anchor.diff:  
   The indexing slow log, similar in functionality to the search slow
   log. The log file name ends with `_index_indexing_slowlog.log`. Log and
  -the thresholds are configured in the elasticsearch.yml file in the same
  -way as the search slowlog. Index slowlog sample:
  +the thresholds are configured in the same way as the search slowlog.
  +Index slowlog sample:
   
   [source,yaml]
   --------------------------------------------------
  
positive.code: The logging file is configured by default using the following
  configuration (found in `log4j2.properties`):
  
  [source,yaml]
  --------------------------------------------------
  appender.index_search_slowlog_rolling.type = RollingFile
  appender.index_search_slowlog_rolling.name = index_search_slowlog_rolling
  
negative.code: index.search.slowlog.threshold.fetch.trace: 200ms
  --------------------------------------------------
  
  All of the above settings are _dynamic_ and are set per-index.
  
  By default, none are enabled (set to `-1`). Levels (`warn`, `info`,
  `debug`, `trace`) allow to control under which logging level the log
  