kopia/kopia · error

error copying results

Error message

error copying results

What it means

getContentFromFullBlob serves a cached full blob: when offset==0 and length==-1 (read everything), it WriteTo's the blob bytes into output. A write failure is wrapped as 'error copying results'. This indicates the output writer failed while consuming cached data.

Solutions

1. Inspect the wrapped error for the failing writer cause
2. Ensure the output buffer/writer passed to GetContent is valid, open, and large enough
3. Retry GetContent; if reproducible with a specific blob, verify the cached blob is not corrupt
4. Avoid reusing a closed WriteBuffer across calls

Example fix

// before
out, err := newOutput(); if err != nil { return err }
_, err = cache.GetContent(ctx, out, contentID, 0, -1)
// after
out, err := newOutput(); if err != nil { return err }
defer func() { if cerr := out.Close(); err == nil { err = cerr } }()
_, err = cache.GetContent(ctx, out, contentID, 0, -1)

if output == nil { return errors.New("output buffer must be non-nil") }

n, err := cache.GetContent(ctx, output, contentID, 0, -1)
if err != nil && strings.Contains(err.Error(), "error copying results") {
    return errors.Wrap(err, "output writer failed while reading cached content")
}

When it happens

Trigger: Calling GetContent with offset 0 and length -1 where the output gather.WriteBuffer/writer errors during WriteTo — e.g. output sink closed, allocation failure, or underlying writer I/O error.

Common situations: Downstream consumer closing output early; out-of-memory for very large blobs; custom writer implementations returning errors mid-copy.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• error closing cache marker file
• error copying data
• failed to get blob with ID
• getContent
• invalid (offset= ,length= ) for blob of size

AI-assisted analysis of kopia/kopia@82495e54b5 (2026-09-07). Data as JSON: /api/errors/fe8025d3121e973c. Report an issue: GitHub.

Appendix: source

Thrown at internal/cache/content_cache.go:83

	c.pc.exclusiveLock(string(blobID))
	defer c.pc.exclusiveUnlock(string(blobID))

	// check again to see if we perhaps lost the race and the data is now in cache.
	if c.pc.getPartial(ctx, BlobIDCacheKey(blobID), offset, length, output) {
		return nil
	}

	var blobData gather.WriteBuffer
	defer blobData.Close()

	if err := c.fetchBlobInternal(ctx, blobID, &blobData); err != nil {
		return err
	}

	if offset == 0 && length == -1 {
		_, err := blobData.Bytes().WriteTo(output)

		return errors.Wrap(err, "error copying results")
	}

	if offset < 0 || offset+length > int64(blobData.Length()) {
		return errors.Errorf("invalid (offset=%v,length=%v) for blob %q of size %v", offset, length, blobID, blobData.Length())
	}

	output.Reset()

	impossible.PanicOnError(blobData.AppendSectionTo(output, int(offset), int(length)))

	return nil
}

func (c *contentCacheImpl) fetchBlobInternal(ctx context.Context, blobID blob.ID, blobData *gather.WriteBuffer) error {
	// read the entire blob
	if err := c.st.GetBlob(ctx, blobID, 0, -1, blobData); err != nil {
		c.pc.reportMissError()

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