runner.bend
bend-kit-runner@0.12.0.1 · 1,793 lines · 0 definitions
1# Durable job runner: a journaled scheduler queue, bounded by a resources pool, with retry and a breaker per target. Source: https://github.com/paymog/bend-kit/tree/main/runner
2import Base
3import bend-kit-bytes@0.3.3.0/bytes.bend as Bytes
4import bend-kit-journal@0.3.0.1/journal.bend as J
5import bend-kit-scheduler@0.4.1.0/queue.bend as Q
6import bend-kit-resources@0.1.0.0/resources.bend as Res
7import bend-kit-retry@0.2.0.0/retry.bend as Retry
8import bend-kit-time@0.3.0.0/time.bend as Time
9import bend-kit-collections@0.1.4.1/heap.bend as H
10import bend-kit-collections@0.1.4.1/omap.bend as O
11import bend-kit-collections@0.1.4.1/hmap.bend as M
12import bend-kit-files@0.3.0.0/files.bend as Files
13
14# Why retry gave up on a ticket: its budget was spent, its deadline passed, its failure must not repeat,
15# or another try would repeat its failure.
16type Why is Data:
17 WhySpent{}
18 WhyLate{}
19 WhyUnsafe{}
20 WhyFailed{}
21
22# A ticket that retry gave up on, with its payload, and when it gave up (wall-clock ms).
23# It stays until Revive, Cancel, or Purge takes it.
24type Dead<-A: Data> is Data:
25 Dead{ticket: Q.Ticket<A>, why: Why, at: Nat}
26
27# One durable transition. Each one is one journal record, appended before the state changes.
28# Select: the queue's select at now. Replay runs it at the same now, so it takes the same ticket.
29# Requeue: the attempt failed; it counts one failure. Defer: the breaker held the ticket back; no attempt ran.
30# Abandon: retry gave up at at; the running ticket becomes dead. Revive: a dead ticket is pending again at deadline, with a new budget.
31# Purge: the dead tickets abandoned before before are dropped. PurgeAll: every dead ticket is dropped.
32# Break: the breaker of target changed to state.
33type Op<-A: Data> is Data:
34 Enqueue{deadline: Nat, payload: A}
35 Select{now: Nat}
36 Complete{id: Nat}
37 Cancel{id: Nat}
38 Requeue{id: Nat, deadline: Nat}
39 Defer{id: Nat, deadline: Nat}
40 Abandon{id: Nat, why: Why, at: Nat}
41 Revive{id: Nat, deadline: Nat}
42 Purge{before: Nat}
43 PurgeAll{}
44 Break{target: String, state: Retry.State}
45
46# The failed attempts of a ticket, and its first deadline, from which the policy deadline counts.
47type Try is Data:
48 Try{fails: Nat, start: Nat}
49
50# A Try for each ticket that is not yet complete, cancelled, or dead, by ticket id.
51def Tries() -> Data:
52 O.OMap<Nat, Try>
53
54# The breaker state of each target that has one, by target. An absent target is closed with no failures.
55def Breakers() -> Data:
56 Map<&2, Retry.State>
57
58def dead.hash(i: Nat) -> U32:
59 U32.from_nat(i)
60
61# The dead tickets, by ticket id.
62def Graves(-A: Data) -> Data:
63 M.HMap<Nat, Dead<A>>
64
65# The durable state: the queue, the tries, the dead tickets, and the breakers.
66type State<-A: Data> is Data:
67 State{queue: Q.State<A>, tries: Tries(), dead: Graves(A), breakers: Breakers()}
68
69def new(-A: Data) -> State<A>:
70 State{Q.new(A), O.OMap.new(Nat, Try), M.HMap.new(Nat, Dead<A>), Map.new(&2, Retry.State)}
71
72def queue(-A: Data, s: State<A>) -> Q.State<A>:
73 State{q, ts, ds, bs} = s
74 q
75
76def tries(-A: Data, s: State<A>) -> Tries():
77 State{q, ts, ds, bs} = s
78 ts
79
80# The dead tickets, by id. A Revive of one makes it pending again; a Cancel or a Purge drops it.
81def dead(-A: Data, s: State<A>) -> Graves(A):
82 State{q, ts, ds, bs} = s
83 ds
84
85def breakers(-A: Data, s: State<A>) -> Breakers():
86 State{q, ts, ds, bs} = s
87 bs
88
89# ---- dead tickets
90
91def dead.get(~A: Data, ds: Graves(A), +i: Nat) -> Maybe<&2, Dead<A>>:
92 M.HMap.get(~Nat, ~Dead<A>, ~dead.hash, ~Nat.is_eq, ds, i)
93
94def dead.drop(~A: Data, ds: Graves(A), +i: Nat) -> Graves(A):
95 M.HMap.del(~Nat, ~Dead<A>, ~dead.hash, ~Nat.is_eq, ds, i)
96
97def dead.bury(~A: Data, m: Maybe<&2, Q.Ticket<A>>, ds: Graves(A), w: Why, +at: Nat) -> Graves(A):
98 match m:
99 case None{}:
100 ds
101 case Some{Q.Ticket{+i, d, x}}:
102 M.HMap.put(~Nat, ~Dead<A>, ~dead.hash, ~Nat.is_eq, ds, i, Dead{Q.Ticket{i, d, x}, w, at})
103
104def dead.list.entries(-A: Data, es: List<&2, M.Entry<Nat, Dead<A>>>, acc: List<&2, Dead<A>>) -> List<&2, Dead<A>>:
105 match es:
106 case Nil{}:
107 acc
108 case Con{M.Entry{k, d}, rest}:
109 dead.list.entries(A, rest, Con{d, acc})
110
111def dead.list.go(-A: Data, ds: Graves(A), acc: List<&2, Dead<A>>) -> List<&2, Dead<A>>:
112 match ds:
113 case M.HNil{}:
114 acc
115 case M.HLeaf{h, es}:
116 dead.list.entries(A, es, acc)
117 case M.HBranch{lo, hi}:
118 dead.list.go(A, lo, dead.list.go(A, hi, acc))
119
120# The dead tickets, in no set order.
121def dead.list(-A: Data, ds: Graves(A)) -> List<&2, Dead<A>>:
122 dead.list.go(A, ds, Nil{})
123
124def dead.old.keep(-A: Data, old: Bool, +i: Nat, rest: List<&2, Nat>) -> List<&2, Nat>:
125 match old:
126 case True{}:
127 Con{i, rest}
128 case False{}:
129 rest
130
131# The ids of the dead tickets abandoned before t.
132def dead.old(-A: Data, ds: List<&2, Dead<A>>, +t: Nat) -> List<&2, Nat>:
133 match ds:
134 case Nil{}:
135 Nil{}
136 case Con{Dead{Q.Ticket{i, d, x}, w, +at}, rest}:
137 dead.old.keep(A, Nat.is_lt(at, t), i, dead.old(A, rest, t))
138
139def dead.drops(~A: Data, ks: List<&2, Nat>, ds: Graves(A)) -> Graves(A):
140 match ks:
141 case Nil{}:
142 ds
143 case Con{k, rest}:
144 dead.drops(~A, rest, dead.drop(~A, ds, k))
145
146# The dead tickets without those abandoned before t. It walks every dead ticket once.
147def dead.purge(~A: Data, +ds: Graves(A), +t: Nat) -> Graves(A):
148 dead.drops(~A, dead.old(A, dead.list(A, ds), t), ds)
149
150# ---- tries
151
152def tries.drop(ts: Tries(), +i: Nat) -> Tries():
153 O.OMap.del(~Nat, ~Try, ~Nat.cmp, ts, i)
154
155def tries.get(ts: Tries(), +i: Nat) -> Maybe<&2, Try>:
156 O.OMap.get(~Nat, ~Try, ~Nat.cmp, ts, i)
157
158def tries.bump.got(m: Maybe<&2, Try>, ts: Tries(), +i: Nat) -> Tries():
159 match m:
160 case None{}:
161 ts
162 case Some{Try{f, st}}:
163 O.OMap.put(~Nat, ~Try, ~Nat.cmp, ts, i, Try{1n+f, st})
164
165def tries.bump(+ts: Tries(), +i: Nat) -> Tries():
166 tries.bump.got(tries.get(ts, i), ts, i)
167
168# ---- breakers
169
170def brk.got(r: Breakers() & Retry.State) -> Retry.State:
171 (m, b) = r
172 b
173
174# The breaker state of target key.
175def brk.get(-A: Data, s: State<A>, key: String) -> Retry.State:
176 brk.got(Map.get(Retry.State, Retry.CircuitClosed{Nil{}}, breakers(A, s), key))
177
178def brk.state(br: Retry.Breaker, old: Retry.State) -> Retry.State:
179 match br:
180 case Retry.BreakerOff{}:
181 old
182 case Retry.BreakerOn{c, st}:
183 st
184
185def brk.nats(a: List<&2, Nat>, b: List<&2, Nat>) -> Bool:
186 match a b:
187 case Nil{} Nil{}:
188 True{}
189 case Con{+x, xs} Con{+y, ys}:
190 Bool.and(Nat.is_eq(x, y), brk.nats(xs, ys))
191 case p q:
192 False{}
193
194def brk.same(a: Retry.State, b: Retry.State) -> Bool:
195 match a b:
196 case Retry.CircuitClosed{xs} Retry.CircuitClosed{ys}:
197 brk.nats(xs, ys)
198 case Retry.CircuitOpen{+x} Retry.CircuitOpen{+y}:
199 Nat.is_eq(x, y)
200 case Retry.CircuitHalf{+x} Retry.CircuitHalf{+y}:
201 Nat.is_eq(x, y)
202 case p q:
203 False{}
204
205def calm.state(b: Retry.State) -> Retry.State:
206 match b:
207 case Retry.CircuitClosed{fs}:
208 Retry.CircuitClosed{fs}
209 case Retry.CircuitOpen{u}:
210 Retry.CircuitOpen{u}
211 case Retry.CircuitHalf{k}:
212 Retry.CircuitHalf{0n}
213
214def calm.map(m: Breakers()) -> Breakers():
215 match m:
216 case MTip{}:
217 MTip{}
218 case MLeaf{k, v}:
219 MLeaf{k, calm.state(v)}
220 case MNode{p, lo, hi}:
221 MNode{p, calm.map(lo), calm.map(hi)}
222
223# The probes of a half-open breaker died with the process that ran them, so open counts none in flight.
224def calm(-A: Data, s: State<A>) -> State<A>:
225 State{q, ts, ds, bs} = s
226 State{q, ts, ds, calm.map(bs)}
227
228# ---- the transition
229
230def step.enqueued(-A: Data, r: Q.State<A> & Nat, ts: Tries(), ds: Graves(A), bs: Breakers(), d: Nat) -> State<A>:
231 (q, i) = r
232 State{q, O.OMap.put(~Nat, ~Try, ~Nat.cmp, ts, i, Try{0n, d}), ds, bs}
233
234def step.selected(-A: Data, r: Q.State<A> & Maybe<&2, Q.Ticket<A>>, ts: Tries(), ds: Graves(A), bs: Breakers()) -> State<A>:
235 (q, t) = r
236 State{q, ts, ds, bs}
237
238def step.requeued(-A: Data, r: Q.State<A> & Bool, ts: Tries(), ds: Graves(A), bs: Breakers()) -> State<A>:
239 (q, b) = r
240 State{q, ts, ds, bs}
241
242# Complete takes the ticket from the running list only: O(running), not O(pending).
243def step.completed(-A: Data, r: Q.State<A> & Maybe<&2, Q.Ticket<A>>, ts: Tries(), ds: Graves(A), bs: Breakers()) -> State<A>:
244 (q, t) = r
245 State{q, ts, ds, bs}
246
247# Abandon takes the ticket from the running list, as Complete does, and keeps it with its payload.
248def step.abandoned(~A: Data, r: Q.State<A> & Maybe<&2, Q.Ticket<A>>, ts: Tries(), ds: Graves(A), bs: Breakers(), w: Why, +at: Nat) -> State<A>:
249 (q, t) = r
250 State{q, ts, dead.bury(~A, t, ds, w, at), bs}
251
252# The revived ticket keeps its payload and takes id i, the key it was dead under.
253def step.revived(~A: Data, m: Maybe<&2, Dead<A>>, +i: Nat, n: Nat, h: H.Heap<Q.Ticket<A>>, r: List<&2, Q.Ticket<A>>, ts: Tries(), ds: Graves(A), bs: Breakers(), +d: Nat) -> State<A>:
254 match m:
255 case None{}:
256 State{Q.State{n, h, r}, ts, ds, bs}
257 case Some{Dead{Q.Ticket{k, old, x}, w, at}}:
258 State{Q.State{n, H.Heap.push(~Q.Ticket<A>, ~(a => b => Q.le(A, a, b)), Q.Ticket{i, d, x}, h), r}, O.OMap.put(~Nat, ~Try, ~Nat.cmp, ts, i, Try{0n, d}), ds, bs}
259
260# A closed breaker with no failures reads the same as an absent one, so it leaves the map.
