Fly.io: checks and maintenance

Do the Fly.io setup first.

Scheduled checks on recent data

Every 5 minutes, check asks two questions of the table and posts to a webhook when either has an answer:

• Which pumps averaged above 80° over the last 10 minutes? A SQL query over recent data. The time filter skips every file whose time range lies outside the window, before any data is read.
• Which pumps have sent nothing for 15 minutes? lake.latest() answers from the last-value index, without scanning the table.

fly secrets set --app $APP ALERT_WEBHOOK="<incoming webhook URL>"

The message body is {"text": "…"}, which Slack's incoming webhooks accept; change it for another service. Change the SQL to check anything the table holds: a rate of change, a counter that stopped increasing, readings outside a band per site. Over longer windows, a rollup keeps the query small.

Maintenance

Each append already merges small files and removes duplicates. Once an hour, jobs also runs maintain: it sorts each finished day into one file, applies retention, and deletes files no version needs. Nothing to set up.