# 118 — `elementsynapse`

Matrix homeserver (Synapse). Backs `@dtoro:avispero`.

## At a glance
- **Hostname:** `elementsynapse`
- **IP:** `192.168.8.242`
- **Host:** **strong** (migrated from hubris 2026-07-05)
- **Privilege:** **unprivileged**
- **Resources:** 1 core / 2 GiB RAM / **16 GiB rootfs** (grown from 8 GiB on 2026-05-15 after disk-full incident)
- **Mounts:** none from `/mnt/library`
- **Public hostname:** [`matrix.hubris.network`](../infrastructure/dns.md) → [caddy](121-caddy.md) → `:8008`
- **`server_name`:** `avispero` (intentionally different from the public URL).
- **Database:** Synapse runs on **SQLite** (`/var/lib/matrix-synapse/homeserver.db`, ~90 MiB). PostgreSQL on `127.0.0.1:5432` is dedicated to the mautrix bridge databases (one per bridge), not Synapse itself.

## Service / port map

| Service        | Listen  | Notes                            |
| -------------- | ------- | -------------------------------- |
| synapse        | `:8008` | Matrix client-server / federation HTTP. Caddy terminates TLS for `matrix.hubris.network`. |
| synapse-admin  | `:5173` | Web UI (vite dev server) for Synapse admin API. |
| mautrix-whatsapp | `:29318` | Docker, `network_mode: host`, compose in `/root/mautrix-whatsapp/`. |
| mautrix-meta     | `127.0.0.1:29319` | Facebook/Instagram bridge, `/root/mautrix-meta/`. |
| mautrix-signal   | `127.0.0.1:29328` | `/root/mautrix-signal/`. |
| mautrix-slack    | `127.0.0.1:29335` | `/root/mautrix-slack/`. |
| mautrix-linkedin | `127.0.0.1:29341` | `/root/mautrix-linkedin/`. |

## Bridges (mautrix)

All five bridges run as plain `docker compose` stacks under `/root/mautrix-<name>/` — no systemd unit, `restart: unless-stopped`. Their appservice registration YAMLs live in `/etc/matrix-synapse/` and are listed in `homeserver.yaml` under `app_service_config_files`. If a bridge daemon is down, Synapse logs `push_bulk … ConnectionRefusedError` and retries every 512 s; restart the bridge with `cd /root/mautrix-<name> && docker compose up -d`.

## Operational notes
- Rootfs is on `pve` LVM-thin, grow with `pct resize 118 rootfs +<N>G` from the host — resize2fs runs automatically.
- `/var/lib/matrix-synapse/media_store` is the dominant grower (~2 GiB at last check). If disk pressure returns, purge remote media via the Synapse admin API before resizing further.

## Known issues
- ~~Disk usage was 86.8% at last legacy monitor reading on 2026-04-21~~ — resolved by growing rootfs to 16 GiB on 2026-05-15.

## Related
- ~~[claudio-bot (123)](archive/123-claudio-bot.md)~~ — decommissioned 2026-06-04, replaced by Hermes Agent
- [Caddy](121-caddy.md)
- [DNS](../infrastructure/dns.md)
- [Monitoring](../infrastructure/monitoring.md)

## Changelog

### 2026-06-06 — DHCP drift fixed: internal `/etc/network/interfaces` was `dhcp` despite Proxmox static config
**Symptom:** Matrix was down. Caddy at `192.168.8.175` couldn't reach `192.168.8.239:8008` — the LXC was actually at `192.168.8.244` because the guest-side dhclient had overridden the PVE-assigned static IP.

**Root cause:** During the 2026-06-02 static-IP migration, `pct set 118 --net0 ... ip=192.168.8.239/24` was applied to the Proxmox config, but the internal `/etc/network/interfaces` still had `iface eth0 inet dhcp`. On every DHCP lease renewal, dhclient grabbed `.244` from Technitium's pool.

**Fix:**
- Replaced `iface eth0 inet dhcp` with `iface eth0 inet static` + `address 192.168.8.239/24` + `gateway 192.168.8.1`
- `ifdown eth0 && ifup eth0` applied the static IP
- Killed lingering dhclient process
- Verified: `curl http://192.168.8.239:8008` returns 302 from Caddy's LXC

**Prevention:** The `check-caddy-backends.sh` cron on hubris now runs every 10 minutes, which would have caught this drift within 10 minutes of occurrence.

### 2026-05-15 — phantom-notification cleanup for `@admin`
After the disk-full incident, the mobile (Element X) badge showed ~125 unread but every room read clean in the UI. Root cause: stale rows in `event_push_actions` that were never reaped — Synapse's read-receipt-driven cleanup didn't catch up. Two contributors:
1. **8 of 12 affected rooms** had read receipts past the "unread" stream_ordering — pure stale state, likely from the disk-full window stalling rotation/cleanup.
2. **The noisiest room** (a Signal-bridged DM) was flooded with `m.room.redaction` events from `@signalbot:avispero` (disappearing messages being deleted). Synapse counts redactions as notifications by default, but Element X doesn't render them — so they were invisible "ghosts".

Fix (after stopping Synapse and backing up `homeserver.db`):
- `DELETE FROM event_push_actions WHERE stream_ordering <= max(receipt_stream)` per (user, room) — clears receipt-superseded rows.
- `DELETE FROM event_push_actions WHERE event_id IN (SELECT event_id FROM events WHERE type='m.room.redaction')` — removes redaction-driven notifications.
- Rebuild `event_push_summary` from the remaining rows (preserve `thread_id='main'` to satisfy the NOT-NULL check constraint).

Result: 125 → 4 (legitimate WhatsApp unreads).

Then, to stop this recurring, an **override push-rule** was installed for `@admin` via the client API:
```
PUT /_matrix/client/v3/pushrules/global/override/suppress_redactions
{ "actions": [], "conditions": [{ "kind": "event_match", "key": "type", "pattern": "m.room.redaction" }] }
```
With empty `actions`, all `m.room.redaction` events are silently ignored by the push system. Inspect/remove via the same endpoint. (Note: rule ids beginning with `.` are reserved for server defaults — custom ids cannot start with a dot.)

### 2026-05-15 — disk-full incident, rootfs grown to 16 GiB, bridges restarted
Element/Synapse was unreliable for ~2 days: messages dropping, sync requests stalling, mautrix bridges (slack/signal/meta/linkedin/whatsapp) all exited around 2026-05-13. Root cause: rootfs reached 100% (19 MB free of 7.8 G); Synapse logs showed `OSError: [Errno 28] No space left on device` during flush. Fix: `pct resize 118 rootfs +8G` (host `pve` VG had plenty of headroom), `journalctl --vacuum-size=50M` to recover ~200 M, `systemctl restart matrix-synapse`, then `docker compose up -d` in each `/root/mautrix-*` directory. Also expanded this wiki page to document the bridges, synapse-admin, and the actual DB backend (Postgres, not the SQLite leftover).

### 2026-04-28 — wiki entry created
Initial documentation.
