[7.x][ML] Add ILM policy to ml stats indices (#53349) (#53392)

Adds a size based ILM policy to automatically
rollover ml stats indices.

Backport of #53349

x-pack/plugin/core/src/main/resources/org/elasticsearch/xpack/core/ml/stats_index_template.json

@@ -10,6 +10,8 @@
       "auto_expand_replicas" : "0-1",
       "hidden": true
     }
+    ${xpack.ml.index.lifecycle.settings}
   },
-  "mappings" : ${xpack.ml.stats.mappings}
+  "mappings" : ${xpack.ml.stats.mappings},
+  "aliases" : {}
 }

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

@@ -56,11 +56,12 @@ public class MlIndexTemplateRegistry extends IndexTemplateRegistry {
         ROOT_RESOURCE_PATH + "inference_index_template.json", Version.CURRENT.id, VERSION_PATTERN,
         Collections.singletonMap(VERSION_ID_PATTERN, String.valueOf(Version.CURRENT.id)));
 
-    private static final IndexTemplateConfig STATS_TEMPLATE = statsTemplate();
+    private static final IndexTemplateConfig STATS_TEMPLATE = statsTemplate(true);
+    private static final IndexTemplateConfig STATS_TEMPLATE_NO_ILM = statsTemplate(false);
 
-    private static final String ML_STATE_ILM_POLICY_NAME = "ml-state-ilm-policy";
+    private static final String ML_SIZE_BASED_ILM_POLICY_NAME = "ml-size-based-ilm-policy";
-    private static final LifecyclePolicyConfig ML_STATE_ILM_POLICY =
+    private static final LifecyclePolicyConfig ML_SIZE_BASED_ILM_POLICY =
-        new LifecyclePolicyConfig(ML_STATE_ILM_POLICY_NAME, ANOMALY_DETECTION_PATH + "state_index_ilm_policy.json");
+        new LifecyclePolicyConfig(ML_SIZE_BASED_ILM_POLICY_NAME, ROOT_RESOURCE_PATH + "size_based_ilm_policy.json");
 
     private static IndexTemplateConfig configTemplate() {
         Map<String, String> variables = new HashMap<>();
@@ -81,7 +82,7 @@ public class MlIndexTemplateRegistry extends IndexTemplateRegistry {
         variables.put(
             "xpack.ml.index.lifecycle.settings",
             ilmEnabled
-                ? ",\"index.lifecycle.name\": \"" + ML_STATE_ILM_POLICY_NAME + "\"\n" +
+                ? ",\"index.lifecycle.name\": \"" + ML_SIZE_BASED_ILM_POLICY_NAME + "\"\n" +
                   ",\"index.lifecycle.rollover_alias\": \"" + AnomalyDetectorsIndex.jobStateIndexWriteAlias() + "\"\n"
                 : "");
 
@@ -102,10 +103,16 @@ public class MlIndexTemplateRegistry extends IndexTemplateRegistry {
             variables);
     }
 
-    private static IndexTemplateConfig statsTemplate() {
+    private static IndexTemplateConfig statsTemplate(boolean ilmEnabled) {
         Map<String, String> variables = new HashMap<>();
         variables.put(VERSION_ID_PATTERN, String.valueOf(Version.CURRENT.id));
         variables.put("xpack.ml.stats.mappings", MlStatsIndex.mapping());
+        variables.put(
+            "xpack.ml.index.lifecycle.settings",
+            ilmEnabled
+                ? ",\"index.lifecycle.name\": \"" + ML_SIZE_BASED_ILM_POLICY_NAME + "\"\n" +
+                ",\"index.lifecycle.rollover_alias\": \"" + MlStatsIndex.writeAlias() + "\"\n"
+                : "");
 
         return new IndexTemplateConfig(MlStatsIndex.TEMPLATE_NAME,
             ROOT_RESOURCE_PATH + "stats_index_template.json",
@@ -126,7 +133,7 @@ public class MlIndexTemplateRegistry extends IndexTemplateRegistry {
             INFERENCE_TEMPLATE,
             META_TEMPLATE,
             NOTIFICATIONS_TEMPLATE,
-            STATS_TEMPLATE);
+            ilmEnabled ? STATS_TEMPLATE : STATS_TEMPLATE_NO_ILM);
     }
 
