[[indices-rollover-index]]
=== Rollover index API
++++
<titleabbrev>Rollover index</titleabbrev>
++++

Assigns an <<indices-aliases, index alias>> to a new index
when the alias's existing index meets a condition you provide.

[source,console]
----
POST /alias1/_rollover/twitter
{
  "conditions": {
    "max_age":   "7d",
    "max_docs":  1000,
    "max_size": "5gb"
  }
}
----
// TEST[s/^/PUT my_old_index_name\nPUT my_old_index_name\/_alias\/alias1\n/]


[[rollover-index-api-request]]
==== {api-request-title}


`POST /<alias>/_rollover/<target-index>`

`POST /<alias>/_rollover/`


[[rollover-index-api-desc]]
==== {api-description-title}

The rollover index API rolls an <<indices-aliases, alias>> to a new index when
the existing index meets a condition you provide. You can use this API to retire
an index that becomes too large or too old.

NOTE: To roll over an index, a condition must be met *when you call the API*.
{es} does not monitor the index after you receive an API response. To
automatically roll over indices when a condition is met, you can use {es}'s
<<index-lifecycle-management, index lifecycle management (ILM) policies>>.

The rollover index API accepts a single alias name
and a list of `conditions`.

If the specified alias points to a single index,
the rollover request:

. Creates a new index
. Adds the alias to the new index
. Removes the alias from the original index

If the specified alias points to multiple indices,
one of these indices must have `is_write_index` set to `true`.
In this case,
the rollover request:

. Creates a new index
. Sets `is_write_index` to `true` for the new index
. Sets `is_write_index` to `false` for the original index


[[rollover-wait-active-shards]]
===== Wait for active shards

Because the rollover operation creates a new index to rollover to, the
<<create-index-wait-for-active-shards,`wait_for_active_shards`>> setting on
index creation applies to the rollover action.


[[rollover-index-api-path-params]]
==== {api-path-parms-title}

`<alias>`::
(Required, string)
Name of the existing index alias
to assign to the target index.


`<target-index>`::
+
--
(Optional*, string)
Name of the target index to create and assign the index alias.

include::{docdir}/indices/create-index.asciidoc[tag=index-name-reqs]

*This parameter is not required
if the alias is assigned to an index name that ends with `-` and a number,
such as `logs-000001`.
In this case,
the name of the new index follows the same pattern,
incrementing the number.
For example,
`logs-000001` increments to `logs-000002`.
This number is zero-padded with a length of 6,
regardless of the prior index name.

If the existing index for the alias does not match this pattern,
this parameter is required.
--


[[rollover-index-api-query-params]]
==== {api-query-parms-title}

`dry_run`::
(Optional, boolean)
If `true`,
the request checks whether the index matches provided conditions
but does not perform a rollover.
Defaults to `false`.

include::{docdir}/rest-api/common-parms.asciidoc[tag=include-type-name]

include::{docdir}/rest-api/common-parms.asciidoc[tag=wait_for_active_shards]

include::{docdir}/rest-api/common-parms.asciidoc[tag=timeoutparms]


[[rollover-index-api-request-body]]
==== {api-request-body-title}

include::{docdir}/rest-api/common-parms.asciidoc[tag=aliases]

`conditions`::
+
--
(Required, object)
Set of conditions the index alias's existing index must met to roll over.

Parameters include:

`max_age`::
(Optional, <<time-units, time units>>)
Maximum age of the index.

`max_docs`::
(Optional, integer)
Maximum number of documents in the index.
Documents added since the last refresh are not included in the document count.
The document count does *not* include documents in replica shards.

