[apm] Annotation API documentation (#65963)

docs/apm/api.asciidoc

@@ -9,14 +9,45 @@
 Some APM app features are provided via a REST API:
 
 * <<agent-config-api>>
-
-TIP: Kibana provides additional <<api,REST APIs>>,
-and general information on <<using-api,how to use APIs>>.
+* <<apm-annotation-api>>
+
+Here's an example CURL request that adds an annotation to the APM app:
+
+[source,curl]
+----
+curl -X POST \
+  http://localhost:5601/api/apm/services/opbeans-java/annotation \
+-H 'Content-Type: application/json' \
+-H 'kbn-xsrf: true' \
+-H 'Authorization: Basic YhUlubWZhM0FDbnlQeE6WRtaW49FQmSGZ4RUWXdX' \
+-d '{
+      "@timestamp": "2020-05-11T10:31:30.452Z",
+      "service": {
+        "version": "1.2"
+      },
+      "message": "Revert upgrade",
+      "tags": [
+        "elastic.co", "customer"
+      ]
+    }'
+----
+
+For more information, the Kibana <<api,REST API reference>> provides information on how to use Kibana APIs,
+like required request headers and authentication options.
+
+// AGENT CONFIG API
+// GET --> Feature (APM) Read
+// CREATE/EDIT/DELETE --> Feature (APM) All
+
+// ANNOTATION API
+// Feature (APM) All
+// Index: `observability-annotations`. Privileges: `create_index`, `create_doc`, `manage`, and `read`.
 
 ////
 *******************************************************
 ////
 
+[role="xpack"]
 [[agent-config-api]]
 === Agent Configuration API
 
@@ -274,6 +305,118 @@ POST /api/apm/settings/agent-configuration/search
 }
 --------------------------------------------------
 
+////
+*******************************************************
+*******************************************************
+////
+
+[role="xpack"]
+[[apm-annotation-api]]
+=== Annotation API
+
+The Annotation API allows you to annotate visualizations in the APM app with significant events, like deployments,
+allowing you to easily see how these events are impacting the performance of your existing applications.
+
+The following APIs are available:
+
+* <<apm-annotation-create>> to create an annotation for APM.
+// * <<obs-annotation-create>> POST /api/observability/annotation
+// * <<obs-annotation-get>> GET /api/observability/annotation/:id
+// * <<obs-annotation-delete>> DELETE /api/observability/annotation/:id
+
+By default, annotations are stored in a newly created `observability-annotations` index.
+The name of this index can be changed in your `config.yml` by editing `xpack.observability.annotations.index`.
+
 ////
 *******************************************************
 ////
+
+[[apm-annotation-create]]
+==== Create or update annotation
+
+[[apm-annotation-config-req]]
+===== Request
+
+`POST /api/apm/services/:serviceName/annotation`
+
+[role="child_attributes"]
+[[apm-annotation-config-req-body]]
+===== Request body
+
+`service`::
+(required, object) Service identifying the configuration to create or update.
++
+.Properties of `service`
+[%collapsible%open]
+======
+`version` :::
+  (required, string) Name of service.
+
+`environment` :::
+  (optional, string) Environment of service.
+======
+
+`@timestamp`::
+(required, string) The date and time of the annotation. Must be in https://www.w3.org/TR/NOTE-datetime[ISO 8601] format.
+
+`message`::
+(optional, string) The message displayed in the annotation. Defaults to `service.version`.
+
+`tags`::
+(optional, array) Tags are used by the APM app to distinguish APM annotations from other annotations.
+Tags may have additional functionality in future releases. Defaults to `[apm]`.
+While you can add additional tags, you cannot remove the `apm` tag.
+
+[[apm-annotation-config-example]]
+===== Example
+
+The following example creates an annotation for a service named `opbeans-java`.
+
+[source,console]
+--------------------------------------------------
+POST /api/apm/services/opbeans-java/annotation
+{
+	"@timestamp": "2020-05-08T10:31:30.452Z",
+	"service": {
+		"version": "1.2"
+	},
+	"message": "Deployment 1.2",
+	"tags": [
+		"elastic.co", "customer"
+	]
+}
+--------------------------------------------------
+
+[[apm-annotation-config-body]]
+===== Response body
+
+[source,js]
+--------------------------------------------------
+{
+  "_index": "observability-annotations",
+  "_id": "Lc9I93EBh6DbmkeV7nFX",
+  "_version": 1,
+  "_seq_no": 12,
+  "_primary_term": 1,
+  "found": true,
+  "_source": {
+    "message": "Deployment 1.2",
+    "@timestamp": "2020-05-08T10:31:30.452Z",
+    "service": {
+      "version": "1.2",
+      "name": "opbeans-java"
+    },
+    "tags": [
+      "apm",
+      "elastic.co",
+      "customer"
+    ],
+    "annotation": {
+      "type": "deployment"
+    },
+    "event": {
+      "created": "2020-05-09T02:34:43.937Z"
+    }
+  }
+}
+--------------------------------------------------

docs/apm/deployment-annotations.asciidoc

@@ -3,15 +3,19 @@
 === Track deployments with annotations
 
 ++++
-<titleabbrev>Track deployments</titleabbrev>
+<titleabbrev>Track deployments with annotations</titleabbrev>
 ++++
 
 For enhanced visibility into your deployments, we offer deployment annotations on all transaction charts.
 This feature automatically tags new deployments, so you can easily see if your deploy has increased response times
 for an end-user, or if the memory/CPU footprint of your application has changed.
 Being able to identify bad deployments quickly enables you to rollback and fix issues without causing costly outages.
 
-Deployment annotations are automatically enabled, and appear when the `service.version` of your app changes.
+Deployment annotations are enabled by default, and can be created with the <<apm-annotation-api,annotation API>>.
+If there are no created annotations for the selected time period,
+the APM app will automatically annotate your data if the `service.version` of your application changes.
+
+NOTE: If custom annotations have been created for the selected time period, any derived annotations, i.e., those created automatically when `service.version` changes, will not be shown.
 
 [role="screenshot"]
 image::apm/images/apm-transaction-annotation.png[Example view of transactions annotation in the APM app in Kibana]

docs/settings/apm-settings.asciidoc

@@ -52,6 +52,9 @@ Changing these settings may disable features of the APM App.
 | `xpack.apm.ui.maxTraceItems` {ess-icon}
   | Maximum number of child items displayed when viewing trace details. Defaults to `1000`.
 
+| `xpack.observability.annotations.index`
+  | Index name where Observability annotations are stored. Defaults to `observability-annotations`.
+
 | `apm_oss.indexPattern` {ess-icon}
   | The index pattern used for integrations with Machine Learning and Query Bar.
   It must match all apm indices. Defaults to `apm-*`.