ML: Add upgrade mode docs, hlrc, and fix bug (#37942)

* ML: Add upgrade mode docs, hlrc, and fix bug

* [DOCS] Fixes build error and edits text

* adjusting docs

* Update docs/reference/ml/apis/set-upgrade-mode.asciidoc

Co-Authored-By: benwtrent <ben.w.trent@gmail.com>

* Update set-upgrade-mode.asciidoc

* Update set-upgrade-mode.asciidoc

client/rest-high-level/src/main/java/org/elasticsearch/client/MLRequestConverters.java

@@ -64,6 +64,7 @@ import org.elasticsearch.client.ml.PutDatafeedRequest;
 import org.elasticsearch.client.ml.PutFilterRequest;
 import org.elasticsearch.client.ml.PutJobRequest;
 import org.elasticsearch.client.ml.RevertModelSnapshotRequest;
+import org.elasticsearch.client.ml.SetUpgradeModeRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequest;
 import org.elasticsearch.client.ml.StopDatafeedRequest;
 import org.elasticsearch.client.ml.UpdateDatafeedRequest;
@@ -624,6 +625,17 @@ final class MLRequestConverters {
         return request;
     }
 
+    static Request setUpgradeMode(SetUpgradeModeRequest setUpgradeModeRequest) {
+        String endpoint = new EndpointBuilder().addPathPartAsIs("_ml", "set_upgrade_mode").build();
+        Request request = new Request(HttpPost.METHOD_NAME, endpoint);
+        RequestConverters.Params params = new RequestConverters.Params(request);
+        params.putParam(SetUpgradeModeRequest.ENABLED.getPreferredName(), Boolean.toString(setUpgradeModeRequest.isEnabled()));
+        if (setUpgradeModeRequest.getTimeout() != null) {
+            params.putParam(SetUpgradeModeRequest.TIMEOUT.getPreferredName(), setUpgradeModeRequest.getTimeout().toString());
+        }
+        return request;
+    }
+
     static Request mlInfo(MlInfoRequest infoRequest) {
         String endpoint = new EndpointBuilder()
             .addPathPartAsIs("_ml", "info")

client/rest-high-level/src/main/java/org/elasticsearch/client/MachineLearningClient.java

@@ -86,6 +86,7 @@ import org.elasticsearch.client.ml.PutJobRequest;
 import org.elasticsearch.client.ml.PutJobResponse;
 import org.elasticsearch.client.ml.RevertModelSnapshotRequest;
 import org.elasticsearch.client.ml.RevertModelSnapshotResponse;
+import org.elasticsearch.client.ml.SetUpgradeModeRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequest;
 import org.elasticsearch.client.ml.StartDatafeedResponse;
 import org.elasticsearch.client.ml.StopDatafeedRequest;
@@ -1838,4 +1839,42 @@ public final class MachineLearningClient {
             listener,
             Collections.emptySet());
     }
+
+    /**
+     * Sets the ML cluster setting upgrade_mode
+     * <p>
+     * For additional info
+     * see <a href="http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-set-upgrade-mode.html">Set Upgrade Mode</a>
+     *
+     * @param request The request to set upgrade mode
+     * @param options  Additional request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @return response
+     * @throws IOException when there is a serialization issue sending the request or receiving the response
+     */
+    public AcknowledgedResponse setUpgradeMode(SetUpgradeModeRequest request, RequestOptions options) throws IOException {
+        return restHighLevelClient.performRequestAndParseEntity(request,
+            MLRequestConverters::setUpgradeMode,
+            options,
+            AcknowledgedResponse::fromXContent,
+            Collections.emptySet());
+    }
+
+    /**
+     * Sets the ML cluster setting upgrade_mode asynchronously
+     * <p>
+     * For additional info
+     * see <a href="http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-set-upgrade-mode.html">Set Upgrade Mode</a>
+     *
+     * @param request The request of Machine Learning info
+     * @param options  Additional request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
+     * @param listener Listener to be notified upon request completion
+     */
+    public void setUpgradeModeAsync(SetUpgradeModeRequest request, RequestOptions options, ActionListener<AcknowledgedResponse> listener) {
+        restHighLevelClient.performRequestAsyncAndParseEntity(request,
+            MLRequestConverters::setUpgradeMode,
+            options,
+            AcknowledgedResponse::fromXContent,
+            listener,
+            Collections.emptySet());
+    }
 }

client/rest-high-level/src/main/java/org/elasticsearch/client/ml/SetUpgradeModeRequest.java

