corrib-flow Worker

Cloudflare Worker that acts as a CORS proxy for waterlevel.ie CSVs and runs the Telegram alert bot for @corribflow_bot.

Prerequisites

Wrangler CLI (npm install -g wrangler)
Cloudflare account (free tier sufficient)
Telegram bot token from @BotFather

One-time setup

1. Create the KV namespace

npx wrangler kv namespace create FLOW_KV

Copy the id from the output into wrangler.toml.

2. Set secrets

npx wrangler secret put TELEGRAM_TOKEN     # from BotFather
npx wrangler secret put WEBHOOK_SECRET     # any random string, e.g. openssl rand -hex 32

WEBHOOK_SECRET must contain only A-Z a-z 0-9 _ - (no colons or slashes).

3. Deploy

npx wrangler deploy

4. Register the Telegram webhook

Run once in a browser or curl (substituting your values):

https://api.telegram.org/bot<TELEGRAM_TOKEN>/setWebhook?url=https://corrib-flow.graza.workers.dev/telegram&secret_token=<WEBHOOK_SECRET>

Expected response: {"ok":true,"result":true,"description":"Webhook was set"}

Cron triggers

Schedule	Dublin time	Purpose
`/15 * * *`	every 15 min	Threshold crossing alerts
`0 4,5,14,15 * * *`	5am and 3pm (DST-aware)	Flow summary + 12h chart

The twice-daily trigger fires at four UTC hours to cover the DST boundary; the handler checks the Dublin local hour and exits early if it isn’t 5 or 15.

KV keys

Key	Contents	TTL
`alertState`	JSON array of thresholds currently crossed	none
`subscribers`	JSON array of Telegram chat IDs	none
`latestFlow`	`{datetime, flowRate, pastFlow}` from last cron run	15 min
`errors`	JSON array of last 10 errors: `{context, error, timestamp}`	none

To inspect recent errors:

npx wrangler kv key get --binding FLOW_KV errors

The context field identifies where the error occurred: broadcastPhoto, /chart, or scheduled:<cron> (e.g. scheduled:*/15 * * * *).

Bot commands

Command	Behaviour
`/start`	Subscribe (capped at 100 subscribers)
`/stop`	Unsubscribe
`/flow`	Reply with current flow (served from KV cache, 15 min max age)
`/chart`	Reply with 12-hour flow chart image from QuickChart

The bot works in group chats as well as direct messages.

Alert thresholds

Alerts fire at 100, 150, 200, 250, 300, 350, 400, 450, 500 cumec.
Downward alerts require flow to drop 10 cumec below the threshold (hysteresis) before firing.

Deploying updates

npx wrangler deploy