Backport of async search changes (#53976)

* Get Async Search: omit _clusters section when empty (#53907)

The _clusters section is omitted by the search API whenever no remote clusters are searched. Async search should do the same, but Get Async Search returns a deserialized response, hence a weird `_clusters` section with all values set to `0` gets returned instead. In fact the recreated Clusters object is not the same object as the EMPTY constant, yet it has the same content.

This commit addresses this by changing the comparison in the `toXContent` method to not print out the section if the number of total clusters is `0`.

* Async search: remove version from response (#53960)

The goal of the version field was to quickly show when you can expect to find something new in the search response, compared to when nothing has changed. This can also be done by looking at the `_shards` section and `num_reduce_phases` returned with the search response. In fact when there has been one or more additional reduction of the results, you can expect new results in the search response. Otherwise, the `_shards` section could notify of additional failures of shards that have completed the query, but that is not a guarantee that their results will be exposed (only when the following partial reduction is performed their results will be available).

That said this commit clarifies this in the docs and removes the version field from the async search response

* Async Search: replicas to auto expand from 0 to 1 (#53964)

This way single node clusters that are green don't go yellow once async search is used, while
all the others still have one replica.

* [DOCS] address timing issue in async search docs tests (#53910)

The docs snippets for submit async search have proven difficult to test as it is not possible to guarantee that you get a response that is not final, even when providing `wait_for_completion=0`. In the docs we want to show though a proper long-running query, and its first response should be partial rather than final.

With this commit we adapt the docs snippets to show a partial response, and replace under the hood all that's needed to make the snippets tests succeed when we get a final response. Also, increased the timeout so we always get a final response.

Closes #53887
Closes #53891

client/rest-high-level/src/main/java/org/elasticsearch/client/asyncsearch/AsyncSearchResponse.java

@@ -41,7 +41,6 @@
 public class AsyncSearchResponse implements ToXContentObject  {
     @Nullable
     private final String id;
-    private final int version;
     @Nullable
     private final SearchResponse searchResponse;
     @Nullable
@@ -55,15 +54,13 @@ public class AsyncSearchResponse implements ToXContentObject  {
     /**
      * Creates an {@link AsyncSearchResponse} with the arguments that are always present in the server response
      */
-    AsyncSearchResponse(int version,
-                               boolean isPartial,
-                               boolean isRunning,
-                               long startTimeMillis,
-                               long expirationTimeMillis,
-                               @Nullable String id,
-                               @Nullable SearchResponse searchResponse,
-                               @Nullable ElasticsearchException error) {
-        this.version = version;
+    AsyncSearchResponse(boolean isPartial,
+                        boolean isRunning,
+                        long startTimeMillis,
+                        long expirationTimeMillis,
+                        @Nullable String id,
+                        @Nullable SearchResponse searchResponse,
+                        @Nullable ElasticsearchException error) {
         this.isPartial = isPartial;
         this.isRunning = isRunning;
         this.startTimeMillis = startTimeMillis;
@@ -81,13 +78,6 @@ public String getId() {
         return id;
     }
 
-    /**
-     * Returns the version of this response.
-     */
-    public int getVersion() {
-        return version;
-    }
-
     /**
      * Returns the current {@link SearchResponse} or <code>null</code> if not available.
      *
@@ -145,7 +135,6 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         if (id != null) {
             builder.field("id", id);
         }
-        builder.field("version", version);
         builder.field("is_partial", isPartial);
         builder.field("is_running", isRunning);
         builder.field("start_time_in_millis", startTimeMillis);
@@ -165,7 +154,6 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
     }
 
     public static final ParseField ID_FIELD = new ParseField("id");
-    public static final ParseField VERSION_FIELD = new ParseField("version");
     public static final ParseField IS_PARTIAL_FIELD = new ParseField("is_partial");
     public static final ParseField IS_RUNNING_FIELD = new ParseField("is_running");
     public static final ParseField START_TIME_FIELD = new ParseField("start_time_in_millis");
@@ -176,16 +164,14 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
     public static final ConstructingObjectParser<AsyncSearchResponse, Void> PARSER = new ConstructingObjectParser<>(
             "submit_async_search_response", true,
             args -> new AsyncSearchResponse(
-                    (int) args[0],
+                    (boolean) args[0],
                     (boolean) args[1],
-                    (boolean) args[2],
+                    (long) args[2],
                     (long) args[3],
-                    (long) args[4],
-                    (String) args[5],
-                    (SearchResponse) args[6],
-                    (ElasticsearchException) args[7]));
+                    (String) args[4],
+                    (SearchResponse) args[5],
+                    (ElasticsearchException) args[6]));
     static {
-        PARSER.declareInt(constructorArg(), VERSION_FIELD);
         PARSER.declareBoolean(constructorArg(), IS_PARTIAL_FIELD);
         PARSER.declareBoolean(constructorArg(), IS_RUNNING_FIELD);
         PARSER.declareLong(constructorArg(), START_TIME_FIELD);
@@ -203,7 +189,7 @@ private static SearchResponse parseSearchResponse(XContentParser p) throws IOExc
         return SearchResponse.innerFromXContent(p);
     }
 
