Users reported that they couldn’t find a few specific documents when searching within SharePoint 2013.  Checking the crawl log showed documents with the error “The item failed due to an error occurring when sending or receiving data to the external content processing enrichment web service.”  I searched the ULS for one of the effected documents and found the error “System.Net.WebException: The remote server returned an error: (413) Request Entity Too Large.”  Checking the web.config for the content enrichment web service showed the maxReceivedMessageSize value was configured to 8 MB.

To resolve the error I increased the value of the maxReceivedMessageSize property and re-indexed the document library.

The interesting thing about this case is that the content enrichment web service is designed to add additional metadata to documents.  When the content enrichment web service failed to receive documents over 8 MB the documents didn’t appear within search at all, it wasn’t just the case that they appeared but without the extra metadata.