# REPORT — a listening socket that served nobody (2026-08-18, early) **Trigger:** two `whole_guest_backup_failed` alert mails, 04:30 and 04:32 CEST. **Outcome:** root cause found on **ep0**, fixed, both missed backups re-driven and landed. **No repo code changed** — this was an operational run. Documentation, register and evidence only. --- ## 1. What was wrong Both alerts were the same incident and neither was on a customer box. `demo-felhom` and `demo-hp` each failed their `felhom-pbs` tier with `Can't connect to 10.77.0.1:8007 (Connection timed out)` — the one thing they share, the Hetzner offsite PBS endpoint. On ep0, `proxmox-backup-proxy` was `active`, held its listening socket, and **served nobody**: ``` ss -lnt '( sport = :8007 )' → LISTEN Recv-Q 1025 Send-Q 1024 ls /proc//fd | wc -l → 1024 # == its soft RLIMIT_NOFILE ``` `Send-Q` on a listener is the accept backlog; `Recv-Q` is the queue depth. At 1025 against 1024 the queue had overflowed, because `accept()` was returning `EMFILE` on every call. **1016 of the 1024 descriptors were sockets and 547 connections sat in `CLOSE-WAIT`** — a connection leak, fed by ~85,000 requests/day, that reached the ceiling after 14 days of uptime. Last request served: 2026-08-17 18:15:32 UTC. Offsite DR was therefore down **≈ 9 h 37 m**. **The observation that settled it:** the daemon was wedged from its own loopback too — `curl https://127.0.0.1:8007/` on ep0 timed out. A listener that cannot serve `127.0.0.1` has no network left to blame, and that check is cheap enough to make early. Full record, including everything that was ruled out first (tunnel, nftables, disk, dead daemon): **`documentation/audits/INCIDENT-ep0-pbs-fd-exhaustion-2026-08-18.md`**. ## 2. What was done 1. `LimitNOFILE=65536` drop-ins for `proxmox-backup-proxy.service` and `proxmox-backup.service`, each carrying its reason inline. **The API daemon was not implicated** (15 fds) and its drop-in says so — a later reader must not mistake it for a second culprit. 2. Restarted both. After: soft limit 65536, fds back to 18, `Recv-Q 0`, loopback `200`. 3. **Verified from the customer side, not only from ep0** — both boxes got `200` in ~0.1 s and `pvesm status` read `felhom-pbs pbs active`. 4. Re-drove the missed backups **through the product path** — `POST /backup?target=felhom-pbs` on each agent's local API, issued from inside the guest's controller container with the controller's own credentials, i.e. the same call the scheduler makes. Not a hand-run `vzdump`. **Result:** `demo-felhom` → `ct/9201/2026-08-18T03:57:43Z` (4.10 GB, 36.4 s); `demo-hp` → `ct/9201/2026-08-18T03:58:43Z` (4.29 GB, 41.5 s). Both directories carry a full manifest on ep0, and both hosts log the re-run vzdump as `OK`. **And the hub agrees** — both boxes' next host reports carry `felhom-pbs success=true` (04:00:33Z and 04:07:35Z), so the operator view went green on the evidence rather than on the fact that a restart was performed. **No data was lost and no backup was skipped** — the daily local tier was never affected (it completed on both boxes at 05:00 and 05:02), and the PBS tier is weekly, so the outage window cost exactly one attempt, which was re-driven the same morning. Evidence copied off ep0 **before** the restart, per standing rule 5: `documentation/audits/evidence-ep0-fd-2026-08-18/` — pre-restart state, post-fix state, access-log tail. ## 3. What I got wrong, and corrected - **`proxmox-backup-manager version` prints *available* then *running*.** It read `4.2.5-1 running version: 4.2.2`, which looks exactly like a daemon left behind by a package upgrade. It is not: `dpkg -l` shows **4.2.2-1 installed**, 4.2.5-1 merely available in the repo, and the on-disk binary is dated 2026-06-18. I restarted the API daemon on that mistaken reading; harmless, and its drop-in is a genuine improvement, but it was not needed. - **I addressed `demo-hp`'s agent at the island address** because `operations/nodes.md` says that box is island-migrated. It is not (**R-338**), and the resulting timeout was briefly read as a fault. ## 4. Findings filed — R-336, R-337, R-338 All three are in `documentation/backlog/OPEN-ITEMS.md` with numbers, per the registers-first rule. - **R-336 — the poll rate is the real defect.