The counters were process-wide globals: one upstream_requests_total, one
cache hit rate, one pair of byte counters. With several vrepos and
fallback upstream lists that answers none of the questions that actually
come up — which mirror is slow, which one is 404-ing everything so every
miss costs an extra round trip, what each one costs in bandwidth.
Everything attributable now carries a label: vrepo for what the client
asked for, vrepo plus the upstream URL for what the proxy had to fetch.
Series are registered from the config at startup, so a label value can
only ever be a configured name — a client asking for random paths lands
in a vrepo="" bucket instead of minting series. Handlers mark the repo
once they have parsed the path and passed auth; proxycache reads it back
off the context, so no call site had to change shape.
Bytes are now counted at the socket, where they are real: each upstream
gets a counting dialer and the server runs on a counting listener, so the
new wire counters include request lines, headers, chunked framing and the
TLS records and handshake. The body counters stay beside them — one is
what the artifact weighs, the other is what the link is billed for. A
cold 68KB jar reads as 68605 body bytes against 75562 on the wire. Client
sockets keep requests for several vrepos on one keep-alive connection, so
those totals stay process-wide rather than split on a guess.
Timings come from httptrace, per wire attempt: connect (DNS included),
TLS handshake, time-to-first-byte and body streaming, plus the inbound
request duration per vrepo. They are histograms, since the average of a
download time hides exactly the tail worth knowing about. Connection
hooks only fire on a real dial, so a quiet connect histogram beside a
busy request counter means the pool is working.
Two knock-on fixes: a transport with a custom DialContext gets no
automatic HTTP/2, so ForceAttemptHTTP2 is now explicit rather than every
upstream silently dropping to HTTP/1.1; and the counting conn implements
ReadFrom so serving a cached file still uses sendfile.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
MRLokopandClaude Opus 5
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