public void writeReindexing(Reindexing reindexing, String cluster) {
        log.log(Level.FINE, () -> "Writing reindexing status '" + reindexing + "' to '" + statusPath(cluster) + "'");
        curator.set(statusPath(cluster), serializer.serialize(reindexing));
    }
If no reindexing data exists (has been wiped), assume current ready documents are already done.
clustercontroller-reindexer/src/main/java/ai/vespa/reindexing/ReindexingCurator.java