April 9 was the release date for the bugfix-release of Elasticsearch 1.5.1, which is based on Lucene 4.10.4. This is the latest stable version of Elasticsearch. Read the short article below for an overview of the changes that you’ll get when you install this new release.


The 1.5.1 release most notably contains an important bug fix that affects the speed of shard allocation to a new node. The first phase of shard recovery copies all the segment files from the source node to the target node—and the transaction log will get all the index, update, or delete requests. At the end of recovery operation, these will replay from the transaction log and be written to the target node. For a very large shard, the transaction log can accumulate many, many such events.

Previously, any new segment merges on the target node were disabled during the recovery operation. A very large transaction log would generate a large number of small new segments, which would often severely decrease the speed of the recovery operations. The fix for issue #10463 enables segment merges on the target shard during recovery.“>

Other bug-fix highlights:

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Also, rivers are now deprecated, which was done in release 1.5. You can read about the entire list of enhancements and bug fixes Elasticsearch 1.5.1 here.“>”>