@@ -0,0 +1,93 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.client.ml;
+
+import org.elasticsearch.action.ActionRequest;
+import org.elasticsearch.action.ActionRequestValidationException;
+import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.unit.TimeValue;
+
+import java.util.Objects;
+
+/**
+ * Sets ML into upgrade_mode
+ */
+public class SetUpgradeModeRequest extends ActionRequest {
+
+
+    public static final ParseField ENABLED = new ParseField("enabled");
+    public static final ParseField TIMEOUT = new ParseField("timeout");
+
+    private boolean enabled;
+    private TimeValue timeout;
+
+    /**
+     * Create a new request
+     *
+     * @param enabled whether to enable `upgrade_mode` or not
+     */
+    public SetUpgradeModeRequest(boolean enabled) {
+        this.enabled = enabled;
+    }
+
+    public boolean isEnabled() {
+        return enabled;
+    }
+
+    public void setEnabled(boolean enabled) {
+        this.enabled = enabled;
+    }
+
+    public TimeValue getTimeout() {
+        return timeout;
+    }
+
+    /**
+     * How long to wait for the request to be completed
+     *
+     * @param timeout default value of 30 seconds
+     */
+    public void setTimeout(TimeValue timeout) {
+        this.timeout = timeout;
+    }
+
+    @Override
+    public ActionRequestValidationException validate() {
+        return null;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(enabled, timeout);
+    }
+
+    @Override
+    public boolean equals(Object other) {
+        if (this == other) {
+            return true;
+        }
+
+        if (other == null || getClass() != other.getClass()) {
+            return false;
+        }
+
+        SetUpgradeModeRequest that = (SetUpgradeModeRequest) other;
+        return Objects.equals(enabled, that.enabled) && Objects.equals(timeout, that.timeout);
+    }
+}

client/rest-high-level/src/test/java/org/elasticsearch/client/MLRequestConvertersTests.java

@@ -61,6 +61,7 @@ import org.elasticsearch.client.ml.PutDatafeedRequest;
 import org.elasticsearch.client.ml.PutFilterRequest;
 import org.elasticsearch.client.ml.PutJobRequest;
 import org.elasticsearch.client.ml.RevertModelSnapshotRequest;
+import org.elasticsearch.client.ml.SetUpgradeModeRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequestTests;
 import org.elasticsearch.client.ml.StopDatafeedRequest;
@@ -818,6 +819,22 @@ public class MLRequestConvertersTests extends ESTestCase {
         assertEquals(sample, requestEntityToString(request));
     }
 
+    public void testSetUpgradeMode() {
+        SetUpgradeModeRequest setUpgradeModeRequest = new SetUpgradeModeRequest(true);
+
+        Request request = MLRequestConverters.setUpgradeMode(setUpgradeModeRequest);
+        assertThat(request.getEndpoint(), equalTo("/_ml/set_upgrade_mode"));
+        assertThat(request.getMethod(), equalTo(HttpPost.METHOD_NAME));
+        assertThat(request.getParameters().get(SetUpgradeModeRequest.ENABLED.getPreferredName()), equalTo(Boolean.toString(true)));
+        assertThat(request.getParameters().containsKey(SetUpgradeModeRequest.TIMEOUT.getPreferredName()), is(false));
+
+        setUpgradeModeRequest.setTimeout(TimeValue.timeValueHours(1));
+        setUpgradeModeRequest.setEnabled(false);
+        request = MLRequestConverters.setUpgradeMode(setUpgradeModeRequest);
+        assertThat(request.getParameters().get(SetUpgradeModeRequest.ENABLED.getPreferredName()), equalTo(Boolean.toString(false)));
+        assertThat(request.getParameters().get(SetUpgradeModeRequest.TIMEOUT.getPreferredName()), is("1h"));
+    }
+
     private static Job createValidJob(String jobId) {
         AnalysisConfig.Builder analysisConfig = AnalysisConfig.builder(Collections.singletonList(
                 Detector.builder().setFunction("count").build()));

client/rest-high-level/src/test/java/org/elasticsearch/client/MachineLearningIT.java