261def step.broke(bs: Breakers(), k: String, b: Retry.State) -> Breakers():
262 match b:
263 case Retry.CircuitClosed{Nil{}}:
264 Map.del(&2, Retry.State, bs, k)
265 case b:
266 Map.set(&2, Retry.State, bs, k, b)
267
268# The state after op. Live and replay both run it, so they agree.
269def step(~A: Data, s: State<A>, op: Op<A>) -> State<A>:
270 match s op:
271 case State{q, ts, ds, bs} Enqueue{+d, x}:
272 step.enqueued(A, Q.enqueue(~A, d, x, q), ts, ds, bs, d)
273 case State{q, ts, ds, bs} Select{now}:
274 step.selected(A, Q.select(~A, now, q), ts, ds, bs)
275 case State{q, ts, ds, bs} Complete{+i}:
276 step.completed(A, Q.complete(A, i, q), tries.drop(ts, i), ds, bs)
277 case State{q, ts, ds, bs} Cancel{+i}:
278 State{Q.cancel(~A, i, q), tries.drop(ts, i), dead.drop(~A, ds, i), bs}
279 case State{q, ts, ds, bs} Requeue{+i, d}:
280 step.requeued(A, Q.requeue(~A, i, d, q), tries.bump(ts, i), ds, bs)
281 case State{q, ts, ds, bs} Defer{i, d}:
282 step.requeued(A, Q.requeue(~A, i, d, q), ts, ds, bs)
283 case State{q, ts, ds, bs} Abandon{+i, w, at}:
284 step.abandoned(~A, Q.complete(A, i, q), tries.drop(ts, i), ds, bs, w, at)
285 case State{Q.State{n, h, r}, ts, +ds, bs} Revive{+i, d}:
286 step.revived(~A, dead.get(~A, ds, i), i, n, h, r, ts, dead.drop(~A, ds, i), bs, d)
287 case State{q, ts, ds, bs} Purge{t}:
288 State{q, ts, dead.purge(~A, ds, t), bs}
289 case State{q, ts, ds, bs} PurgeAll{}:
290 State{q, ts, M.HMap.new(Nat, Dead<A>), bs}
291 case State{q, ts, ds, bs} Break{k, b}:
292 State{q, ts, ds, step.broke(bs, k, b)}
293
294def apply.op(~A: Data, m: Maybe<&2, Op<A>>, s: State<A>) -> Maybe<&2, State<A>>:
295 match m:
296 case None{}:
297 None{}
298 case Some{op}:
299 Some{step(~A, s, op)}
300
301# Folds one record into the replayed state. A record that does not decode ends the replay with None.
302def apply(~A: Data, ~R: Type, ~dec: R -> Maybe<&2, Op<A>>, acc: Maybe<&2, State<A>>, r: R) -> Maybe<&2, State<A>>:
303 match acc:
304 case None{}:
305 None{}
306 case Some{s}:
307 apply.op(~A, dec(r), s)
308
309# A journal record. Compaction writes one Snap of the whole state; every other record is one op.
310type Rec<-A: Data> is Data:
311 Snap{state: State<A>}
312 Do{op: Op<A>}
313
314def load.rec(~A: Data, m: Maybe<&2, Rec<A>>, s: State<A>) -> Maybe<&2, State<A>>:
315 match m:
316 case None{}:
317 None{}
318 case Some{Snap{t}}:
319 Some{t}
320 case Some{Do{op}}:
321 Some{step(~A, s, op)}
322
323# Folds one record into the replayed state: a Snap replaces it, and an op steps it, as apply does.
324# A record that does not decode ends the replay with None.
325def load(~A: Data, ~R: Type, ~dec: R -> Maybe<&2, Rec<A>>, acc: Maybe<&2, State<A>>, r: R) -> Maybe<&2, State<A>>:
326 match acc:
327 case None{}:
328 None{}
329 case Some{s}:
330 load.rec(~A, dec(r), s)
331
332# ---- pool
333
334# Picked: a due ticket and one unit of the pool for it. Idle: no due ticket, or no free unit; the pool is unchanged.
335type Pick<-A: Data> is Type:
336 Picked{pool: Res.Pool, ticket: Q.Ticket<A>, grant: Res.Grant}
337 Idle{pool: Res.Pool}
338
339def pick.took(-A: Data, r: Res.Reserve, t: Q.Ticket<A>) -> Pick<A>:
340 match r:
341 case Res.Took{p, g}:
342 Picked{p, t, g}
343 case Res.Refused{p}:
344 Idle{p}
345
346def pick.due(-A: Data, m: Maybe<&2, Q.Ticket<A>>, p: Res.Pool) -> Pick<A>:
347 match m:
348 case None{}:
349 Idle{p}
350 case Some{t}:
351 pick.took(A, Res.reserve(p, 1n), t)
352
353def pick.sel(-A: Data, r: Q.State<A> & Maybe<&2, Q.Ticket<A>>, p: Res.Pool) -> Pick<A>:
354 (q, m) = r
355 pick.due(A, m, p)
356
357# The ticket that Select{now} takes, with one unit of p, when there is a ticket due and a unit free.
358def pick(~A: Data, p: Res.Pool, s: State<A>, now: Nat) -> Pick<A>:
359 State{q, ts, ds, bs} = s
360 pick.sel(A, Q.select(~A, now, q), p)
361
362# ---- retry
363
364# The budget left for ticket i: the policy's attempts less its failures, until its start plus the policy deadline.
365def budget.of(+attempts: Nat, t: Maybe<&2, Try>, d: Maybe<&2, Nat>) -> Retry.Budget:
366 match t d:
367 case None{} m:
368 Retry.Budget{attempts, None{}}
369 case Some{Try{f, st}} None{}:
370 Retry.Budget{Nat.sub(attempts, f), None{}}
371 case Some{Try{f, +st}} Some{ms}:
372 Retry.Budget{Nat.sub(attempts, f), Some{Nat.add(st, ms)}}
373
374def budget(p: Retry.Policy, t: Maybe<&2, Try>) -> Retry.Budget:
375 Retry.Policy{a, base, cap, d} = p
376 budget.of(a, t, d)
377
378# The failures so far: the index of the next retry.
379def fails(t: Maybe<&2, Try>) -> Nat:
380 match t:
381 case None{}:
382 0n
383 case Some{Try{f, st}}:
384 f
385
386# Why retry stopped a transient failure: no attempt is left, or the next wait would reach the deadline.
387def gave(b: Retry.Budget) -> Why:
388 Retry.Budget{left, d} = b
389 match left:
390 case 0n:
391 WhySpent{}
392 case 1n+k:
393 WhyLate{}
394
395# A settled attempt completes its ticket; retry gave up at now on any other.
396def stopped(-A: Data, o: Retry.Outcome, b: Retry.Budget, +id: Nat, +now: Nat) -> Op<A>:
397 match o:
398 case Retry.Settled{}:
399 Complete{id}
400 case Retry.Failed{}:
401 Abandon{id, WhyFailed{}, now}
402 case Retry.Unsafe{}:
403 Abandon{id, WhyUnsafe{}, now}
404 case Retry.Transient{w}:
405 Abandon{id, gave(b), now}
406
407def after.plan(-A: Data, pl: Retry.Plan, o: Retry.Outcome, b: Retry.Budget, +id: Nat, +now: Nat) -> Op<A>:
408 match pl:
409 case Retry.PlanStop{}:
410 stopped(A, o, b, id, now)
411 case Retry.PlanWait{w}:
412 Requeue{id, Nat.add(now, w)}
413
414# The record after an attempt of ticket id ends at now with o: requeue at now plus retry's wait,
415# complete when o is settled, or abandon when retry gave up.
416def after(-A: Data, +o: Retry.Outcome, p: Retry.Policy, +b: Retry.Budget, +id: Nat, +n: Nat, +now: Nat, +r: Nat) -> Op<A>:
417 after.plan(A, Retry.plan(o, p, b, n, now, r), o, b, id, now)
418
419# When an open breaker lets attempts start again.
420def until(br: Retry.Breaker, +now: Nat) -> Nat:
421 match br:
422 case Retry.BreakerOn{c, Retry.CircuitOpen{u}}:
423 u
424 case Retry.BreakerOn{c, Retry.CircuitClosed{fs}}:
425 Nat.add(now, Retry.Circuit.cooldown(c))
426 case Retry.BreakerOn{c, Retry.CircuitHalf{k}}:
427 Nat.add(now, Retry.Circuit.cooldown(c))
428 case Retry.BreakerOff{}:
429 now
430
431# The record for a ticket that admit refused: Defer to when the breaker may admit, or Abandon when its budget is spent or late.
432def held(-A: Data, why: Retry.Deny, br: Retry.Breaker, +id: Nat, +now: Nat) -> Op<A>:
433 match why:
434 case Retry.DenyOpen{}:
435 Defer{id, until(br, now)}
436 case Retry.DenyLate{}:
437 Abandon{id, WhyLate{}, now}
438 case Retry.DenySpent{}:
439 Abandon{id, WhySpent{}, now}
440
441# ---- the record codec: a u32le tag, then u64le fields; an Enqueue then holds the payload.
442# An Abandon is tag 8, then id, why.code, and at. A Purge is tag 11 and before; a PurgeAll is tag 12.
443# A Break is tag 10, then its target and its breaker state.
444
445def why.code(w: Why) -> Nat:
446 match w:
447 case WhySpent{}:
448 0n
449 case WhyLate{}:
450 1n
451 case WhyUnsafe{}:
452 2n
453 case WhyFailed{}:
454 3n
455
456def W() -> Nat:
457 Nat.mul(65536n, 65536n)
458
459# Nat fields hold values under 2^64.
460def put.u64(b: Bytes.Bytes, +at: U32, +n: Nat) -> Bytes.Bytes:
461 Bytes.set.u32le(Bytes.set.u32le(b, at, U32.from_nat(Nat.mod(n, W()))), (at + 4 : U32), U32.from_nat(Nat.div(n, W())))
462
463def head(+tag: U32, +a: Nat, +c: Nat) -> Bytes.Bytes:
464 put.u64(put.u64(Bytes.set.u32le(Bytes.new(20), 0, tag), 4, a), 12, c)
465
466def snap.u32(out: Bytes.Bytes, +v: U32) -> Bytes.Bytes:
467 Bytes.append(out, Bytes.set.u32le(Bytes.new(4), 0, v))
468
469def snap.u64(out: Bytes.Bytes, +n: Nat) -> Bytes.Bytes:
470 Bytes.append(out, put.u64(Bytes.new(8), 0, n))
471
472def snap.chars(s: String, out: Bytes.Bytes) -> Bytes.Bytes:
473 match s:
474 case SNil{}:
475 out
476 case SCon{Chr{c}, t}:
477 snap.chars(t, snap.u32(out, c))
478
479# A target is a u32 count of chars, then each char as a u32.
480def snap.key(out: Bytes.Bytes, +k: String) -> Bytes.Bytes:
481 snap.chars(k, snap.u32(out, Bytes.count(k, 0)))
482
483def snap.nats(xs: List<&2, Nat>, out: Bytes.Bytes) -> Bytes.Bytes:
484 match xs:
485 case Nil{}:
486 out
487 case Con{x, rest}:
488 snap.nats(rest, snap.u64(out, x))
489
490# A breaker state is a u32 kind. 0 is closed: a u32 count, then each failure as a u64. 1 is open: until. 2 is half-open: busy.
