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Advanced

Settings most people never need to change. Each has a sensible default, and each exists because somebody's system is not most systems.

The last two on this page are about storage rather than detection. If you are running from an SD card, or simply want to know what they cost, Built to Be Efficient explains it with real numbers and suggests settings by machine.

Notification settle delay

When a device develops a problem, the integration waits before telling anyone, so a device that hiccups and recovers within moments never rings your phone. A fixed delay cannot serve a fleet where one device reports every ten seconds and another every four hours, so the delay scales: it is a percentage of each device's own grace, the patience the freeze engine has already computed for it.

At the default of 30 percent, a device that reports every ten seconds settles in about a minute, and a device with a three-hour rhythm settles in about half an hour. Raise it and fewer transient problems reach you, at the cost of hearing about real ones later. Lower it and notifications become prompter and noisier. Detection is not affected; problems are recorded and listed the moment they are found, and this delays only the message.

Device Sentinel does not send messages yet, so this setting has nothing to delay today. It is here so the behaviour is settled before the first one goes out.

Episode recording threshold

The silence_episodes.md report records devices that went unusually quiet, for later study: it is how the integration learns whether a silent device was stuck or simply resting. A row opens when a device has been silent for this share of the distance between its normal rhythm and its freeze line.

At the default of 50 percent, a row opens halfway to the freeze line. Lower it and the file records more, including mild wobbles that recover on their own, which is useful when investigating a flaky device. Raise it and the file records only silences that came close to judgment. This affects one forensic file and nothing else: no detection, no notification, no learning.

How much history to keep

Device Sentinel keeps a daily record for every device: the longest gap between reports, the lowest signal reading, how long the signal spent below the floor, and the battery level. These are what let slow changes be seen at all. A battery does not measurably discharge in a fortnight, a signal floor wants a season to settle, and three months of reporting gaps is what would eventually allow the two-week judgment window itself to be examined rather than assumed.

The setting runs from thirty days to a year, in steps of thirty, and defaults to ninety. More history means a larger stored file, and that file is rewritten whenever something happens, so the cost is real on a Raspberry Pi with an SD card and negligible on a machine with an SSD. On a fleet of roughly a hundred and twenty devices, thirty days is around 230 KB, ninety around 350 KB, and a full year around 900 KB.

This setting never changes what is detected. Every judgment, the freeze window and the signal floor alike, is computed from the most recent two weeks whatever this says. That is why it cannot be set below thirty days: no choice can starve the window that does the judging. Two systems with different settings detect identically; they differ only in how much they remember.

Reducing it takes effect at the next midnight rather than the moment you move the slider, so a mistake can be undone before any history is lost.

Storage write interval

The integration tracks activity for every device, which changes constantly. Writing every change to disk would mean a write every minute or two forever, which wears SD cards and adds up on any system. Instead, routine activity is held in memory and written on this interval. Anything important, a new problem, a recovery, an acknowledgment, a checked box, is always written immediately regardless.

The default is 15 minutes. On an SD card, longer is kinder. On an SSD, shorter narrows the window of activity data that a power cut could lose, which at worst costs the affected devices a few minutes of clock and heals with their next report. The range is 1 to 60 minutes.