-    public static AsyncSearchResponse fromXContent(XContentParser parser) throws IOException {
+    public static AsyncSearchResponse fromXContent(XContentParser parser) {
         return PARSER.apply(parser, null);
     }
 

client/rest-high-level/src/test/java/org/elasticsearch/client/asyncsearch/AsyncSearchIT.java

@@ -40,7 +40,6 @@ public void testSubmitAsyncSearchRequest() throws IOException {
         // 15 sec should be enough to make sure we always complete right away
         request.setWaitForCompletion(new TimeValue(15, TimeUnit.SECONDS));
         AsyncSearchResponse response = highLevelClient().asyncSearch().submitAsyncSearch(request, RequestOptions.DEFAULT);
-        assertTrue(response.getVersion() >= 0);
         assertFalse(response.isPartial());
         assertTrue(response.getStartTime() > 0);
         assertTrue(response.getExpirationTime() > 0);

client/rest-high-level/src/test/java/org/elasticsearch/client/asyncsearch/AsyncSearchResponseTests.java

@@ -36,7 +36,6 @@ public class AsyncSearchResponseTests
 
     @Override
     protected org.elasticsearch.xpack.core.search.action.AsyncSearchResponse createServerTestInstance(XContentType xContentType) {
-        int version = randomIntBetween(0, Integer.MAX_VALUE);
         boolean isPartial = randomBoolean();
         boolean isRunning = randomBoolean();
         long startTimeMillis = randomLongBetween(0, Long.MAX_VALUE);
@@ -48,7 +47,7 @@ protected org.elasticsearch.xpack.core.search.action.AsyncSearchResponse createS
                 : new SearchResponse(InternalSearchResponse.empty(), randomAlphaOfLength(10), 1, 1, 0, randomIntBetween(0, 10000),
                         ShardSearchFailure.EMPTY_ARRAY, Clusters.EMPTY);
         org.elasticsearch.xpack.core.search.action.AsyncSearchResponse testResponse =
-                new org.elasticsearch.xpack.core.search.action.AsyncSearchResponse(id, version, searchResponse, error, isPartial, isRunning,
+                new org.elasticsearch.xpack.core.search.action.AsyncSearchResponse(id, searchResponse, error, isPartial, isRunning,
                         startTimeMillis, expirationTimeMillis);
         return testResponse;
     }
@@ -62,7 +61,6 @@ protected AsyncSearchResponse doParseToClientInstance(XContentParser parser) thr
     protected void assertInstances(org.elasticsearch.xpack.core.search.action.AsyncSearchResponse expected, AsyncSearchResponse parsed) {
         assertNotSame(parsed, expected);
         assertEquals(expected.getId(), parsed.getId());
-        assertEquals(expected.getVersion(), parsed.getVersion());
         assertEquals(expected.isRunning(), parsed.isRunning());
         assertEquals(expected.isPartial(), parsed.isPartial());
         assertEquals(expected.getStartTime(), parsed.getStartTime());

docs/reference/search/async-search.asciidoc

@@ -30,9 +30,8 @@ POST /sales*/_async_search?size=0
     }
 }
 --------------------------------------------------
-// TEST[skip:"AwaitsFix https://github.com/elastic/elasticsearch/issues/53891"]
 // TEST[setup:sales]
-// TEST[s/size=0/size=0&wait_for_completion=0/]
+// TEST[s/size=0/size=0&wait_for_completion=10s&clean_on_completion=false/]
 
