Reindexing Elasticsearch with Logstash 2.0

logstash.conf

input {
  elasticsearch {
    hosts => [ "HOSTNAME_HERE" ]
    port => "9200"
    index => "INDEXNAME_HERE"
    size => 1000
    scroll => "5m"
    docinfo => true
    scan => true
  }
}

output {
  elasticsearch {
    hosts => [ "HOSTNAME_HERE" ]
    index => "%{[@metadata][_index]}"
    document_type => "%{[@metadata][_type]}"
    document_id => "%{[@metadata][_id]}"
  }
  stdout {
    codec => "dots"
  }
}

Hi, I use the default index naming "logstash-" for a daily index. I have altered the number of shards from the default 5 to 1. I need to re-index my indices. I don't want to re-index into a new index eg "logstash-new-" but instead I want the existing indices to end up being spread across their single shard (instead of the current 5 shards per index).

How can I use this logstash script to do this?

Is there a better way to do this - eg re-index into new indices eg "logstash-new-", delete the original "logstash-" indices, then re-index back into "logstash-" from the new "logstash-new-" indices?

Many thanks.

Reindex API is a nice option:
https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html#_reindex_daily_indices

Also look into automatic scroll slicing that allows scrolls to be processed by multiple threads in parallel giving a nice speed boost.

Can anybody please explain that scroll option? I do reindex with logstash and it loops endlessly - the data from source index is randomly duplicated to output