     @Override
@@ -141,7 +148,7 @@ public class MlIndexTemplateRegistry extends IndexTemplateRegistry {
 
     @Override
     protected List<LifecyclePolicyConfig> getPolicyConfigs() {
-        return Collections.singletonList(ML_STATE_ILM_POLICY);
+        return Collections.singletonList(ML_SIZE_BASED_ILM_POLICY);
     }
 
     @Override

x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/MlIndexTemplateRegistryTests.java

@@ -29,6 +29,7 @@ import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.xpack.core.XPackSettings;
 import org.elasticsearch.xpack.core.ilm.LifecycleAction;
 import org.elasticsearch.xpack.core.ilm.RolloverAction;
+import org.elasticsearch.xpack.core.ml.MlStatsIndex;
 import org.elasticsearch.xpack.core.ml.job.persistence.AnomalyDetectorsIndexFields;
 import org.junit.Before;
 import org.mockito.ArgumentCaptor;
@@ -98,7 +99,7 @@ public class MlIndexTemplateRegistryTests extends ESTestCase {
             .filter(r -> r.name().equals(AnomalyDetectorsIndexFields.STATE_INDEX_PREFIX))
             .findFirst()
             .orElseThrow(() -> new AssertionError("expected the ml state index template to be put"));
-        assertThat(req.settings().get("index.lifecycle.name"), equalTo("ml-state-ilm-policy"));
+        assertThat(req.settings().get("index.lifecycle.name"), equalTo("ml-size-based-ilm-policy"));
         assertThat(req.settings().get("index.lifecycle.rollover_alias"), equalTo(".ml-state-write"));
     }
 
@@ -122,6 +123,46 @@ public class MlIndexTemplateRegistryTests extends ESTestCase {
         assertThat(req.settings().get("index.lifecycle.rollover_alias"), is(nullValue()));
     }
 
+    public void testStatsTemplateWithIlm() {
+        MlIndexTemplateRegistry registry =
+            new MlIndexTemplateRegistry(
+                Settings.builder()
+                    .put(XPackSettings.INDEX_LIFECYCLE_ENABLED.getKey(), true)
+                    .build(),
+                clusterService, threadPool, client, xContentRegistry);
+
+        registry.clusterChanged(createClusterChangedEvent(nodes));
+
+        verify(client.admin().indices(), times(7)).putTemplate(putIndexTemplateRequestCaptor.capture(), anyObject());
+
+        PutIndexTemplateRequest req = putIndexTemplateRequestCaptor.getAllValues().stream()
+            .filter(r -> r.name().equals(MlStatsIndex.TEMPLATE_NAME))
+            .findFirst()
+            .orElseThrow(() -> new AssertionError("expected the ml stats index template to be put"));
+        assertThat(req.settings().get("index.lifecycle.name"), equalTo("ml-size-based-ilm-policy"));
+        assertThat(req.settings().get("index.lifecycle.rollover_alias"), equalTo(".ml-stats-write"));
+    }
+
+    public void testStatsTemplateWithNoIlm() {
+        MlIndexTemplateRegistry registry =
+            new MlIndexTemplateRegistry(
+                Settings.builder()
+                    .put(XPackSettings.INDEX_LIFECYCLE_ENABLED.getKey(), false)
+                    .build(),
+                clusterService, threadPool, client, xContentRegistry);
+
+        registry.clusterChanged(createClusterChangedEvent(nodes));
+
+        verify(client.admin().indices(), times(7)).putTemplate(putIndexTemplateRequestCaptor.capture(), anyObject());
+
+        PutIndexTemplateRequest req = putIndexTemplateRequestCaptor.getAllValues().stream()
+            .filter(r -> r.name().equals(MlStatsIndex.TEMPLATE_NAME))
+            .findFirst()
+            .orElseThrow(() -> new AssertionError("expected the ml stats index template to be put"));
+        assertThat(req.settings().get("index.lifecycle.name"), is(nullValue()));
+        assertThat(req.settings().get("index.lifecycle.rollover_alias"), is(nullValue()));
+    }
+
     @SuppressWarnings("unchecked")
     private static <Response> Answer<Response> withResponse(Response response) {
         return invocationOnMock -> {