491def snap.brk(out: Bytes.Bytes, b: Retry.State) -> Bytes.Bytes:
492 match b:
493 case Retry.CircuitClosed{+fs}:
494 snap.nats(fs, snap.u32(snap.u32(out, 0), U32.from_nat(List.length(&2, Nat, fs))))
495 case Retry.CircuitOpen{u}:
496 snap.u64(snap.u32(out, 1), u)
497 case Retry.CircuitHalf{k}:
498 snap.u64(snap.u32(out, 2), k)
499
500def encode(~A: Data, ~penc: A -> Bytes.Bytes, op: Op<A>) -> Bytes.Bytes:
501 match op:
502 case Enqueue{+d, x}:
503 Bytes.append(put.u64(Bytes.set.u32le(Bytes.new(12), 0, 1), 4, d), penc(x))
504 case Select{+now}:
505 head(2, now, 0n)
506 case Complete{+i}:
507 head(3, i, 0n)
508 case Cancel{+i}:
509 head(4, i, 0n)
510 case Requeue{+i, +d}:
511 head(5, i, d)
512 case Defer{+i, +d}:
513 head(6, i, d)
514 case Abandon{+i, w, +at}:
515 Bytes.append(head(8, i, why.code(w)), put.u64(Bytes.new(8), 0, at))
516 case Revive{+i, +d}:
517 head(9, i, d)
518 case Purge{+t}:
519 head(11, t, 0n)
520 case PurgeAll{}:
521 head(12, 0n, 0n)
522 case Break{k, b}:
523 snap.brk(snap.key(snap.u32(Bytes.new(0), 10), k), b)
524
525def get.field(m: Maybe<&2, U32>) -> U32:
526 match m:
527 case None{}:
528 0
529 case Some{x}:
530 x
531
532def get.u32(r: Bytes.Bytes & Maybe<&2, U32>) -> Bytes.Bytes & U32:
533 (b, m) = r
534 (b, get.field(m))
535
536def get.hi(+lo: U32, r: Bytes.Bytes & Maybe<&2, U32>) -> Bytes.Bytes & Nat:
537 (b, m) = r
538 (b, Nat.add(U32.to_nat(lo), Nat.mul(U32.to_nat(get.field(m)), W())))
539
540def get.lo(+at: U32, r: Bytes.Bytes & Maybe<&2, U32>) -> Bytes.Bytes & Nat:
541 (b, m) = r
542 +lo = get.field(m)
543 get.hi(lo, Bytes.get.u32le(b, (at + 4 : U32)))
544
545def get.u64(b: Bytes.Bytes, +at: U32) -> Bytes.Bytes & Nat:
546 get.lo(at, Bytes.get.u32le(b, at))
547
548# ---- the snapshot codec: tag 7 and the next id, then the heap, the running list, the tries, the dead tickets, and the breakers.
549# A u32 flag starts each tree node and list cell (1) and marks each end (0), so decode rebuilds the same shape.
550# A ticket is its u64 id and deadline, then a u32 length and the payload.
551# The dead tickets are a trie: each node is a u32 kind, 0 empty, 1 a bucket, or 2 a branch, then its lo and hi nodes.
552# A bucket is its u32 hash, then a list of entries: the u64 key, the ticket, a u32 why.code, and the u64 abandon time.
553# A breaker is its target, then its state, as in a Break record.
554
555def snap.payload(out: Bytes.Bytes, p: Bytes.Bytes) -> Bytes.Bytes:
556 Bytes.Bytes{+len, buf} = p
557 Bytes.append(snap.u32(out, len), Bytes.Bytes{len, buf})
558
559def snap.ticket(~A: Data, ~penc: A -> Bytes.Bytes, out: Bytes.Bytes, t: Q.Ticket<A>) -> Bytes.Bytes:
560 Q.Ticket{+i, +d, x} = t
561 snap.payload(snap.u64(snap.u64(out, i), d), penc(x))
562
563def snap.heap(~A: Data, ~penc: A -> Bytes.Bytes, h: H.Heap<Q.Ticket<A>>, out: Bytes.Bytes) -> Bytes.Bytes:
564 match h:
565 case H.HLeaf{}:
566 snap.u32(out, 0)
567 case H.HNode{+n, t, l, r}:
568 snap.heap(~A, ~penc, r, snap.heap(~A, ~penc, l, snap.ticket(~A, ~penc, snap.u64(snap.u32(out, 1), n), t)))
569
570def snap.run(~A: Data, ~penc: A -> Bytes.Bytes, xs: List<&2, Q.Ticket<A>>, out: Bytes.Bytes) -> Bytes.Bytes:
571 match xs:
572 case Nil{}:
573 snap.u32(out, 0)
574 case Con{t, rest}:
575 snap.run(~A, ~penc, rest, snap.ticket(~A, ~penc, snap.u32(out, 1), t))
576
577def snap.tries(ts: Tries(), out: Bytes.Bytes) -> Bytes.Bytes:
578 match ts:
579 case O.OTip{}:
580 snap.u32(out, 0)
581 case O.OBin{+n, +k, Try{+f, +st}, lo, hi}:
582 snap.tries(hi, snap.tries(lo, snap.u64(snap.u64(snap.u64(snap.u32(snap.u32(out, 1), n), k), f), st)))
583
584def snap.entries(~A: Data, ~penc: A -> Bytes.Bytes, es: List<&2, M.Entry<Nat, Dead<A>>>, out: Bytes.Bytes) -> Bytes.Bytes:
585 match es:
586 case Nil{}:
587 snap.u32(out, 0)
588 case Con{M.Entry{k, Dead{t, w, at}}, rest}:
589 snap.entries(~A, ~penc, rest, snap.u64(snap.u32(snap.ticket(~A, ~penc, snap.u64(snap.u32(out, 1), k), t), U32.from_nat(why.code(w))), at))
590
591def snap.graves(~A: Data, ~penc: A -> Bytes.Bytes, ds: Graves(A), out: Bytes.Bytes) -> Bytes.Bytes:
592 match ds:
593 case M.HNil{}:
594 snap.u32(out, 0)
595 case M.HLeaf{h, es}:
596 snap.entries(~A, ~penc, es, snap.u32(snap.u32(out, 1), h))
597 case M.HBranch{lo, hi}:
598 snap.graves(~A, ~penc, hi, snap.graves(~A, ~penc, lo, snap.u32(out, 2)))
599
600def snap.brks(xs: List<&2, Sigma<&2, &2, String, _ => Retry.State>>, out: Bytes.Bytes) -> Bytes.Bytes:
601 match xs:
602 case Nil{}:
603 snap.u32(out, 0)
604 case Con{(k, b), rest}:
605 snap.brks(rest, snap.brk(snap.key(snap.u32(out, 1), k), b))
606
607# The Snap record of s.
608def encode.snap(~A: Data, ~penc: A -> Bytes.Bytes, s: State<A>) -> Bytes.Bytes:
609 State{Q.State{+n, h, run}, ts, ds, bs} = s
610 snap.brks(Map.to_list(&2, Retry.State, bs),
611 snap.graves(~A, ~penc, ds, snap.tries(ts, snap.run(~A, ~penc, run, snap.heap(~A, ~penc, h, snap.u64(snap.u32(Bytes.new(0), 7), n))))))
612
613def encode.rec(~A: Data, ~penc: A -> Bytes.Bytes, r: Rec<A>) -> Bytes.Bytes:
614 match r:
615 case Snap{s}:
616 encode.snap(~A, ~penc, s)
617 case Do{op}:
618 encode(~A, ~penc, op)
619
620# A snapshot reader: the record, and the offset of the next field.
621type Rd is Type:
622 Rd{b: Bytes.Bytes, at: U32}
623
624# One step of the snapshot decoder. None: a field runs past the record or does not decode.
625def Dec(-T: Type) -> Type:
626 Rd -> Maybe<&1, Rd & T>
627
628def Dec.next(-A: Type, -B: Type, m: Maybe<&1, Rd & A>, f: A -> Dec(B)) -> Maybe<&1, Rd & B>:
629 match m:
630 case None{}:
631 None{}
632 case Some{(r, x)}:
633 f(x)(r)
634
635def Dec.bind(-A: Type, -B: Type, m: Dec(A), f: A -> Dec(B)) -> Dec(B):
636 r => Dec.next(A, B, m(r), f)
637
638def Dec.pure(-A: Type, x: A) -> Dec(A):
639 r => Some{(r, x)}
640
641def Dec.fail(-A: Type) -> Dec(A):
642 r => None{}
643
644def rd.u32.of(m: Maybe<&2, U32>, b: Bytes.Bytes, +at: U32) -> Maybe<&1, Rd & U32>:
645 match m:
646 case None{}:
647 None{}
648 case Some{x}:
649 Some{(Rd{b, (at + 4 : U32)}, x)}
650
651def rd.u32.got(+at: U32, r: Bytes.Bytes & Maybe<&2, U32>) -> Maybe<&1, Rd & U32>:
652 (b, m) = r
653 rd.u32.of(m, b, at)
654
655def rd.u32.at(r: Rd) -> Maybe<&1, Rd & U32>:
656 Rd{b, +at} = r
657 rd.u32.got(at, Bytes.get.u32le(b, at))
658
659def rd.u32() -> Dec(U32):
660 r => rd.u32.at(r)
661
662def rd.u64.of(+lo: U32, +hi: U32) -> Nat:
663 Nat.add(U32.to_nat(lo), Nat.mul(U32.to_nat(hi), W()))
664
665def rd.u64() -> Dec(Nat):
666 do Dec<Nat>:
667 lo : U32 <- rd.u32()
668 hi : U32 <- rd.u32()
669 return rd.u64.of(lo, hi)
670
671def rd.cut.got(+at: U32, +n: U32, r: Bytes.Bytes & Bytes.Bytes) -> Maybe<&1, Rd & Bytes.Bytes>:
672 (b, p) = r
673 Some{(Rd{b, (at + n : U32)}, p)}
674
675def rd.cut.if(ok: Bool, b: Bytes.Bytes, +at: U32, +n: U32) -> Maybe<&1, Rd & Bytes.Bytes>:
676 match ok:
677 case False{}:
678 None{}
679 case True{}:
680 rd.cut.got(at, n, Bytes.slice(b, at, n))
681
682def rd.cut.at(+n: U32, r: Rd) -> Maybe<&1, Rd & Bytes.Bytes>:
683 Rd{Bytes.Bytes{+len, buf}, +at} = r
684 rd.cut.if(Bytes.fits(len, at, n), Bytes.Bytes{len, buf}, at, n)
685
686# The next n octets.
687def rd.cut(+n: U32) -> Dec(Bytes.Bytes):
688 r => rd.cut.at(n, r)
689
690def rd.flag.of(+m: U32) -> Dec(Bool):
691 Bool.pick(Dec(Bool), U32.is_eq(m, 0), Dec.pure(Bool, False{}), Bool.pick(Dec(Bool), U32.is_eq(m, 1), Dec.pure(Bool, True{}), Dec.fail(Bool)))
692
693# A u32 flag: 1 is True, 0 is False, and any other value fails.
694def rd.flag() -> Dec(Bool):
695 Dec.bind(U32, Bool, rd.u32(), m => rd.flag.of(m))
696
697def rd.payload(-A: Data, +i: Nat, +d: Nat, m: Maybe<&2, A>) -> Dec(Q.Ticket<A>):
698 match m:
699 case None{}:
700 Dec.fail(Q.Ticket<A>)
701 case Some{x}:
702 Dec.pure(Q.Ticket<A>, Q.Ticket{i, d, x})
703
704def rd.ticket(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>) -> Dec(Q.Ticket<A>):
705 do Dec<Q.Ticket<A>>:
706 i : Nat <- rd.u64()
707 d : Nat <- rd.u64()
708 n : U32 <- rd.u32()
709 p : Bytes.Bytes <- rd.cut(n)
710 rd.payload(A, i, d, pdec(p))
711
712# Each rd.* tree reader takes the flag already read. fuel bounds the depth: every node holds at least one 4-octet flag.
