Tolerate Vert.x 5 pause/resume on ended requests (fixes silent test hangs)

[adamw]

Problem

The Vert.x 4 → 5 upgrade (80c5e37, 2026-06-10) changed HttpServerRequestImpl.pause()/fetch()/resume() semantics: they now checkEnded() and throw IllegalStateException("Request has already been read") once the request body END event has been delivered. In Vert.x 4 these calls were safe no-ops after end.

Tapir's vertx streaming bridge invokes pause()/resume() from fire-and-forget fibers and Vert.x callbacks:

• server/vertx-server/cats/src/main/scala/sttp/tapir/server/vertx/cats/streams/fs2.scala — back-pressure loop in a started-and-never-joined fiber
• server/vertx-server/zio/src/main/scala/sttp/tapir/server/vertx/zio/streams/zio.scala — same pattern, forkDaemon-ed
• server/vertx-server/src/main/scala/sttp/tapir/server/vertx/streams/Pipe.scala — drain handlers / pipe start
• server/vertx-server/src/main/scala/sttp/tapir/server/vertx/handlers/package.scala — streamPauseHandler for every streaming/WS endpoint

Under CI load, a pause/resume racing the END event now throws, silently killing the back-pressure fiber (or skipping cleanup such as socket.close()), leaving stream consumers waiting forever. This is the suspected root cause of the intermittent silent hangs in the vertx cats/zio suites seen on dependency PRs #5373 / #5362, where CI went quiet until the 15-minute retry timeout.

Fix

Restore Vert.x 4 semantics at tapir's call sites by ignoring the post-end IllegalStateException: after END there is nothing left to pause/resume, so dropping the call is semantically correct. No fibers/streams were restructured — only the pause/resume calls on the request/read-stream are guarded (.attempt.void in fs2, .ignore in zio, a small ignoringReadEnded helper in Pipe.scala, and a try/catch in streamPauseHandler).

Companion PR: #5382 adds defensive timeouts + a thread-dump watchdog on the CI side; this PR is the root-cause side.

Verification

All variants compile (2.12 / 2.13 / 3): vertxServer{,2_12,3}, vertxServerCats{,2_12,3}, vertxServerZio{,2_12,3}.

Test suites:

• vertxServerCats2_12/test: Tests: succeeded 292, failed 0 — all passed
• vertxServerZio3/test: Tests: succeeded 295, failed 0 — all passed
• vertxServer/test (2.13): Tests: succeeded 554, failed 0 — all passed

Stress run of the formerly racy path — vertxServerCats2_12/testOnly sttp.tapir.server.vertx.cats.CatsVertxServerTest 5 times in a loop: 5/5 passed (285 tests each).

🤖 Generated with Claude Code