| 1 | // This file is the timers.spec column's grammar: parse the three stored |
| 2 | // shapes ("every <duration>", "cron <5 fields>", "at <unix>"), compute each |
| 3 | // one's next fire from now (spec §6.1's coalescing — always from now, never |
| 4 | // from the scheduled time), and render the canonical text back for |
| 5 | // Converge and Runner to store and for `carlos schedule ls` to show. |
| 6 | |
| 7 | package schedule |
| 8 | |
| 9 | import ( |
| 10 | "errors" |
| 11 | "fmt" |
| 12 | "strconv" |
| 13 | "strings" |
| 14 | "time" |
| 15 | ) |
| 16 | |
| 17 | const ( |
| 18 | KindSchedule = "schedule" |
| 19 | KindOnce = "once" |
| 20 | |
| 21 | MinEvery = time.Minute |
| 22 | MaxEvery = 720 * time.Hour |
| 23 | MaxOnceAhead = 400 * 24 * time.Hour |
| 24 | |
| 25 | // MaxOncePerHost bounds how many pending "at" jobs a single box may |
| 26 | // hold at once — a later task's (the runner's) enforcement point, kept |
| 27 | // here with the other schedule-wide limits. |
| 28 | MaxOncePerHost = 1000 |
| 29 | ) |
| 30 | |
| 31 | // Spec is the parsed timers.spec column — one of three shapes, and the only |
| 32 | // thing the runner needs to know to compute the next fire. |
| 33 | type Spec struct { |
| 34 | Kind string |
| 35 | Every time.Duration |
| 36 | Cron *CronExpr |
| 37 | At time.Time |
| 38 | } |
| 39 | |
| 40 | // ParseSpec reads the canonical column text: "every <duration>", |
| 41 | // "cron <5 fields>", "at <unix>". String is its inverse. |
| 42 | func ParseSpec(s string) (Spec, error) { |
| 43 | kind, rest, _ := strings.Cut(strings.TrimSpace(s), " ") |
| 44 | rest = strings.TrimSpace(rest) |
| 45 | switch kind { |
| 46 | case "every": |
| 47 | d, err := time.ParseDuration(rest) |
| 48 | if err != nil { |
| 49 | return Spec{}, fmt.Errorf("every: %w", err) |
| 50 | } |
| 51 | if err := ValidEvery(d); err != nil { |
| 52 | return Spec{}, err |
| 53 | } |
| 54 | return Spec{Kind: KindSchedule, Every: d}, nil |
| 55 | case "cron": |
| 56 | c, err := ParseCron(rest) |
| 57 | if err != nil { |
| 58 | return Spec{}, err |
| 59 | } |
| 60 | return Spec{Kind: KindSchedule, Cron: c}, nil |
| 61 | case "at": |
| 62 | n, err := strconv.ParseInt(rest, 10, 64) |
| 63 | if err != nil { |
| 64 | return Spec{}, fmt.Errorf("at: %q is not a unix time", rest) |
| 65 | } |
| 66 | return Spec{Kind: KindOnce, At: time.Unix(n, 0).UTC()}, nil |
| 67 | } |
| 68 | return Spec{}, fmt.Errorf("spec %q: want every|cron|at", s) |
| 69 | } |
| 70 | |
| 71 | // ValidEvery is the member-facing bound: whole minutes, 1m to 30d. |
| 72 | func ValidEvery(d time.Duration) error { |
| 73 | switch { |
| 74 | case d < MinEvery: |
| 75 | return errors.New("every: shortest interval is 1m") |
| 76 | case d > MaxEvery: |
| 77 | return errors.New("every: longest interval is 720h (30 days)") |
| 78 | case d%time.Minute != 0: |
| 79 | return errors.New("every: whole minutes only") |
| 80 | } |
| 81 | return nil |
| 82 | } |
| 83 | |
| 84 | func (s Spec) String() string { |
| 85 | switch { |
| 86 | case s.Every > 0: |
| 87 | return "every " + shortEvery(s.Every) |
| 88 | case s.Cron != nil: |
| 89 | return "cron " + s.Cron.String() |
| 90 | default: |
| 91 | return "at " + strconv.FormatInt(s.At.Unix(), 10) |
| 92 | } |
| 93 | } |
| 94 | |
| 95 | // shortEvery renders d the way a member typed it, not the way |
| 96 | // time.Duration.String does: stdlib always spells out hours, minutes AND |
| 97 | // seconds ("6h" comes back "6h0m0s"), which is what a box would have stored |
| 98 | // as the timers.spec column and what `carlos schedule ls` would have shown |
| 99 | // verbatim. ValidEvery only ever lets a whole number of minutes through, so |
| 100 | // d has no seconds component to render; this drops whichever of hours/ |
| 101 | // minutes is zero instead of printing it. |
| 102 | func shortEvery(d time.Duration) string { |
| 103 | h := d / time.Hour |
| 104 | m := (d % time.Hour) / time.Minute |
| 105 | switch { |
| 106 | case h == 0: |
| 107 | return fmt.Sprintf("%dm", m) |
| 108 | case m == 0: |
| 109 | return fmt.Sprintf("%dh", h) |
| 110 | default: |
| 111 | return fmt.Sprintf("%dh%dm", h, m) |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | // Next is the first fire strictly after now — epoch-aligned for every, |
| 116 | // minute-stepped for cron, the instant itself for a pending once and the |
| 117 | // zero time for a once that has passed. Always from now, never from the |
| 118 | // scheduled time: that is what coalesces a missed run into one (spec §6.1). |
| 119 | func (s Spec) Next(now time.Time) time.Time { |
| 120 | now = now.UTC() |
| 121 | switch { |
| 122 | case s.Every > 0: |
| 123 | n := now.Unix() |
| 124 | e := int64(s.Every / time.Second) |
| 125 | return time.Unix((n/e+1)*e, 0).UTC() |
| 126 | case s.Cron != nil: |
| 127 | return s.Cron.Next(now) |
| 128 | default: |
| 129 | if !s.At.After(now) { |
| 130 | return time.Time{} |
| 131 | } |
| 132 | return s.At.UTC() |
| 133 | } |
| 134 | } |
| 135 | |
amadan