Fix resume tail corruption after terminated streams

2026-03-28 02:30:30 +01:00
parent 30737f9320
commit a1d72b6dbc
2 changed files with 202 additions and 38 deletions
@@ -119,11 +119,13 @@ const ARCHIVE_SETTLE_MIN_DELAY_MS = 1500;

 const ARCHIVE_SETTLE_POLL_MS = 250;

-const ARCHIVE_SETTLE_MAX_WAIT_MS = 5000;
-
-const MAX_SAME_DIRECT_URL_ATTEMPTS = 3;
-
-const REALDEBRID_TOTAL_MISMATCH_TOLERANCE_BYTES = 64 * 1024;
+const ARCHIVE_SETTLE_MAX_WAIT_MS = 5000;
+
+const MAX_SAME_DIRECT_URL_ATTEMPTS = 3;
+
+const RESUME_REWIND_BYTES = 256 * 1024;
+
+const REALDEBRID_TOTAL_MISMATCH_TOLERANCE_BYTES = 64 * 1024;

 const LARGE_BINARY_FILE_RE = /\.(?:part\d+\.rar|rar|r\d{2,3}|zip(?:\.\d+)?|7z(?:\.\d+)?|tar|gz|bz2|xz|iso|mkv|mp4|avi|mov|wmv|m4v|ts|m2ts|webm|mp3|flac|aac|wav)$/i;

@@ -422,14 +424,29 @@ function shouldRejectSuspiciousSmallDownload(
  return binaryLike;
 }

-function isFetchFailure(errorText: string): boolean {
-  const text = String(errorText || "").toLowerCase();
-  return text.includes("fetch failed") || text.includes("socket hang up") || text.includes("econnreset") || text.includes("network error");
-}
-
-function isHttp416Text(errorText: string): boolean {
-  return /(^|\D)416(\D|$)/.test(String(errorText || ""));
-}
+function isFetchFailure(errorText: string): boolean {
+  const text = String(errorText || "").toLowerCase();
+  return text.includes("fetch failed") || text.includes("socket hang up") || text.includes("econnreset") || text.includes("network error");
+}
+
+function shouldRewindResumeTail(errorText: string): boolean {
+  const text = String(errorText || "").toLowerCase();
+  if (!text) {
+    return false;
+  }
+  return text.includes("terminated")
+    || text.includes("stall_timeout")
+    || text.includes("slow_throughput")
+    || text.includes("write_drain_timeout")
+    || text.includes("premature close")
+    || text.includes("unexpected eof")
+    || text.includes("download_underflow")
+    || isFetchFailure(text);
+}
+
+function isHttp416Text(errorText: string): boolean {
+  return /(^|\D)416(\D|$)/.test(String(errorText || ""));
+}

