Follow-up to backlog#1191 (optional sub-item). The main accept loop
spawned one task per socket with no global bound, so a connection flood
could exhaust file descriptors and memory and take existing traffic
down with it.
- New RUSTFS_API_MAX_CONNECTIONS (default 0 = unlimited, no semaphore
constructed, accept loop unchanged).
- When set, the loop acquires an owned semaphore permit BEFORE
accept(): at saturation it simply stops accepting and lets the
kernel backlog absorb bursts (TCP-native backpressure) instead of
accept-then-close churn. The permit moves into the connection task
and is released by RAII on any exit path, including TLS handshake
failures.
- Saturation is observable via the
rustfs_http_server_connection_cap_saturated_total counter, a
connection_cap_state startup event, and a per-wait debug event;
shutdown stays responsive while parked on the semaphore.
- The cap covers everything on the main listener (S3, admin, console,
internode gRPC); the constant docs carry sizing guidance.
- E2E coverage: ten sequential Connection-close requests against cap 2
prove permits never leak; two stalled connections saturating cap 2
leave a third unserved until their permits are released, after which
the queued request is accepted and answered.
Follow-up to #4895 (backlog#1191 deferred sub-item). The client-IP
dimension gives per-client fairness; this adds a collective per-bucket
budget so one hot bucket cannot monopolize the server regardless of how
many client IPs the traffic is spread across.
- Generalize RateLimiter over its key type with a Borrow-based check()
so &str lookups against String bucket keys stay allocation-free on
the hit path; client-IP call sites are unchanged in behavior.
- RateLimitLayer now carries optional client and bucket limiters; a
request must pass every configured dimension, and rejections report
which one tripped via a new 'dimension' metric label.
- Bucket extraction mirrors s3s host routing: virtual-hosted-style
resolves the Host/authority prefix against the same expanded domain
set (with port variants) the s3s router uses; otherwise the first
path segment. Admin and table-catalog namespaces are never buckets.
- New env vars RUSTFS_API_RATE_LIMIT_BUCKET_RPM/_BURST (default 0 =
dimension off) under the existing enable switch; bucket-only
configurations (client RPM 0) are supported.
- Bucket names are attacker-chosen, so the bounded-shards design
(100k keys, lossless idle sweeps, most-idle eviction) is the memory
defense; a test floods 10k random names and asserts the cap holds.
- Unit tests for extraction, shared bucket budgets across IPs, both-
dimensions interaction, and the extended env matrix; e2e test proves
bucket-only throttling on the real server with an unrelated bucket
unaffected.
feat(api): wire opt-in per-client S3 API rate limiting (backlog#1191)
RustFS shipped three rate-limiter implementations and none was wired to
any request path: the tower layer never returned 429 (its over-limit
branch passed requests through) and was never instantiated, the console
env switches only logged, and the Swift token bucket was never called.
Replace them with one working, default-off implementation:
- Rewrite rustfs/src/server/rate_limit.rs as a sharded per-client-IP
token-bucket limiter (32 mutex shards instead of one global RwLock
write per request), bounded at 100k tracked IPs with lossless
refilled-idle sweeps, returning 429 + Retry-After + x-ratelimit-*
headers and an S3-style XML body.
- Key on trusted-proxy-validated ClientInfo.real_ip, else the socket
peer address; never read spoofable X-Forwarded-For/X-Real-IP headers.
Requests without a resolvable identity fail open. The echoed request
id is charset-gated to prevent reflected XML injection.
- Wire the layer once at startup via option_layer between
CatchPanicLayer and ReadinessGateLayer (external stack only), gated by
new RUSTFS_API_RATE_LIMIT_ENABLE/_RPM/_BURST constants; health and
profiling probes, internode RPC/gRPC, and the console are exempt.
- Make RUSTFS_CONSOLE_RATE_LIMIT_ENABLE/_RPM actually enforce by
reusing the same limiter core through an axum middleware.
- Delete the dead Swift ratelimit module, its isolated tests, and the
stale logging-guardrail entry; keep the live SwiftError 429 mapping.
- Add unit tests (exhaustion/recovery with injected time, concurrency,
cap eviction, spoofed-header and fail-open behavior, env matrix) and
e2e tests proving 429 + Retry-After on the real server and zero
behavior change with default configuration.
Zhengchao An