mesh-controller/internal/inventory/durations.go

package inventory

import (
	"context"
	"time"
)

// The durations the core's bounds are set from (novox/hq to-be 45 Phase 0): see migration 0066.

// The kinds of duration recorded.
const (
	DurationApply    = "apply"
	DurationPlanTier = "plan-tier"
	DurationBuild    = "build"
	// DurationWalkPhase is one phase of an ended walk, per class (novox/hq ADR 0282 decision 6): subject
	// "<class>/<phase>", and "<class>/total" for its merge to every machine running it.
	DurationWalkPhase = "walk-phase"
	// DurationBusy is a machine's wait for a busy container (novox/hq ADR 0335): from its first report of a
	// send, which said a container waits because it is busy, to the report that says it replaced — the same
	// send's ref as its `apply` row, whose detail is ApplyBusy. Its own measure, never in the apply's.
	DurationBusy = "busy-wait"
)

// ApplyBusy is the detail of an `apply` duration whose report said a container waits because it is busy: the
// machine answered, and is not yet running what it was sent (novox/hq ADR 0335).
const ApplyBusy = "busy"

// DurationKinds are every kind, in the order `durations` shows them.
var DurationKinds = []string{DurationApply, DurationPlanTier, DurationBuild, DurationWalkPhase,
	DurationBusy}

// DurationsKeptFor is how long a duration is kept: long enough to set a bound from, and to correct it
// in Phase 1's first live week.
const DurationsKeptFor = 30 * 24 * time.Hour

// Duration is one measurement.
type Duration struct {
	Kind    string        `json:"kind"`
	Subject string        `json:"subject"`
	Node    string        `json:"node,omitempty"`
	Ref     string        `json:"ref"`
	Started time.Time     `json:"started"`
	Took    time.Duration `json:"took"`
	Detail  string        `json:"detail,omitempty"`
}

// RecordDuration keeps one measurement, once: the same thing measured again is not a second row.
func (i *Inventory) RecordDuration(ctx context.Context, d Duration) error {
	if d.Took < 0 {
		return nil // a clock that went back measures nothing
	}
	_, err := i.store.Pool().Exec(ctx,
		`insert into duration (kind, subject, node, ref, started, took_ms, detail)
		 values ($1, $2, $3, $4, $5, $6, $7) on conflict do nothing`,
		d.Kind, d.Subject, d.Node, d.Ref, d.Started, d.Took.Milliseconds(), d.Detail)
	return err
}

// RecordApplyDuration measures a machine's report of the declaration it was last sent: from the send
// to the first report of it. A report of anything else, or of a send already measured, measures
// nothing — a machine reconciling reports the same declaration every few minutes.
func (i *Inventory) RecordApplyDuration(ctx context.Context, node, declared, outcome string) error {
	if declared == "" {
		return nil
	}
	_, err := i.store.Pool().Exec(ctx,
		`insert into duration (kind, subject, node, ref, started, took_ms, detail)
		 select $1, n.name, n.name, n.sent || '@' || to_char(n.sent_at at time zone 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.US'),
		        n.sent_at, (extract(epoch from (now() - n.sent_at)) * 1000)::bigint, $4
		   from node n
		  where n.name = $2 and n.sent = $3 and n.sent_at is not null
		 on conflict do nothing`,
		DurationApply, node, declared, outcome)
	return err
}

// RecordBusyDuration measures a machine's wait for a busy container, at the report that says it replaced
// (novox/hq ADR 0335): from the end of its `apply` duration of the send it was last sent, which said it waited, to
// now. Nothing when that send's first report did not say a wait, and once per send.
func (i *Inventory) RecordBusyDuration(ctx context.Context, node, declared string) error {
	if declared == "" {
		return nil
	}
	_, err := i.store.Pool().Exec(ctx,
		`insert into duration (kind, subject, node, ref, started, took_ms, detail)
		 select $1, d.subject, d.node, d.ref, d.started + d.took_ms * interval '1 millisecond',
		        greatest(0, (extract(epoch from (now() - (d.started + d.took_ms * interval '1 millisecond'))) * 1000)::bigint), ''
		   from duration d join node n on n.name = d.node
		  where d.kind = $2 and d.subject = $3 and d.detail = $5 and n.sent = $4 and n.sent_at is not null
		    and d.ref = n.sent || '@' || to_char(n.sent_at at time zone 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.US')
		 on conflict do nothing`,
		DurationBusy, DurationApply, node, declared, ApplyBusy)
	return err
}

// Durations is every measurement of a kind since a moment, oldest first; every kind when kind is empty.
func (i *Inventory) Durations(ctx context.Context, kind string, since time.Time) ([]Duration, error) {
	rows, err := i.store.Pool().Query(ctx,
		`select kind, subject, node, ref, started, took_ms, detail from duration
		  where ($1 = '' or kind = $1) and recorded >= $2 order by recorded`, kind, since)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []Duration
	for rows.Next() {
		var d Duration
		var ms int64
		if err := rows.Scan(&d.Kind, &d.Subject, &d.Node, &d.Ref, &d.Started, &ms, &d.Detail); err != nil {
			return nil, err
		}
		d.Took = time.Duration(ms) * time.Millisecond
		out = append(out, d)
	}
	return out, rows.Err()
}

// WalkPhasesKept says whether any phase of a walk is kept as a walk-phase duration, and whether its total is.
func (i *Inventory) WalkPhasesKept(ctx context.Context, plan string) (anyKept, totalKept bool, err error) {
	err = i.store.Pool().QueryRow(ctx,
		`select count(*) > 0, count(*) filter (where ref = $2) > 0 from duration where kind = $1 and ref like $3`,
		DurationWalkPhase, plan+"/total", plan+"/%").Scan(&anyKept, &totalKept)
	return anyKept, totalKept, err
}

// ForgetOldDurations removes what is older than DurationsKeptFor, and says how many.
func (i *Inventory) ForgetOldDurations(ctx context.Context) (int64, error) {
	tag, err := i.store.Pool().Exec(ctx, `delete from duration where recorded < $1`,
		time.Now().Add(-DurationsKeptFor))
	if err != nil {
		return 0, err
	}
	return tag.RowsAffected(), nil
}