What keeps going, and what stopped moving

Status: Accepted · Audience: Operator · Area: N — Companion

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Purpose

Two things a stack does while nobody is looking, and both fail by going quiet.

B10 hands a long-running command — the guard on the data location, the clock that closes requests nobody ruled on — to the machine’s own service manager, so it outlives the terminal that started it. N10 already shows what each one guarantees and whether it is running (N10-R10). What it does not do is let the operator hand one over, or take one back, from here.

The guard can also be started from here without handing it to anything. Asked for over the web API, it is a job the stack keeps only while somebody keeps asking about it, and the app asks while its screen is open. That guard lives as long as the screen does, and it is a different thing from a hosted one.

C7 reads the whole queue at once and says what has stopped and why. N2 makes stuck downloads reachable (N2-R9) and N16 shows what self-healing did about them. What neither says is how a stopped queue reads on a small screen without losing the one distinction that makes it worth reading: which kind of stopped, and whether the cause is one thing or twenty.

Behaviour

Hosting a command is offered here, as an act of its own

The operator names a command and asks for it to be kept running. That is the whole request, and it is never arrived at as a side effect of anything else (B10-R6). Taking one back is offered the same way.

What installing does to the machine is said with it: whether the command was started, where its words are now written, and every file it wrote. Removing says every file it took back. A hosted command with nowhere visible to speak is one the operator cannot tell from a failure.

A platform nothing can be configured on says so, and says what to do

Where the machine has no service manager lemonfiber configures, the stack says so and gives an instruction. The app shows both and offers no install — offering one would be offering an act the stack has already said it cannot perform here.

Standing is six things, and installed is not one of them

Hosted, installed but unverified, stopped, orphaned, not hosted, unsupported. The app shows which, as N10-R10 already requires of what is not running. The case this page adds is right after an install: what comes back says whether the manager is running the command now, and the app reports that rather than the install having succeeded.

A guard can be started here, and lives while the screen asks

The data-root guard (C5) looks at the data location every few seconds and, the moment it is gone or has become a different volume, stops the forms it was started for, so the services do not write a phantom library onto whatever is left. It never starts them again (C5-R8, C5-R9).

The app offers starting one for the forms the operator names. Before it starts, the app says what it would guard and what it would do: the data location, how often it looks, and the command it would run when that location goes.

Started over the web API, the guard is a job with no ending of its own, and the stack keeps such a job only while somebody asks about it. The app asks while its screen is open, on the cadence it declares (N1-R27), and releases the guard when the screen is left. So the guard lives only while this screen keeps asking, and the app says so plainly — before it starts and for as long as it runs. A guard that is meant to outlive the screen is a hosted one, offered above as an act of its own, and the app never presents a screen-held guard as hosted.

A guard that ended says how

A guard ends in one of four ways, and each is a different afternoon. It saw the data location go, and says which forms it stopped, whether stopping them worked, and why it ended. It was ended without seeing anything: released when the screen was left, or let go because nothing asked about it. It never started, because there was no data location to guard or it was already gone, and the stack says which. Or the stack no longer knows it, because the stack itself restarted and nothing it was running survived that.

Stopped is the field worth reading twice. A guard that saw the drive go and could not stop the services has not protected anything, and the app never shows it as though it had.

A stopped queue says which kind of stopped

Stalled, slow, completed but never imported, failing to import again and again, fetched over and over, orphaned on disk, and waiting on something that never matches. Each is a different thing to do, and the stack orders them worst first. The app keeps the categories and the order. Slow is the one most worth keeping apart: it needs patience, not a fix, and shown as stuck it teaches an operator to ignore the list.

One cause is one row

Twenty downloads stopped by a full disk are one thing to fix. The stack says so — one row naming the cause, with how many items it stands for — and the app shows that row rather than twenty (G4 G4-R3).

The service’s own words about what is blocking it

Where a service said what was in its way, those words are carried. A permission denial from an import log is the thing the operator can act on, and the app shows it as it was said.

How long, not only whether

Each row carries how long it has been that way. That is what makes stuck a sentence an operator can weigh, and it is shown with the row.

A queue that could not be read is not an empty queue

Where one service’s queue would not answer, or is one lemonfiber cannot read at all, the list may be short. The app says so, naming each service and its reason where the stack names them, and never renders a short list as a clear one (C7-R11, C7-R15).

A stuck item leads to where it got to

Each stuck item is named so its trace can be asked for, and the app takes the operator there (N8) rather than to a count.

States

Edge cases

• Installing a command already hosted. What is there is replaced, the answer names every file it touched, and there are never two.
• Removing a command that was never hosted. Said, and not shown as a failure.
• A hosted command whose program moved after an update. Orphaned, with the program it names, and never shown as hosting anything.
• A full disk stopping every download at once. One row, the disk, with a count — not a screen of downloads.
• Something seeding at a hundred percent. Not stuck, and not on this list.
• The phone locks while a guard’s screen is open. Nothing asks while it is locked, and the stack lets the guard go once it has gone unasked for long enough. Coming back, the app shows the guard as let go, not as still guarding.
• A guard that saw the data location go and could not stop the services. Shown as that, and never as a guard that protected the library.

Requirements

Notes

What the contract carries.

The per-category list is on dashboard, which the stack publishes on its event stream; a screen holding that stream reads it on N1-R67’s terms.

Two acts C7 names are not offered here, because nothing serves them. Marking an item as intentionally unmanaged (C7-R12) and adjusting the thresholds (C7-R5) have no action on the route the app reaches. N1-R17 applies: the app does not approximate either.

Related

• N1 — parity, and what the app may claim
• N2 — stuck downloads, reachable
• N8 — where one item got to
• N10 — what a long-running command guarantees
• N16 — what self-healing did about the queue
• B10 — hosting long-running commands
• C7 — queue health and stuck items