* fix(proxy): harden MITM proxy reliability and scale for bulk installs
Deep-dive analysis of dropped connections during large installs (5000+
packages with concurrent downloads) surfaced three issues, each verified
with a reproduction test before fixing.
1. Transient upstream errors tore down whole keep-alive tunnels.
goproxy returns false (closing the entire MITM client tunnel) when a
single upstream round-trip errors. Under load, CDN-fronted registries
(e.g. Cloudflare for registry.npmjs.org) intermittently reset
connections, so one transient reset dropped a pooled keep-alive socket
and surfaced to the package manager as ECONNRESET / "socket hang up".
Fix: route upstream round-trips through a resilient round tripper that
retries idempotent, body-less requests with bounded linear backoff,
absorbing transient resets and keeping the tunnel alive. A reproduction
test shows the tunnel count drop from 3 to 1 across a transient failure.
2. Head-of-line amplification against the external analysis service.
Concurrent requests for the same package version each issued their own
gRPC call. Fix: de-duplicate in-flight analyses with singleflight so a
burst of identical requests collapses into one upstream call.
3. Per-request goproxy verbose logging on the hot path.
proxy.Verbose was always on, formatting several log lines per request
even when discarded below debug level. Fix: enable goproxy verbose
logging only when PMG runs at debug level.
Note: the hypothesis that the http.Server Read/WriteTimeout leaks onto
hijacked CONNECT tunnels was investigated and disproven (Go clears the
deadlines on Hijack); the behavioral guard tests for long-lived
connections and slow transfers are retained.
* fix: Type assertion error handling
---------
Co-authored-by: Claude <noreply@anthropic.com>
