fix: 503 при сбое GetScan вместо ложного 404 scan not found

- Store.GetScan возвращает (job, ok, error); Postgres отдаёт err при ошибке БД/JSON

- API: getScanOrWriteError → 503 scan storage temporarily unavailable

- Web UI: понятное сообщение для HTTP 503 при опросе скана

Made-with: Cursor

internal/api/handler.go

@@ -14,6 +14,9 @@ import (
 	"nettopo-go/internal/webui"
 )
 
+// errScanStorageUnavailable — ответ API при сбое GetScan (БД, а не «нет такого scan_id»).
+const errScanStorageUnavailable = "scan storage temporarily unavailable"
+
 type Handler struct {
 	store         scans.Store
 	run           *scans.Runner
@@ -83,6 +86,26 @@ func scanPathID(r *http.Request) string {
 	return strings.TrimSpace(raw)
 }
 
+// getScanOrWriteError загружает скан; при ошибке хранилища пишет 503, при отсутствии строки — 404 с notFoundMsg (или «scan not found»).
+func (h *Handler) getScanOrWriteError(w http.ResponseWriter, id, notFoundMsg string) (scans.ScanJob, bool) {
+	job, found, err := h.store.GetScan(id)
+	if err != nil {
+		log.Printf("GetScan id=%q (len=%d): %v", id, len(id), err)
+		writeError(w, http.StatusServiceUnavailable, errScanStorageUnavailable)
+		return scans.ScanJob{}, false
+	}
+	if !found {
+		msg := notFoundMsg
+		if msg == "" {
+			msg = "scan not found"
+		}
+		log.Printf("getScan: not found id=%q (len=%d) msg=%q", id, len(id), msg)
+		writeError(w, http.StatusNotFound, msg)
+		return scans.ScanJob{}, false
+	}
+	return job, true
+}
+
 func (h *Handler) Routes() http.Handler {
 	mux := http.NewServeMux()
 	webFS := http.FileServer(http.FS(webui.FS))
@@ -189,12 +212,10 @@ func (h *Handler) getScansDiff(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "both from and to are required")
 		return
 	}
-	if _, ok := h.store.GetScan(fromID); !ok {
+	if _, ok := h.getScanOrWriteError(w, fromID, "from scan not found"); !ok {
-		writeError(w, http.StatusNotFound, "from scan not found")
 		return
 	}
-	if _, ok := h.store.GetScan(toID); !ok {
+	if _, ok := h.getScanOrWriteError(w, toID, "to scan not found"); !ok {
-		writeError(w, http.StatusNotFound, "to scan not found")
 		return
 	}
 
@@ -221,10 +242,8 @@ func (h *Handler) getScan(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	job, ok := h.store.GetScan(id)
+	job, ok := h.getScanOrWriteError(w, id, "")
 	if !ok {
-		log.Printf("getScan: not found id=%q (len=%d)", id, len(id))
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 
@@ -241,9 +260,8 @@ func (h *Handler) postCancelScan(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	cur, ok := h.getScanOrWriteError(w, id, "")
-		log.Printf("postCancelScan: not found id=%q (len=%d)", id, len(id))
+	if !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 	runnerSignaled := false
@@ -254,7 +272,6 @@ func (h *Handler) postCancelScan(w http.ResponseWriter, r *http.Request) {
 		writeJSON(w, http.StatusOK, map[string]any{"ok": true, "runner_canceled": true})
 		return
 	}
-	cur, _ := h.store.GetScan(id)
 	if cur.Status == "queued" {
 		fin := time.Now().UTC()
 		_, _ = h.store.UpdateScan(id, scans.ScanUpdate{Status: "canceled", FinishedAt: &fin})
@@ -270,8 +287,7 @@ func (h *Handler) getScanHosts(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 
@@ -296,8 +312,7 @@ func (h *Handler) getScanPorts(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 
@@ -322,8 +337,7 @@ func (h *Handler) getScanSNMP(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 
@@ -348,8 +362,7 @@ func (h *Handler) getScanLLDP(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 
@@ -374,8 +387,7 @@ func (h *Handler) getScanInterfaces(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 	ip := strings.TrimSpace(r.URL.Query().Get("ip"))
@@ -403,8 +415,7 @@ func (h *Handler) getScanPortDevices(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 	ip := strings.TrimSpace(r.URL.Query().Get("ip"))
@@ -463,8 +474,7 @@ func (h *Handler) getScanMacLocations(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 	raw := strings.TrimSpace(r.URL.Query().Get("mac"))
@@ -612,8 +622,7 @@ func (h *Handler) getScanLinks(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 
@@ -675,8 +684,7 @@ func (h *Handler) getScanTopology(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "scan id is required")
 		return
 	}
-	if _, ok := h.store.GetScan(id); !ok {
+	if _, ok := h.getScanOrWriteError(w, id, ""); !ok {
-		writeError(w, http.StatusNotFound, "scan not found")
 		return
 	}
 

internal/scans/postgres_store.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"log"
 	"sort"
 	"strings"
@@ -98,7 +99,7 @@ insert into scan_jobs (
 	return job, nil
 }
 
