test(cache): make stalled-remote-cache a proxy for the remote cache

[wan9chi]

Motivation

The e2e cases for a remote cache that never answers need some requests to stall while others behave normally. For example, an upload case needs its fetch to reach a backend and miss before the upload stalls. vtt stalled-remote-cache was its own endpoint and stalled every request, so it couldn't do that. #718 will replace remote-cache-server with the real cache service, which can't stall requests itself. So the stalling has to happen in front of whatever backend a test runs.

Changes

• Proxy. vtt stalled-remote-cache [--stall ROUTE]... COMMAND [ARGS...] is now a proxy for the endpoint in VP_REMOTE_CACHE_URL, which must be http://<host>:<port>/<path>. It runs the command with VP_REMOTE_CACHE_URL set to the proxy.
  • A request to a stalled route below the endpoint, such as /store, is never answered, and it emits a stalled milestone.
  • Other requests are forwarded with connection: close, so each one comes in on its own connection and is checked on its own.
  • A forwarded request gets a 502 if the endpoint can't be reached.
• Fetch cases. ctrl_c_during_fetch and fast_fail_during_fetch stall /fetch, with an unreachable endpoint behind the proxy. They still run on every platform without Node.js.
• New ctrl_c_during_upload case. It runs remote-cache-server vtt stalled-remote-cache --stall /store vt run build. The fetch reaches the backend and misses, the upload stalls, and Ctrl-C cancels it.
• remote-cache-server now ignores Ctrl-C and leaves it to its command, so it still prints its request log afterwards.

Notes for reviewers

• Lost milestones on Windows. A milestone there is the console title, and ConPTY sends it on its next render. If the command sets a milestone at about the same time as the proxy, the earlier one can be lost. The doc comment says so. Cases that need remote-cache-server are skipped on Windows anyway.
• Conflict with feat(remote-cache): add self-hosted public cache server #718. feat(remote-cache): add self-hosted public cache server #718 rewrites packages/tools/src/remote-cache/cli.ts, so the line that ignores Ctrl-C needs to move into its version.

🤖 Generated with Claude Code

[github-actions]

fspy benchmark

linux

dynamic/launch             change  +0.37%  [ -6.84% ..  +8.02%]  overhead  +269.24%
dynamic/access             change  +0.15%  [ -0.87% ..  +1.98%]  overhead   +13.49%
dynamic/access-relative    change  -0.11%  [ -1.30% ..  +0.87%]  overhead   +59.47%
dynamic/access-contended   change  -1.56%  [ -5.35% ..  +2.11%]  overhead   +14.39%
static/launch              change  +0.50%  [ -5.95% ..  +7.04%]  overhead  +727.56%
static/access              change  -0.15%  [ -1.44% ..  +0.97%]  overhead  +794.48%
static/access-relative     change  +0.15%  [ -1.05% ..  +1.97%]  overhead +1354.76%
static/access-contended    change  -0.31%  [ -2.00% ..  +0.48%]  overhead +3098.26%

macos

dynamic/launch             change  +0.71%  [ -2.16% ..  +4.68%]  overhead  +216.21%
dynamic/access             change  -0.70%  [-16.13% ..  +7.81%]  overhead    +3.01%
dynamic/access-relative    change  -1.44%  [-53.14% ..  +6.17%]  overhead  +271.54%
dynamic/access-contended   change  +1.28%  [ -4.54% ..  +6.50%]  overhead    +4.47%

windows

dynamic/launch             change  -0.22%  [ -4.99% ..  +6.48%]  overhead   +24.21%
dynamic/access             change  +1.58%  [ -4.30% .. +13.18%]  overhead    +2.34%
dynamic/access-relative    change  +0.00%  [ -9.69% .. +10.48%]  overhead    +1.66%
dynamic/access-contended   change  +1.09%  [ -7.30% ..  +7.59%]  overhead    +2.27%