Well. I just renamed timestamp field from JSON and have got next error:
ERROR [Messages] Failed to index [3] messages. Please check the index error log in your web interface for the reason. Error: One or more of the items in the Bulk request failed, check BulkResult.getItems() for more information.
{"type":"mapper_parsing_exception","reason":"failed to parse [level]","caused_by":{"type":"number_format_exception","reason":"For input string: \"INFO\""}}