Reactor on tsvinc

Every Route Registered. Every Request 404'd.

Mon, 06 Jul 2026 00:00:00 +0000

Thirty-three routes registered. Startup log confirms it. The /routes management endpoint lists every one. And under load, every single request returns 404.

This is the reactive Micronaut branch of the space observatory benchmark — 28 upstream API calls, 10 HTTP clients, all pointed at a Go mock server that deliberately injects failures (HTTP 500, 504-after-delay, abrupt connection close). The imperative sibling branch works. The lighter synth variant works. This one: 100% 404.

flatMap's Second Argument Saved 1.7 Million Requests

Mon, 15 Jun 2026 00:00:00 +0000

Midway through a code review of the reactive pipeline, staring at this line in NeoService.java:

.flatMap(neo -> saveAsteroidWithApproaches(sessionId, neo))

That’s Flux.flatMap() with one argument. The function. No concurrency limit. Reactor’s default: 256 concurrent inner subscriptions.

The R2DBC connection pool has 20 connections. Netty has 4 worker threads. flatMap will cheerfully create 256 concurrent database save operations on 20 connections and 4 threads, queuing 236 of them in memory. Every one holds a NeoAsteroidRecord entity, a NeoCloseApproach list, and whatever intermediate state Reactor needs for the inner publisher chain.

Seven Fixes, Zero Errors

Fri, 12 Jun 2026 00:00:00 +0000

The fix for “JVM dies at 256 MB under load” was not a JVM flag.

Part 4 ended with Serial GC — the only GC that fits in 256 MB — serving 4,550 requests before the OOM killer showed up. 81% error rate. Same flags, same container, same load profile. Seven code changes later: 1,740,000 requests. Zero errors.

No GC tuning. No new JVM flags at all. The problem was never the runtime. It was the code asking the runtime to hold things it didn’t need to hold.