Send a webhook or email

A Cell set keeps per-key counters and flags. When a flag turns on (ON RISE) or off (ON FALL), it can call a URL or send an email.

Webhook when an order ships

Keep the secret part of the URL out of the statement:

CREATE SECRET slack_path AS 'T000/B000/XXXX';

CREATE CELLS shipping ON orders KEY id (
  shipped BIT ALL status = 'shipped',
  items   COUNT
)
  ON RISE shipped NOTIFY 'https://hooks.slack.com/services/{{secret:slack_path}}'
  BODY '{"text": "Order {{key}} shipped with {{items}} items."}';

The call is a JSON POST with a 5-second timeout. {{key}} is the key, {{items}} is the items cell. Without BODY, the body is a JSON object with the set, key, bit, edge and all cell values.

Email when an item runs out

Create a mailer once. With Google:

aios google auth alerts@example.com      # sign in once, in a browser

CREATE MAILER alerts OAUTH 'google' ACCOUNT 'alerts@example.com' FROM_NAME 'Stock alerts';

CREATE CELLS stock ON items KEY sku (
  out BIT ALL stock <= 0
)
  ON RISE out MAIL alerts TO 'purchasing@example.com'
  SUBJECT 'Out of stock: {{key}}' BODY 'SKU {{key}} is out of stock.';

For an SMTP server with a password, store the password as a secret and use CREATE MAILER m USER 'u' PASSWORD SECRET smtp_pw HOST 'smtp.example.com' FROM 'alerts@example.com'.

Check it

SHOW CELLS shipping ACTS;      -- the last 64 calls and whether they worked

A failed call is tried again on that key's next change. More: Cells.