Adding java docs

Signed-off-by: Bharathwaj G <bharath78910@gmail.com>

server/src/internalClusterTest/java/org/opensearch/search/searchafter/SearchAfterIT.java

@@ -209,6 +209,7 @@ public void testPitWithSearchAfter() throws Exception {
         assertEquals(3, sr.getHits().getHits().length);
         sr = client().prepareSearch().addSort("field1", SortOrder.ASC).setQuery(matchAllQuery()).searchAfter(new Object[] { 0 }).get();
         assertEquals(4, sr.getHits().getHits().length);
+        client().admin().indices().prepareDelete("test").get();
     }
 
     public void testWithNullStrings() throws InterruptedException {

server/src/internalClusterTest/java/org/opensearch/search/slice/SearchSliceIT.java

@@ -176,6 +176,7 @@ public void testSearchSortWithPIT() throws Exception {
                 .addSort(SortBuilders.fieldSort("random_int"));
             assertSearchSlicesWithPIT(request, field, max, numDocs);
         }
+        client().admin().indices().prepareDelete("test").get();
     }
 
     private void assertSearchSlicesWithPIT(SearchRequestBuilder request, String field, int numSlice, int numDocs) {

server/src/main/java/org/opensearch/action/search/CreatePITAction.java

@@ -10,6 +10,9 @@
 
 import org.opensearch.action.ActionType;
 
+/**
+ * Action type for creating PIT reader context
+ */
 public class CreatePITAction extends ActionType<CreatePITResponse> {
     public static final CreatePITAction INSTANCE = new CreatePITAction();
     public static final String NAME = "indices:data/write/pit";

server/src/main/java/org/opensearch/action/search/UpdatePitContextResponse.java

@@ -14,6 +14,9 @@
 
 import java.io.IOException;
 
+/**
+ * Update PIT context response with creation time, keep alive etc.
+ */
 public class UpdatePitContextResponse extends TransportResponse {
     private final String pitId;
 

server/src/main/java/org/opensearch/index/shard/SearchOperationListener.java

@@ -277,6 +277,10 @@ public void validateReaderContext(ReaderContext readerContext, TransportRequest
             ExceptionsHelper.reThrowIfNotNull(exception);
         }
 
+        /**
+         * Executed when a new Point-In-Time {@link ReaderContext} was created
+         * @param readerContext the created reader context
+         */
         @Override
         public void onNewPitContext(ReaderContext readerContext) {
             for (SearchOperationListener listener : listeners) {
@@ -288,6 +292,11 @@ public void onNewPitContext(ReaderContext readerContext) {
             }
         }
 
+        /**
+         * Executed when a Point-In-Time search {@link SearchContext} is freed.
+         * This happens on deletion of a Point-In-Time or on it's keep-alive is expiring.
+         * @param readerContext the freed search context
+         */
         @Override
         public void onFreePitContext(ReaderContext readerContext) {
             for (SearchOperationListener listener : listeners) {

server/src/main/java/org/opensearch/rest/action/search/RestCreatePITAction.java

@@ -24,6 +24,9 @@
 import static java.util.Collections.unmodifiableList;
 import static org.opensearch.rest.RestRequest.Method.POST;
 
+/**
+ * Rest action for creating PIT context
+ */
 public class RestCreatePITAction extends BaseRestHandler {
     @Override
     public String getName() {

server/src/main/java/org/opensearch/search/SearchService.java

@@ -170,6 +170,9 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
         Property.NodeScope,
         Property.Dynamic
     );
+    /**
+     * This setting will help validate the max keep alive that can be set during creation or extension for a PIT reader context
+     */
     public static final Setting<TimeValue> MAX_PIT_KEEPALIVE_SETTING = Setting.positiveTimeSetting(
         "pit.max_keep_alive",
         timeValueHours(24),
@@ -222,6 +225,10 @@ public class SearchService extends AbstractLifecycleComponent implements IndexEv
         Property.NodeScope
     );
 
+    /**
+     * This setting defines the maximum number of active PIT reader contexts in the node , since each PIT context
+     * has a resource cost attached to it
+     */
     public static final Setting<Integer> MAX_OPEN_PIT_CONTEXT = Setting.intSetting(
         "search.max_open_pit_context",
         500,

server/src/main/java/org/opensearch/search/internal/ReaderContext.java

@@ -138,6 +138,9 @@ public Engine.Searcher acquireSearcher(String source) {
         return searcherSupplier.acquireSearcher(source);
     }
 
+    /**
+     * Update keep alive if it is greater than current keep alive
+     */
     public void tryUpdateKeepAlive(long keepAlive) {
         this.keepAlive.updateAndGet(curr -> Math.max(curr, keepAlive));
     }

server/src/test/java/org/opensearch/action/search/CreatePitControllerTests.java

@@ -50,6 +50,10 @@
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
+/**
+ * Functional tests for various methods in create pit controller. Covers update pit phase specifically since
+ * integration tests don't cover it.
+ */
 public class CreatePitControllerTests extends OpenSearchTestCase {
 
     DiscoveryNode node1 = null;

server/src/test/java/org/opensearch/search/PitMultiNodeTests.java

@@ -27,6 +27,9 @@
 import static org.opensearch.action.support.WriteRequest.RefreshPolicy.IMMEDIATE;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
 
+/**
+ * Multi node integration tests for PIT creation and search operation with PIT ID.
+ */
 @OpenSearchIntegTestCase.ClusterScope(scope = OpenSearchIntegTestCase.Scope.SUITE, numDataNodes = 2)
 public class PitMultiNodeTests extends OpenSearchIntegTestCase {
 

server/src/test/java/org/opensearch/search/PitSingleNodeTests.java

@@ -31,6 +31,9 @@
 import static org.opensearch.index.query.QueryBuilders.termQuery;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertHitCount;
 
+/**
+ * Single node integration tests for various PIT use cases such as create pit, search etc
+ */
 public class PitSingleNodeTests extends OpenSearchSingleNodeTestCase {
     @Override
     protected boolean resetNodeAfterTest() {

server/src/test/java/org/opensearch/search/pit/RestCreatePitActionTests.java

@@ -25,6 +25,9 @@
 
 import static org.hamcrest.Matchers.equalTo;
 
+/**
+ * Tests to verify behavior of create pit rest action
+ */
 public class RestCreatePitActionTests extends OpenSearchTestCase {
     public void testRestCreatePit() throws Exception {
         SetOnce<Boolean> createPitCalled = new SetOnce<>();