713def rd.heap(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +fuel: Nat, node: Bool) -> Dec(H.Heap<Q.Ticket<A>>):
714 match fuel node:
715 case 0n b:
716 Dec.fail(H.Heap<Q.Ticket<A>>)
717 case 1n+f False{}:
718 Dec.pure(H.Heap<Q.Ticket<A>>, H.HLeaf{})
719 case 1n+f True{}:
720 do Dec<H.Heap<Q.Ticket<A>>>:
721 n : Nat <- rd.u64()
722 t : Q.Ticket<A> <- rd.ticket(~A, ~pdec)
723 lf : Bool <- rd.flag()
724 l : H.Heap<Q.Ticket<A>> <- rd.heap(~A, ~pdec, f, lf)
725 rf : Bool <- rd.flag()
726 r : H.Heap<Q.Ticket<A>> <- rd.heap(~A, ~pdec, f, rf)
727 return H.HNode{n, t, l, r}
728
729def rd.run(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +fuel: Nat, more: Bool) -> Dec(List<&2, Q.Ticket<A>>):
730 match fuel more:
731 case 0n b:
732 Dec.fail(List<&2, Q.Ticket<A>>)
733 case 1n+f False{}:
734 Dec.pure(List<&2, Q.Ticket<A>>, Nil{})
735 case 1n+f True{}:
736 do Dec<List<&2, Q.Ticket<A>>>:
737 t : Q.Ticket<A> <- rd.ticket(~A, ~pdec)
738 m : Bool <- rd.flag()
739 rest : List<&2, Q.Ticket<A>> <- rd.run(~A, ~pdec, f, m)
740 return Con{t, rest}
741
742def rd.tries(+fuel: Nat, node: Bool) -> Dec(O.OMap<Nat, Try>):
743 match fuel node:
744 case 0n b:
745 Dec.fail(O.OMap<Nat, Try>)
746 case 1n+f False{}:
747 Dec.pure(O.OMap<Nat, Try>, O.OTip{})
748 case 1n+f True{}:
749 do Dec<O.OMap<Nat, Try>>:
750 n : U32 <- rd.u32()
751 k : Nat <- rd.u64()
752 fails : Nat <- rd.u64()
753 st : Nat <- rd.u64()
754 lf : Bool <- rd.flag()
755 lo : O.OMap<Nat, Try> <- rd.tries(f, lf)
756 hf : Bool <- rd.flag()
757 hi : O.OMap<Nat, Try> <- rd.tries(f, hf)
758 return O.OBin{n, k, Try{fails, st}, lo, hi}
759
760def rd.why(+c: U32) -> Dec(Why):
761 Bool.pick(Dec(Why), U32.is_eq(c, 0), Dec.pure(Why, WhySpent{}),
762 Bool.pick(Dec(Why), U32.is_eq(c, 1), Dec.pure(Why, WhyLate{}),
763 Bool.pick(Dec(Why), U32.is_eq(c, 2), Dec.pure(Why, WhyUnsafe{}),
764 Bool.pick(Dec(Why), U32.is_eq(c, 3), Dec.pure(Why, WhyFailed{}), Dec.fail(Why)))))
765
766def rd.entries(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +fuel: Nat, more: Bool) -> Dec(List<&2, M.Entry<Nat, Dead<A>>>):
767 match fuel more:
768 case 0n b:
769 Dec.fail(List<&2, M.Entry<Nat, Dead<A>>>)
770 case 1n+f False{}:
771 Dec.pure(List<&2, M.Entry<Nat, Dead<A>>>, Nil{})
772 case 1n+f True{}:
773 do Dec<List<&2, M.Entry<Nat, Dead<A>>>>:
774 k : Nat <- rd.u64()
775 t : Q.Ticket<A> <- rd.ticket(~A, ~pdec)
776 c : U32 <- rd.u32()
777 w : Why <- rd.why(c)
778 at : Nat <- rd.u64()
779 m : Bool <- rd.flag()
780 rest : List<&2, M.Entry<Nat, Dead<A>>> <- rd.entries(~A, ~pdec, f, m)
781 return Con{M.Entry{k, Dead{t, w, at}}, rest}
782
783# A trie node whose kind is already read: nil is kind 0, leaf kind 1, and branch kind 2. Any other kind fails.
784def rd.graves(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +fuel: Nat, nil: Bool, leaf: Bool, branch: Bool) -> Dec(Graves(A)):
785 match fuel nil leaf branch:
786 case 0n a b c:
787 Dec.fail(Graves(A))
788 case 1n+f True{} b c:
789 Dec.pure(Graves(A), M.HNil{})
790 case 1n+f False{} True{} c:
791 do Dec<Graves(A)>:
792 h : U32 <- rd.u32()
793 m : Bool <- rd.flag()
794 es : List<&2, M.Entry<Nat, Dead<A>>> <- rd.entries(~A, ~pdec, f, m)
795 return M.HLeaf{h, es}
796 case 1n+f False{} False{} True{}:
797 do Dec<Graves(A)>:
798 +lk : U32 <- rd.u32()
799 lo : Graves(A) <- rd.graves(~A, ~pdec, f, U32.is_eq(lk, 0), U32.is_eq(lk, 1), U32.is_eq(lk, 2))
800 +hk : U32 <- rd.u32()
801 hi : Graves(A) <- rd.graves(~A, ~pdec, f, U32.is_eq(hk, 0), U32.is_eq(hk, 1), U32.is_eq(hk, 2))
802 return M.HBranch{lo, hi}
803 case 1n+f False{} False{} False{}:
804 Dec.fail(Graves(A))
805
806# Each rd.* sequence reader takes the count or flag already read. fuel bounds its length: every item holds at least 4 octets.
807def rd.chars(+fuel: Nat, end: Bool, +n: U32) -> Dec(String):
808 match fuel end:
809 case 0n b:
810 Dec.fail(String)
811 case 1n+f True{}:
812 Dec.pure(String, SNil{})
813 case 1n+f False{}:
814 +k = (n - 1 : U32)
815 do Dec<String>:
816 c : U32 <- rd.u32()
817 rest : String <- rd.chars(f, U32.is_eq(k, 0), k)
818 return SCon{Chr{c}, rest}
819
820def rd.key(+fuel: Nat) -> Dec(String):
821 do Dec<String>:
822 +n : U32 <- rd.u32()
823 rd.chars(fuel, U32.is_eq(n, 0), n)
824
825def rd.nats(+fuel: Nat, end: Bool, +n: U32) -> Dec(List<&2, Nat>):
826 match fuel end:
827 case 0n b:
828 Dec.fail(List<&2, Nat>)
829 case 1n+f True{}:
830 Dec.pure(List<&2, Nat>, Nil{})
831 case 1n+f False{}:
832 +k = (n - 1 : U32)
833 do Dec<List<&2, Nat>>:
834 x : Nat <- rd.u64()
835 rest : List<&2, Nat> <- rd.nats(f, U32.is_eq(k, 0), k)
836 return Con{x, rest}
837
838def rd.closed(+fuel: Nat) -> Dec(Retry.State):
839 do Dec<Retry.State>:
840 +n : U32 <- rd.u32()
841 fs : List<&2, Nat> <- rd.nats(fuel, U32.is_eq(n, 0), n)
842 return Retry.CircuitClosed{fs}
843
844def rd.brk.of(+fuel: Nat, +kind: U32) -> Dec(Retry.State):
845 Bool.pick(Dec(Retry.State), U32.is_eq(kind, 0), rd.closed(fuel),
846 Bool.pick(Dec(Retry.State), U32.is_eq(kind, 1), Dec.bind(Nat, Retry.State, rd.u64(), u => Dec.pure(Retry.State, Retry.CircuitOpen{u})),
847 Bool.pick(Dec(Retry.State), U32.is_eq(kind, 2), Dec.bind(Nat, Retry.State, rd.u64(), k => Dec.pure(Retry.State, Retry.CircuitHalf{k})), Dec.fail(Retry.State))))
848
849def rd.brk(+fuel: Nat) -> Dec(Retry.State):
850 Dec.bind(U32, Retry.State, rd.u32(), k => rd.brk.of(fuel, k))
851
852def rd.break(-A: Data, +fuel: Nat) -> Dec(Op<A>):
853 do Dec<Op<A>>:
854 k : String <- rd.key(fuel)
855 b : Retry.State <- rd.brk(fuel)
856 return Break{k, b}
857
858def rd.brks(+fuel: Nat, more: Bool, acc: Map<&2, Retry.State>) -> Dec(Map<&2, Retry.State>):
859 match fuel more:
860 case 0n b:
861 Dec.fail(Map<&2, Retry.State>)
862 case 1n+f False{}:
863 Dec.pure(Map<&2, Retry.State>, acc)
864 case 1n+f True{}:
865 do Dec<Map<&2, Retry.State>>:
866 k : String <- rd.key(f)
867 b : Retry.State <- rd.brk(f)
868 m : Bool <- rd.flag()
869 rd.brks(f, m, Map.set(&2, Retry.State, acc, k, b))
870
871def rd.state(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +fuel: Nat) -> Dec(State<A>):
872 do Dec<State<A>>:
873 n : Nat <- rd.u64()
874 hf : Bool <- rd.flag()
875 h : H.Heap<Q.Ticket<A>> <- rd.heap(~A, ~pdec, fuel, hf)
876 rf : Bool <- rd.flag()
877 run : List<&2, Q.Ticket<A>> <- rd.run(~A, ~pdec, fuel, rf)
878 tf : Bool <- rd.flag()
879 ts : O.OMap<Nat, Try> <- rd.tries(fuel, tf)
880 +dk : U32 <- rd.u32()
881 ds : Graves(A) <- rd.graves(~A, ~pdec, fuel, U32.is_eq(dk, 0), U32.is_eq(dk, 1), U32.is_eq(dk, 2))
882 bf : Bool <- rd.flag()
883 bs : Map<&2, Retry.State> <- rd.brks(fuel, bf, Map.new(&2, Retry.State))
884 return State{Q.State{n, h, run}, ts, ds, bs}
885
886# The value read, when the reader ended at len, the record's end.
887def rd.done(-T: Data, +len: U32, m: Maybe<&1, Rd & T>) -> Maybe<&2, T>:
888 match m:
889 case None{}:
890 None{}
891 case Some{(Rd{b, +at}, +x)}:
892 Bool.pick(Maybe<&2, T>, U32.is_eq(at, len), Some{x}, None{})
893
894# The Abandon of ticket a at e whose why.code is c, or None for any other code.
895def decode.abandon(-A: Data, +a: Nat, +c: Nat, +e: Nat) -> Maybe<&2, Op<A>>:
896 Bool.pick(Maybe<&2, Op<A>>, Nat.is_eq(c, 0n), Some{Abandon{a, WhySpent{}, e}},
897 Bool.pick(Maybe<&2, Op<A>>, Nat.is_eq(c, 1n), Some{Abandon{a, WhyLate{}, e}},
898 Bool.pick(Maybe<&2, Op<A>>, Nat.is_eq(c, 2n), Some{Abandon{a, WhyUnsafe{}, e}},
899 Bool.pick(Maybe<&2, Op<A>>, Nat.is_eq(c, 3n), Some{Abandon{a, WhyFailed{}, e}}, None{}))))
900
901def decode.small(-A: Data, ok: Bool, +tag: U32, +a: Nat, +c: Nat) -> Maybe<&2, Op<A>>:
902 match ok:
903 case False{}:
904 None{}
905 case True{}:
906 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 2), Some{Select{a}},
907 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 3), Some{Complete{a}},
908 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 4), Some{Cancel{a}},
909 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 5), Some{Requeue{a, c}},
910 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 6), Some{Defer{a, c}},
911 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 9), Some{Revive{a, c}},
912 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 11), Some{Purge{a}},
913 Bool.pick(Maybe<&2, Op<A>>, U32.is_eq(tag, 12), Some{PurgeAll{}}, None{}))))))))
914
915def decode.long(-A: Data, ok: Bool, +a: Nat, +c: Nat, r: Bytes.Bytes & Nat) -> Maybe<&2, Op<A>>:
916 match ok:
917 case False{}:
918 None{}
919 case True{}:
920 (b, +e) = r
921 decode.abandon(A, a, c, e)
922
923def decode.payload(-A: Data, m: Maybe<&2, A>, +d: Nat) -> Maybe<&2, Op<A>>:
924 match m:
925 case None{}:
926 None{}
927 case Some{x}:
928 Some{Enqueue{d, x}}
929
930def decode.c.if(-A: Data, abandon: Bool, +tag: U32, +len: U32, +a: Nat, +c: Nat, b: Bytes.Bytes) -> Maybe<&2, Op<A>>:
931 match abandon:
932 case True{}:
933 decode.long(A, U32.is_eq(len, 28), a, c, get.u64(b, 20))
934 case False{}:
935 decode.small(A, U32.is_eq(len, 20), tag, a, c)
936
937# An Abandon is 28 octets; every other op without a payload is 20.
938def decode.c(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +tag: U32, +len: U32, +a: Nat, r: Bytes.Bytes & Nat) -> Maybe<&2, Op<A>>:
939 (b, +c) = r
940 decode.c.if(A, U32.is_eq(tag, 8), tag, len, a, c, b)
941
942def decode.kind(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, enq: Bool, +tag: U32, +len: U32, +a: Nat, b: Bytes.Bytes) -> Maybe<&2, Op<A>>:
943 match enq:
944 case True{}:
945 decode.payload(A, pdec(Bytes.snd(Bytes.slice(b, 12, (len - 12 : U32)))), a)
946 case False{}:
947 decode.c(~A, ~pdec, tag, len, a, get.u64(b, 12))
948
949def decode.a(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +tag: U32, +len: U32, r: Bytes.Bytes & Nat) -> Maybe<&2, Op<A>>:
950 (b, +a) = r
951 decode.kind(~A, ~pdec, U32.is_eq(tag, 1), tag, len, a, b)
952
953def decode.tag.if(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, brk: Bool, +tag: U32, +len: U32, b: Bytes.Bytes) -> Maybe<&2, Op<A>>:
954 match brk:
955 case True{}:
956 rd.done(Op<A>, len, rd.break(A, U32.to_nat((len / 4 + 1 : U32)))(Rd{b, 4}))
957 case False{}:
958 decode.a(~A, ~pdec, tag, len, get.u64(b, 4))
959
960def decode.tag(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +len: U32, r: Bytes.Bytes & U32) -> Maybe<&2, Op<A>>:
961 (b, +tag) = r
962 decode.tag.if(~A, ~pdec, U32.is_eq(tag, 10), tag, len, b)
963
964def decode.len(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, ok: Bool, +len: U32, b: Bytes.Bytes) -> Maybe<&2, Op<A>>:
965 match ok:
966 case False{}:
967 None{}
968 case True{}:
969 decode.tag(~A, ~pdec, len, get.u32(Bytes.get.u32le(b, 0)))
970
971# The op of a record, or None when it is not one that encode writes.
