# n8n DWH Bronze Layer Pipeline — Design & Plan

**Date:** 2026-04-24
**Status:** Awaiting approval
**Repo:** `/Users/davidkiania/Downloads/55_ts_coolify_gemini_prod`

---

## Context

Fireside's Tracksolid fleet pipeline currently ingests telemetry into a single production DB (`tracksolid_db`, TimescaleDB/PostGIS on Coolify at `stage.rahamafresh.com`). There is no downstream data warehouse, so every analytical query hits the live operational DB — risking contention as Grafana panels and ad-hoc analysis scale. A full medallion-architecture bronze DDL exists on disk (`dwh/260423_dwh_ddl_v1.sql`) but has never been populated.

The user wants to build the **first layer of that DWH** using n8n (already running on the same Coolify instance, already connected to both source and target DBs). The design has two n8n workflows:

1. **Workflow 1 — Extract**: pull tables from the source `tracksolid_db` (Coolify-hosted TimescaleDB, reached via the same internal Docker network n8n is on), write CSVs to rustfs blob storage.
2. **Workflow 2 — Load**: pick up those CSVs and upsert into the bronze schema inside `tracksolid_dwh` (PostGIS) on the separate server `31.97.44.246:5888`.

**Confirmed connection targets:**
- **Source:** `tracksolid_db` on the Coolify stack — n8n connects via internal Docker network (trial confirmed working).
- **Target:** `tracksolid_dwh` at `31.97.44.246:5888` — a separate PostGIS instance. Schemas `bronze`, `silver`, `gold`, plus `dwh_control` all live in this one database.

The intermediate rustfs CSV layer (a) gives a durable audit trail of every extract, (b) decouples source-DB availability from target-DB availability (a remote-DB outage doesn't lose data — the CSV waits in `exports/`), and (c) matches how rustfs is already used in the stack (pg_dump backups).

---

## Architecture

```
  ┌──────────────────────────────────────────────────┐
  │             n8n  (Coolify instance)              │
  │                                                  │
  │   Workflow 1: dwh_extract                        │
  │   Schedule: cron 0 5,8,11,14,17,20,23 * * *      │
  │             (Africa/Nairobi, 7 runs/day)         │
  │   Steps per table:                               │
  │     1. Read watermark from target control table  │
  │     2. Query source with watermark bounds        │
  │     3. Render rows as CSV                        │
  │     4. Upload CSV to rustfs                      │
  │     5. Insert row into dwh_control.extract_runs  │
  │        (status='uploaded')                       │
  │     6. Execute Workflow 2 for this CSV           │
  │                                                  │
  │   Workflow 2: dwh_load_bronze                    │
  │   Trigger: Execute Workflow (from Workflow 1)    │
  │   Input: { table, csv_path, run_id,              │
  │            run_started_at }                      │
  │   Steps:                                         │
  │     1. Download CSV from rustfs                  │
  │     2. Parse CSV                                 │
  │     3. BEGIN                                     │
  │          INSERT ... ON CONFLICT DO NOTHING       │
  │          UPDATE extract_watermarks               │
  │          UPDATE extract_runs SET status='loaded' │
  │        COMMIT                                    │
  │     4. Move CSV: dwh/exports/ → dwh/processed/   │
  └──────────────────────────────────────────────────┘
         │                    │                    │
         ▼                    ▼                    ▼
   tracksolid_db       rustfs (fleet-db)    tracksolid_dwh (PostGIS)
   (Coolify internal)  /dwh/exports/        31.97.44.246:5888
                       /dwh/processed/      dwh_control.extract_watermarks
                                            dwh_control.extract_runs
                                            bronze.devices
                                            bronze.position_history
                                            bronze.trips
                                            bronze.alarms
                                            bronze.parking_events
                                            bronze.device_events
                                            bronze.live_positions
                                            bronze.ingestion_log
```

**Rustfs path convention:**
- Active export: `s3://fleet-db/dwh/exports/{table}/{YYYYMMDD_HHMM}_EAT.csv`
- After successful load: moved to `s3://fleet-db/dwh/processed/{table}/{YYYYMMDD_HHMM}_EAT.csv`
- Never deleted — this is the audit trail.

