[role="xpack"]
[testenv="platinum"]
[[ml-start-datafeed]]
=== Start {dfeeds-cap} API
++++
<titleabbrev>Start {dfeeds-cap}</titleabbrev>
++++

Starts one or more {dfeeds}.
A {dfeed} must be started in order to retrieve data from {es}.
A {dfeed} can be started and stopped multiple times throughout its lifecycle.

==== Request

`POST _xpack/ml/datafeeds/<feed_id>/_start`

==== Description

NOTE: Before you can start a {dfeed}, the job must be open. Otherwise, an error
occurs.

When you start a {dfeed}, you can specify a start time.  This enables you to
include a training period, providing you have this data available in {es}.
If you want to analyze from the beginning of a dataset, you can specify any date
earlier than that beginning date.

If you do not specify a start time and the {dfeed} is associated with a new
job, the analysis starts from the earliest time for which data is available.

When you start a {dfeed}, you can also specify an end time. If you do so, the
job analyzes data from the start time until the end time, at which point the
analysis stops.  This scenario is useful for a one-off batch analysis.  If you
do not specify an end time, the {dfeed} runs continuously.

The `start` and `end` times can be specified by using one of the
following formats: +

- ISO 8601 format with milliseconds, for example `2017-01-22T06:00:00.000Z`
- ISO 8601 format without milliseconds, for example `2017-01-22T06:00:00+00:00`
- Seconds from the Epoch, for example `1390370400`

Date-time arguments using either of the ISO 8601 formats must have a time zone
designator, where Z is accepted as an abbreviation for UTC time.

NOTE: When a URL is expected (for example, in browsers), the `+` used in time
zone designators must be encoded as `%2B`.

If the system restarts, any jobs that had {dfeeds} running are also restarted.

When a stopped {dfeed} is restarted, it continues processing input data from
the next millisecond after it was stopped. If new data was indexed for that
exact millisecond between stopping and starting, it will be ignored.
If you specify a `start` value that is earlier than the timestamp of the latest
processed record, the {dfeed} continues from 1 millisecond after the timestamp
of the latest processed record.


==== Path Parameters

`feed_id` (required)::
(string) Identifier for the {dfeed}

==== Request Body

`end`::
  (string) The time that the {dfeed} should end. This value is exclusive.
  The default value is an empty string.

`start`::
  (string) The time that the {dfeed} should begin. This value is inclusive.
  The default value is an empty string.

`timeout`::
  (time) Controls the amount of time to wait until a {dfeed} starts.
  The default value is 20 seconds.


==== Authorization

You must have `manage_ml`, or `manage` cluster privileges to use this API.
For more information, see
{xpack-ref}/security-privileges.html[Security Privileges].


==== Security Integration

When {security} is enabled, your {dfeed} will remember which roles the last
user to create or update it had at the time of creation/update, and run the query
using those same roles.


==== Examples

The following example starts the `datafeed-it-ops-kpi` {dfeed}:

[source,js]
--------------------------------------------------
POST _xpack/ml/datafeeds/datafeed-total-requests/_start
{
  "start": "2017-04-07T18:22:16Z"
}
--------------------------------------------------
// CONSOLE
// TEST[skip:setup:server_metrics_openjob]

When the {dfeed} starts, you receive the following results:
[source,js]
----
{
  "started": true
}
----
// TESTRESPONSE