972def decode(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, b: Bytes.Bytes) -> Maybe<&2, Op<A>>:
973 Bytes.Bytes{+len, buf} = b
974 decode.len(~A, ~pdec, U32.is_ge(len, 12), len, Bytes.Bytes{len, buf})
975
976# The state of a Snap record whose tag is already checked. The decoder must end at the record's end.
977def decode.snap(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, b: Bytes.Bytes) -> Maybe<&2, State<A>>:
978 Bytes.Bytes{+len, buf} = b
979 rd.done(State<A>, len, rd.state(~A, ~pdec, U32.to_nat((len / 4 + 1 : U32)))(Rd{Bytes.Bytes{len, buf}, 4}))
980
981def decode.snapped(-A: Data, m: Maybe<&2, State<A>>) -> Maybe<&2, Rec<A>>:
982 match m:
983 case None{}:
984 None{}
985 case Some{s}:
986 Some{Snap{s}}
987
988def decode.did(-A: Data, m: Maybe<&2, Op<A>>) -> Maybe<&2, Rec<A>>:
989 match m:
990 case None{}:
991 None{}
992 case Some{op}:
993 Some{Do{op}}
994
995def decode.rec.if(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, snap: Bool, b: Bytes.Bytes) -> Maybe<&2, Rec<A>>:
996 match snap:
997 case True{}:
998 decode.snapped(A, decode.snap(~A, ~pdec, b))
999 case False{}:
1000 decode.did(A, decode(~A, ~pdec, b))
1001
1002def decode.rec.tag(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, r: Bytes.Bytes & U32) -> Maybe<&2, Rec<A>>:
1003 (b, +tag) = r
1004 decode.rec.if(~A, ~pdec, U32.is_eq(tag, 7), b)
1005
1006# The Rec of a journal record, or None when it is neither a Snap nor an op that encode.rec writes.
1007def decode.rec(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, b: Bytes.Bytes) -> Maybe<&2, Rec<A>>:
1008 decode.rec.tag(~A, ~pdec, get.u32(Bytes.get.u32le(b, 0)))
1009
1010# ---- the runner
1011
1012# policy: retry's policy for each ticket. circuit: the breaker of each target. idle: ms that drain waits when no attempt started.
1013# compact: tick compacts the journal once records past this many octets were appended since open or the last compaction; 0 never.
1014type Config is Data:
1015 Config{policy: Retry.Policy, circuit: Retry.Circuit, idle: U32, compact: U32}
1016
1017# The journal, its path, its file cap, and its length at open or at the last compaction.
1018type Log is Type:
1019 Log{journal: J.Journal, path: String, limit: U32, base: U32}
1020
1021# An attempt that runs: its unit of the pool, the budget that admit left, and its target.
1022type Flight<-A: Data> is Type:
1023 Flight{ticket: Q.Ticket<A>, grant: Res.Grant, budget: Retry.Budget, target: String}
1024
1025def Out(-X: Type) -> Type:
1026 Result<&1, &1, U32 & String, X>
1027
1028# A message to the fiber that owns the runner. Ended: an attempt finished. Add and Drop: another fiber asks for an enqueue or a cancel.
1029type Msg<-A: Data> is Type:
1030 Ended{id: Nat, outcome: Retry.Outcome}
1031 Add{deadline: Nat, payload: A, reply: Chan(Out(Nat))}
1032 Drop{id: Nat, reply: Chan(Out(Unit))}
1033
1034# An open runner. Replaying its journal gives its state; its pool bounds the attempts that run at once.
1035# Each attempt sends its outcome, and each other fiber its ask, on inbox. flights are the attempts that run.
1036type Runner<-A: Data> is Type:
1037 Runner{log: Log, state: State<A>, pool: Res.Pool, config: Config, inbox: Chan(Msg<A>), flights: List<&1, Flight<A>>}
1038
1039# The runner, the claim fuel left, and the first error.
1040def Claimed(-A: Data) -> Type:
1041 Runner<A> & Nat & Out(Unit)
1042
1043def Ran(-A: Data) -> Type:
1044 Runner<A> & Out(Unit)
1045
1046# Wall-clock ms since the Unix epoch. Deadlines must keep their meaning across a restart.
1047def clock() -> IO(Nat):
1048 do IO<Nat>:
1049 t : Time.Instant <- Time.now()
1050 return Time.Duration.to_ms_nat(Time.Instant.since_epoch(t))
1051
1052def first(a: Out(Unit), b: Out(Unit)) -> Out(Unit):
1053 match a:
1054 case Fail{e}:
1055 Fail{e}
1056 case Done{u}:
1057 b
1058
1059def log.appended(+path: String, +limit: U32, +base: U32, x: J.Journal & Out(Unit)) -> Log & Out(Unit):
1060 (j, o) = x
1061 (Log{j, path, limit, base}, o)
1062
1063def log.append(l: Log, p: Bytes.Bytes) -> IO(Log & Out(Unit)):
1064 Log{j, +path, +limit, +base} = l
1065 do IO<Log & Out(Unit)>:
1066 x : J.Journal & Out(Unit) <- J.append(j, p)
1067 return log.appended(path, limit, base, x)
1068
1069def log.close(l: Log) -> IO(Unit):
1070 Log{j, path, limit, base} = l
1071 J.close(j)
1072
1073# The journal reads with limit as its record cap, so that a snapshot fits; appends keep max.
1074def log.of(j: J.Journal, +max: U32, path: String, +limit: U32) -> Log:
1075 J.Journal{file, cap, +end, ok} = j
1076 Log{J.Journal{file, max, end, ok}, path, limit, end}
1077
1078def commit.done(~A: Data, x: Log & Out(Unit), s: State<A>, +op: Op<A>, p: Res.Pool, c: Config, ib: Chan(Msg<A>), fs: List<&1, Flight<A>>) -> Ran(A):
1079 match x:
1080 case (j, Done{u}):
1081 (Runner{j, step(~A, s, op), p, c, ib, fs}, Done{u})
1082 case (j, Fail{e}):
1083 (Runner{j, s, p, c, ib, fs}, Fail{e})
1084
1085# Appends op, and applies it once the append is durable. After a failed append the state is as it was,
1086# and the journal refuses every later append until the runner is reopened.
1087def commit(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +op: Op<A>) -> IO(Ran(A)):
1088 Runner{j, s, p, c, ib, fs} = r
1089 do IO<Ran(A)>:
1090 x : Log & Out(Unit) <- log.append(j, encode(~A, ~penc, op))
1091 return commit.done(~A, x, s, op, p, c, ib, fs)
1092
1093def enqueue.done(-A: Data, +id: Nat, y: Ran(A)) -> Runner<A> & Out(Nat):
1094 match y:
1095 case (r, Done{u}):
1096 (r, Done{id})
1097 case (r, Fail{e}):
1098 (r, Fail{e})
1099
1100# Adds a job that is due at deadline (wall-clock ms) and answers its ticket id once the record is durable.
1101def enqueue(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +deadline: Nat, x: A) -> IO(Runner<A> & Out(Nat)):
1102 Runner{j, +s, p, c, ib, fs} = r
1103 do IO<Runner<A> & Out(Nat)>:
1104 y : Ran(A) <- commit(~A, ~penc, Runner{j, s, p, c, ib, fs}, Enqueue{deadline, x})
1105 return enqueue.done(A, Q.next_id(A, queue(A, s)), y)
1106
1107# Cancels ticket id. A running attempt finishes, but its ticket is never selected again. A dead ticket is dropped.
1108def cancel(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +id: Nat) -> IO(Ran(A)):
1109 commit(~A, ~penc, r, Cancel{id})
1110
1111# Makes dead ticket id pending again at deadline (wall-clock ms), with its payload and a new retry budget.
1112# A ticket that is not dead does not change.
1113def revive(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +id: Nat, +deadline: Nat) -> IO(Ran(A)):
1114 commit(~A, ~penc, r, Revive{id, deadline})
1115
1116# Drops, as one record, the dead tickets that retry gave up on before `before` (wall-clock ms).
1117def purge(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +before: Nat) -> IO(Ran(A)):
1118 commit(~A, ~penc, r, Purge{before})
1119
1120# Drops every dead ticket, as one record.
1121def purge.all(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>) -> IO(Ran(A)):
1122 commit(~A, ~penc, r, PurgeAll{})
1123
1124# ---- asks from other fibers
1125
1126# The runner back, and its inbox. Another fiber passes the inbox to ask.enqueue and ask.cancel.
1127def inbox(-A: Data, r: Runner<A>) -> Runner<A> & Chan(Msg<A>):
1128 Runner{j, s, p, c, +ib, fs} = r
1129 (Runner{j, s, p, c, ib, fs}, ib)
1130
1131def ask.answer(-X: Type, m: Maybe<&1, Out(X)>) -> Out(X):
1132 match m:
1133 case None{}:
1134 Fail{(32, "runner: the runner closed before it answered")}
1135 case Some{o}:
1136 o
1137
1138def ask.sent(-A: Data, -X: Type, x: Result<&1, &1, Msg<A>, Unit>, +rep: Chan(Out(X))) -> IO(Out(X)):
1139 match x:
1140 case Fail{m}:
1141 IO.pure(Out(X), Fail{(32, "runner: the inbox is closed")})
1142 case Done{u}:
1143 do IO<Out(X)>:
1144 a : Maybe<&1, Out(X)> <- Chan.recv(Out(X), rep)
1145 return ask.answer(X, a)
1146
1147# Sends m, built with a new reply channel, on the inbox and waits for the reply.
1148def ask(-A: Data, -X: Type, +ib: Chan(Msg<A>), m: Chan(Out(X)) -> Msg<A>) -> IO(Out(X)):
1149 do IO<Out(X)>:
1150 +rep : Chan(Out(X)) <- Chan.new(Out(X), 1)
1151 x : Result<&1, &1, Msg<A>, Unit> <- Chan.send(Msg<A>, ib, m(rep))
1152 ask.sent(A, X, x, rep)
1153
1154# From another fiber: adds a job due at deadline, and answers its ticket id once the record is durable.
1155# The answer comes when the fiber that owns the runner reads the inbox, in tick or drain.
1156def ask.enqueue(-A: Data, +ib: Chan(Msg<A>), +deadline: Nat, x: A) -> IO(Out(Nat)):
1157 ask(A, Nat, ib, rep => Add{deadline, x, rep})
1158
1159# From another fiber: cancels ticket id, as cancel does. The answer comes when the owner reads the inbox.
1160def ask.cancel(-A: Data, +ib: Chan(Msg<A>), +id: Nat) -> IO(Out(Unit)):
1161 ask(A, Unit, ib, rep => Drop{id, rep})
1162
1163# ---- one round
1164
1165# A grant of this runner's pool always fits it, so Kept does not happen.
1166def release.got(-A: Data, x: Res.Release, j: Log, s: State<A>, c: Config, ib: Chan(Msg<A>), fs: List<&1, Flight<A>>) -> Runner<A>:
1167 match x:
1168 case Res.Released{p}:
1169 Runner{j, s, p, c, ib, fs}
1170 case Res.Kept{p, g}:
1171 Runner{j, s, p, c, ib, fs}
1172
1173def release(-A: Data, r: Runner<A>, g: Res.Grant) -> Runner<A>:
1174 Runner{j, s, p, c, ib, fs} = r
1175 release.got(A, Res.release(p, g), j, s, c, ib, fs)
1176
1177def claim.held(-A: Data, y: Ran(A), g: Res.Grant, next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1178 match y:
1179 case (r, Fail{e}):
1180 IO.pure(Claimed(A), (release(A, r, g), 0n, Fail{e}))
1181 case (r, Done{u}):
1182 next(release(A, r, g))
1183
1184def claim.tag(-A: Data, +id: Nat, o: Retry.Outcome) -> IO(Msg<A>):
1185 IO.pure(Msg<A>, Ended{id, o})
1186
1187def trip.if(~A: Data, ~penc: A -> Bytes.Bytes, same: Bool, r: Runner<A>, +key: String, st: Retry.State) -> IO(Ran(A)):
1188 match same:
1189 case True{}:
1190 IO.pure(Ran(A), (r, Done{Unit{}}))
1191 case False{}:
1192 commit(~A, ~penc, r, Break{key, st})
1193
1194# Appends a Break when the target's breaker left old, so that a reopen restores it.
