add settings and validators

Signed-off-by: Kiran Prakash <awskiran@amazon.com>

Author: kiranprakash154

server/src/main/java/org/opensearch/indices/IndicesRequestCache.java

@@ -38,6 +38,7 @@
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.util.Accountable;
 import org.apache.lucene.util.RamUsageEstimator;
+import org.opensearch.OpenSearchParseException;
 import org.opensearch.common.CheckedSupplier;
 import org.opensearch.common.cache.CacheType;
 import org.opensearch.common.cache.ICache;
@@ -52,6 +53,7 @@
 import org.opensearch.common.settings.Setting;
 import org.opensearch.common.settings.Setting.Property;
 import org.opensearch.common.settings.Settings;
+import org.opensearch.common.unit.RatioValue;
 import org.opensearch.common.unit.TimeValue;
 import org.opensearch.common.util.concurrent.ConcurrentCollections;
 import org.opensearch.core.common.bytes.BytesReference;
@@ -123,6 +125,17 @@ public final class IndicesRequestCache extends AbstractLifecycleComponent
         new TimeValue(0),
         Property.NodeScope
     );
+    public static final Setting<TimeValue> INDICES_REQUEST_CACHE_CLEAN_INTERVAL_SETTING = Setting.positiveTimeSetting(
+        "indices.requests.cache.cleanup.interval",
+        TimeValue.timeValueMinutes(1),
+        Property.NodeScope
+    );
+    public static final Setting<String> INDICES_REQUEST_CACHE_STALENESS_THRESHOLD_SETTING = new Setting<>(
+        "indices.requests.cache.cleanup.staleness_threshold",
+        "0%",
+        IndicesRequestCache::validateStalenessSetting,
+        Property.NodeScope
+    );
 
     private final static long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(Key.class);
 
@@ -729,4 +742,26 @@ long count() {
     int numRegisteredCloseListeners() { // for testing
         return registeredClosedListeners.size();
     }
+
+    /**
+     * Validates the staleness setting for the cache cleanup threshold.
+     *
+     * <p>This method checks if the provided staleness threshold is a valid percentage or a valid double value.
+     * If the staleness threshold is not valid, it throws an OpenSearchParseException.
+     *
+     * @param staleThreshold The staleness threshold to validate.
+     * @return The validated staleness threshold.
+     * @throws OpenSearchParseException If the staleness threshold is not a valid percentage or double value.
+     *
+     * <p>package private for testing
+     */
+    static String validateStalenessSetting(String staleThreshold) {
+        try {
+            RatioValue.parseRatioValue(staleThreshold);
+        } catch (OpenSearchParseException e) {
+            e.addSuppressed(e);
+            throw e;
+        }
+        return staleThreshold;
+    }
 }