static-h2

26/26 validation checks pass locally.

cc @vietj @tsegismont — would be cool to see how raw Vert.x stacks up against the frameworks built on top of it!