Leave a delivery cut off by a stop for the next start (closes #527)

Stopping the engine cancels the context every http and slack request is
sent with. An attempt cut off that way was recorded as failed, which for
a target with no retries, or on a last retry, ended the delivery failed
and nothing sent it again.

The shared retry core now records nothing for a failed attempt when the
engine's context is cancelled: no result, no circuit breaker outcome, no
status change. The delivery stays pending or retrying and startup
recovery sends it again. A target's own timeout is still a failed
attempt. The README's Graceful shutdown bullet, Shutdown section and the
at-least-once note say so.

Model: opus-5-5

README.md

@@ -1317,8 +1317,8 @@ webhooker solves this by acting as a durable intermediary:
    nothing is lost if downstream targets are unavailable.
 
 2. **Guaranteed delivery** — Events are queued for delivery to each configured
-   target. Failed deliveries are retried with configurable backoff. Delivery
+   target. Failed deliveries are retried with configurable backoff. Every
-   attempts are logged with status codes, response bodies, and timing.
+   delivery attempt is logged with status codes, response bodies, and timing.
 
     **That guarantee is at-least-once, not exactly-once.** When a send reaches
     its target but the write recording that outcome fails, the delivery is
@@ -1332,7 +1332,7 @@ webhooker solves this by acting as a durable intermediary:
     payload itself carries.
 
 3. **Observability** — Full request/response logging for every webhook received
-   and for delivery attempts. Prometheus metrics expose volume, latency, and
+   and every delivery attempted. Prometheus metrics expose volume, latency, and
    error rates. The web UI provides real-time visibility into event flow.
 
 4. **Fan-out** — A single incoming webhook can be delivered to multiple targets
@@ -2208,16 +2208,14 @@ This means:
   buffer rather than spawning more goroutines.
 - **Independent results** — each worker records its own delivery result in the
   per-webhook database without coordination.
-- **Graceful shutdown** — the stop hook cancels the workers' context. A worker
+- **Graceful shutdown** — the stop hook cancels the workers' context, and each
-  may still take tasks already queued before it exits. An `http` or `slack`
+  worker exits once its current task returns. Cancelling cuts off an `http` or
-  request in flight is cut off, and one started after the cancel fails at once.
+  `slack` request still in flight; that attempt is not recorded, and the next
-  Neither is recorded or counted in the metrics, and the next start sends the
+  start sends the delivery again (see Shutdown). The stop hook waits for the
-  delivery again (see Shutdown). A `database` or `log` task runs as normal. The
+  pool via `lifecycle.WaitForShutdown`, which bounds that wait by fx's stop
-  stop hook waits for the pool via `lifecycle.WaitForShutdown`, which bounds
+  timeout rather than blocking forever on a wedged worker. On timeout it logs at
-  that wait by fx's stop timeout rather than blocking forever on a wedged
+  `ERROR` and returns an error, and the goroutines that did not finish are still
-  worker. On timeout it logs at `ERROR` and returns an error, and the goroutines
+  running — an unclean shutdown is reported rather than hidden.
-  that did not finish are still running — an unclean shutdown is reported rather
-  than hidden.
 
 **Recovery paths:**
 
@@ -2323,7 +2321,7 @@ getting anywhere.
 | Metric                                 | Type      | Meaning                                                                                                                                                                                                                                                                                                   |
 | -------------------------------------- | --------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | `webhooker_events_received_total`      | counter   | Events received and durably stored. Compare against the delivery counters on one dashboard                                                                                                                                                                                                                |
-| `webhooker_delivery_attempts_total`    | counter   | Delivery attempts actually dispatched to a target. A delivery a circuit breaker refused is not one: it is counted as a retry instead, but only when the refusal moves it into `retrying`. An attempt cut off by a stop is not counted (see Shutdown)                                                      |
+| `webhooker_delivery_attempts_total`    | counter   | Delivery attempts actually dispatched to a target. A delivery a circuit breaker refused is not one: it is counted as a retry instead, but only when the refusal moves it into `retrying`                                                                                                                  |
 | `webhooker_deliveries_succeeded_total` | counter   | Deliveries that reached `delivered`                                                                                                                                                                                                                                                                       |
 | `webhooker_deliveries_failed_total`    | counter   | Deliveries that failed terminally and will not be retried                                                                                                                                                                                                                                                 |
 | `webhooker_delivery_retries_total`     | counter   | Deliveries put back into `retrying`                                                                                                                                                                                                                                                                       |
@@ -3302,8 +3300,8 @@ by the stop context, so a wedge there consumes the 5 seconds before the HTTP
 server hook is ever entered. The hooks after the server are microsecond-scale in
 normal operation.
 
