This does not appear to be an error, but a diagnostic message logged to a component channel (CirussSearch). These tend to be for when you're debugging an error to see what else happened during that request. If these show up in a triaging dashboard, you may want to adjust the default view so as to only show channels error and exception + any diagnostic channels relating to code your team maintains.

I'm boldly closing this for now, but please do feel free to re-open this if it was specifically was meant to be investigated. While warnings like this are normal (and useful to keep in the logs), it's possible that perhaps it is happening far more frequently than expected, or perhaps it is part of a larger sprint of investigation.