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: index.search.slowlog.threshold.fetch.trace: 200ms
  --------------------------------------------------
  
  All of the above settings are _dynamic_ and can be 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
  
negative.code: index.indexing.slowlog.source: 1000
  --------------------------------------------------
  
  All of the above settings are _dynamic_ and are set per-index.
  
  By default Elasticsearch will log the first 1000 characters of the _source in
  the slowlog. You can change that with `index.indexing.slowlog.source`. Setting
  it to `false` or `0` will skip logging the source entirely an setting it to
  `true` will log the entire source regardless of size.
  
  The index slow log file is configured by default in the `log4j2.properties`
  file:
  
  [source,properties]
  --------------------------------------------------
  appender.index_indexing_slowlog_rolling.type = RollingFile
  appender.index_indexing_slowlog_rolling.name = index_indexing_slowlog_rolling
  appender.index_indexing_slowlog_rolling.fileName = ${sys:es.logs}_index_indexing_slowlog.log
  appender.index_indexing_slowlog_rolling.layout.type = PatternLayout
  appender.index_indexing_slowlog_rolling.layout.pattern = [%d{ISO8601}][%-5p][%-25c] %marker%.10000m%n
  appender.index_indexing_slowlog_rolling.filePattern = ${sys:es.logs}_index_indexing_slowlog-%d{yyyy-MM-dd}.log
  appender.index_indexing_slowlog_rolling.policies.type = Policies
  appender.index_indexing_slowlog_rolling.policies.time.type = TimeBasedTriggeringPolicy
  appender.index_indexing_slowlog_rolling.policies.time.interval = 1
  appender.index_indexing_slowlog_rolling.policies.time.modulate = true
  
  logger.index_indexing_slowlog.name = index.indexing.slowlog.index
  logger.index_indexing_slowlog.level = trace
  logger.index_indexing_slowlog.appenderRef.index_indexing_slowlog_rolling.ref = index_indexing_slowlog_rolling
  logger.index_indexing_slowlog.additivity = false
  --------------------------------------------------
  