Add deprecation check for ILM poll interval <1s (#41096)

ILM poll intervals of less than 1 second will not be allowed, so add a
deprecation check for that.

Even though I'm pretty sure zero production clusters will do this, it's
best to be thorough.

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/ClusterDeprecationChecks.java

@@ -10,6 +10,8 @@ import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.metadata.MappingMetaData;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.ingest.IngestService;
 import org.elasticsearch.ingest.PipelineConfiguration;
@@ -23,6 +25,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
 
 import static org.elasticsearch.search.SearchModule.INDICES_MAX_CLAUSE_COUNT_SETTING;
+import static org.elasticsearch.xpack.core.indexlifecycle.LifecycleSettings.LIFECYCLE_POLL_INTERVAL_SETTING;
 
 public class ClusterDeprecationChecks {
     private static final Logger logger = LogManager.getLogger(ClusterDeprecationChecks.class);
@@ -88,4 +91,29 @@ public class ClusterDeprecationChecks {
         }
         return null;
     }
+
+    static DeprecationIssue checkPollIntervalTooLow(ClusterState state) {
+        String pollIntervalString = state.metaData().settings().get(LIFECYCLE_POLL_INTERVAL_SETTING.getKey());
+        if (Strings.isNullOrEmpty(pollIntervalString)) {
+            return null;
+        }
+
+        TimeValue pollInterval;
+        try {
+            pollInterval = TimeValue.parseTimeValue(pollIntervalString, LIFECYCLE_POLL_INTERVAL_SETTING.getKey());
+        } catch (IllegalArgumentException e) {
+            logger.error("Failed to parse [{}] value: [{}]", LIFECYCLE_POLL_INTERVAL_SETTING.getKey(), pollIntervalString);
+            return null;
+        }
+
+        if (pollInterval.compareTo(TimeValue.timeValueSeconds(1)) < 0) {
+            return new DeprecationIssue(DeprecationIssue.Level.CRITICAL,
+                "Index Lifecycle Management poll interval is set too low",
+                "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-8.0.html" +
+                    "#ilm-poll-interval-limit",
+                "The Index Lifecycle Management poll interval setting [" + LIFECYCLE_POLL_INTERVAL_SETTING.getKey() + "] is " +
+                    "currently set to [" + pollIntervalString + "], but must be 1s or greater");
+        }
+        return null;
+    }
 }

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationChecks.java

@@ -34,7 +34,8 @@ public class DeprecationChecks {
     static List<Function<ClusterState, DeprecationIssue>> CLUSTER_SETTINGS_CHECKS =
         Collections.unmodifiableList(Arrays.asList(
             ClusterDeprecationChecks::checkUserAgentPipelines,
-            ClusterDeprecationChecks::checkTemplatesWithTooManyFields
+            ClusterDeprecationChecks::checkTemplatesWithTooManyFields,
+            ClusterDeprecationChecks::checkPollIntervalTooLow
         ));
 
 

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/ClusterDeprecationChecksTests.java

@@ -19,6 +19,7 @@ import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.ingest.IngestService;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.xpack.core.deprecation.DeprecationIssue;
+import org.hamcrest.Matchers;
 
 import java.io.IOException;
 import java.util.Collections;
@@ -26,6 +27,7 @@ import java.util.List;
 
 import static java.util.Collections.singletonList;
 import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
+import static org.elasticsearch.xpack.core.indexlifecycle.LifecycleSettings.LIFECYCLE_POLL_INTERVAL_SETTING;
 import static org.elasticsearch.xpack.deprecation.DeprecationChecks.CLUSTER_SETTINGS_CHECKS;
 import static org.elasticsearch.xpack.deprecation.IndexDeprecationChecksTests.addRandomFields;
 
@@ -155,4 +157,42 @@ public class ClusterDeprecationChecksTests extends ESTestCase {
                 "to fail if fields are not explicitly specified in the query.");
         assertEquals(singletonList(expected), issues);
     }
+
+    public void testPollIntervalTooLow() {
+        {
+            final String tooLowInterval = randomTimeValue(1, 999, "ms", "micros", "nanos");
+            MetaData badMetaDtata = MetaData.builder()
+                .persistentSettings(Settings.builder()
+                    .put(LIFECYCLE_POLL_INTERVAL_SETTING.getKey(), tooLowInterval)
+                    .build())
+                .build();
+            ClusterState badState = ClusterState.builder(new ClusterName("test"))
+                .metaData(badMetaDtata)
+                .build();
+
+            DeprecationIssue expected = new DeprecationIssue(DeprecationIssue.Level.CRITICAL,
+                "Index Lifecycle Management poll interval is set too low",
+                "https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking-changes-8.0.html" +
+                    "#ilm-poll-interval-limit",
+                "The Index Lifecycle Management poll interval setting [" + LIFECYCLE_POLL_INTERVAL_SETTING.getKey() + "] is " +
+                    "currently set to [" + tooLowInterval + "], but must be 1s or greater");
+            List<DeprecationIssue> issues = DeprecationChecks.filterChecks(CLUSTER_SETTINGS_CHECKS, c -> c.apply(badState));
+            assertEquals(singletonList(expected), issues);
+        }
+
+        // Test that other values are ok
+        {
+            final String okInterval = randomTimeValue(1, 9999, "d", "h", "s");
+            MetaData okMetaData = MetaData.builder()
+                .persistentSettings(Settings.builder()
+                    .put(LIFECYCLE_POLL_INTERVAL_SETTING.getKey(), okInterval)
+                    .build())
+                .build();
+            ClusterState okState = ClusterState.builder(new ClusterName("test"))
+                .metaData(okMetaData)
+                .build();
+            List<DeprecationIssue> noIssues = DeprecationChecks.filterChecks(CLUSTER_SETTINGS_CHECKS, c -> c.apply(okState));
+            assertThat(noIssues, Matchers.hasSize(0));
+        }
+    }
 }