Change default half-life to 5mins (also set reasonably upper and lower bounds)

Author: PeteGillinElastic

server/src/main/java/org/elasticsearch/index/shard/IndexingStatsSettings.java

@@ -14,16 +14,16 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.TimeValue;
 
-import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * Container for cluster settings related to {@link IndexingStats}.
  */
 public class IndexingStatsSettings {
 
-    // TODO: Change this default to something sensible:
-    static final TimeValue RECENT_WRITE_LOAD_HALF_LIFE_DEFAULT = new TimeValue(10000, TimeUnit.DAYS);
+    static final TimeValue RECENT_WRITE_LOAD_HALF_LIFE_DEFAULT = TimeValue.timeValueMinutes(5); // Aligns with the interval between DSL runs
+    static final TimeValue RECENT_WRITE_LOAD_HALF_LIFE_MIN = TimeValue.timeValueSeconds(1); // A sub-second half-life makes no sense
+    static final TimeValue RECENT_WRITE_LOAD_HALF_LIFE_MAX = TimeValue.timeValueDays(100_000); // Long.MAX_VALUE nanos, rounded down
 
     /**
      * A cluster setting giving the half-life, in seconds, to use for the Exponentially Weighted Moving Rate calculation used for the
@@ -34,7 +34,8 @@ public class IndexingStatsSettings {
     public static final Setting<TimeValue> RECENT_WRITE_LOAD_HALF_LIFE_SETTING = Setting.timeSetting(
         "indices.stats.recent_write_load.half_life",
         RECENT_WRITE_LOAD_HALF_LIFE_DEFAULT,
-        TimeValue.ZERO,
+        RECENT_WRITE_LOAD_HALF_LIFE_MIN,
+        RECENT_WRITE_LOAD_HALF_LIFE_MAX,
         Setting.Property.Dynamic,
         Setting.Property.NodeScope
     );

server/src/test/java/org/elasticsearch/index/shard/IndexingStatsSettingsTests.java

@@ -14,6 +14,9 @@
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.test.ESTestCase;
 
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
 import static org.hamcrest.Matchers.equalTo;
 
 public class IndexingStatsSettingsTests extends ESTestCase {
@@ -40,4 +43,60 @@ public void testRecentWriteLoadHalfLife_updateValue() {
         );
         assertThat(settings.getRecentWriteLoadHalfLifeForNewShards(), equalTo(TimeValue.timeValueMinutes(90)));
     }
+
+    public void testRecentWriteLoadHalfLife_minValue() {
+        IndexingStatsSettings settings = new IndexingStatsSettings(
+            ClusterSettings.createBuiltInClusterSettings(
+                Settings.builder()
+                    .put(
+                        IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_SETTING.getKey(),
+                        IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_MIN.toString()
+                    )
+                    .build()
+            )
+        );
+        assertThat(settings.getRecentWriteLoadHalfLifeForNewShards(), equalTo(IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_MIN));
+    }
+
+    public void testRecentWriteLoadHalfLife_valueTooSmall() {
+        long tooFewMillis = IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_MIN.getMillis() / 2;
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> new IndexingStatsSettings(
+                ClusterSettings.createBuiltInClusterSettings(
+                    Settings.builder().put(IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_SETTING.getKey(), tooFewMillis + "ms").build()
+                )
+            )
+        );
+    }
+
+    public void testRecentWriteLoadHalfLife_maxValue() {
+        IndexingStatsSettings settings = new IndexingStatsSettings(
+            ClusterSettings.createBuiltInClusterSettings(
+                Settings.builder()
+                    .put(
+                        IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_SETTING.getKey(),
+                        IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_MAX.toString()
+                    )
+                    .build()
+            )
+        );
+        assertThat(settings.getRecentWriteLoadHalfLifeForNewShards(), equalTo(IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_MAX));
+    }
+
+    public void testRecentWriteLoadHalfLife_valueTooLarge() {
+        int tooManyDays = BigDecimal.valueOf(Long.MAX_VALUE)
+            .add(BigDecimal.ONE)
+            .divide(BigDecimal.valueOf(24 * 60 * 60 * 1_000_000_000L), RoundingMode.UP)
+            .setScale(0, RoundingMode.UP)
+            .intValueExact();
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> new IndexingStatsSettings(
+                ClusterSettings.createBuiltInClusterSettings(
+                    Settings.builder().put(IndexingStatsSettings.RECENT_WRITE_LOAD_HALF_LIFE_SETTING.getKey(), tooManyDays + "d").build()
+                )
+            )
+        );
+    }
 }