Currently ElasticSearchSink indexName is appended with "YYYY-MM-DD" to generate actual ElasticSearch index name and allow index rolling on a daily basis. This works well for simpler use cases but is restrictive imho. User should be able to add indexSuffix as per their own use case and also keep the indexSuffix empty if requirement demands.
agent.sinks.essink.indexName = flume becomes flume-2013-10-10.
It will be really useful to have HDFS Sink filepath style indexSuffix naming i.e. "YYYY" will roll the indexes yearly, "YYYY-MM" will create indices monthly.