* Clarified documentation regarding results_index_rollover_max_size

* Added the ability to set results_index_rollover_max_size to -1B to configure the nightly maintenance task not to trigger indices rollover

Author: edsavage

docs/reference/elasticsearch/configuration-reference/machine-learning-settings.md

@@ -87,7 +87,7 @@ $$$xpack.ml.max_open_jobs$$$
 :   ([Dynamic](docs-content://deploy-manage/stack-settings.md#dynamic-cluster-setting)) The rate at which the nightly maintenance task deletes expired model snapshots and results. The setting is a proxy to the [`requests_per_second`](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-delete-by-query) parameter used in the delete by query requests and controls throttling. When the {{operator-feature}} is enabled, this setting can be updated only by operator users. Valid values must be greater than `0.0` or equal to `-1.0`, where `-1.0` means a default value is used. Defaults to `-1.0`
 
 `xpack.ml.results_index_rollover_max_size`
-:   ([Dynamic](docs-content://deploy-manage/stack-settings.md#dynamic-cluster-setting)) The maximum size the anomaly detection results indices can reach before being rolled over by the nightly maintenance task. When the {{operator-feature}} is enabled, this setting can be updated only by operator users. Valid values must be greater than or equal to `0B`. A value of `0B` means the indices will always be rolled over. Defaults to `50GB`.
+:   ([Dynamic](docs-content://deploy-manage/stack-settings.md#dynamic-cluster-setting)) The maximum size the anomaly detection results indices can reach before being rolled over by the nightly maintenance task. When the {{operator-feature}} is enabled, this setting can be updated only by operator users. Valid values must be greater than or equal to `-1B`. A value of `-1B` means the indices will never be rolled over. A value of `0B` means the indices will always be rolled over, regardless of size. Defaults to `50GB`.
 
 `xpack.ml.node_concurrent_job_allocations`
 :   ([Dynamic](docs-content://deploy-manage/stack-settings.md#dynamic-cluster-setting)) The maximum number of jobs that can concurrently be in the `opening` state on each node. Typically, jobs spend a small amount of time in this state before they move to `open` state. Jobs that must restore large models when they are opening spend more time in the `opening` state. When the {{operator-feature}} is enabled, this setting can be updated only by operator users. Defaults to `2`.

x-pack/plugin/ml/src/internalClusterTest/java/org/elasticsearch/xpack/ml/integration/MlDailyMaintenanceServiceRolloverResultsIndicesIT.java

@@ -102,6 +102,24 @@ public void testTriggerRollResultsIndicesIfNecessaryTask_givenNoIndices() throws
         }
     }
 
+    public void testTriggerRollResultsIndicesIfNecessaryTask_givenMinusOnRolloverMaxSize() throws Exception {
+        // The null case, nothing to do.
+
+        // set the rollover max size to -1B so the indices should not be rolled over
+        maintenanceService.setRolloverMaxSize(ByteSizeValue.MINUS_ONE);
+
+        // Create jobs that will use the default results indices - ".ml-anomalies-shared-*"
+        Job.Builder[] jobs_with_default_index = { createJob("job_using_default_index"), createJob("another_job_using_default_index") };
+
+        // Create jobs that will use custom results indices - ".ml-anomalies-custom-fred-*"
+        Job.Builder[] jobs_with_custom_index = {
+            createJob("job_using_custom_index").setResultsIndexName("fred"),
+            createJob("another_job_using_custom_index").setResultsIndexName("fred") };
+
+        runTestScenarioWithNoRolloverOccurring(jobs_with_default_index, "shared");
+        runTestScenarioWithNoRolloverOccurring(jobs_with_custom_index, "custom-fred");
+    }
+
     public void testTriggerRollResultsIndicesIfNecessaryTask_givenUnmetConditions() throws Exception {
         // Create jobs that will use the default results indices - ".ml-anomalies-shared-*"
         Job.Builder[] jobs_with_default_index = { createJob("job_using_default_index"), createJob("another_job_using_default_index") };
@@ -111,8 +129,8 @@ public void testTriggerRollResultsIndicesIfNecessaryTask_givenUnmetConditions()
             createJob("job_using_custom_index").setResultsIndexName("fred"),
             createJob("another_job_using_custom_index").setResultsIndexName("fred") };
 
-        runTestScenarioWithUnmetConditions(jobs_with_default_index, "shared");
-        runTestScenarioWithUnmetConditions(jobs_with_custom_index, "custom-fred");
+        runTestScenarioWithNoRolloverOccurring(jobs_with_default_index, "shared");
+        runTestScenarioWithNoRolloverOccurring(jobs_with_custom_index, "custom-fred");
     }
 
     public void testTriggerRollResultsIndicesIfNecessaryTask_withMixedIndexTypes() throws Exception {
@@ -207,7 +225,7 @@ public void testTriggerRollResultsIndicesIfNecessaryTask() throws Exception {
         runTestScenario(jobs_with_custom_index, "custom-fred");
     }
 
-    private void runTestScenarioWithUnmetConditions(Job.Builder[] jobs, String indexNamePart) throws Exception {
+    private void runTestScenarioWithNoRolloverOccurring(Job.Builder[] jobs, String indexNamePart) throws Exception {
         String firstJobId = jobs[0].getId();
         String secondJobId = jobs[1].getId();
         String indexWildcard = AnomalyDetectorsIndex.jobResultsIndexPrefix() + indexNamePart + "*";

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

@@ -722,7 +722,7 @@ public void loadExtensions(ExtensionLoader loader) {
     public static final Setting<ByteSizeValue> RESULTS_INDEX_ROLLOVER_MAX_SIZE = Setting.byteSizeSetting(
         "xpack.ml.results_index_rollover_max_size",
         ByteSizeValue.of(50, ByteSizeUnit.GB),
-        ByteSizeValue.ofBytes(0L),
+        ByteSizeValue.ofBytes(-1L),
         ByteSizeValue.ofBytes(Long.MAX_VALUE),
         Property.OperatorDynamic,
         Property.NodeScope

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

@@ -81,9 +81,10 @@
  */
 public class MlDailyMaintenanceService implements Releasable {
 
-    // The service to use for creating log messages.
     private static final Logger logger = LogManager.getLogger(MlDailyMaintenanceService.class);
 
+    // The maximum value of a random offset used to calculate the time the nightly maintenance tasks are triggered on a given cluster.
+    // This is added in order to avoid multiple clusters running the maintenance tasks at the same time.
     private static final int MAX_TIME_OFFSET_MINUTES = 120;
 
     private final ThreadPool threadPool;
@@ -419,7 +420,7 @@ public void triggerRollResultsIndicesIfNecessaryTask(ActionListener<Acknowledged
         ClusterState clusterState = clusterService.state();
 
         String[] indices = findIndicesNeedingRollover(clusterState);
-        if (indices.length == 0) {
+        if (rolloverMaxSize == ByteSizeValue.MINUS_ONE || indices.length == 0) {
             // Early bath
             finalListener.onResponse(AcknowledgedResponse.TRUE);
             return;