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Elastic Docs ›Elasticsearch Guide [2.0] ›Indices APIs

Upgrade

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Upgrade

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The upgrade API allows to upgrade one or more indices to the latest Lucene format through an API. The upgrade process converts any segments written with older formats.

When to use the upgrade API

Newer versions of Lucene often come with a new index format which provides bug fixes and performance improvements. In order to take advantage of these improvements, the segments in each shard need to be rewritten using the latest Lucene format.

Automatic upgradingIndices that are actively being written to will automatically write new segments in the latest format. The background merge process which combines multiple small segments into a single bigger segment will also write the new merged segment in the latest format.

Optional manual upgradesSome old segments may never be merged away because they are already too big to be worth merging, and indices that no longer receive changes will not be upgraded automatically. Upgrading segments is not required for most Elasticsearch upgrades because it can read older formats from the current and previous major version of Lucene.

You can, however, choose to upgrade old segments manually to take advantage of the latest format. The upgrade API will rewrite any old segments in the latest Lucene format. It can be run on one index, multiple or all indices, so you can control when it is run and how many indices it should upgrade.

When you must use the upgrade APIElasticsearch can only read formats from the current and previous major version of Lucene. For instance, Elasticsearch 2.x (Lucene 5) can read disk formats from Elasticsearch 0.90 and 1.x (Lucene 4), but not from Elasticsearch 0.20 and before (Lucene 3).

In fact, an Elasticsearch 2.0 cluster will refuse to start if any indices created before Elasticsearch 0.90 are present, and it will refuse to open them if they are imported as dangling indices later on. It will not be possible to restore an index created with Elasticsearch 0.20.x and before into a 2.0 cluster.

These ancient indices must either be deleted or upgraded before migrating to Elasticsearch 2.0. Upgrading will:

  • Rewrite old segments in the latest Lucene format.
  • Add the index.version.minimum_compatible setting to the index, to mark it as 2.0 compatible

Instead of upgrading all segments that weren’t written with the most recent version of Lucene, you can choose to do the minimum work required before moving to Elasticsearch 2.0, by specifying the only_ancient_segments option, which will only rewrite segments written by Lucene 3.

Start an upgrade

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$ curl -XPOST 'http://localhost:9200/twitter/_upgrade'

Upgrading is an I/O intensive operation, and is limited to processing a single shard per node at a time. It also is not allowed to run at the same time as optimize.

This call will block until the upgrade is complete. If the http connection is lost, the request will continue in the background, and any new requests will block until the previous upgrade is complete.

Request Parameters

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The upgrade API accepts the following request parameters:

only_ancient_segments

If true, only very old segments (from a previous Lucene major release) will be upgraded. While this will do the minimal work to ensure the next major release of Elasticsearch can read the segments, it’s dangerous because it can leave other very old segments in sub-optimal formats. Defaults to false.

Check upgrade status

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Use a GET request to monitor how much of an index is upgraded. This can also be used prior to starting an upgrade to identify which indices you want to upgrade at the same time.

The ancient byte values that are returned indicate total bytes of segments whose version is extremely old (Lucene major version is different from the current version), showing how much upgrading is necessary when you run with only_ancient_segments=true.

curl 'http://localhost:9200/twitter/_upgrade?pretty&human'
{
  "size": "21gb",
  "size_in_bytes": "21000000000",
  "size_to_upgrade": "10gb",
  "size_to_upgrade_in_bytes": "10000000000"
  "size_to_upgrade_ancient": "1gb",
  "size_to_upgrade_ancient_in_bytes": "1000000000"
  "indices": {
    "twitter": {
      "size": "21gb",
      "size_in_bytes": "21000000000",
      "size_to_upgrade": "10gb",
      "size_to_upgrade_in_bytes": "10000000000"
      "size_to_upgrade_ancient": "1gb",
      "size_to_upgrade_ancient_in_bytes": "1000000000"
    }
  }
}

The level of details in the upgrade status command can be controlled by setting level parameter to cluster, index (default) or shard levels. For example, you can run the upgrade status command with level=shard to get detailed upgrade information of each individual shard.

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