@@ -84,6 +84,7 @@ import org.elasticsearch.client.ml.PutJobRequest;
 import org.elasticsearch.client.ml.PutJobResponse;
 import org.elasticsearch.client.ml.RevertModelSnapshotRequest;
 import org.elasticsearch.client.ml.RevertModelSnapshotResponse;
+import org.elasticsearch.client.ml.SetUpgradeModeRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequest;
 import org.elasticsearch.client.ml.StartDatafeedResponse;
 import org.elasticsearch.client.ml.StopDatafeedRequest;
@@ -1614,4 +1615,30 @@ public class MachineLearningIT extends ESRestHighLevelClientTestCase {
         assertEquals("timestamp", structure.getTimestampField());
         assertFalse(structure.needClientTimezone());
     }
+
+    public void testEnableUpgradeMode() throws Exception {
+        MachineLearningClient machineLearningClient = highLevelClient().machineLearning();
+
+        MlInfoResponse mlInfoResponse = machineLearningClient.getMlInfo(new MlInfoRequest(), RequestOptions.DEFAULT);
+        assertThat(mlInfoResponse.getInfo().get("upgrade_mode"), equalTo(false));
+
+        AcknowledgedResponse setUpgrademodeResponse = execute(new SetUpgradeModeRequest(true),
+            machineLearningClient::setUpgradeMode,
+            machineLearningClient::setUpgradeModeAsync);
+
+        assertThat(setUpgrademodeResponse.isAcknowledged(), is(true));
+
+
+        mlInfoResponse = machineLearningClient.getMlInfo(new MlInfoRequest(), RequestOptions.DEFAULT);
+        assertThat(mlInfoResponse.getInfo().get("upgrade_mode"), equalTo(true));
+
+        setUpgrademodeResponse = execute(new SetUpgradeModeRequest(false),
+            machineLearningClient::setUpgradeMode,
+            machineLearningClient::setUpgradeModeAsync);
+
+        assertThat(setUpgrademodeResponse.isAcknowledged(), is(true));
+
+        mlInfoResponse = machineLearningClient.getMlInfo(new MlInfoRequest(), RequestOptions.DEFAULT);
+        assertThat(mlInfoResponse.getInfo().get("upgrade_mode"), equalTo(false));
+    }
 }

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/MlClientDocumentationIT.java

@@ -99,6 +99,7 @@ import org.elasticsearch.client.ml.PutJobRequest;
 import org.elasticsearch.client.ml.PutJobResponse;
 import org.elasticsearch.client.ml.RevertModelSnapshotRequest;
 import org.elasticsearch.client.ml.RevertModelSnapshotResponse;
+import org.elasticsearch.client.ml.SetUpgradeModeRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequest;
 import org.elasticsearch.client.ml.StartDatafeedResponse;
 import org.elasticsearch.client.ml.StopDatafeedRequest;
@@ -3078,6 +3079,57 @@ public class MlClientDocumentationIT extends ESRestHighLevelClientTestCase {
         }
     }
 