-func (s *PostgresStore) GetScan(id string) (ScanJob, bool) {
+func (s *PostgresStore) GetScan(id string) (ScanJob, bool, error) {
 	query := `
 select id, name, status, cidrs::text, exclude_ips::text, options::text,
        progress, stats::text, coalesce(snmp_credentials_id::text, ''),
@@ -130,28 +131,28 @@ limit 1`
 		&finishedAt,
 	)
 	if errors.Is(err, sql.ErrNoRows) {
-		return ScanJob{}, false
+		return ScanJob{}, false, nil
 	}
 	if err != nil {
 		log.Printf("postgres GetScan id=%q: row scan: %v", id, err)
-		return ScanJob{}, false
+		return ScanJob{}, false, fmt.Errorf("postgres GetScan id=%q: %w", id, err)
 	}
 
 	if err = json.Unmarshal([]byte(cidrsRaw), &job.CIDRs); err != nil {
 		log.Printf("postgres GetScan id=%q: cidrs json (len=%d): %v", id, len(cidrsRaw), err)
-		return ScanJob{}, false
+		return ScanJob{}, false, fmt.Errorf("postgres GetScan id=%q cidrs: %w", id, err)
 	}
 	if err = json.Unmarshal([]byte(excludeRaw), &job.ExcludeIPs); err != nil {
 		log.Printf("postgres GetScan id=%q: exclude_ips json: %v", id, err)
-		return ScanJob{}, false
+		return ScanJob{}, false, fmt.Errorf("postgres GetScan id=%q exclude_ips: %w", id, err)
 	}
 	if err = json.Unmarshal([]byte(optionsRaw), &job.Options); err != nil {
 		log.Printf("postgres GetScan id=%q: options json: %v", id, err)
-		return ScanJob{}, false
+		return ScanJob{}, false, fmt.Errorf("postgres GetScan id=%q options: %w", id, err)
 	}
 	if err = json.Unmarshal([]byte(statsRaw), &job.Stats); err != nil {
 		log.Printf("postgres GetScan id=%q: stats json: %v", id, err)
-		return ScanJob{}, false
+		return ScanJob{}, false, fmt.Errorf("postgres GetScan id=%q stats: %w", id, err)
 	}
 	if startedAt.Valid {
 		job.StartedAt = startedAt.Time
@@ -160,7 +161,7 @@ limit 1`
 		job.FinishedAt = finishedAt.Time
 	}
 
-	return job, true
+	return job, true, nil
 }
 
 func (s *PostgresStore) ListScans(limit int) []ScanJob {
@@ -230,7 +231,11 @@ limit $1`
 }
 
 func (s *PostgresStore) UpdateScan(id string, update ScanUpdate) (ScanJob, bool) {
-	current, ok := s.GetScan(id)
+	current, ok, err := s.GetScan(id)
+	if err != nil {
+		log.Printf("postgres UpdateScan: GetScan id=%q: %v", id, err)
+		return ScanJob{}, false
+	}
 	if !ok {
 		return ScanJob{}, false
 	}

internal/scans/runner.go

@@ -88,7 +88,11 @@ func (r *Runner) CancelScan(id string) bool {
 }
 
 func (r *Runner) markJobCanceledFromStore(jobID string) {
-	cur, ok := r.store.GetScan(jobID)
+	cur, ok, err := r.store.GetScan(jobID)
+	if err != nil {
+		log.Printf("runner markJobCanceledFromStore GetScan %q: %v", jobID, err)
+		return
+	}
 	if !ok {
 		return
 	}
@@ -106,7 +110,10 @@ func (r *Runner) markJobCanceledFromStore(jobID string) {
 }
 
 func (r *Runner) run(ctx context.Context, job ScanJob) {
-	if cur, ok := r.store.GetScan(job.ID); ok && cur.Status == "canceled" {
+	if cur, ok, err := r.store.GetScan(job.ID); err != nil {
+		log.Printf("runner run GetScan %q: %v", job.ID, err)
+		return
+	} else if ok && cur.Status == "canceled" {
 		return
 	}
 	if err := ctx.Err(); err != nil && errors.Is(err, context.Canceled) {

internal/scans/store.go

@@ -61,7 +61,8 @@ type ScanUpdate struct {
 
 type Store interface {
 	CreateScan(CreateScanRequest) (ScanJob, error)
-	GetScan(id string) (ScanJob, bool)
+	// GetScan: при found==false и err==nil записи нет; err!=nil — сбой хранилища (например БД).
+	GetScan(id string) (ScanJob, bool, error)
 	ListScans(limit int) []ScanJob
 	UpdateScan(id string, update ScanUpdate) (ScanJob, bool)
 	SaveHostResult(scanID string, host HostResult) error
@@ -195,11 +196,11 @@ func (s *MemoryStore) CreateScan(req CreateScanRequest) (ScanJob, error) {
 	return job, nil
 }
 
-func (s *MemoryStore) GetScan(id string) (ScanJob, bool) {
+func (s *MemoryStore) GetScan(id string) (ScanJob, bool, error) {
 	s.mu.RLock()
 	job, ok := s.jobs[id]
 	s.mu.RUnlock()
-	return job, ok
+	return job, ok, nil
 }
 
 func (s *MemoryStore) ListScans(limit int) []ScanJob {

internal/webui/index.html

@@ -233,8 +233,16 @@
 
       async function fetchScanJob(id) {
         const res = await fetch(`/api/scans/${encodeURIComponent(id)}`);
-        if (!res.ok) throw new Error(`HTTP ${res.status}: ${await res.text()}`);
+        const body = await res.text();
-        return res.json();
+        if (!res.ok) {
+          if (res.status === 503) {
+            throw new Error(
+              `Временно недоступно хранилище сканов (HTTP ${res.status}). Повторите через несколько секунд. ${body}`
+            );
+          }
+          throw new Error(`HTTP ${res.status}: ${body}`);
+        }
+        return JSON.parse(body);
       }
 
       /** Просит сервер остановить скан (отмена воркера + статус canceled в БД). */