Avoid redundant full scan after warm restart

docs/architecture.md

@@ -57,7 +57,8 @@ server. The daemon publishes complete folders atomically and increments a durabl
 revision; the reader polls that revision and refreshes changed manga after publication.
 The reader restores a disposable full-index snapshot at startup so browsing need not
 wait for a filesystem walk. Shallow directory stamps identify changed manga; a
-background and daily full reconciliation catches in-place manual edits.
+daily full reconciliation catches in-place manual edits. The last full-scan time
+survives restarts, so restarting does not itself force another complete walk.
 
 | Path | Lines | Responsibility |
 |------|------:|----------------|

docs/import.md

@@ -33,6 +33,11 @@ MangaCircus does not copy or convert anything. "Import" means **indexing the lib
 | **Rescan** (Settings → Admin, or `POST /api/admin/rescan {}`) | On demand; the request returns when the scan is done | used |
 | **Full rescan** (`POST /api/admin/rescan {"full":true}`) | On demand | ignored: every image header is read again |
 
+The saved index records when its last full reconciliation finished. A warm restart
+does a shallow check but does not reset the daily full-scan clock; if that scan is
+overdue, the reader schedules it within a minute. Set `FULL_SCAN_INTERVAL=0` to
+disable automatic full reconciliations, while retaining admin Rescan.
+
 Scans are **single-flight**. A trigger during a scan queues one coalesced follow-up,
 with a full reconciliation taking precedence over a shallow check. Publication
 revisions trigger a shallow check; if no changed directory is visible, the reader

server.js

@@ -86,6 +86,7 @@ for (const [k, s] of Object.entries(db.sessions)) if (Date.now() - s.t > 365 * 8
 
 // ---------- library index ----------
 let lib = { mangas: [], byId: new Map() }, scanning = null, pendingScan = null, scanState = {}, scanCache = {}, scanStamps = {};
+let lastFullAt = 0, lastFullAttemptAt = 0;
 try { scanCache = JSON.parse(fs.readFileSync(CACHE_FILE, 'utf8')); } catch { /* first run */ }
 try {
   const saved = JSON.parse(fs.readFileSync(INDEX_FILE, 'utf8'));
@@ -95,6 +96,7 @@ try {
   const present = new Set(fs.readdirSync(LIB, { withFileTypes: true }).filter(e => e.isDirectory()).map(e => e.name));
   if (restored.mangas.length && !restored.mangas.some(m => present.has(m.id))) throw new Error('Library mount differs from snapshot');
   lib = restored; scanCache = saved.cache; scanStamps = saved.stamps;
+  lastFullAt = Number(saved.fullAt) || Number(saved.at) || 0;
   scanState = { at: saved.at, mode: 'snapshot', stale: true, mangas: lib.mangas.length, error: null };
   console.log(`[scan] restored ${lib.mangas.length} manga from saved index; verifying in background`);
 } catch (e) { if (e.code !== 'ENOENT') console.warn(`[scan] ignoring saved index: ${e.message}`); }
@@ -112,8 +114,10 @@ async function performScan(mode) {
       if (mode !== 'changed' || changed.length) {
         announce(index);
         lib = index; scanCache = cache; scanStamps = stamps;
+        if (mode !== 'changed') lastFullAt = Date.now();
         writeAtomic(CACHE_FILE, JSON.stringify(cache));
-        writeAtomic(INDEX_FILE, JSON.stringify({ version: 1, root: LIB, at: Date.now(), mangas: snapshotIndex(index), cache, stamps }));
+        writeAtomic(INDEX_FILE, JSON.stringify({ version: 1, root: LIB, at: Date.now(), fullAt: lastFullAt,
+          mangas: snapshotIndex(index), cache, stamps }));
       }
       let chapters = 0, pages = 0;
       for (const m of lib.mangas) for (const ch of m.chapters) { chapters++; for (const v of ch.versions) pages += v.pages.length; }
@@ -633,13 +637,18 @@ http.createServer(async (req, res) => {
   }
 }).listen(PORT, () => console.log(`MangaCircus on http://localhost:${PORT}  (library: ${LIB}, data: ${DATA})`));
 
-if (lib.mangas.length) {
-  refreshChanged();
-  // Catch in-place manual edits that cannot change a parent directory stamp.
-  setTimeout(() => rescan(), 60000).unref();
-} else rescan();
+if (lib.mangas.length) refreshChanged();
+else rescan();
 if (SCAN_MINUTES > 0) setInterval(() => refreshChanged(), SCAN_MINUTES * 60000).unref();
-if (FULL_SCAN_MINUTES > 0) setInterval(() => rescan(), FULL_SCAN_MINUTES * 60000).unref();
+// Persist the last reconciliation time. Restarting a healthy reader should not
+// trigger another full tree walk; overdue reconciliations run within a minute.
+if (FULL_SCAN_MINUTES > 0) setInterval(() => {
+  const now = Date.now();
+  if (now - Math.max(lastFullAt, lastFullAttemptAt) >= FULL_SCAN_MINUTES * 60000) {
+    lastFullAttemptAt = now;
+    rescan();
+  }
+}, 60000).unref();
 
 // A completed scraper publish increments a durable revision. Polling it here keeps the
 // reader index fresh without exposing an unauthenticated rescan endpoint to the daemon.