-The delivery engine cancels a delivery request in flight. That attempt is not
+The delivery engine does not wait for a delivery request in flight: it cancels
-recorded or counted in the metrics, and the delivery keeps its `pending` or
+it. That attempt is not recorded and the delivery keeps its `pending` or
 `retrying` status, so startup recovery sends it again on the next start (see
 Recovery paths under Bounded Worker Pool). If the receiver already had it, it
 receives it twice: the at-least-once duplicate described under Rationale.

internal/delivery/delivery_totals_test.go

@@ -32,9 +32,8 @@ func targetTotals(
 
 // TestUpdateDeliveryStatus_FinishTimeAndTargetTotals pins what a status
 // write records for the webhook page's statistics: the time a delivery
-// finished, set only when it becomes delivered or failed and stored in
+// finished, set only when it becomes delivered or failed, and one more
-// the same form as created_at, and one more on its target's delivered
+// on its target's delivered or failed total.
-// or failed total.
 func TestUpdateDeliveryStatus_FinishTimeAndTargetTotals(t *testing.T) {
 	t.Parallel()
 
@@ -76,16 +75,6 @@ func TestUpdateDeliveryStatus_FinishTimeAndTargetTotals(t *testing.T) {
 			if tt.finished {
 				require.NotNil(t, stored.FinishedAt)
 				assert.False(t, stored.FinishedAt.Before(before))
-
-				var createdAt, finishedAt string
-
-				require.NoError(t, db.Raw(
-					`SELECT CAST(created_at AS TEXT),
-						CAST(finished_at AS TEXT)
-					FROM deliveries WHERE id = ?`, d.ID,
-				).Row().Scan(&createdAt, &finishedAt))
-				assertStoredTime(t, createdAt)
-				assertStoredTime(t, finishedAt)
 			} else {
 				assert.Nil(t, stored.FinishedAt)
 			}

internal/delivery/engine.go

@@ -1701,11 +1701,8 @@ func writeDeliveryStatus(
 			database.DeliveryStatusFailed,
 		}).
 		Updates(map[string]any{
-			"status": status,
+			"status":      status,
-			// GORM's clock, the one that stamps created_at. A bare
+			"finished_at": time.Now(),
-			// time.Now() carries a monotonic clock reading, which the
-			// driver would store as an " m=+…" suffix.
-			"finished_at": tx.NowFunc(),
 		})
 	if res.Error != nil || res.RowsAffected == 0 {
 		return res.Error
@@ -1909,13 +1906,12 @@ func (e *Engine) takeForRedispatch(
 		return false
 	}
 
-	// GORM's clock, as writeDeliveryStatus explains.
 	res := webhookDB.
 		Model(&database.Delivery{}).
 		Where(
 			"id = ? AND status = ?", deliveryID, eligible,
 		).
-		UpdateColumn("updated_at", webhookDB.NowFunc())
+		UpdateColumn("updated_at", time.Now())
 
 	if res.Error != nil {
 		e.log.Error(

internal/delivery/engine_lifecycle_test.go

@@ -370,13 +370,12 @@ func requireRequeued(
 // failure. Stopping the engine cancels the request; for a target with
 // no retries that was the delivery's only attempt, recorded as failed
 // with "context canceled", and nothing ever sent it again. The
-// delivery must instead stay pending, with no result and no count in
+// delivery must instead stay pending, with no result, for restart
-// the attempt metrics, for restart recovery to send.
+// recovery to send.
 func TestEngine_StopLeavesFireAndForgetAttemptPending(t *testing.T) {
 	t.Parallel()
 
 	s := newISetup(t)
-	reg := mIsolate(t, s)
 	lc := startEngineViaHook(t, s.Engine)
 
 	task, arrived := seedHeldDelivery(
@@ -390,8 +389,6 @@ func TestEngine_StopLeavesFireAndForgetAttemptPending(t *testing.T) {
 		t, s.WebhookDB, task.DeliveryID, database.DeliveryStatusPending,
 	)
 	assert.Empty(t, iResults(t, s.WebhookDB, task.DeliveryID))
-	assert.Zero(t, mCounter(t, reg, mAttempts, mTypeHTTP))
-	assert.Zero(t, mHTTPDurations(t, reg))
 
 	requireRequeued(t, s, s.Engine.ExportDeliveryCh(), task)
 }

internal/delivery/engine_test.go

@@ -117,18 +117,6 @@ func seedDelivery(
 	return d
 }
 
-// assertStoredTime asserts that text, a timestamp as SQLite holds it,
-// is in the form GORM stores created_at in: the layout of
-// time.Time.String, with no " m=+…" monotonic clock reading after it.
-func assertStoredTime(t *testing.T, text string) {
-	t.Helper()
-
-	_, err := time.Parse(
-		"2006-01-02 15:04:05.999999999 -0700 MST", text,
-	)
-	assert.NoError(t, err, "stored as %q", text)
-}
-
 // httpDeliveryFixture holds the task and delivery needed
 // for HTTP delivery tests.
 type httpDeliveryFixture struct {

internal/delivery/inflight_test.go

@@ -462,8 +462,7 @@ func TestScheduledRetryIsNotSweptDuringBackoff(t *testing.T) {
 