---

## Table-by-Table Extraction Strategy

### Snapshot tables (TRUNCATE + full reload every run)

Small state-based tables where "current state" matters, not history.

| Source table | Rows | Bronze target |
|---|---|---|
| `tracksolid.devices` | 63 | `bronze.devices` |
| `tracksolid.live_positions` | 19 | `bronze.live_positions` |

**Load pattern:**
```sql
BEGIN;
  TRUNCATE bronze.devices;
  INSERT INTO bronze.devices (...) VALUES (...);
  UPDATE dwh_control.extract_watermarks SET last_loaded_at = NOW() WHERE table_name='devices';
COMMIT;
```

### Incremental tables (watermark + append-with-dedup)

Append-only event/history tables. Watermark is the **DB insertion timestamp**, not the device-reported timestamp, so out-of-order device clocks / delayed pushes can't cause silent data loss.

| Source table | Watermark column | Natural unique key (exists in source) | Bronze conflict target |
|---|---|---|---|
| `tracksolid.position_history` | `recorded_at` | `(imei, gps_time)` | `(imei, gps_time)` |
| `tracksolid.trips` | `updated_at` | `(imei, start_time)` | `id` |
| `tracksolid.alarms` | `updated_at` | `(imei, alarm_type, alarm_time)` | `id` |
| `tracksolid.parking_events` | `updated_at` | `(imei, start_time, event_type)` | `id` |
| `tracksolid.device_events` | `created_at` | `(imei, event_type, event_time)` | `id` |
| `tracksolid.ingestion_log` | `run_at` | PK `id` | `id` |

**Extract pattern (closed upper bound to avoid boundary drift):**
```sql
SELECT <cols>, ST_AsEWKT(geom) AS geom_ewkt
FROM tracksolid.position_history
WHERE recorded_at >  :last_extracted_at
  AND recorded_at <= :run_started_at
ORDER BY recorded_at;
```

**Load pattern (idempotent):**
```sql
BEGIN;
  INSERT INTO bronze.position_history (imei, gps_time, geom, lat, lng, ...)
  SELECT imei, gps_time, ST_GeomFromEWKT(geom_ewkt), lat, lng, ...
  FROM csv_stage
  ON CONFLICT (imei, gps_time) DO NOTHING;

  UPDATE dwh_control.extract_watermarks
     SET last_extracted_at = :run_started_at,
         last_loaded_at    = NOW(),
         rows_loaded_last_run = <count>
   WHERE table_name = 'position_history';

  UPDATE dwh_control.extract_runs
     SET status = 'loaded', run_finished_at = NOW(), rows_loaded = <count>
   WHERE run_id = :run_id;
COMMIT;
```

### First-run behaviour

`extract_watermarks` seeded with `last_extracted_at = '2026-01-01T00:00:00Z'` so the first run back-fills all historical data in a single CSV per table.

### Skipped for now (no data, webhooks pending)

`obd_readings`, `fault_codes`, `fuel_readings`, `temperature_readings`, `lbs_readings`, `heartbeats` — add later by copying the incremental pattern and seeding a watermark row.

---

## PostGIS Geometry Handling

Six source tables have `geometry(Point, 4326)` columns: `live_positions`, `position_history`, `trips` (start+end), `parking_events`, `alarms`.

- **Extract:** `ST_AsEWKT(geom) AS geom_ewkt` — preserves SRID inline (`SRID=4326;POINT(...)`)
- **Load:** `ST_GeomFromEWKT(csv.geom_ewkt)` — no separate SRID step, no loss on round-trip
- **NULL safety:** `CASE WHEN geom IS NULL THEN NULL ELSE ST_AsEWKT(geom) END`

---

## Control Tables (to add to `tracksolid_dwh`)

New migration file: `dwh/261001_dwh_control.sql` — applied once to `tracksolid_dwh@31.97.44.246:5888`.

```sql
CREATE SCHEMA IF NOT EXISTS dwh_control;

CREATE TABLE dwh_control.extract_watermarks (
  table_name           TEXT PRIMARY KEY,
  last_extracted_at    TIMESTAMPTZ NOT NULL DEFAULT '2026-01-01T00:00:00Z',
  last_loaded_at       TIMESTAMPTZ,
  rows_loaded_last_run INT,
  updated_at           TIMESTAMPTZ DEFAULT NOW()
);

CREATE TABLE dwh_control.extract_runs (
  run_id           BIGSERIAL PRIMARY KEY,
  table_name       TEXT NOT NULL,
  run_started_at   TIMESTAMPTZ NOT NULL,
  run_finished_at  TIMESTAMPTZ,
  rows_extracted   INT,
  rows_loaded      INT,
  csv_path         TEXT,
  status           TEXT CHECK (status IN ('extracting','uploaded','loading','loaded','failed')),
  error_message    TEXT
);

CREATE INDEX idx_extract_runs_table_time ON dwh_control.extract_runs (table_name, run_started_at DESC);
CREATE INDEX idx_extract_runs_status_time ON dwh_control.extract_runs (status, run_finished_at DESC);

-- Seed one row per incremental table
INSERT INTO dwh_control.extract_watermarks (table_name) VALUES
  ('position_history'), ('trips'), ('alarms'),
  ('parking_events'),  ('device_events'), ('ingestion_log');
```

