Add structured logging and better error handling

internal/jobs/safety.go

@@ -0,0 +1,42 @@
+package jobs
+
+import (
+	"log/slog"
+	"runtime/debug"
+)
+
+const shortIDLength = 8
+
+func (job *Job) logger() *slog.Logger {
+	return slog.With("download", job.id[:min(len(job.id), shortIDLength)])
+}
+
+func (job *Job) isDownloaded() bool {
+	job.mutex.Lock()
+	defer job.mutex.Unlock()
+	return job.downloaded
+}
+
+func (manager *Manager) runInBackground(job *Job, task string, work func()) {
+	go func() {
+		defer job.workers.Done()
+		defer func() {
+			recovered := recover()
+			if recovered == nil {
+				return
+			}
+			job.logger().Error("background task crashed",
+				"task", task,
+				"panic", recovered,
+				"stack", string(debug.Stack()),
+			)
+			status := StatusFailed
+			if job.isDownloaded() {
+				status = StatusReady
+			}
+			job.setStatus(status, "Internal error during "+task+". The server log has the details.")
+			job.saveRecord()
+		}()
+		work()
+	}()
+}