1195def trip(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +key: String, +old: Retry.State, br: Retry.Breaker) -> IO(Ran(A)):
1196 +st = brk.state(br, old)
1197 trip.if(~A, ~penc, brk.same(old, st), r, key, st)
1198
1199def claim.go(~A: Data, ~penc: A -> Bytes.Bytes, ~work: A -> IO(Retry.Outcome), +now: Nat, gate: Retry.Gate, +br: Retry.Breaker, b: Retry.Budget, +key: String,
1200 r: Runner<A>, +id: Nat, d: Nat, +x: A, g: Res.Grant, next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1201 match gate:
1202 case Retry.GateGo{}:
1203 Runner{j, s, p, c, +ib, fs} = r
1204 do IO<Claimed(A)>:
1205 u : Chan(Msg<A>) <- IO.fork.go(Msg<A>, IO.bind(Retry.Outcome, Msg<A>, work(x), o => claim.tag(A, id, o)), ib)
1206 next(Runner{j, s, p, c, ib, Con{Flight{Q.Ticket{id, d, x}, g, b, key}, fs}})
1207 case Retry.GateNo{why}:
1208 do IO<Claimed(A)>:
1209 y : Ran(A) <- commit(~A, ~penc, r, held(A, why, br, id, now))
1210 claim.held(A, y, g, next)
1211
1212def claim.tripped(~A: Data, ~penc: A -> Bytes.Bytes, ~work: A -> IO(Retry.Outcome), +now: Nat, y: Ran(A), gate: Retry.Gate, +br: Retry.Breaker, b: Retry.Budget, +key: String,
1213 +id: Nat, d: Nat, +x: A, g: Res.Grant, next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1214 match y:
1215 case (r, Fail{e}):
1216 IO.pure(Claimed(A), (release(A, r, g), 0n, Fail{e}))
1217 case (r, Done{u}):
1218 claim.go(~A, ~penc, ~work, now, gate, br, b, key, r, id, d, x, g, next)
1219
1220# A change to the breaker is durable before the attempt starts.
1221def claim.gate(~A: Data, ~penc: A -> Bytes.Bytes, ~work: A -> IO(Retry.Outcome), +now: Nat, a: Retry.Breaker & Retry.Budget & Retry.Gate, +key: String, +old: Retry.State,
1222 r: Runner<A>, +id: Nat, d: Nat, +x: A, g: Res.Grant, next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1223 (+br, b, gate) = a
1224 do IO<Claimed(A)>:
1225 y : Ran(A) <- trip(~A, ~penc, r, key, old, br)
1226 claim.tripped(~A, ~penc, ~work, now, y, gate, br, b, key, id, d, x, g, next)
1227
1228# The selected ticket asks its target's breaker and its own budget for an attempt.
1229def claim.admit(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +now: Nat, r: Runner<A>, t: Q.Ticket<A>, g: Res.Grant,
1230 next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1231 Runner{j, +s, p, +c, ib, fs} = r
1232 Config{pol, circ, idle, every} = c
1233 Q.Ticket{+id, d, +x} = t
1234 +key = target(x)
1235 +old = brk.get(A, s, key)
1236 claim.gate(~A, ~penc, ~work, now, Retry.admit(Retry.BreakerOn{circ, old}, budget(pol, tries.get(tries(A, s), id)), now), key, old,
1237 Runner{j, s, p, c, ib, fs}, id, d, x, g, next)
1238
1239def claim.selected(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +now: Nat, y: Ran(A),
1240 t: Q.Ticket<A>, g: Res.Grant, next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1241 match y:
1242 case (r, Fail{e}):
1243 IO.pure(Claimed(A), (release(A, r, g), 0n, Fail{e}))
1244 case (r, Done{u}):
1245 claim.admit(~A, ~penc, ~target, ~work, now, r, t, g, next)
1246
1247def claim.pick(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +left: Nat, +now: Nat, k: Pick<A>, j: Log, s: State<A>,
1248 c: Config, ib: Chan(Msg<A>), fs: List<&1, Flight<A>>, next: Runner<A> -> IO(Claimed(A))) -> IO(Claimed(A)):
1249 match k:
1250 case Idle{p}:
1251 IO.pure(Claimed(A), (Runner{j, s, p, c, ib, fs}, Nat.add(1n, left), Done{Unit{}}))
1252 case Picked{p, t, g}:
1253 do IO<Claimed(A)>:
1254 y : Ran(A) <- commit(~A, ~penc, Runner{j, s, p, c, ib, fs}, Select{now})
1255 claim.selected(~A, ~penc, ~target, ~work, now, y, t, g, next)
1256
1257# Starts an attempt for each due ticket while the pool has a free unit; each attempt sends its outcome on the inbox.
1258# fuel bounds the tickets taken, and the fuel left comes back.
1259def claim(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), fuel: Nat, +now: Nat, r: Runner<A>) -> IO(Claimed(A)):
1260 match fuel:
1261 case 0n:
1262 IO.pure(Claimed(A), (r, 0n, Done{Unit{}}))
1263 case 1n+n:
1264 Runner{j, +s, p, c, ib, fs} = r
1265 +m = n
1266 claim.pick(~A, ~penc, ~target, ~work, m, now, pick(~A, p, s, now), j, s, c, ib, fs, (r2 => claim(~A, ~penc, ~target, ~work, m, now, r2)))
1267
1268def settle.done(-A: Data, y: Ran(A), g: Res.Grant, err: Out(Unit), next: Runner<A> -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1269 (r, res) = y
1270 next(release(A, r, g), first(err, res))
1271
1272def settle.br(~A: Data, ~penc: A -> Bytes.Bytes, +op: Op<A>, y: Ran(A), g: Res.Grant, err: Out(Unit),
1273 next: Runner<A> -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1274 match y:
1275 case (r, Fail{e}):
1276 next(release(A, r, g), first(err, Fail{e}))
1277 case (r, Done{u}):
1278 do IO<Runner<A> & Out(Bool)>:
1279 z : Ran(A) <- commit(~A, ~penc, r, op)
1280 settle.done(A, z, g, err, next)
1281
1282# Tells the target's breaker, appends the outcome's op, and returns the attempt's unit to the pool.
1283# The op of a cancelled ticket changes no state: the queue no longer holds it.
1284def settle.op(~A: Data, ~penc: A -> Bytes.Bytes, +o: Retry.Outcome, b: Retry.Budget, +id: Nat, +key: String, +now: Nat, +rnd: Nat, r: Runner<A>, g: Res.Grant,
1285 err: Out(Unit), next: Runner<A> -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1286 Runner{j, +s, p, +c, ib, fs} = r
1287 Config{pol, circ, idle, every} = c
1288 +old = brk.get(A, s, key)
1289 do IO<Runner<A> & Out(Bool)>:
1290 y : Ran(A) <- trip(~A, ~penc, Runner{j, s, p, c, ib, fs}, key, old, Retry.Breaker.done(Retry.BreakerOn{circ, old}, now, Retry.failed(o)))
1291 settle.br(~A, ~penc, after(A, o, pol, b, id, fails(tries.get(tries(A, s), id)), now, rnd), y, g, err, next)
1292
1293def random(r: Out(U32)) -> Nat:
1294 match r:
1295 case Done{x}:
1296 U32.to_nat(x)
1297 case Fail{e}:
1298 0n
1299
1300def take.keep(-A: Data, m: Maybe<&1, Flight<A>>, xs: List<&1, Flight<A>>) -> List<&1, Flight<A>>:
1301 match m:
1302 case None{}:
1303 xs
1304 case Some{f}:
1305 Con{f, xs}
1306
1307def take.at(-A: Data, eq: Bool, f: Flight<A>, r: Maybe<&1, Flight<A>> & List<&1, Flight<A>>) -> Maybe<&1, Flight<A>> & List<&1, Flight<A>>:
1308 match eq:
1309 case True{}:
1310 (m, xs) = r
1311 (Some{f}, take.keep(A, m, xs))
1312 case False{}:
1313 (m, xs) = r
1314 (m, Con{f, xs})
1315
1316# The flight of ticket id, and the other flights.
1317def take(-A: Data, fs: List<&1, Flight<A>>, +id: Nat) -> Maybe<&1, Flight<A>> & List<&1, Flight<A>>:
1318 match fs:
1319 case Nil{}:
1320 (None{}, Nil{})
1321 case Con{Flight{Q.Ticket{+i, d, x}, g, b, k}, rest}:
1322 take.at(A, Nat.is_eq(i, id), Flight{Q.Ticket{i, d, x}, g, b, k}, take(A, rest, id))
1323
1324def settle.flight(~A: Data, ~penc: A -> Bytes.Bytes, mf: Maybe<&1, Flight<A>>, +o: Retry.Outcome, +now: Nat, +rnd: Nat, r: Runner<A>, err: Out(Unit),
1325 next: Runner<A> -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1326 match mf:
1327 case None{}:
1328 next(r, err)
1329 case Some{Flight{Q.Ticket{id, d, x}, g, b, key}}:
1330 settle.op(~A, ~penc, o, b, id, key, now, rnd, r, g, err, next)
1331
1332def settle.take(~A: Data, ~penc: A -> Bytes.Bytes, t: Maybe<&1, Flight<A>> & List<&1, Flight<A>>, +o: Retry.Outcome, +now: Nat, +rnd: Nat,
1333 j: Log, s: State<A>, p: Res.Pool, c: Config, ib: Chan(Msg<A>), err: Out(Unit),
1334 next: Runner<A> -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1335 (mf, fs) = t
1336 settle.flight(~A, ~penc, mf, o, now, rnd, Runner{j, s, p, c, ib, fs}, err, next)
1337
1338# Settles the flight of ticket id with outcome o.
1339def settle(~A: Data, ~penc: A -> Bytes.Bytes, +id: Nat, +o: Retry.Outcome, +now: Nat, +rnd: Nat, r: Runner<A>, err: Out(Unit),
1340 next: Runner<A> -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1341 Runner{j, s, p, c, ib, fs} = r
1342 settle.take(~A, ~penc, take(A, fs, id), o, now, rnd, j, s, p, c, ib, err, next)
1343
1344# Sends the failure to the asker, and keeps it as the round's error.
1345def asked.failed(-A: Data, -X: Type, +rep: Chan(Out(X)), r: Runner<A>, +c: U32, +m: String, err: Out(Unit),
1346 next: Runner<A> -> Nat -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1347 do IO<Runner<A> & Out(Bool)>:
1348 x : Result<&1, &1, Out(X), Unit> <- Chan.send(Out(X), rep, Fail{(c, m)})
1349 next(r, 0n, first(err, Fail{(c, m)}))
1350
1351def asked.fail(-A: Data, -X: Type, +rep: Chan(Out(X)), r: Runner<A>, e: U32 & String, err: Out(Unit),
1352 next: Runner<A> -> Nat -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1353 (c, m) = e
1354 asked.failed(A, X, rep, r, c, m, err, next)
1355
1356def added(-A: Data, +rep: Chan(Out(Nat)), y: Runner<A> & Out(Nat), err: Out(Unit),
1357 next: Runner<A> -> Nat -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1358 match y:
1359 case (r, Done{+i}):
1360 do IO<Runner<A> & Out(Bool)>:
1361 x : Result<&1, &1, Out(Nat), Unit> <- Chan.send(Out(Nat), rep, Done{i})
1362 next(r, 1n, err)
1363 case (r, Fail{e}):
1364 asked.fail(A, Nat, rep, r, e, err, next)
1365
1366def dropped(-A: Data, +rep: Chan(Out(Unit)), y: Ran(A), err: Out(Unit),
1367 next: Runner<A> -> Nat -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1368 match y:
1369 case (r, Done{u}):
1370 do IO<Runner<A> & Out(Bool)>:
1371 x : Result<&1, &1, Out(Unit), Unit> <- Chan.send(Out(Unit), rep, Done{Unit{}})
1372 next(r, 0n, err)
1373 case (r, Fail{e}):
1374 asked.fail(A, Unit, rep, r, e, err, next)
1375
1376# Settles an ended attempt, or appends an ask's op and answers it. next gets the claim fuel the message adds: 1 for an enqueue.