---

## Scheduling

- **Cron:** `0 5,8,11,14,17,20,23 * * *` with TZ `Africa/Nairobi` (set in n8n schedule node).
- **7 runs/day:** 05:00, 08:00, 11:00, 14:00, 17:00, 20:00, 23:00 EAT.
- **Fits the 6–8/day requirement** with even 3-hour gaps in daytime and a silent overnight window (23:00 → 05:00 = 6h) which is fine because device traffic is minimal after hours.
- First run of each day (05:00) will carry the overnight backlog — this is the expected behaviour of the watermark design.

---

## Error Handling & Observability

### Per-table isolation
Workflow 1 iterates tables in sequence; a failure on one table does not block others. Every table's result (success or failure) is logged to `dwh_control.extract_runs`.

### Retryable failures
If Workflow 2 fails mid-load: transaction rolls back → watermark stays → CSV stays in `exports/` → next scheduled run re-processes it (natural retry).

### Alerting (Grafana panels on `tracksolid_dwh`, read via `dwh_ro` role — see below)
- **Freshness:** `SELECT table_name, NOW() - MAX(run_finished_at) AS lag FROM dwh_control.extract_runs WHERE status='loaded' GROUP BY 1 HAVING NOW() - MAX(run_finished_at) > INTERVAL '4 hours';`
- **Failures in last hour:** `SELECT * FROM dwh_control.extract_runs WHERE status='failed' AND run_started_at > NOW() - INTERVAL '1 hour';`
- **Row count sanity:** `rows_extracted != rows_loaded` flags CSV parse or load issues.

### n8n-level error workflow
Attach an "Error Workflow" in both n8n workflows that posts to a webhook (existing pattern in `n8n-workflows/`) for immediate notification.

---

## Security & Credentials

Both DB credentials already exist in n8n (connections trialled and working). The required credential shapes are:

| n8n credential | Host / Port / DB | Recommended user | Usage |
|---|---|---|---|
| `tracksolid_source` | Coolify internal `timescale_db:5432` → DB `tracksolid_db` | `grafana_ro` (read-only) | Source extract queries |
| `tracksolid_dwh_target` | `31.97.44.246:5888` → DB `tracksolid_dwh` | `dwh_owner` (scoped) | Bronze writes + control-table updates |
| `rustfs_s3` | `${RUSTFS_ENDPOINT}` | `${RUSTFS_ACCESS_KEY}` | CSV upload/download/move |

### Credential-hardening recommendations (current state vs target state)

The trial connection string uses `postgres` (superuser) over a public IP. Two hardening steps to take before production:

1. **Create a scoped `dwh_owner` role** on `tracksolid_dwh` — owns only `bronze` + `dwh_control` schemas, cannot touch other DBs or cluster roles. n8n's `tracksolid_dwh_target` credential switches to this user.
2. **Create a `dwh_ro` role** for Grafana panels — read-only across `bronze` + `dwh_control`. This is what the freshness/failure dashboards in §Error Handling use.
3. **Enforce `sslmode=require`** on the `tracksolid_dwh_target` connection string (public-IP hop, cleartext otherwise).
4. **Rotate the `postgres` password** that was shared in chat history — one-off cleanup, not a plan blocker.

All four are one-migration-file tasks and fit naturally into the `dwh/261001_dwh_control.sql` setup step.

