feat(jobs): worker pool with retry/dead-letter/panic-recovery

internal/jobs/worker.go

@@ -0,0 +1,148 @@
+package jobs
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"sync"
+	"time"
+
+	"github.com/yan1h/agent-coding-workflow/internal/infra/clock"
+)
+
+// WorkerOptions configures a single Worker. ID identifies the worker in
+// jobs.leased_by. Backoff is the per-attempt retry delay sequence; if attempts
+// exceeds len(Backoff), the last entry is used.
+type WorkerOptions struct {
+	ID           string
+	PollInterval time.Duration
+	Backoff      []time.Duration
+	Clock        clock.Clock
+	Log          *slog.Logger
+}
+
+// Worker pulls leased jobs from the repository, dispatches them to handlers,
+// and writes back the appropriate completion / retry / dead-letter state.
+type Worker struct {
+	repo     Repository
+	handlers map[JobType]Handler
+	opts     WorkerOptions
+	wg       sync.WaitGroup
+}
+
+// NewWorker builds a Worker. The caller registers handlers by JobType.
+func NewWorker(repo Repository, handlers map[JobType]Handler, opts WorkerOptions) *Worker {
+	if opts.PollInterval <= 0 {
+		opts.PollInterval = 100 * time.Millisecond
+	}
+	if opts.Clock == nil {
+		opts.Clock = clock.Real()
+	}
+	if opts.Log == nil {
+		opts.Log = slog.Default()
+	}
+	if len(opts.Backoff) == 0 {
+		opts.Backoff = []time.Duration{30 * time.Second}
+	}
+	return &Worker{repo: repo, handlers: handlers, opts: opts}
+}
+
+// Run loops until ctx is canceled, polling for and processing jobs.
+func (w *Worker) Run(ctx context.Context) {
+	w.wg.Add(1)
+	defer w.wg.Done()
+	t := time.NewTicker(w.opts.PollInterval)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-t.C:
+			w.pollOnce(ctx)
+		}
+	}
+}
+
+// Wait blocks until the goroutine started by Run returns.
+func (w *Worker) Wait() { w.wg.Wait() }
+
+func (w *Worker) pollOnce(ctx context.Context) {
+	job, err := w.repo.Lease(ctx, w.opts.ID)
+	if err != nil {
+		w.opts.Log.Error("job.lease_failed", "err", err.Error())
+		return
+	}
+	if job == nil {
+		return
+	}
+	w.execute(ctx, *job)
+}
+
+func (w *Worker) execute(ctx context.Context, job Job) {
+	w.opts.Log.Info("job.start", "id", job.ID, "type", job.Type, "attempt", job.Attempts)
+	start := w.opts.Clock.Now()
+
+	h, ok := w.handlers[job.Type]
+	if !ok {
+		_ = w.repo.DeadLetter(ctx, job.ID, fmt.Sprintf("unknown job type: %s", job.Type))
+		w.opts.Log.Error("job.dead_letter", "id", job.ID, "type", job.Type, "reason", "unknown_type")
+		return
+	}
+
+	err := w.runHandler(ctx, h, job)
+	if err == nil {
+		_ = w.repo.Complete(ctx, job.ID)
+		w.opts.Log.Info("job.complete",
+			"id", job.ID, "type", job.Type, "attempt", job.Attempts,
+			"duration_ms", w.opts.Clock.Now().Sub(start).Milliseconds())
+		return
+	}
+
+	// Permanent or attempts exhausted -> dead-letter
+	if IsPermanent(err) || job.Attempts >= job.MaxAttempts {
+		msg := truncate(err.Error(), 2000)
+		_ = w.repo.DeadLetter(ctx, job.ID, msg)
+		w.opts.Log.Error("job.dead_letter",
+			"id", job.ID, "type", job.Type, "attempts", job.Attempts, "err", msg)
+		return
+	}
+
+	// Retryable
+	delay := backoffFor(w.opts.Backoff, int(job.Attempts))
+	next := w.opts.Clock.Now().Add(delay)
+	msg := truncate(err.Error(), 2000)
+	_ = w.repo.FailWithRetry(ctx, job.ID, next, msg)
+	w.opts.Log.Warn("job.fail_retry",
+		"id", job.ID, "type", job.Type, "attempt", job.Attempts,
+		"err", msg, "next_at", next.Format(time.RFC3339))
+}
+
+// runHandler wraps Handle with panic recovery, converting panics into retryable errors.
+func (w *Worker) runHandler(ctx context.Context, h Handler, job Job) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("handler panic: %v", r)
+		}
+	}()
+	return h.Handle(ctx, job)
+}
+
+// backoffFor returns the backoff for attempt index (1-based "after first try").
+// If index exceeds the slice, the last element is used.
+func backoffFor(seq []time.Duration, attempt int) time.Duration {
+	if attempt <= 0 {
+		return seq[0]
+	}
+	idx := attempt - 1
+	if idx >= len(seq) {
+		idx = len(seq) - 1
+	}
+	return seq[idx]
+}
+
+func truncate(s string, n int) string {
+	if len(s) <= n {
+		return s
+	}
+	return s[:n]
+}