+    public void testSetUpgradeMode() throws Exception {
+        RestHighLevelClient client = highLevelClient();
+        {
+            // tag::set-upgrade-mode-request
+            SetUpgradeModeRequest request = new SetUpgradeModeRequest(true); // <1>
+            request.setTimeout(TimeValue.timeValueMinutes(10)); // <2>
+            // end::set-upgrade-mode-request
+
+            // Set to false so that the cluster setting does not have to be unset at the end of the test.
+            request.setEnabled(false);
+
+            // tag::set-upgrade-mode-execute
+            AcknowledgedResponse acknowledgedResponse = client.machineLearning().setUpgradeMode(request, RequestOptions.DEFAULT);
+            // end::set-upgrade-mode-execute
+
+            // tag::set-upgrade-mode-response
+            boolean acknowledged = acknowledgedResponse.isAcknowledged(); // <1>
+            // end::set-upgrade-mode-response
+            assertThat(acknowledged, is(true));
+        }
+        {
+            SetUpgradeModeRequest request = new SetUpgradeModeRequest(false);
+
+            // tag::set-upgrade-mode-execute-listener
+            ActionListener<AcknowledgedResponse> listener = new ActionListener<AcknowledgedResponse>() {
+                @Override
+                public void onResponse(AcknowledgedResponse acknowledgedResponse) {
+                    // <1>
+                }
+
+                @Override
+                public void onFailure(Exception e) {
+                    // <2>
+                }
+            };
+            // end::set-upgrade-mode-execute-listener
+
+            // Replace the empty listener by a blocking listener in test
+            final CountDownLatch latch = new CountDownLatch(1);
+            listener = new LatchedActionListener<>(listener, latch);
+
+            // tag::set-upgrade-mode-execute-async
+            client.machineLearning()
+                .setUpgradeModeAsync(request, RequestOptions.DEFAULT, listener); // <1>
+            // end::set-upgrade-mode-execute-async
+
+            assertTrue(latch.await(30L, TimeUnit.SECONDS));
+
+        }
+    }
+
     private String createFilter(RestHighLevelClient client) throws IOException {
         MlFilter.Builder filterBuilder = MlFilter.builder("my_safe_domains")
             .setDescription("A list of safe domains")

docs/java-rest/high-level/ml/set-upgrade-mode.asciidoc

@@ -0,0 +1,40 @@
+--
+:api: set-upgrade-mode
+:request: SetUpgradeModeRequest
+:response: AcknowledgedResponse
+--
+[id="{upid}-{api}"]
+=== Set Upgrade Mode API
+
+The Set Upgrade Mode API temporarily halts all {ml} job and {dfeed} tasks when `enabled=true`. Their
+reported states remain unchanged. Consequently, when exiting upgrade mode the halted {ml} jobs and
+{dfeeds} will return to their previous state.
+
+It accepts a +{request}+ object and responds with a +{response}+ object.
+
+When `enabled=true`, no new jobs can be opened, and no job or {dfeed} tasks will
+be running. Be sure to set `enabled=false` once upgrade actions are completed.
+
+[id="{upid}-{api}-request"]
+==== Set Upgrade Mode Request
+
+A +{request}+ object gets created setting the desired `enabled` state.
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests-file}[{api}-request]
+--------------------------------------------------
+<1> Constructing a new request referencing enabling upgrade mode
+<2> Optionally setting the `timeout` value for how long the
+execution should wait.
+
+[id="{upid}-{api}-response"]
+==== Set Upgrade Mode Response
+
+["source","java",subs="attributes,callouts,macros"]
+--------------------------------------------------
+include-tagged::{doc-tests-file}[{api}-response]
+--------------------------------------------------
+<1> `isAcknowledged()` from the +{response}+ indicates if the setting was set successfully.
+
+include::../execution.asciidoc[]

docs/java-rest/high-level/supported-apis.asciidoc

@@ -295,6 +295,7 @@ The Java High Level REST Client supports the following Machine Learning APIs:
 * <<{upid}-update-model-snapshot>>
 * <<{upid}-get-ml-info>>
 * <<{upid}-delete-expired-data>>
+* <<{upid}-set-upgrade-mode>>
 
 include::ml/put-job.asciidoc[]
 include::ml/get-job.asciidoc[]
@@ -338,6 +339,7 @@ include::ml/revert-model-snapshot.asciidoc[]
 include::ml/update-model-snapshot.asciidoc[]
 include::ml/get-info.asciidoc[]
 include::ml/delete-expired-data.asciidoc[]
+include::ml/set-upgrade-mode.asciidoc[]
 
 == Migration APIs
 

docs/reference/ml/apis/ml-api.asciidoc

@@ -72,7 +72,7 @@ machine learning APIs and in advanced job configuration options in Kibana.
 