---

## Files to Create / Modify

| Path | Action | Purpose |
|---|---|---|
| `dwh/261001_dwh_control.sql` | **new** | Control-schema migration (watermarks + run log) |
| `dwh/260423_dwh_ddl_v1.sql` | **review** | Confirm bronze tables have matching unique constraints; patch if missing |
| `n8n-workflows/dwh_extract.json` | **new** | Workflow 1 export |
| `n8n-workflows/dwh_load_bronze.json` | **new** | Workflow 2 export |
| `docs/DWH_PIPELINE.md` | **new** | Operations runbook (see verification section) |
| `CLAUDE.md` §3, §4, §5, §10 | **update** | Add `tracksolid_dwh@31.97.44.246:5888` to §3 Connection Params; add bronze schema + n8n DWH workflows to codebase map; remove DWH item from Open Items |

**Existing utilities to reuse (do NOT reinvent):**
- Rustfs env vars already wired in `docker-compose.yaml` (`RUSTFS_ENDPOINT`, `RUSTFS_ACCESS_KEY`, `RUSTFS_SECRET_KEY`, `RUSTFS_BUCKET`) — Workflow nodes read from the same `.env`.
- Backup rustfs client logic in `backup/backup_db.sh` is the reference pattern for S3 auth shape.
- Existing n8n workflow pattern in `n8n-workflows/jimi_pushgps.json` et al. for webhook trigger + HTTP-forward shape.

---

## Verification

### Pre-deployment checks (before first cron trigger)
1. **Bronze DDL applied:** `psql -h 31.97.44.246 -p 5888 -U dwh_owner -d tracksolid_dwh -c "\dt bronze.*"` lists 16 tables.
2. **Control schema applied:** same connection, `\dt dwh_control.*` lists `extract_watermarks`, `extract_runs`.
3. **Watermarks seeded:** `SELECT * FROM dwh_control.extract_watermarks;` returns 6 rows, all with `last_extracted_at = 2026-01-01`.
4. **Roles created:** `\du` lists `dwh_owner` and `dwh_ro`; `postgres` superuser no longer used for n8n.
5. **n8n credentials:** Test each credential individually in n8n UI — all three connect successfully (source via internal network, target via `31.97.44.246:5888` with `sslmode=require`).
6. **Rustfs path exists:** `aws --endpoint ${RUSTFS_ENDPOINT} s3 ls s3://fleet-db/dwh/` — if missing, create `exports/` and `processed/` prefixes.

### First-run verification (manually trigger Workflow 1)
1. `SELECT * FROM dwh_control.extract_runs ORDER BY run_id DESC LIMIT 20;` — 8 rows (one per table processed), all `status='loaded'`.
2. `SELECT table_name, rows_loaded_last_run FROM dwh_control.extract_watermarks;` — non-zero for all incremental tables that have source data.
3. Row-count parity:
   ```sql
   -- on source (tracksolid_db, Coolify internal)
   SELECT COUNT(*) FROM tracksolid.position_history;
   -- on target (tracksolid_dwh @ 31.97.44.246:5888)
   SELECT COUNT(*) FROM bronze.position_history;
   ```
   Numbers should match ± rows inserted in the narrow window between the two queries.
4. **Geometry round-trip check:**
   ```sql
   SELECT ST_AsText(geom) FROM bronze.position_history LIMIT 5;
   -- should return valid POINT(lng lat) values, not NULL or garbage
   ```
5. **Rustfs audit:** `aws s3 ls s3://fleet-db/dwh/processed/` — 8 CSV files present (one per table), originals no longer in `exports/`.

### Steady-state verification (after 24h / 7 runs)
1. `SELECT table_name, NOW() - MAX(run_finished_at) FROM dwh_control.extract_runs WHERE status='loaded' GROUP BY 1;` — max lag < 3h 15min for every table.
2. `SELECT COUNT(*) FROM dwh_control.extract_runs WHERE status='failed';` — zero.
3. Grafana dashboard (to be added in a follow-up plan) shows freshness and row counts per table.

---

## Out of Scope (follow-up work)

- Silver/gold layer transformations (the DWH DDL defines schemas but no queries yet).
- Bronze schema evolution tooling (manual migrations are acceptable for one pipeline).
- Backfill of tables where webhooks aren't yet registered (OBD, fuel, temperature, LBS).
- Grafana dashboard panels for the DWH — worth its own spec once we have a week of data to design around.

---

## Open Questions (none blocking)

All design decisions resolved in the brainstorming session. Confirmed:
- Source: `tracksolid_db` on Coolify, reached via internal Docker network.
- Target: `tracksolid_dwh` at `31.97.44.246:5888` (public IP), schemas `bronze`/`silver`/`gold` + `dwh_control`.
- Trial connections already working in n8n.

If any endpoint/credential changes during implementation, those are n8n-credential updates only — no design change.