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notify.sx: reminders + digests as durable flows over an injected transport. A flow requests delivery (suspend); the host dispatch sends and resumes with the outcome. At-least-once + idempotent (transport dedups by msg id; replay logs outcomes). Retry rides suspend/resume with distinct per-attempt tags, bounded by maxn. Digest delivers a batch with per-message outcomes. 182/182 green. Delivery core is the delivery-on-sx extraction seam. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
39 lines
2.8 KiB
Plaintext
39 lines
2.8 KiB
Plaintext
;; lib/events/notify.sx — durable notification delivery flows over an injected
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;; transport (lib/flow).
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;;
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;; Reminders and digests are durable `flow`s: a flow `request`s delivery (a
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;; suspend point), the HOST performs the actual send via an injected `dispatch`
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;; (the transport — email/push/etc.), and resumes the flow with the outcome.
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;; Because flow uses deterministic replay, a completed delivery is never re-run
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;; on recovery; the host owns IO and persistence.
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;;
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;; Delivery is AT-LEAST-ONCE with idempotency. Each message carries an id (the
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;; idempotency key). Two protections stop double-delivery:
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;; 1. The transport dedups by id — a re-send of a delivered id is a no-op
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;; that still reports ok, so a retry never produces two pings.
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;; 2. flow's replay log records each resolved request, so recovery replays the
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;; logged outcome instead of re-issuing the send.
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;;
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;; Retry/backoff rides flow suspend/resume: each attempt issues a request with a
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;; DISTINCT tag `(deliver <id> <n>)` — distinct tags keep deterministic replay
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;; correct across retries. The dispatch returns (ok info) to finish or
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;; (retry reason) to try again, bounded by `maxn` (then (failed id reason)).
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;;
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;; A message is a 3-element list (id recipient body). The transport is generic
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;; and injected — when feed/notify lands, both consumers share one transport,
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;; so this delivery core is a candidate for extraction to `delivery-on-sx`.
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;;
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;; The Scheme flow source below loads into a flow env (see lib/flow/api.sx).
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;; `ev/notify-run` prepends it to a caller program and evaluates in the shared
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;; flow env.
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(define
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ev-notify-flows-src
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"(define (ev-msg-id m) (car m))\n (define (ev-msg-recipient m) (car (cdr m)))\n (define (ev-msg-body m) (car (cdr (cdr m))))\n (define (ev-mem x xs)\n (if (null? xs) #f (if (equal? x (car xs)) #t (ev-mem x (cdr xs)))))\n (define (ev-notify-attempt m n maxn)\n (let ((r (request (list (quote deliver) (ev-msg-id m) n) m)))\n (if (eq? (car r) (quote ok))\n (list (quote delivered) (ev-msg-id m) n)\n (if (>= n maxn)\n (list (quote failed) (ev-msg-id m) (car (cdr r)))\n (ev-notify-attempt m (+ n 1) maxn)))))\n (define (ev-deliver-reminder maxn)\n (flow-node (lambda (m) (ev-notify-attempt m 1 maxn))))\n (define (ev-digest-step ms maxn)\n (if (null? ms)\n (list)\n (cons (ev-notify-attempt (car ms) 1 maxn)\n (ev-digest-step (cdr ms) maxn))))\n (define (ev-deliver-digest maxn)\n (flow-node (lambda (ms) (ev-digest-step ms maxn))))")
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;; Run a Scheme flow program with the notify flows preloaded, in the shared
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;; flow env. Returns the program's value (SX-native).
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(define
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ev/notify-run
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(fn (prog) (flow-run (str ev-notify-flows-src "\n" prog))))
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