 [float]
 [[ml-api-file-structure-endpoint]]
-=== File Structure
+=== File structure
 
 * <<ml-find-file-structure,Find file structure>>
 
@@ -84,10 +84,16 @@ machine learning APIs and in advanced job configuration options in Kibana.
 
 [float]
 [[ml-api-delete-expired-data-endpoint]]
-=== Delete Expired Data
+=== Delete expired data
 
 * <<ml-delete-expired-data,Delete expired data>>
 
+[float]
+[[ml-set-upgrade-mode-endpoint]]
+=== Set upgrade mode
+
+* <<ml-set-upgrade-mode, Set upgrade mode>>
+
 //ADD
 include::post-calendar-event.asciidoc[]
 include::put-calendar-job.asciidoc[]
@@ -137,7 +143,8 @@ include::post-data.asciidoc[]
 include::preview-datafeed.asciidoc[]
 //REVERT
 include::revert-snapshot.asciidoc[]
-//START/STOP
+//SET/START/STOP
+include::set-upgrade-mode.asciidoc[]
 include::start-datafeed.asciidoc[]
 include::stop-datafeed.asciidoc[]
 //UPDATE

docs/reference/ml/apis/set-upgrade-mode.asciidoc

@@ -0,0 +1,103 @@
+[role="xpack"]
+[testenv="platinum"]
+[[ml-set-upgrade-mode]]
+=== Set upgrade mode API
+++++
+<titleabbrev>Set upgrade mode</titleabbrev>
+++++
+
+Sets a cluster wide upgrade_mode setting that prepares {ml} indices for an
+upgrade. 
+
+==== Request
+//////////////////////////
+
+[source,js]
+--------------------------------------------------
+POST /_ml/set_upgrade_mode?enabled=false&timeout=10m
+--------------------------------------------------
+// CONSOLE
+// TEST
+// TEARDOWN
+
+//////////////////////////
+
+
+`POST _ml/set_upgrade_mode`
+
+==== Description
+
+When upgrading your cluster, in some circumstances you must restart your nodes and
+reindex your {ml} indices. In those circumstances, there must be no {ml} jobs running. 
+You can close the {ml} jobs, do the upgrade, then open all the jobs again. 
+Alternatively, you can use this API to temporarily halt tasks associated 
+with the jobs and {dfeeds} and prevent new jobs from opening. You can also use this 
+API during upgrades that do not require you to reindex your {ml} indices, 
+though stopping jobs is not a requirement in that case.
+
+For more information, see {stack-ref}/upgrading-elastic-stack.html[Upgrading the {stack}].
+
+
+When `enabled=true` this API temporarily halts all job and {dfeed} tasks and
+prohibits new job and {dfeed} tasks from starting.
+
+Subsequently, you can call the API with the enabled parameter set to false,
+which causes {ml} jobs and {dfeeds} to return to their desired states.
+
+You can see the current value for the `upgrade_mode` setting by using the
+<<get-ml-info,get {ml} info API>>.
+
+IMPORTANT:  No new {ml} jobs can be opened while the `upgrade_mode` setting is
+`true`.
+
+==== Query Parameters
+
+`enabled`::
+  (boolean) When `true`, this enables `upgrade_mode`. Defaults to `false`
+
+`timeout`::
+  (time) The time to wait for the request to be completed.
+  The default value is 30 seconds.
+
+==== Authorization
+
+You must have `manage_ml`, or `manage` cluster privileges to use this API.
+For more information, see
+{stack-ov}/security-privileges.html[Security privileges].
+
+
+==== Examples
+
+The following example enables `upgrade_mode` for the cluster:
+
+[source,js]
+--------------------------------------------------
+POST _ml/set_upgrade_mode?enabled=true&timeout=10m
+--------------------------------------------------
+// CONSOLE
+// TEST
+
+When the call is successful, an acknowledged response is returned. For example:
+
+[source,js]
+----
+{
+  "acknowledged": true
+}
+----
+// TESTRESPONSE
+
+The acknowledged response will only be returned once all {ml} jobs and {dfeeds} have
+finished writing to the {ml} internal indices. This means it is safe to reindex those
+internal indices without causing failures. You must wait for the acknowledged
+response before reindexing to ensure that all writes are completed.
+
+When the upgrade is complete, you must set `upgrade_mode` to `false` for
+{ml} jobs to start running again. For example:
+
+[source,js]
+--------------------------------------------------
+POST _ml/set_upgrade_mode?enabled=false&timeout=10m
+--------------------------------------------------
+// CONSOLE
+// TEST

