modules/notify/ — alerts to people, escalating until someone answers (layer 1)#

Every module so far ends at a decision in the log (§7.7): a trough is empty, bed 3 needs water, it will frost in the tunnel tonight. A decision nobody reads protects nothing. notify.py carries decisions to people, in each person's language, on the phone they have:

• Push, through ntfy: free software (Apache-2.0 and GPL-2.0), self-hostable, with an app on F-Droid, Google Play and the App Store. Each message has an I'm on it button.
• SMS, through a cellular modem on the farm's own computer, driven by ModemManager (mmcli). A basic phone gets the alert, and no internet is needed. Replying OK 417 acknowledges it.

§11 asks that alerts escalate and need acknowledgement. A route says which rules go to whom, in tiers. Escalation works like this:

1. The first tier is told at once.
2. If nobody in it says "on it" within the route's time, the next tier is told.
3. If nobody in a tier could be reached at all, the next tier is told without waiting.
4. Once someone acknowledges, escalation stops, and everyone else who was told hears who took it.
5. When the module that raised the alert clears it, everyone who was told hears that too.

An alert ends when a newer answer to the same question arrives (tonight's frost warning replaces last night's) or when its answer goes stale (valid_until; see modules/rules).

The notifier never imports the module whose decision it carries. Each decision names its own sentence and what it is about, and each module's language pack is data.

The roster#

Who gets what is the farm's private configuration, not the log:

{"farm": "Harrow Bend", "timezone": "America/Chicago",
 "channels": {"ntfy": {"server": "https://ntfy.example.org", "ack_topic": "hb-acks"},
              "sms": {"modem": "any"}},
 "people": {
   "maria": {"id": "0192…", "name": "María", "language": "es",
             "contacts": [{"via": "sms", "address": "+16155550101"}]},
   "sam":   {"id": "0192…", "name": "Sam", "language": "en", "units": "us", "quiet": ["21:00", "06:00"],
             "contacts": [{"via": "ntfy", "address": "hb-sam"},
                          {"via": "sms", "address": "+16155550102"}]}},
 "routes": [
   {"rules": ["water-*"], "tiers": [["maria"], ["sam"]], "escalate_after_min": 30, "urgent": true},
   {"rules": ["frost-watch", "covered-frost-watch"], "tiers": [["sam", "maria"]], "notify_clear": false},
   {"rules": ["soil-water-now"], "tiers": [["maria"]]}]}

• Contacts are tried in order. If push fails, the SMS goes out, and the log records both attempts.

• Quiet hours hold anything not marked urgent until morning. An empty trough is urgent; tomorrow's watering is not.

• Units are each person's: "metric" (the default) or "us". A message with numbers in it is said in the person's units where its module wrote a sentence for them (°F and inches for sowing and watering, litres a minute for zone flow); otherwise as it was written (rules.render).

• A rule no route names goes nowhere. It still stands on the board.

• A weekly digest, if the roster asks for one ("digest": {"to": ["sam"], "weekday": "mon", "time": "08:00", "cost_per_segment": 0.0075, "currency": "USD"}), tells the week in one message:

  Harrow Bend: Last week: 2 alerts; 1 taken by someone, 1 passed up for want of an answer. 2 messages: 1 by SMS (5 segments, about 0.04 USD) and 1 by push. 0 could not be delivered.

  That is the test's week: two troughs at once, sent to María as one Spanish SMS; she took one, and the other climbed to Sam.

  It goes once, at its hour in the farm's own time; a notifier that was down then does not send it a day late. Quiet hours are read on the farm's clock, so a change of hour (CDT to CST) moves "6 am" with it.

The log names people and never their numbers. Each message sent or tried is written back as a notification event, and each acknowledgement as an acknowledgement event, the same kind the water monitor writes. A notification event records:

• the decision, and the person by the id the log uses everywhere (§7.4);
• the channel kind, the outcome and the SMS segments it cost.

Phone numbers and topics stay in the roster. An export, or a view of the log shared with a researcher, carries who was told, never how to reach them.

