webhooker/internal/delivery/target.go

package delivery

import (
	"context"
	"net/http"
	"time"

	"gorm.io/gorm"
	"sneak.berlin/go/webhooker/internal/database"
)

// Scheduler re-enqueues a task for a future delivery attempt.
// The engine provides one to each target so a target can own
// its retries durably: it records the attempt, marks the
// delivery retrying, and asks the Scheduler to deliver the
// next attempt after delay — exactly what the engine does for
// its own restart recovery.
type Scheduler interface {
	ScheduleRetry(task Task, delay time.Duration)
}

// Target delivers an event to one target type. Each type is
// an implementation. A Target owns its whole delivery: it
// makes the attempt, records the DeliveryResult and updates
// the DeliveryStatus, and — for targets that retry — decides
// whether to retry, computes its own backoff, gates with its
// own circuit breaker, and reschedules via the injected
// Scheduler. Fire-and-forget targets simply record a single
// attempt.
type Target interface {
	Deliver(
		ctx context.Context,
		webhookDB *gorm.DB,
		d *database.Delivery,
		task *Task,
		sched Scheduler,
	)
}

// rescheduler is implemented by targets that own durable
// retries. The engine's restart recovery and periodic sweep
// use it to let the target recompute the schedule for an
// orphaned retrying delivery, keeping the retry schedule
// target-owned. Fire-and-forget targets do not implement it
// and their (never-occurring) retrying deliveries are
// skipped.
type rescheduler interface {
	// remainingBackoff returns how long to wait before the
	// next attempt of a recovered retrying delivery.
	remainingBackoff(
		webhookDB *gorm.DB,
		deliveryID string,
		attemptNum int,
	) time.Duration

	// backoffElapsed reports whether the backoff window for
	// the last attempt has already passed, so the periodic
	// sweep can re-enqueue the delivery now.
	backoffElapsed(
		webhookDB *gorm.DB,
		deliveryID string,
		attemptNum int,
	) bool
}

// attemptResult is the outcome of a single delivery attempt,
// as reported by a target's per-attempt function to the
// shared retry core.
type attemptResult struct {
	statusCode int
	respBody   string
	duration   int64
	success    bool
	errMsg     string
}

// initTargets builds the target registry, wiring each target
// to the engine's persistence helpers and giving the HTTP and
// Slack targets the shared SSRF-safe client. It is called by
// both New and the test constructors so the registry is
// always populated.
func (e *Engine) initTargets(client *http.Client) {
	httpT := &httpTarget{
		httpCore: &httpCore{eng: e},
		client:   client,
	}

	slackT := &slackTarget{
		httpCore: &httpCore{eng: e},
		client:   client,
	}

	e.httpTarget = httpT

	e.targets = map[database.TargetType]Target{
		database.TargetTypeHTTP:     httpT,
		database.TargetTypeSlack:    slackT,
		database.TargetTypeDatabase: &databaseTarget{eng: e},
		database.TargetTypeLog:      &logTarget{eng: e},
	}
}