1377def handle(~A: Data, ~penc: A -> Bytes.Bytes, m: Msg<A>, +now: Nat, +rnd: Nat, r: Runner<A>, err: Out(Unit),
1378 next: Runner<A> -> Nat -> Out(Unit) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1379 match m:
1380 case Ended{+id, +o}:
1381 settle(~A, ~penc, id, o, now, rnd, r, err, (r2 => e2 => next(r2, 0n, e2)))
1382 case Add{+d, x, +rep}:
1383 IO.bind(Runner<A> & Out(Nat), Runner<A> & Out(Bool), enqueue(~A, ~penc, r, d, x), y => added(A, rep, y, err, next))
1384 case Drop{+i, +rep}:
1385 IO.bind(Ran(A), Runner<A> & Out(Bool), cancel(~A, ~penc, r, i), y => dropped(A, rep, y, err, next))
1386
1387def merged(-A: Data, e: Out(Unit), k: Claimed(A)) -> Claimed(A):
1388 (r, n, err) = k
1389 (r, n, first(e, err))
1390
1391def empty.heap(-A: Data, h: H.Heap<Q.Ticket<A>>) -> Bool:
1392 match h:
1393 case H.HLeaf{}:
1394 True{}
1395 case H.HNode{n, t, l, r}:
1396 False{}
1397
1398def empty.list(-A: Data, xs: List<&2, Q.Ticket<A>>) -> Bool:
1399 match xs:
1400 case Nil{}:
1401 True{}
1402 case Con{t, rest}:
1403 False{}
1404
1405# No ticket is pending or running. Dead tickets wait for a Revive, so they do not count.
1406def idle(-A: Data, s: State<A>) -> Bool:
1407 State{Q.State{n, h, run}, ts, ds, bs} = s
1408 Bool.and(empty.heap(A, h), empty.list(A, run))
1409
1410def pending(-A: Data, s: State<A>) -> Nat:
1411 State{Q.State{n, h, run}, ts, ds, bs} = s
1412 H.Heap.size(Q.Ticket<A>, h)
1413
1414# The flights back, and whether none runs.
1415def flights.none(-A: Data, fs: List<&1, Flight<A>>) -> List<&1, Flight<A>> & Bool:
1416 match fs:
1417 case Nil{}:
1418 (Nil{}, True{})
1419 case Con{f, rest}:
1420 (Con{f, rest}, False{})
1421
1422# ---- compaction
1423
1424# Kept: compaction failed before the rename, and the old journal stands.
1425# Lost: the rename happened, but the new journal did not open. Moved: the journal at path is the snapshot.
1426type Swap is Type:
1427 Kept{err: U32 & String}
1428 Lost{err: U32 & String}
1429 Moved{journal: J.Journal}
1430
1431def swap.reopened(x: Out(J.Journal & Unit)) -> Swap:
1432 match x:
1433 case Fail{e}:
1434 Lost{e}
1435 case Done{(j, u)}:
1436 Moved{j}
1437
1438# The reopen fsyncs the directory, so the rename is durable before the next append.
1439def swap.renamed(+path: String, +limit: U32, x: Out(Unit)) -> IO(Swap):
1440 match x:
1441 case Fail{e}:
1442 IO.pure(Swap, Kept{e})
1443 case Done{u}:
1444 do IO<Swap>:
1445 y : Out(J.Journal & Unit) <- J.open(~Unit, ~(a => b => a), path, limit, limit, Unit{})
1446 return swap.reopened(y)
1447
1448def swap.written(+path: String, +tmp: String, +limit: U32, x: J.Journal & Out(Unit)) -> IO(Swap):
1449 match x:
1450 case (t, Fail{e}):
1451 do IO<Swap>:
1452 J.close(t)
1453 return Kept{e}
1454 case (t, Done{u}):
1455 do IO<Swap>:
1456 J.close(t)
1457 y : Out(Unit) <- Files.rename(tmp, path)
1458 swap.renamed(path, limit, y)
1459
1460def swap.opened(+path: String, +tmp: String, +limit: U32, x: Out(J.Journal & Unit), snap: Bytes.Bytes) -> IO(Swap):
1461 match x:
1462 case Fail{e}:
1463 IO.pure(Swap, Kept{e})
1464 case Done{(t, u)}:
1465 do IO<Swap>:
1466 y : J.Journal & Out(Unit) <- J.append(t, snap)
1467 swap.written(path, tmp, limit, y)
1468
1469# Writes snap as the only record of path.compact, fsyncs it, and renames it over path.
1470def swap(+path: String, +limit: U32, snap: Bytes.Bytes) -> IO(Swap):
1471 +tmp = path ++ ".compact"
1472 do IO<Swap>:
1473 gone : Out(Unit) <- Files.remove(tmp)
1474 x : Out(J.Journal & Unit) <- J.open(~Unit, ~(a => b => a), tmp, limit, limit, Unit{})
1475 swap.opened(path, tmp, limit, x, snap)
1476
1477def log.stop(j: J.Journal) -> J.Journal:
1478 J.Journal{file, max, end, ok} = j
1479 J.Journal{file, max, end, False{}}
1480
1481def compact.moved(x: Swap, j: J.Journal, +max: U32, path: String, +limit: U32, +base: U32) -> IO(Log & Out(Unit)):
1482 match x:
1483 case Kept{e}:
1484 IO.pure(Log & Out(Unit), (Log{j, path, limit, base}, Fail{e}))
1485 case Lost{e}:
1486 IO.pure(Log & Out(Unit), (Log{log.stop(j), path, limit, base}, Fail{e}))
1487 case Moved{k}:
1488 do IO<Log & Out(Unit)>:
1489 J.close(j)
1490 return (log.of(k, max, path, limit), Done{Unit{}})
1491
1492def compact.if(~A: Data, ~penc: A -> Bytes.Bytes, ok: Bool, j: J.Journal, +max: U32, +path: String, +limit: U32, +base: U32, s: State<A>) -> IO(Log & Out(Unit)):
1493 match ok:
1494 case False{}:
1495 IO.pure(Log & Out(Unit), (Log{j, path, limit, base}, Fail{(5, "runner: an append failed; reopen the runner")}))
1496 case True{}:
1497 do IO<Log & Out(Unit)>:
1498 x : Swap <- swap(path, limit, encode.snap(~A, ~penc, s))
1499 compact.moved(x, j, max, path, limit, base)
1500
1501def compact.done(-A: Data, x: Log & Out(Unit), s: State<A>, p: Res.Pool, c: Config, ib: Chan(Msg<A>), fs: List<&1, Flight<A>>) -> Ran(A):
1502 (l, o) = x
1503 (Runner{l, s, p, c, ib, fs}, o)
1504
1505# Writes the state as one Snap record into a new journal, fsyncs it, and renames it over the old one.
1506# A crash leaves one of the two journals, and both replay to this state. After a failure the old
1507# journal stands; when the failure came after the rename, appends stop until the runner is reopened.
1508def compact(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>) -> IO(Ran(A)):
1509 Runner{Log{j, path, limit, base}, +s, p, c, ib, fs} = r
1510 J.Journal{file, +max, end, +ok} = j
1511 do IO<Ran(A)>:
1512 x : Log & Out(Unit) <- compact.if(~A, ~penc, ok, J.Journal{file, max, end, ok}, max, path, limit, base, s)
1513 return compact.done(A, x, s, p, c, ib, fs)
1514
1515def tick.ran(e: Out(Unit), b: Bool) -> Out(Bool):
1516 match e:
1517 case Fail{x}:
1518 Fail{x}
1519 case Done{u}:
1520 Done{b}
1521
1522def tick.compacted(-A: Data, +b: Bool, y: Ran(A)) -> Runner<A> & Out(Bool):
1523 (r, e) = y
1524 (r, tick.ran(e, b))
1525
1526def tick.due(~A: Data, ~penc: A -> Bytes.Bytes, due: Bool, +b: Bool, r: Runner<A>) -> IO(Runner<A> & Out(Bool)):
1527 match due:
1528 case False{}:
1529 IO.pure(Runner<A> & Out(Bool), (r, Done{b}))
1530 case True{}:
1531 do IO<Runner<A> & Out(Bool)>:
1532 y : Ran(A) <- compact(~A, ~penc, r)
1533 return tick.compacted(A, b, y)
1534
1535def tick.size(~A: Data, ~penc: A -> Bytes.Bytes, r: Runner<A>, +b: Bool) -> IO(Runner<A> & Out(Bool)):
1536 Runner{Log{J.Journal{file, max, +end, ok}, path, limit, +base}, s, p, +c, ib, fs} = r
1537 Config{pol, circ, idle, +every} = c
1538 tick.due(~A, ~penc, Bool.and(Bool.not(U32.is_eq(every, 0)), U32.is_gt((end - base : U32), every)), b,
1539 Runner{Log{J.Journal{file, max, end, ok}, path, limit, base}, s, p, c, ib, fs})
1540
1541# Compacts once the journal grew past Config.compact octets since open or the last compaction.
1542def tick.grown(~A: Data, ~penc: A -> Bytes.Bytes, t: Runner<A> & Out(Bool)) -> IO(Runner<A> & Out(Bool)):
1543 match t:
1544 case (r, Fail{e}):
1545 IO.pure(Runner<A> & Out(Bool), (r, Fail{e}))
1546 case (r, Done{b}):
1547 tick.size(~A, ~penc, r, b)
1548
1549def tick.polled(-A: Data, x: Poll<&1, &1, Maybe<&1, Msg<A>>, Unit>) -> Maybe<&1, Msg<A>>:
1550 match x:
1551 case Ready{m}:
1552 m
1553 case Wait{u}:
1554 None{}
1555
1556def tick.wait(-A: Data, t: List<&1, Flight<A>> & Bool, j: Log, s: State<A>, p: Res.Pool, c: Config, +ib: Chan(Msg<A>)) ->
1557 IO(Runner<A> & Maybe<&1, Msg<A>>):
1558 (fs, none) = t
1559 match none:
1560 case False{}:
1561 do IO<Runner<A> & Maybe<&1, Msg<A>>>:
1562 m : Maybe<&1, Msg<A>> <- Chan.recv(Msg<A>, ib)
1563 return (Runner{j, s, p, c, ib, fs}, m)
1564 case True{}:
1565 do IO<Runner<A> & Maybe<&1, Msg<A>>>:
1566 x : Poll<&1, &1, Maybe<&1, Msg<A>>, Unit> <- Chan.try_recv(Msg<A>, ib, 0)
1567 return (Runner{j, s, p, c, ib, fs}, tick.polled(A, x))
1568
1569# The next message. While an attempt runs, it waits for one; when none runs, it takes one only when the inbox holds one.
1570def tick.next(-A: Data, r: Runner<A>) -> IO(Runner<A> & Maybe<&1, Msg<A>>):
1571 Runner{j, s, p, c, ib, fs} = r
1572 tick.wait(A, flights.none(A, fs), j, s, p, c, ib)
1573
1574# Handles the message, then claims due tickets into free units with the claim fuel left. None ends the round.
1575def tick.got(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), x: Runner<A> & Maybe<&1, Msg<A>>, +ran: Bool, +left: Nat,
1576 err: Out(Unit), next: Claimed(A) -> IO(Runner<A> & Out(Bool))) -> IO(Runner<A> & Out(Bool)):
1577 (r, m) = x
1578 match m:
1579 case None{}:
1580 IO.pure(Runner<A> & Out(Bool), (r, tick.ran(err, ran)))
1581 case Some{msg}:
1582 do IO<Runner<A> & Out(Bool)>:
1583 +now : Nat <- clock()
1584 rnd : Out(U32) <- IO.random_u32()
1585 handle(~A, ~penc, msg, now, random(rnd), r, err, (r2 => more => e2 =>
1586 IO.bind(Claimed(A), Runner<A> & Out(Bool), claim(~A, ~penc, ~target, ~work, Nat.add(left, more), now, r2), k2 => next(merged(A, e2, k2)))))
1587
1588# Handles messages until no attempt runs and the inbox is empty. fuel bounds the messages; attempts that still run
1589# when it ends stay in the runner, and the next tick settles them.
1590def tick.run(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), fuel: Nat, +ran: Bool, k: Claimed(A)) ->
1591 IO(Runner<A> & Out(Bool)):
1592 match fuel:
1593 case 0n:
1594 (r, left, err) = k
1595 IO.pure(Runner<A> & Out(Bool), (r, tick.ran(err, ran)))
1596 case 1n+n:
1597 (r, +left, err) = k
1598 do IO<Runner<A> & Out(Bool)>:
1599 x : Runner<A> & Maybe<&1, Msg<A>> <- tick.next(A, r)
1600 tick.got(~A, ~penc, ~target, ~work, x, ran, left, err, (k2 => tick.run(~A, ~penc, ~target, ~work, n, True{}, k2)))
1601
1602# Fuel for each pending ticket, each attempt that may already run, and the last look at the inbox.
