elasticsearch/docs/reference/data-streams/set-up-a-data-stream.asciidoc

[role="xpack"]
[[set-up-a-data-stream]]
== Set up a data stream

To set up a data stream, follow these steps:

. <<configure-a-data-stream-ilm-policy>>.
. <<create-a-data-stream-template>>.
. <<create-a-data-stream>>.
. <<secure-a-data-stream>>.

You can also <<convert-an-index-alias-to-a-data-stream,convert an existing index
alias to a data stream>>.

[discrete]
[[configure-a-data-stream-ilm-policy]]
=== Optional: Configure an {ilm-init} lifecycle policy

While optional, we recommend you configure an <<set-up-lifecycle-policy,{ilm}
({ilm-init}) policy>> to automate the management of your data stream's backing
indices.

In {kib}, open the menu and go to *Stack Management > Index Lifecycle Policies*.
Click *Index Lifecycle Policies*.

[role="screenshot"]
image::images/ilm/create-policy.png[Index Lifecycle Policies page]

[%collapsible]
.API example
====
Use the <<ilm-put-lifecycle,create lifecycle policy API>> to configure a policy:

[source,console]
----
PUT /_ilm/policy/my-data-stream-policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_size": "25GB"
          }
        }
      },
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}
----
====

[discrete]
[[create-a-data-stream-template]]
=== Create an index template

. In {kib}, open the menu and go to *Stack Management > Index Management*.
. In the *Index Templates* tab, click *Create template*.
. In the Create template wizard, use the *Data stream* toggle to indicate the
template is used for data streams.
. Use the wizard to finish defining your template. Specify:

* One or more index patterns that match the data stream's name.

* Mappings and settings for the stream's backing indices.

* A priority for the index template
+
[IMPORTANT]
====
{es} has built-in index templates for the `metrics-*-*`, `logs-*-*`, and
`synthetics-*-*` index patterns, each with a priority of `100`.
{ingest-guide}/fleet-overview.html[{agent}] uses these templates to
create data streams.

If you use {agent}, assign your index templates a priority lower than `100` to
avoid overriding the built-in templates. Otherwise, use a non-overlapping index
pattern or assign templates with an overlapping pattern a `priority` higher than
`100`.

For example, if you don't use {agent} and want to create a template for the
`logs-*` index pattern, assign your template a priority of `200`. This ensures
your template is applied instead of the built-in template for `logs-*-*`.
====

If the index template doesn't specify a mapping for the `@timestamp` field, {es}
maps `@timestamp` as a `date` field  with default options.

If using {ilm-init}, specify your lifecycle policy in the `index.lifecycle.name`
setting.

TIP: Carefully consider your template's mappings and settings. Later changes may
require reindexing. See <<data-streams-change-mappings-and-settings>>.

[role="screenshot"]
image::images/data-streams/create-index-template.png[Create template page]

[%collapsible]
.API example
====
Use the <<indices-put-template,put index template API>> to create an index
template. The template must include an empty `data_stream` object, indicating
it's used for data streams.

[source,console]
----
PUT /_index_template/my-data-stream-template
{
  "index_patterns": [ "my-data-stream*" ],
  "data_stream": { },
  "priority": 200,
  "template": {
    "settings": {
      "index.lifecycle.name": "my-data-stream-policy"
    }
  }
}
----
// TEST[continued]
====

[discrete]
[[create-a-data-stream]]
=== Create the data stream

To automatically create the data stream, submit an
<<add-documents-to-a-data-stream,indexing request>> to the stream. The stream's
name must match one of your template's index patterns.

[source,console]
----
POST /my-data-stream/_doc/
{
  "@timestamp": "2099-03-07T11:04:05.000Z",
  "user": {
    "id": "vlb44hny"
  },
  "message": "Login attempt failed"
}
----
// TEST[continued]

You can also use the <<indices-create-data-stream,create data stream API>> to
manually create the data stream. The stream's name must match one of your
template's index patterns.

[source,console]
----
PUT /_data_stream/my-data-stream
----
// TEST[continued]
// TEST[s/my-data-stream/my-data-stream-alt/]

When you create a data stream, {es} automatically creates a backing index for
the stream. This index also acts as the stream's first write index.

[discrete]
[[convert-an-index-alias-to-a-data-stream]]
=== Convert an index alias to a data stream

Prior to {es} 7.9, you would typically use an <<indices-aliases,index alias>>
with a write index to manage time series data. Data streams replace most of
this functionality and usually require less maintenance.

To convert an index alias with a write index to a new data stream with the same
name, use the <<indices-migrate-to-data-stream,migrate to data stream API>>.
During conversion, the alias’s indices become hidden backing indices for the
stream. The alias’s write index becomes the stream’s write index. Note the data
stream still requires a matching <<create-a-data-stream-template,index
template>>.

////
[source,console]
----
POST idx1/_doc/
{
    "message" : "testing",
    "@timestamp" : "2099-01-01"
}

POST idx2/_doc/
{
    "message" : "testing2",
    "@timestamp" : "2099-01-01"
}

POST /_aliases
{
  "actions": [
    {
      "add": {
        "index": "idx1",
        "alias": "my-time-series-data",
        "is_write_index": true
      }
    },
    {
      "add": {
        "index": "idx2",
        "alias": "my-time-series-data"
      }
    }
  ]
}

PUT /_index_template/template
{
  "index_patterns": ["my-time-series-data"],
  "data_stream": { }
}
----
// TEST[continued]
////

[source,console]
----
POST /_data_stream/_migrate/my-time-series-data
----
// TEST[continued]

[discrete]
[[secure-a-data-stream]]
=== Secure the data stream

To control access to the data stream and its
data, use <<data-stream-privileges,{es}'s {security-features}>>.

[discrete]
[[get-info-about-a-data-stream]]
=== Get information about a data stream

In {kib}, open the menu and go to *Stack Management > Index Management*. In the
*Data Streams* tab, click the data stream's name.

[role="screenshot"]
image::images/data-streams/data-streams-list.png[Data Streams tab]

[%collapsible]
.API example
====
Use the <<indices-get-data-stream,get data stream API>> to retrieve information
about one or more data streams:

////
[source,console]
----
POST /my-data-stream/_rollover/
----
// TEST[continued]
////

[source,console]
----
GET /_data_stream/my-data-stream
----
// TEST[continued]
====

[discrete]
[[delete-a-data-stream]]
=== Delete a data stream

To delete a data stream and its backing indices, open the {kib} menu and go to
*Stack Management > Index Management*. In the *Data Streams* tab, click the
trash can icon.

[role="screenshot"]
image::images/data-streams/data-streams-list.png[Data Streams tab]

[%collapsible]
.API example
====
Use the <<indices-delete-data-stream,delete data stream API>> to delete a data
stream and its backing indices:

[source,console]
----
DELETE /_data_stream/my-data-stream
----
// TEST[continued]
====

////
[source,console]
----
DELETE /_data_stream/*
DELETE /_index_template/*
DELETE /_ilm/policy/my-data-stream-policy
----
// TEST[continued]
////