107 lines
2.8 KiB
Plaintext
107 lines
2.8 KiB
Plaintext
[[mapping-ttl-field]]
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=== `_ttl` field
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Some types of documents, such as session data or special offers, come with an
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expiration date. The `_ttl` field allows you to specify the minimum time a
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document should live, after which time the document is deleted automatically.
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[TIP]
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.Prefer index-per-timeframe to TTL
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======================================================
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With TTL , expired documents first have to be marked as deleted then later
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purged from the index when segments are merged. For append-only time-based
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data such as log events, it is much more efficient to use an index-per-day /
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week / month instead of TTLs. Old log data can be removed by simply deleting
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old indices.
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======================================================
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The `_ttl` field may be enabled as follows:
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[source,js]
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-------------------------------
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PUT my_index
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{
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"mappings": {
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"my_type": {
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"_ttl": {
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"enabled": true
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}
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}
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}
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}
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PUT my_index/my_type/1?ttl=10m <1>
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{
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"text": "Will expire in 10 minutes"
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}
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PUT my_index/my_type/2 <2>
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{
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"text": "Will not expire"
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}
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-------------------------------
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// AUTOSENSE
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<1> This document will expire 10 minutes after being indexed.
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<2> This document has no TTL set and will not expire.
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The expiry time is calculated as the value of the
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<<mapping-timestamp-field,`_timestamp`>> field (or `now()` if the `_timestamp`
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is not enabled) plus the `ttl` specified in the indexing request.
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==== Default TTL
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You can provide a default `_ttl`, which will be applied to indexing requests where the `ttl` is not specified:
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[source,js]
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-------------------------------
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PUT my_index
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{
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"mappings": {
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"my_type": {
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"_ttl": {
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"enabled": true,
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"defaut": "5m"
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}
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}
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}
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}
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PUT my_index/my_type/1?ttl=10m <1>
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{
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"text": "Will expire in 10 minutes"
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}
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PUT my_index/my_type/2 <2>
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{
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"text": "Will expire in 5 minutes"
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}
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-------------------------------
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// AUTOSENSE
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<1> This document will expire 10 minutes after being indexed.
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<2> This document has no TTL set and so will expire after the default 5 minutes.
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The `default` value can use <<time-units,time units>> like `d` for days, and
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will use `ms` as the default unit if no time unit is provided.
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You can dynamically update the `default` value using the put mapping
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API. It won't change the `_ttl` of already indexed documents but will be
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used for future documents.
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==== Note on documents expiration
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Expired documents will be automatically deleted periodoically. The following
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settings control the expiry process:
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`indices.ttl.interval`::
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How often the purge process should run. Defaults to `60s`. Expired documents
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may still be retrieved before they are purged.
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`indices.ttl.bulk_size`::
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How many deletions are handled by a single <<docs-bulk,`bulk`>> request. The
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default value is `10000`.
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