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlMetadata.java

@@ -137,7 +137,7 @@ public class MlMetadata implements XPackPlugin.XPackMetaDataCustom {
         }
         this.datafeeds = datafeeds;
         this.groupOrJobLookup = new GroupOrJobLookup(jobs.values());
-        if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (in.getVersion().onOrAfter(Version.V_6_7_0)) {
             this.upgradeMode = in.readBoolean();
         } else {
             this.upgradeMode = false;
@@ -148,7 +148,7 @@ public class MlMetadata implements XPackPlugin.XPackMetaDataCustom {
     public void writeTo(StreamOutput out) throws IOException {
         writeMap(jobs, out);
         writeMap(datafeeds, out);
-        if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_6_7_0)) {
             out.writeBoolean(upgradeMode);
         }
     }
@@ -201,7 +201,7 @@ public class MlMetadata implements XPackPlugin.XPackMetaDataCustom {
                     MlMetadataDiff::readJobDiffFrom);
             this.datafeeds = DiffableUtils.readJdkMapDiff(in, DiffableUtils.getStringKeySerializer(), DatafeedConfig::new,
                     MlMetadataDiff::readDatafeedDiffFrom);
-            if (in.getVersion().onOrAfter(Version.V_7_0_0)) {
+            if (in.getVersion().onOrAfter(Version.V_6_7_0)) {
                 upgradeMode = in.readBoolean();
             } else {
                 upgradeMode = false;
@@ -224,7 +224,7 @@ public class MlMetadata implements XPackPlugin.XPackMetaDataCustom {
         public void writeTo(StreamOutput out) throws IOException {
             jobs.writeTo(out);
             datafeeds.writeTo(out);
-            if (out.getVersion().onOrAfter(Version.V_7_0_0)) {
+            if (out.getVersion().onOrAfter(Version.V_6_7_0)) {
                 out.writeBoolean(upgradeMode);
             }
         }

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/action/TransportSetUpgradeModeAction.java

@@ -164,6 +164,13 @@ public class TransportSetUpgradeModeAction extends TransportMasterNodeAction<Set
                     wrappedListener.onFailure(new ElasticsearchTimeoutException("Unknown error occurred while updating cluster state"));
                     return;
                 }
+
+                // There are no tasks to worry about starting/stopping
+                if (tasksCustomMetaData == null || tasksCustomMetaData.tasks().isEmpty()) {
+                    wrappedListener.onResponse(new AcknowledgedResponse(true));
+                    return;
+                }
+
                 // Did we change from disabled -> enabled?
                 if (request.isEnabled()) {
                     isolateDatafeeds(tasksCustomMetaData, isolateDatafeedListener);

x-pack/plugin/src/test/resources/rest-api-spec/api/ml.set_upgrade_mode.json

@@ -1,6 +1,6 @@
 {
   "ml.set_upgrade_mode": {
-    "documentation": "TODO",
+    "documentation": "http://www.elastic.co/guide/en/elasticsearch/reference/current/ml-set-upgrade-mode.html",
     "methods": [ "POST" ],
     "url": {
       "path": "/_ml/set_upgrade_mode",