1603def tick.at(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +now: Nat, r: Runner<A>) -> IO(Runner<A> & Out(Bool)):
1604 Runner{j, +s, +p, c, ib, fs} = r
1605 +fuel = Nat.add(2n, Nat.add(pending(A, s), Res.capacity(p)))
1606 do IO<Runner<A> & Out(Bool)>:
1607 k : Claimed(A) <- claim(~A, ~penc, ~target, ~work, fuel, now, Runner{j, s, p, c, ib, fs})
1608 tick.run(~A, ~penc, ~target, ~work, fuel, False{}, k)
1609
1610# One round: start an attempt for each due ticket the pool admits. Then read the inbox: as each attempt finishes, record its outcome,
1611# return its unit, and start the next due ticket in that unit; append and answer each ask from another fiber.
1612# The round ends when no attempt runs and the inbox is empty. Then compact the journal when it grew past Config.compact.
1613# Done{True} when an attempt ran or an ask was answered. work runs on its own; target names the breaker that guards it.
1614def tick(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), r: Runner<A>) -> IO(Runner<A> & Out(Bool)):
1615 do IO<Runner<A> & Out(Bool)>:
1616 now : Nat <- clock()
1617 t : Runner<A> & Out(Bool) <- tick.at(~A, ~penc, ~target, ~work, now, r)
1618 tick.grown(~A, ~penc, t)
1619
1620def finished.of(-A: Data, +quiet: Bool, t: List<&1, Flight<A>> & Bool, j: Log, s: State<A>, p: Res.Pool, c: Config, ib: Chan(Msg<A>)) ->
1621 Runner<A> & Bool:
1622 (fs, none) = t
1623 (Runner{j, s, p, c, ib, fs}, Bool.and(quiet, none))
1624
1625# The runner back, and whether no ticket is pending or running and no attempt runs.
1626def finished(-A: Data, r: Runner<A>) -> Runner<A> & Bool:
1627 Runner{j, +s, p, c, ib, fs} = r
1628 finished.of(A, idle(A, s), flights.none(A, fs), j, s, p, c, ib)
1629
1630def drain.handled(-A: Data, t: Runner<A> & Out(Bool), next: Runner<A> -> IO(Ran(A))) -> IO(Ran(A)):
1631 match t:
1632 case (r, Fail{e}):
1633 IO.pure(Ran(A), (r, Fail{e}))
1634 case (r, Done{b}):
1635 next(r)
1636
1637def drain.woke(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +idle: U32,
1638 x: Poll<&1, &1, Maybe<&1, Msg<A>>, Unit>, r: Runner<A>, next: Runner<A> -> IO(Ran(A))) -> IO(Ran(A)):
1639 match x:
1640 case Ready{Some{m}}:
1641 do IO<Ran(A)>:
1642 t : Runner<A> & Out(Bool) <- tick.got(~A, ~penc, ~target, ~work, (r, Some{m}), True{}, 0n, Done{Unit{}},
1643 (k => tick.run(~A, ~penc, ~target, ~work, 0n, True{}, k)))
1644 drain.handled(A, t, next)
1645 case Ready{None{}}:
1646 do IO<Ran(A)>:
1647 IO.sleep(idle)
1648 next(r)
1649 case Wait{u}:
1650 next(r)
1651
1652def drain.wait(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +idle: U32, r: Runner<A>,
1653 next: Runner<A> -> IO(Ran(A))) -> IO(Ran(A)):
1654 Runner{j, s, p, c, +ib, fs} = r
1655 do IO<Ran(A)>:
1656 x : Poll<&1, &1, Maybe<&1, Msg<A>>, Unit> <- Chan.try_recv(Msg<A>, ib, idle)
1657 drain.woke(~A, ~penc, ~target, ~work, idle, x, Runner{j, s, p, c, ib, fs}, next)
1658
1659def drain.ticked(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), +idle: U32,
1660 t: Runner<A> & Out(Bool), next: Runner<A> -> IO(Ran(A))) -> IO(Ran(A)):
1661 match t:
1662 case (r, Fail{e}):
1663 IO.pure(Ran(A), (r, Fail{e}))
1664 case (r, Done{True{}}):
1665 next(r)
1666 case (r, Done{False{}}):
1667 drain.wait(~A, ~penc, ~target, ~work, idle, r, next)
1668
1669def drain.if(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), done: Bool, r: Runner<A>, next: Runner<A> -> IO(Ran(A))) -> IO(Ran(A)):
1670 match done:
1671 case True{}:
1672 IO.pure(Ran(A), (r, Done{Unit{}}))
1673 case False{}:
1674 Runner{j, s, p, +c, ib, fs} = r
1675 Config{pol, circ, +idle, every} = c
1676 do IO<Ran(A)>:
1677 t : Runner<A> & Out(Bool) <- tick(~A, ~penc, ~target, ~work, Runner{j, s, p, c, ib, fs})
1678 drain.ticked(~A, ~penc, ~target, ~work, idle, t, next)
1679
1680def drain.at(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), x: Runner<A> & Bool, next: Runner<A> -> IO(Ran(A))) -> IO(Ran(A)):
1681 (r, done) = x
1682 drain.if(~A, ~penc, ~target, ~work, done, r, next)
1683
1684def drain.end(-A: Data, x: Runner<A> & Bool) -> Ran(A):
1685 (r, done) = x
1686 (r, Bool.pick(Out(Unit), done, Done{Unit{}}, Fail{(62, "runner: drain ran out of rounds")}))
1687
1688# Ticks until no ticket is pending or running and no attempt runs. After a round that did nothing, it waits up to idle ms
1689# for a message, and handles one that arrives at once.
1690# Fails when fuel rounds leave work.
1691def drain(~A: Data, ~penc: A -> Bytes.Bytes, ~target: A -> String, ~work: A -> IO(Retry.Outcome), fuel: Nat, r: Runner<A>) -> IO(Ran(A)):
1692 match fuel:
1693 case 0n:
1694 IO.pure(Ran(A), drain.end(A, finished(A, r)))
1695 case 1n+n:
1696 drain.at(~A, ~penc, ~target, ~work, finished(A, r), (r2 => drain(~A, ~penc, ~target, ~work, n, r2)))
1697
1698def orphans.next(-A: Data, y: Ran(A), err: Out(Unit), next: Runner<A> -> Out(Unit) -> IO(Ran(A))) -> IO(Ran(A)):
1699 (r, e) = y
1700 next(r, first(err, e))
1701
1702# A running ticket at open lost its attempt in a crash: it is requeued at now, as a failed attempt.
1703def orphans(~A: Data, ~penc: A -> Bytes.Bytes, ts: List<&2, Q.Ticket<A>>, +now: Nat, r: Runner<A>, err: Out(Unit)) -> IO(Ran(A)):
1704 match ts:
1705 case Nil{}:
1706 IO.pure(Ran(A), (r, err))
1707 case Con{Q.Ticket{id, d, x}, rest}:
1708 do IO<Ran(A)>:
1709 y : Ran(A) <- commit(~A, ~penc, r, Requeue{id, now})
1710 orphans.next(A, y, err, (r2 => e2 => orphans(~A, ~penc, rest, now, r2, e2)))
1711
1712def close.answer(-A: Data, m: Msg<A>) -> IO(Unit):
1713 match m:
1714 case Ended{id, o}:
1715 IO.pure(Unit, Unit{})
1716 case Add{d, x, rep}:
1717 do IO<Unit>:
1718 y : Result<&1, &1, Out(Nat), Unit> <- Chan.send(Out(Nat), rep, Fail{(32, "runner: the runner closed")})
1719 return Unit{}
1720 case Drop{i, rep}:
1721 do IO<Unit>:
1722 y : Result<&1, &1, Out(Unit), Unit> <- Chan.send(Out(Unit), rep, Fail{(32, "runner: the runner closed")})
1723 return Unit{}
1724
1725def close.polled(-A: Data, x: Poll<&1, &1, Maybe<&1, Msg<A>>, Unit>, next: Unit -> IO(Unit)) -> IO(Unit):
1726 match x:
1727 case Ready{Some{m}}:
1728 do IO<Unit>:
1729 close.answer(A, m)
1730 next(Unit{})
1731 case Ready{None{}}:
1732 IO.pure(Unit, Unit{})
1733 case Wait{u}:
1734 IO.pure(Unit, Unit{})
1735
1736# Answers each ask left in the closed inbox with a failure. fuel bounds the messages it reads.
1737def close.drain(-A: Data, fuel: Nat, +ib: Chan(Msg<A>)) -> IO(Unit):
1738 match fuel:
1739 case 0n:
1740 IO.pure(Unit, Unit{})
1741 case 1n+n:
1742 do IO<Unit>:
1743 x : Poll<&1, &1, Maybe<&1, Msg<A>>, Unit> <- Chan.try_recv(Msg<A>, ib, 0)
1744 close.polled(A, x, (u => close.drain(A, n, ib)))
1745
1746# Closes the inbox and the journal. Each ask still in the inbox gets a failure, and no op is appended for it.
1747def close(-A: Data, r: Runner<A>) -> IO(Unit):
1748 Runner{j, s, +p, c, +ib, fs} = r
1749 do IO<Unit>:
1750 Chan.close(Msg<A>, ib)
1751 close.drain(A, Nat.add(2n, Res.capacity(p)), ib)
1752 log.close(j)
1753
1754def open.done(-A: Data, y: Ran(A)) -> IO(Out(Runner<A>)):
1755 match y:
1756 case (r, Fail{e}):
1757 do IO<Out(Runner<A>)>:
1758 close(A, r)
1759 return Fail{e}
1760 case (r, Done{u}):
1761 IO.pure(Out(Runner<A>), Done{r})
1762
1763def open.got(~A: Data, ~penc: A -> Bytes.Bytes, x: Out(J.Journal & Maybe<&2, State<A>>), +max: U32, path: String, +limit: U32, c: Config, +capacity: Nat) ->
1764 IO(Out(Runner<A>)):
1765 match x:
1766 case Fail{e}:
1767 IO.pure(Out(Runner<A>), Fail{e})
1768 case Done{(j, None{})}:
1769 do IO<Out(Runner<A>)>:
1770 J.close(j)
1771 return Fail{(22, "runner: a journal record is not a runner record")}
1772 case Done{(j, Some{+s})}:
1773 do IO<Out(Runner<A>)>:
1774 now : Nat <- clock()
1775 ib : Chan(Msg<A>) <- Chan.new(Msg<A>, (U32.from_nat(capacity) + 1 : U32))
1776 y : Ran(A) <- orphans(~A, ~penc, Q.running(A, queue(A, s)), now, Runner{log.of(j, max, path, limit), calm(A, s), Res.new(0n, capacity), c, ib, Nil{}}, Done{Unit{}})
1777 open.done(A, y)
1778
1779def replay.step(~A: Data, ~pdec: Bytes.Bytes -> Maybe<&2, A>, acc: Maybe<&2, State<A>>, b: Bytes.Bytes) -> Maybe<&2, State<A>>:
1780 load(~A, ~Bytes.Bytes, ~(y => decode.rec(~A, ~pdec, y)), acc, b)
1781
1782# Opens the runner at path: replays its journal into the state, then requeues each ticket that was running.
1783# capacity bounds the attempts that run at once. max caps an op record's octets; limit caps the journal file and a snapshot.
1784# Fails when the journal fails to open, or a committed record is not a snapshot or an op.
1785def open(~A: Data, ~penc: A -> Bytes.Bytes, ~pdec: Bytes.Bytes -> Maybe<&2, A>, +path: String, +max: U32, +limit: U32, c: Config, +capacity: Nat) -> IO(Out(Runner<A>)):
1786 do IO<Out(Runner<A>)>:
1787 x : Out(J.Journal & Maybe<&2, State<A>>) <- J.open(~Maybe<&2, State<A>>, ~(acc => b => replay.step(~A, ~pdec, acc, b)), path, limit, limit, Some{new(A)})
1788 open.got(~A, ~penc, x, max, path, limit, c, capacity)
1789
1790# The runner back, and a copy of its state.
1791def state(-A: Data, r: Runner<A>) -> Runner<A> & State<A>:
1792 Runner{j, +s, p, c, ib, fs} = r
1793 (Runner{j, s, p, c, ib, fs}, s)