railway-postgres-setup

## Railway PostgreSQL Setup - Single PostgreSQL instance (v16.11) shared by n8n and Mattermost - n8n uses `railway` database, Mattermost uses `postgres` database - Umami has its own service but is NOT connected to this PostgreSQL (needs separate DATABASE_URL config) - Volume: upgraded from 500MB to 1GB on 2026-03-14 - Redis service for n8n, Valkey service for Umami ## Incident: 2026-03-13 21:34 UTC — PostgreSQL PANIC crash - Root cause: `No space left on device` on WAL file fdatasync - WAL default `max_wal_size` was 1GB, could exceed the 500MB volume during spikes - Actual data usage was only ~40MB across all databases - Volume usage chart showed steady ~100MB — crash was caused by transient WAL spike ## Changes applied (2026-03-14) ```sql ALTER SYSTEM SET max_wal_size = '128MB'; -- was 1GB ALTER SYSTEM SET min_wal_size = '32MB'; -- was 80MB ALTER SYSTEM SET temp_file_limit = '50MB'; -- was unlimited (-1) ``` - `checkpoint_completion_target` was already 0.9 (good) - Volume upgraded from 500MB to 1GB for extra headroom