`max_size`::
(Optional, <<byte-units, byte units>>)
Maximum estimated size of the primary shard of the index.
--

include::{docdir}/rest-api/common-parms.asciidoc[tag=mappings]

include::{docdir}/rest-api/common-parms.asciidoc[tag=settings]


[[rollover-index-api-example]]
==== {api-examples-title}

[[rollover-index-basic-ex]]
===== Basic example

[source,console]
--------------------------------------------------
PUT /logs-000001 <1>
{
  "aliases": {
    "logs_write": {}
  }
}

# Add > 1000 documents to logs-000001

POST /logs_write/_rollover <2>
{
  "conditions": {
    "max_age":   "7d",
    "max_docs":  1000,
    "max_size":  "5gb"
  }
}
--------------------------------------------------
// TEST[setup:huge_twitter]
// TEST[s/# Add > 1000 documents to logs-000001/POST _reindex?refresh\n{"source":{"index":"twitter"},"dest":{"index":"logs-000001"}}/]
<1> Creates an index called `logs-0000001` with the alias `logs_write`.
<2> If the index pointed to by `logs_write` was created 7 or more days ago, or
    contains 1,000 or more documents, or has an index size at least around 5GB, then the `logs-000002` index is created
    and the `logs_write` alias is updated to point to `logs-000002`.

The API returns the following response:

[source,console-result]
--------------------------------------------------
{
  "acknowledged": true,
  "shards_acknowledged": true,
  "old_index": "logs-000001",
  "new_index": "logs-000002",
  "rolled_over": true, <1>
  "dry_run": false, <2>
  "conditions": { <3>
    "[max_age: 7d]": false,
    "[max_docs: 1000]": true,
    "[max_size: 5gb]": false,
  }
}
--------------------------------------------------

<1> Whether the index was rolled over.
<2> Whether the rollover was dry run.
<3> The result of each condition.

[[rollover-index-settings-ex]]
===== Specify settings for the target index

The settings, mappings, and aliases for the new index are taken from any
matching <<indices-templates,index templates>>. Additionally, you can specify
`settings`, `mappings`, and `aliases` in the body of the request, just like the
<<indices-create-index,create index>> API. Values specified in the request
override any values set in matching index templates. For example, the following
`rollover` request overrides the `index.number_of_shards` setting:

[source,console]
--------------------------------------------------
PUT /logs-000001
{
  "aliases": {
    "logs_write": {}
  }
}

POST /logs_write/_rollover
{
  "conditions" : {
    "max_age": "7d",
    "max_docs": 1000,
    "max_size": "5gb"
  },
  "settings": {
    "index.number_of_shards": 2
  }
}
--------------------------------------------------


[[rollover-index-specify-index-ex]]
===== Specify a target index name

If the name of the existing index ends with `-` and a number -- e.g.
`logs-000001` -- then the name of the new index will follow the same pattern,
incrementing the number (`logs-000002`). The number is zero-padded with a length
of 6, regardless of the old index name.

If the old name doesn't match this pattern then you must specify the name for
the new index as follows:

[source,console]
--------------------------------------------------
POST /my_alias/_rollover/my_new_index_name
{
  "conditions": {
    "max_age":   "7d",
    "max_docs":  1000,
    "max_size": "5gb"
  }
}
--------------------------------------------------
// TEST[s/^/PUT my_old_index_name\nPUT my_old_index_name\/_alias\/my_alias\n/]


[[_using_date_math_with_the_rollover_api]]
===== Use date math with a rollover

It can be useful to use <<date-math-index-names,date math>> to name the
rollover index according to the date that the index rolled over, e.g.
`logstash-2016.02.03`.  The rollover API supports date math, but requires the
index name to end with a dash followed by a number, e.g.
`logstash-2016.02.03-1` which is incremented every time the index is rolled
over. For instance:

[source,console]
--------------------------------------------------
# PUT /<logs-{now/d}-1> with URI encoding:
PUT /%3Clogs-%7Bnow%2Fd%7D-1%3E <1>
{
  "aliases": {
    "logs_write": {}
  }
}

PUT logs_write/_doc/1
{
  "message": "a dummy log"
}

POST logs_write/_refresh

# Wait for a day to pass

POST /logs_write/_rollover <2>
{
  "conditions": {
    "max_docs":   "1"
  }
}
--------------------------------------------------
// TEST[s/now/2016.10.31%7C%7C/]