 // TestRedispatchStampsTheRow pins the cadence control: a stranded
 // delivery that has just been handed out is not selected again by the
-// next tick a minute later. The stamp is stored in the same form as
+// next tick a minute later.
-// created_at.
 func TestRedispatchStampsTheRow(t *testing.T) {
 	t.Parallel()
 
@@ -494,13 +493,4 @@ func TestRedispatchStampsTheRow(t *testing.T) {
 		"a re-dispatched delivery must be stamped so the "+
 			"next tick does not select it again",
 	)
-
-	var createdAt, updatedAt string
-
-	require.NoError(t, s.WebhookDB.Raw(
-		`SELECT CAST(created_at AS TEXT), CAST(updated_at AS TEXT)
-		FROM deliveries WHERE id = ?`, d.ID,
-	).Row().Scan(&createdAt, &updatedAt))
-	assertStoredTime(t, createdAt)
-	assertStoredTime(t, updatedAt)
 }

internal/delivery/target.go

@@ -32,8 +32,7 @@ type Scheduler interface {
 // Engine.observeAttempt, alongside the DeliveryResult it records for
 // it. Deliver is also entered for attempts that never happen — an
 // open circuit breaker refuses one — so the count cannot be taken
-// from around this call. An attempt cut off by a stop is neither
+// from around this call.
-// counted nor recorded.
 type Target interface {
 	Deliver(
 		ctx context.Context,

internal/delivery/target_database_archive.go

@@ -277,11 +277,7 @@ func (w *archiveWriter) write(
 		}
 	}
 
-	// GORM's clock, the one that stamps created_at in the other
+	row.ArchivedAt = time.Now()
-	// databases, so this is stored in the same form. A bare time.Now()
-	// carries a monotonic clock reading, which the driver would store
-	// as an " m=+…" suffix.
-	row.ArchivedAt = w.db.NowFunc()
 
 	err := w.db.Create(&row).Error
 	if err != nil {

internal/delivery/target_database_test.go

@@ -150,13 +150,6 @@ func TestArchiveWriter_WritesRow(t *testing.T) {
 	assert.Equal(t, row.ContentType, got[0].ContentType)
 	assert.JSONEq(t, `{"hello":"world"}`, got[0].Body)
 	assert.False(t, got[0].ArchivedAt.IsZero())
-
-	var archivedAt string
-
-	require.NoError(t, w.DB().Raw(
-		"SELECT CAST(archived_at AS TEXT) FROM archived_events",
-	).Row().Scan(&archivedAt))
-	assertStoredTime(t, archivedAt)
 }
 
 func TestArchiveWriter_RecreatesAfterRemoval(

internal/delivery/target_http.go

@@ -81,11 +81,11 @@ func (c *httpCore) deliver(
 }
 
 // interruptedByStop reports whether an attempt failed because the
-// engine is stopping, which cancels the context its request is made
+// engine is stopping, which cancels the context its request was sent
 // with. Such an attempt is not recorded: no DeliveryResult, no circuit
-// breaker outcome, no status change, no count in the attempt metrics.
+// breaker outcome, no status change. The delivery stays pending or
-// The delivery stays pending or retrying, and startup recovery sends
+// retrying, and startup recovery sends it again on the next start.
-// it again on the next start.
+// The request did go out, so the attempt metrics still count it.
 //
 // A target's own timeout leaves that context alone, so its attempt is
 // still recorded as the failure it is.
@@ -115,12 +115,12 @@ func (c *httpCore) fireAndForget(
 	d *database.Delivery,
 	res attemptResult,
 ) {
+	c.eng.observeAttempt(d.Target.Type, res.elapsed())
+
 	if c.interruptedByStop(ctx, d, res) {
 		return
 	}
 
-	c.eng.observeAttempt(d.Target.Type, res.elapsed())
-
 	err := c.eng.recordResult(
 		webhookDB, d, 1, res.success,
 		res.statusCode, res.respBody, res.errMsg,
@@ -170,12 +170,12 @@ func (c *httpCore) withRetry(
 
 	res := attempt()
 
+	c.eng.observeAttempt(d.Target.Type, res.elapsed())
+
 	if c.interruptedByStop(ctx, d, res) {
 		return
 	}
 
-	c.eng.observeAttempt(d.Target.Type, res.elapsed())
-
 	err := c.eng.recordResult(
 		webhookDB, d, attemptNum, res.success,
 		res.statusCode, res.respBody, res.errMsg,