 function shouldPreflightFinalizeItemFromDisk(item: DownloadItem): boolean {
  const text = `${item.fullStatus || ""} ${item.lastError || ""}`.toLowerCase();
@@ -8385,22 +8402,50 @@ export class DownloadManager extends EventEmitter {
    const retryDisplayLimit = retryLimitLabel(configuredRetryLimit);
    const maxAttemptsBySetting = configuredRetryLimit <= 0 ? Number.MAX_SAFE_INTEGER : configuredRetryLimit + 1;
    const maxAttempts = Math.max(1, Math.min(MAX_SAME_DIRECT_URL_ATTEMPTS, maxAttemptsBySetting));
-
-    let lastError = "";
-    let effectiveTargetPath = targetPath;
-    for (let attempt = 1; attempt <= maxAttempts; attempt += 1) {
-      let existingBytes = 0;
-      try {
-        const stat = await fs.promises.stat(effectiveTargetPath);
-        existingBytes = stat.size;
-      } catch {
-        // file does not exist
-      }
-      // Guard against pre-allocated sparse files from a crashed session:
-      // if file size exceeds persisted downloadedBytes by >1MB, the file was
-      // likely pre-allocated but only partially written before a hard crash.
-      if (existingBytes > 0 && item.downloadedBytes > 0 && existingBytes > item.downloadedBytes + 1048576) {
-        try {
+
+    let lastError = "";
+    let effectiveTargetPath = targetPath;
+    let resumeRewindBytesNextAttempt = 0;
+    for (let attempt = 1; attempt <= maxAttempts; attempt += 1) {
+      let existingBytes = 0;
+      try {
+        const stat = await fs.promises.stat(effectiveTargetPath);
+        existingBytes = stat.size;
+      } catch {
+        // file does not exist
+      }
+      if (existingBytes > 0 && resumeRewindBytesNextAttempt > 0) {
+        const previousBytes = existingBytes;
+        const rewindBytes = Math.min(existingBytes, resumeRewindBytesNextAttempt);
+        const resumeStart = Math.max(0, existingBytes - rewindBytes);
+        try {
+          await fs.promises.truncate(effectiveTargetPath, resumeStart);
+          existingBytes = resumeStart;
+          item.downloadedBytes = Math.min(item.downloadedBytes, existingBytes);
+          logAttemptEvent("WARN", "Resume-Schutz aktiv: Teil-Datei vor Retry zurueckgespult", {
+            attempt,
+            previousBytes,
+            rewindBytes,
+            resumeStart
+          });
+        } catch (rewindError) {
+          logAttemptEvent("WARN", "Resume-Schutz: Rueckspulen der Teil-Datei fehlgeschlagen", {
+            attempt,
+            previousBytes,
+            rewindBytes,
+            error: compactErrorText(rewindError)
+          });
+        } finally {
+          resumeRewindBytesNextAttempt = 0;
+        }
+      } else if (resumeRewindBytesNextAttempt > 0) {
+        resumeRewindBytesNextAttempt = 0;
+      }
+      // Guard against pre-allocated sparse files from a crashed session:
+      // if file size exceeds persisted downloadedBytes by >1MB, the file was
+      // likely pre-allocated but only partially written before a hard crash.
+      if (existingBytes > 0 && item.downloadedBytes > 0 && existingBytes > item.downloadedBytes + 1048576) {
+        try {
          await fs.promises.truncate(effectiveTargetPath, item.downloadedBytes);
          existingBytes = item.downloadedBytes;
        } catch { /* best-effort */ }
@@ -9285,13 +9330,24 @@ export class DownloadManager extends EventEmitter {
          error: lastError,
          targetPath: effectiveTargetPath
        });
-        if (normalizedLastError.startsWith("range_ignored_on_resume:")) {
-          throw new Error(`direct_link_retry_exhausted:${normalizedLastError}`);
-        }
-        if (attempt < maxAttempts) {
-          item.retries += 1;
-          item.fullStatus = `Downloadfehler, retry ${attempt}/${maxAttempts} (Direktlink)`;
-          this.emitState();
+        if (normalizedLastError.startsWith("range_ignored_on_resume:")) {
+          throw new Error(`direct_link_retry_exhausted:${normalizedLastError}`);
+        }
+        if (attempt < maxAttempts && written > existingBytes && shouldRewindResumeTail(normalizedLastError)) {
+          resumeRewindBytesNextAttempt = Math.max(resumeRewindBytesNextAttempt, RESUME_REWIND_BYTES);
+          logAttemptEvent("WARN", "Resume-Schutz vorgemerkt: naechster Retry startet mit Rewind", {
+            attempt,
+            existingBytes,
+            written,
+            appendedBytes: Math.max(0, written - existingBytes),
+            rewindBytes: resumeRewindBytesNextAttempt,
+            error: normalizedLastError
+          });
+        }
+        if (attempt < maxAttempts) {
+          item.retries += 1;
+          item.fullStatus = `Downloadfehler, retry ${attempt}/${maxAttempts} (Direktlink)`;
+          this.emitState();
          await sleep(retryDelayWithJitter(attempt, 250));
          continue;
        }