<1> Creates an index named with today's date (e.g.) `logs-2016.10.31-1`
<2> Rolls over to a new index with today's date, e.g. `logs-2016.10.31-000002` if run immediately, or `logs-2016.11.01-000002` if run after 24 hours

//////////////////////////

[source,console]
--------------------------------------------------
GET _alias
--------------------------------------------------
// TEST[continued]

[source,console-result]
--------------------------------------------------
{
  "logs-2016.10.31-000002": {
    "aliases": {
      "logs_write": {}
    }
  },
  "logs-2016.10.31-1": {
    "aliases": {}
  }
}
--------------------------------------------------

//////////////////////////

These indices can then be referenced as described in the
<<date-math-index-names,date math documentation>>.  For example, to search
over indices created in the last three days, you could do the following:

[source,console]
--------------------------------------------------
# GET /<logs-{now/d}-*>,<logs-{now/d-1d}-*>,<logs-{now/d-2d}-*>/_search
GET /%3Clogs-%7Bnow%2Fd%7D-*%3E%2C%3Clogs-%7Bnow%2Fd-1d%7D-*%3E%2C%3Clogs-%7Bnow%2Fd-2d%7D-*%3E/_search
--------------------------------------------------
// TEST[continued]
// TEST[s/now/2016.10.31%7C%7C/]


[[rollover-index-api-dry-run-ex]]
===== Dry run

The rollover API supports `dry_run` mode, where request conditions can be
checked without performing the actual rollover.

[source,console]
--------------------------------------------------
POST /logs_write/_rollover?dry_run
{
  "conditions" : {
    "max_age": "7d",
    "max_docs": 1000,
    "max_size": "5gb"
  }
}
--------------------------------------------------
// TEST[s/^/PUT logs-000001\nPUT logs-000001\/_alias\/logs_write\n/]


[[indices-rollover-is-write-index]]
===== Roll over a write index

The rollover alias when rolling over a write index that has `is_write_index` explicitly set to `true` is not
swapped during rollover actions. Since having an alias point to multiple indices is ambiguous in distinguishing
which is the correct write index to roll over, it is not valid to rollover an alias that points to multiple indices.
For this reason, the default behavior is to swap which index is being pointed to by the write-oriented alias. This
was `logs_write` in some of the above examples. Since setting `is_write_index` enables an alias to point to multiple indices
while also being explicit as to which is the write index that rollover should target, removing the alias from the rolled over
index is not necessary. This simplifies things by allowing for one alias to behave both as the write and read aliases for
indices that are being managed with Rollover.

Look at the behavior of the aliases in the following example where `is_write_index` is set on the rolled over index.

[source,console]
--------------------------------------------------
PUT my_logs_index-000001
{
  "aliases": {
    "logs": { "is_write_index": true } <1>
  }
}

PUT logs/_doc/1
{
  "message": "a dummy log"
}

POST logs/_refresh

POST /logs/_rollover
{
  "conditions": {
    "max_docs":   "1"
  }
}

PUT logs/_doc/2 <2>
{
  "message": "a newer log"
}
--------------------------------------------------

<1> configures `my_logs_index` as the write index for the `logs` alias
<2> newly indexed documents against the `logs` alias will write to the new index

[source,console-result]
--------------------------------------------------
{
  "_index" : "my_logs_index-000002",
  "_type" : "_doc",
  "_id" : "2",
  "_version" : 1,
  "result" : "created",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 0,
  "_primary_term" : 1
}
--------------------------------------------------

//////////////////////////
[source,console]
--------------------------------------------------
GET my_logs_index-000001,my_logs_index-000002/_alias
--------------------------------------------------
// TEST[continued]
//////////////////////////

After the rollover, the alias metadata for the two indices will have the `is_write_index` setting
reflect each index's role, with the newly created index as the write index.

[source,console-result]
--------------------------------------------------
{
  "my_logs_index-000002": {
    "aliases": {
      "logs": { "is_write_index": true }
    }
  },
  "my_logs_index-000001": {
    "aliases": {
      "logs": { "is_write_index" : false }
    }
  }
}
--------------------------------------------------
