nextcloud/server · error · Exception

Error importing calendar data: UID <$uid> - $errorMessage

Error message

Error importing calendar data: UID <$uid> - $errorMessage

What it means

Wraps any exception raised by the CalDavBackend while creating or updating the calendar object for a UID (createCalendarObject / updateCalendarObject) during import. ImportService catches it, and when the error mode is ERROR_FAIL rethrows it prefixed with 'Error importing calendar data: UID <uid> -' keeping the original exception as previous. In non-failing mode the message is yielded in an Error ImportObjectEvent instead.

Solutions

  1. Inspect the chained exception via getPrevious() (and your Nextcloud log) to find the real backend error before acting
  2. For duplicate/URI races, re-run the import; the getCalendarObjectByUID() lookup makes re-imports idempotent per UID
  3. Split very large imports into smaller batches and check DB health (max_allowed_packet, locks, disk space)

Example fix

// before
try {
    foreach ($service->import($source, $calendar, $options) as $event) {}
} catch (\Exception $e) {
    die($e->getMessage()); // only sees the wrapper
}

// after
try {
    foreach ($service->import($source, $calendar, $options) as $event) {}
} catch (\Exception $e) {
    $root = $e->getPrevious() ?? $e;
    $this->logger->error('Import failed for UID: ' . $root->getMessage());
}
Defensive patterns

Strategy: try-catch

Validate before calling

// nothing caller-side prevents a backend fault; check calendar writability beforehand:
if ($calendar->isReadOnly()) {
    throw new RuntimeException('calendar is read-only');
}

Try / catch

try {
    foreach ($service->import($source, $calendar, $options) as $event) {}
} catch (\Exception $e) {
    $root = $e->getPrevious() ?? $e; // real backend error
    $this->logger->error('calendar import failed', ['exception' => $root]);
    // transient DB/lock issues: safe to retry; the per-UID upsert makes it idempotent
}

Prevention

When it happens

Trigger: A backend/DB failure during import: database unreachable or lock timeout, constraint violation on the object URI, serialized data rejected by storage, or another low-level CalDavBackend error while options->getErrors() === CalendarImportOptions::ERROR_FAIL.

Common situations: Importing large files that exhaust DB connection limits or transaction time; concurrent writes to the same calendar (duplicate URI race); MariaDB/MySQL row-size limits on large calendar objects; storage quota errors.

Related errors

AI-assisted analysis of nextcloud/server@ecdeb153ff (2026-08-17). Data as JSON: /api/errors/d556b2105746dd3a. Report an issue: GitHub.

Appendix: source

Thrown at apps/dav/lib/CalDAV/Import/ImportService.php:374

							$calendarId,
							$oid,
							$objectData
						);
						yield new ImportObjectEvent(
							disposition: ImportDisposition::Updated,
							identifier: $uid,
						);
					} else {
						yield new ImportObjectEvent(
							disposition: ImportDisposition::Exists,
							identifier: $uid,
						);
					}
				}
			} catch (Exception $e) {
				$errorMessage = $e->getMessage();
				if ($options->getErrors() === $options::ERROR_FAIL) {
					throw new Exception('Error importing calendar data: UID <' . $uid . '> - ' . $errorMessage, 0, $e);
				}
				yield new ImportObjectEvent(
					disposition: ImportDisposition::Error,
					identifier: $uid,
					errors: [$errorMessage]
				);
			}
		}
	}

	/**
	 * Validate a component
	 *
	 * @param VCalendar $vObject
	 * @param bool $repair attempt to repair the component
	 * @param int $level minimum level of issues to return
	 * @return list<mixed>
	 */

View on GitHub (pinned to ecdeb153ff)