feat(agent): process fd/RSS ceilings gate connection admission (W2.5) - #49
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AgentLimits gains with_process_budget(max_fds, max_rss_mb); when either ceiling is set the agent samples the kernel view (/proc/self/fd + VmRSS on Linux, /dev/fd + proc_pidinfo on macOS, re-statting at most every 200ms) and refuses new connections while usage sits at or above the ceiling — before a connection slot or stream task is consumed. Refusals reuse ConnectionBudgetExhausted; unobservable platforms keep serving. Settings expose limits.max_fds/max_rss_mb (positive, flag-overridable via --max-fds/--max-rss-mb) and the metrics snapshot reports rds_agent_process_fds/rds_agent_process_rss_bytes where observed. Generated with [Devin](https://devin.ai) Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Generated with [Devin](https://devin.ai) Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
scenario.rs already generates ping payloads via rand::random elsewhere; the literal `1` tripped the CodeQL rust/hard-coded-cryptographic-value rule (critical alert on main). Same treatment. Generated with [Devin](https://devin.ai) Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>
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Summary
AgentLimits::with_process_budget(max_fds, max_rss_mb)installs aprocess-level resource gate: while the kernel reports the agent at or
above the configured fd/RSS ceiling, new connections are refused at
admission — the pending
Incomingis dropped (runner) or theestablished conn is closed (
serve) — before a slot or task is spent./proc/self/fd+VmRSSon Linux and/dev/fd+proc_pidinfoon macOS, cached 200ms so procfs scans stay off theaccept hot path. Platforms that cannot observe a quantity keep serving
rather than gate on a guess.
limits.max_fds/limits.max_rss_mb(positive NonZero,JSON +
--max-fds/--max-rss-mbflags, merged with file precedence).ConnectionBudgetExhausted; metricssnapshot reports
rds_agent_process_fds/rds_agent_process_rss_byteswhere the kernel reports them.
Test plan
syskernel sanity +ResourceGateunit tests (none/impossible/generous ceilings)
serverefuses anestablished conn; above-usage ceiling admits and pings normally
cargo fmt --check, clippy default + x11 lanes, workspace tests —all green locally
Still open under W2.5: per-service fairness inside the stream budget,
disk/media cancellation breadth, storm-grade RSS/FD stress proof.
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