[DOCS] Add data stream overview and intro (#57724)

Backporting #57596 to 7.x branch.

Added data streams overview page and
an introduction to data streams.

Relates to #53100

Co-authored-by: Dan Hermann danhermann@users.noreply.github.com
Co-authored-by: James Rodewig james.rodewig@elastic.co

docs/reference/data-streams.asciidoc

@@ -0,0 +1,117 @@
+[chapter]
+[[data-streams]]
+= Data Streams
+
+You can use data streams to index time-based data that's continuously generated.
+A data stream groups indices from the same time-based data source.
+A data stream tracks its indices, known as _backing indices_, using an ordered
+list.
+
+A data stream's backing indices are <<index-hidden,hidden>>.
+While all backing indices handle read requests, the most recently created
+backing index is the data stream's only write index.  A data stream only
+accepts <<docs-index_,index requests>> with `op_type` set to `create`. To update
+or delete specific documents in a data stream, submit a <<docs-delete,delete>>
+or <<docs-update,update>> API request to the backing index containing the
+document.
+
+To create a data stream, set up a <<indices-templates,composable index
+template>> containing:
+
+* A name or wildcard pattern for the data stream in the `index_patterns` property.
+* A `data_stream` definition that contains the `timestamp_field` property.
+  The `timestamp_field` must be the primary timestamp field 
+   for the data source. This field must be included in every
+   document indexed to the data stream.
+
+When you index one or more documents to a not-yet-existent target matching
+the template's name or pattern, {es} automatically creates the corresponding
+data stream. You can also manually create a data stream using the
+<<indices-create-data-stream,create data stream API>>. However, a composable
+template for the stream is still required.
+
+You can use the <<indices-rollover-index,rollover API>> to roll a data stream
+over to a new index when the current write index meets specified criteria, such
+as a maximum age or size. A rollover creates a new backing index and updates the
+data stream's list of backing indices. This new index then becomes the stream's
+new write index. See <<rollover-data-stream-ex>>.
+
+[discrete]
+[[create-data-stream]]
+== Create a data stream
+
+Create a composable template with a `data_stream` definition:
+
+[source,console]
+-----------------------------------
+PUT /_index_template/logs_template
+{
+  "index_patterns": ["logs-*"],
+  "data_stream": {
+    "timestamp_field": "@timestamp"
+  }
+}
+-----------------------------------
+
+Start indexing data to a target matching composable template's wildcard pattern:
+
+[source,console]
+----
+POST /logs-foobar/_doc
+{
+  "@timestamp": "2050-11-15T14:12:12",
+  ...
+}
+----
+// TEST[continued]
+// TEST[s/,//]
+// TEST[s/\.\.\.//]
+
+Response:
+
+[source,console-result]
+--------------------------------------------------
+{
+    "_shards" : {
+        "total" : 2,
+        "failed" : 0,
+        "successful" : 1
+    },
+    "_index" : "logs-foobar-000001",
+    "_type" : "_doc",
+    "_id" : "W0tpsmIBdwcYyG50zbta",
+    "_version" : 1,
+    "_seq_no" : 0,
+    "_primary_term" : 1,
+    "result": "created"
+}
+--------------------------------------------------
+// TESTRESPONSE[s/W0tpsmIBdwcYyG50zbta/$body._id/]
+
+Or create a data stream using the create data stream API:
+
+[source,console]
+--------------------------------------------------
+PUT /_data_stream/logs-barbaz
+--------------------------------------------------
+// TEST[continued]
+
+////
+[source,console]
+-----------------------------------
+DELETE /_data_stream/logs-foobar
+DELETE /_data_stream/logs-barbaz
+DELETE /_index_template/logs_template
+-----------------------------------
+// TEST[continued]
+////
+
+[discrete]
+[[data-streams-apis]]
+== Data stream APIs
+
+The following APIs are available for managing data streams:
+
+* To get information about data streams, use the <<indices-get-data-stream, get data stream API>>.
+* To delete data streams, use the <<indices-delete-data-stream, delete data stream API>>.
+* To manually create a data stream, use the <<indices-create-data-stream, create data stream API>>.

docs/reference/index.asciidoc

@@ -58,6 +58,8 @@ include::high-availability.asciidoc[]
 
 include::snapshot-restore/index.asciidoc[]
 
+include::data-streams.asciidoc[]
+
 include::{xes-repo-dir}/security/index.asciidoc[]
 
 include::{xes-repo-dir}/watcher/index.asciidoc[]

docs/reference/redirects.asciidoc

@@ -609,12 +609,6 @@ See <<slm-api-stop>>.
 
 See <<ccs-gateway-seed-nodes>> and <<ccs-min-roundtrips>>.
 
-[role="exclude",id="data-streams"]
-=== Data stream APIs
-
-See <<indices-create-data-stream>>, <<indices-get-data-stream>>, and
-<<indices-delete-data-stream>>.
-
 [role="exclude",id="modules-indices"]
 === Indices module