Documentation
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Overview ¶
Package state is the fleet-state verb's one decision: a bench is UP, DOWN or HELD by its heartbeat key and that key's TTL.
THE KEY IS THE BENCH'S OWN WORD THAT IT IS THERE (SPEC-STATE ## Presence -- keys with TTL: the key expires on its own and the beat renews it). The state follows the key and nothing else. That is the whole of the #2161 repair: a bench at load 21 on 16 cores used to read DOWN, because everything asked of it timed out under the load it was carrying, while it was writing its heartbeat key the entire time. Load is a fact on the row beside the state and is NEVER a say in it (the same law as the fill's brake, pulse/fillstore.go: the load only brakes placement, it never shrinks a lease). So:
UP -- the key is within its TTL and carries no hold: the bench is there.
HELD -- the key is within its TTL and carries a hold: the bench is there
and taking no work. A hold rides the key, so it expires with it:
a hold is a state of a bench that is there, never a tombstone.
DOWN -- the key has expired (or was never written): no word from the bench
within its own TTL.
The TTL is per key, written with it: one beat may promise a minute, the beat before a planned sleep may promise an hour. A bench whose key expires is DOWN within TTL+5 s -- the decision is at the TTL itself, so any observer is inside the allowance.
THE PAGE IS NEVER AUTHORITY. `nova-sprint fleet-state` prints one Row per bench and `nova-sprint fleet-live` lists Live over the same decision, both read from the fleet store by ReadRedis (redis.go). A page made from those lines (rowan-tools' queue/control/fleet-state.tsv) is never read back by anything in this tree (TestNoReaderOfFleetStateTSV holds the grep). A projection read back is a snapshot pretending to be the present -- the keys are the present.
Index ¶
Constants ¶
const Registry = "benches"
Registry is the set every registered bench is a member of.
Variables ¶
This section is empty.
Functions ¶
func DesiredKey ¶
func Live ¶
Live is what `nova-sprint fleet-live` lists: the names whose heartbeat key still counts, in the order given. It answers presence, not eligibility -- a HELD bench is here (that is what held means), and a DOWN bench's key has expired and it is not. Whether a bench may take work is State == Up, and that is the admission owner's question, not this one.
Types ¶
type Bench ¶
type Bench struct {
Name string
Load float64
Cores int
// Key is the bench's heartbeat key. Nil means the bench has never written
// one, which is as down as one that expired: a bench that has said nothing
// is not up.
Key *Key
}
Bench is one machine as the fleet-state rows carry it. Load and Cores are the bench's load facts, kept beside the key so one caller's readings travel together -- and kept out of the decision entirely (the #2161 case: load 21 on 16 cores that still writes its heartbeat key is UP).
type Key ¶
Key is one bench's heartbeat key: when it was last written, how long one write counts, and whether that write carried a hold. The TTL is the life of one write, not a property of the bench -- the bench chooses it per beat and renews by writing again. A write with no TTL expires at once.
type State ¶
type State string
State is what fleet-state says of one bench.
const ( // Up says the bench is there: its heartbeat key is within its TTL. Up State = "UP" // Held says the bench is there and taking no work: a hold rode its key and // the key still counts. Held State = "HELD" // Down says the bench has not been heard from within its key's TTL. Down State = "DOWN" )
Source Files