** ~1 request/second against a DR endpoint written to weekly. `LimitNOFILE` raises the ceiling; **it does not fix the leak**, it converts a fortnightly outage into a multi-year one. - **R-337 — a status endpoint that trailed its own artifact, then caught up. WATCHING, not a defect.** `demo-hp`'s `/backup/status` was still serving the superseded 03:27:00Z failure at ~04:03Z while the snapshot sat on ep0 and the host logged `OK`; `demo-felhom` updated within ~40 s. **I filed this as a defect and that was premature** — the next host report (04:07:35Z) carried the success and the skew cleared with no intervention. Rewritten as WATCHING, with the explicit instruction not to open a fix until someone establishes whether this is just collection cadence. Recorded at all because during the recovery it read as a second failure, and it was not one. - **R-338 — `demo-hp` is not on the R-50 island and `nodes.md` says it is.** No `island_bridge` keys, guest has no `eth1`, `vmbr9` has zero members, and the agent's local API is bound to the customer LAN — the exposure R-50 existed to remove. **Not done, deliberately:** PBS 4.2.5-1 was not applied. Upgrading a production offsite endpoint was outside what this run was authorised to do, and its changelog should be read for the connection- handling leak first. ## 5. Gates — one pre-existing conviction, and a stated bypass `python3 scripts/repo_gates.py --fast` → **rc=1, CONVICTED: golden-currency.** Eight of nine gates pass. The conviction is **R-334, inherited and not caused here**: newest released controller **0.216.0**, newest golden bake **0.214.0**, so a new install misses two releases. The gate reads `felhom-controller/CHANGELOG.md` and `documentation/tests/golden-*` — **this session touched neither**, and its whole diff is documentation. Baking is possible; **vouching is operator-password-gated, and a baked-but-unvouched golden is worse than none**, so it is not a one-sided job CC can finish. **This push therefore used `git push --no-verify`, stated here per `.claude/rules/gates.md`.** R-334 is updated in the register with the new numbers rather than left reading 0.215.0. **CI checked by run ID, as the checklist requires: run `348`, `head_sha ebfd0967c`, conclusion `failure`, elapsed 13 s** (04:09:45→04:09:58Z). Expected and inherited — CI's only step is `python3 scripts/repo_gates.py --fast`, the same entry point that convicts golden-currency locally, with the sibling repos fetched. The 13 s runtime places it in the workflow's own "honest gate failure" band rather than the R-265 reap band, so the result is the gate speaking, not the runner. **I could not read the run log to name the gate from CI's own mouth** — `actions/runs/348/logs` and `actions/tasks/348/logs` both 404, `actions/runs/348/jobs` returns an empty list, authenticated as `admin`, and the web log endpoint 302s. So this is an inference from the local run plus the workflow definition, not a direct reading, and it is stated as such. **Expect one `[felhom CI] gates FAILED in admin/felhom.eu` mail for run 348** — the workflow alarms on failure by design. It is this push, and it is the golden-currency row, not a new fault; the same mails on 12 and 14 August have the same cause. *(Noted for accuracy: the first gate run was piped to `tail`, which returned `rc=0` — `tail`'s exit code, not the gate's. It was re-run unpiped to read the real `rc=1`. That is standing rule 1's trap in its smaller form, and the number reported above is the unpiped one.)* ## 6. What to watch The positive observable is the descriptor count, not the absence of an alert — an empty alert queue is equally consistent with "healthy" and "wedged again": ```bash ssh root@ 'PID=$(systemctl show proxmox-backup-proxy -p MainPID --value); \ ls /proc/$PID/fd | wc -l; ss -lnt "( sport = :8007 )"' ``` Healthy is ~20 fds and `Recv-Q 0`. **A count climbing between restarts means R-336's leak is still live.**