Its memory stays a week long. An alert that ended more than seven days ago is forgotten. Of the events it wrote itself, it remembers only those its cursor has not read back yet. A year of daily alerts, tested, leaves about a week of them in memory, and the log keeps everything.

It restarts where the log says it was. A restarted notifier neither sends everything again nor forgets an alert half-escalated, and escalation keeps its original clock. It sends first and writes second, so a crash in between can repeat a message, never lose one.

Which replies count. A reply acknowledges alerts in three cases:

• it says yes in the sender's language or in English and gives an alert's number;
• it is one or more numbers alone;
• it says yes with no number: then it takes every open alert its sender was told about. Two troughs on one silent radio are one errand, sent as one message, and "Sí, voy" covers both.

A reply that says no is never an acknowledgement, whatever else it contains. "No puedo 417", "si no puedo" and "can't 417" are all ignored, and the alert keeps climbing. The yes and no words are lists in each language pack (notify.ack_words, notify.no_words), so a new language brings its own.

On Harrow Bend#

test_notify.py runs the water monitor's §15 season on the virtual farm alongside the notifier, looking every ten minutes. The radio is out for twelve hours on day 2, and the south trough's float sticks on day 9. María reads Spanish on a basic phone; Sam has the push app. Nobody answers, so every alert climbs to Sam.

Alerts due together go as one message. When the radio both troughs hang off went quiet, María got one SMS listing both, with a number for each, and Sam got one push with one button that takes both. Sent one alert at a time, the same season was 16 messages and 23 segments. The log still holds one notification per alert, tied by a batch id, with the message's cost counted once.

What was checked, and what was not#

• Unit and process tests: escalation, restart, quiet hours, replies, both channels, and the notifier as a module process. Its grant reads every module's decisions and nothing of the farm's readings, and it publishes over real HTTP.
• A real ntfy server (v2.11.0, in a container on this machine), in two setups:
  • Open: publish, press the button the way the phone app does, and read the acknowledgement back.
  • Deny-by-default, with the recommended tokens: the notifier's token publishes and reads; the button's token can write the acknowledgement topic and gets 403 on anything else. Anonymous access gets 403.
• The sandboxed service: run live under a user systemd manager with the drop-in's settings. It read its token and roster as credentials, fell back to no ntfy token when that file was missing, reached the host over its socket, and published to the ntfy server. systemd-analyze security scores the unit at 1.3 ("OK"), against 0.4 for a module with no network.
• Not checked: SMS on a real modem. There is none here. The mmcli commands and the JSON they return are taken from ModemManager 1.23's source (cli/mmcli-output.c, cli/mmcli-modem-messaging.c) and tested against a fake that answers the same way. Also unchecked: whether the service's user may send through ModemManager, which polkit decides and which may need a rule. Check both on the first gateway with a SIM.

FIELDMESH_NTFY_SERVER=http://127.0.0.1:18432 python3 -m unittest test_notify.TestAgainstARealNtfyServer

Running it#

python3 sdk/modhost.py grant --log farm.jsonl --manifest modules/notify/module.json \
    --token-out /etc/fieldmesh/modules/notify.token
python3 -I modules/notify/notify.py --socket /run/fieldmesh/modules.sock --config roster.json

The grant reads decisions and acknowledgements from every module, and the grant record says so. Under systemd it is fieldmesh-module@notify with its drop-in (deploy/systemd/). No dependencies beyond Python's standard library, plus mmcli for SMS.

Choosing a push server (Q29):

• ntfy.sh works today, but there the topic name is the only lock.

• A self-hosted server with auth-default-access: deny-all and two tokens is the setup checked above:

  • the notifier's: read-write on hb-*;
  • the phones': write-only on the acknowledgement topic, read-only on their own topic.

  The server must be one the phones can reach, which a farm's own computer often is not.

Code AGPL-3.0-or-later (LICENSE); strings in packs/ under the notify. prefix, with the Spanish an unreviewed draft.

Next: SMS checked on a real modem.