 The response contains an identifier of the search being executed.
 You can use this ID to later retrieve the search's final results.
@@ -43,7 +42,6 @@ results are returned as part of the <<search-api-response-body,`response`>> obje
 --------------------------------------------------
 {
   "id" : "FmRldE8zREVEUzA2ZVpUeGs2ejJFUFEaMkZ5QTVrSTZSaVN3WlNFVmtlWHJsdzoxMDc=", <1>
-  "version" : 0,
   "is_partial" : true, <2>
   "is_running" : true, <3>
   "start_time_in_millis" : 1583945890986,
@@ -70,12 +68,17 @@ results are returned as part of the <<search-api-response-body,`response`>> obje
 }
 --------------------------------------------------
 // TESTRESPONSE[s/FmRldE8zREVEUzA2ZVpUeGs2ejJFUFEaMkZ5QTVrSTZSaVN3WlNFVmtlWHJsdzoxMDc=/$body.id/]
+// TESTRESPONSE[s/"is_partial" : true/"is_partial": $body.is_partial/]
+// TESTRESPONSE[s/"is_running" : true/"is_running": $body.is_running/]
 // TESTRESPONSE[s/1583945890986/$body.start_time_in_millis/]
 // TESTRESPONSE[s/1584377890986/$body.expiration_time_in_millis/]
 // TESTRESPONSE[s/"took" : 1122/"took": $body.response.took/]
+// TESTRESPONSE[s/"num_reduce_phases" : 0,//]
 // TESTRESPONSE[s/"total" : 562/"total": $body.response._shards.total/]
 // TESTRESPONSE[s/"successful" : 3/"successful": $body.response._shards.successful/]
 // TESTRESPONSE[s/"value" : 157483/"value": $body.response.hits.total.value/]
+// TESTRESPONSE[s/"relation" : "gte"/"relation": $body.response.hits.total.relation/]
+// TESTRESPONSE[s/"hits" : \[ \]\n\s\s\s\s\}/"hits" : \[\]},"aggregations":  $body.response.aggregations/]
 
 <1> Identifier of the async search that can be used to monitor its progress, retrieve its results, and/or delete it.
 <2> Whether the returned search results are partial or final
@@ -135,17 +138,16 @@ GET /_async_search/FmRldE8zREVEUzA2ZVpUeGs2ejJFUFEaMkZ5QTVrSTZSaVN3WlNFVmtlWHJsd
 --------------------------------------------------
 {
   "id" : "FmRldE8zREVEUzA2ZVpUeGs2ejJFUFEaMkZ5QTVrSTZSaVN3WlNFVmtlWHJsdzoxMDc=",
-  "version" : 2, <1>
-  "is_partial" : true, <2>
-  "is_running" : true, <3>
+  "is_partial" : true, <1>
+  "is_running" : true, <2>
   "start_time_in_millis" : 1583945890986,
-  "expiration_time_in_millis" : 1584377890986, <4>
+  "expiration_time_in_millis" : 1584377890986, <3>
   "response" : {
     "took" : 12144,
     "timed_out" : false,
-    "num_reduce_phases" : 38,
+    "num_reduce_phases" : 46, <4>
     "_shards" : {
-      "total" : 562,
+      "total" : 562, <5>
       "successful" : 188,
       "skipped" : 0,
       "failed" : 0
@@ -158,7 +160,7 @@ GET /_async_search/FmRldE8zREVEUzA2ZVpUeGs2ejJFUFEaMkZ5QTVrSTZSaVN3WlNFVmtlWHJsd
       "max_score" : null,
       "hits" : [ ]
     },
-    "aggregations" : { <5>
+    "aggregations" : { <6>
       "sale_date" :  {
         "buckets" : []
       }
@@ -176,17 +178,18 @@ GET /_async_search/FmRldE8zREVEUzA2ZVpUeGs2ejJFUFEaMkZ5QTVrSTZSaVN3WlNFVmtlWHJsd
 // TESTRESPONSE[s/"successful" : 188/"successful": $body.response._shards.successful/]
 // TESTRESPONSE[s/"value" : 456433/"value": $body.response.hits.total.value/]
 // TESTRESPONSE[s/"buckets" : \[\]/"buckets": $body.response.aggregations.sale_date.buckets/]
-// TESTRESPONSE[s/"num_reduce_phases" : 38,//]
-
-<1> The returned `version` is useful to identify whether the response contains
-additional results compared to previously obtained responses. If the version
-stays the same, no new results have become available, otherwise a higher version
-number indicates that more shards have completed their execution of the query
-and their partial results are also included in the response.
-<2> Whether the returned search results are partial or final
-<3> Whether the search is still being executed or it has completed
-<4> When the async search will expire
-<5> Partial aggregations results, coming from the shards that have already
+// TESTRESPONSE[s/"num_reduce_phases" : 46,//]
+
+<1> Whether the returned search results are partial or final
+<2> Whether the search is still being executed or it has completed
+<3> When the async search will expire
+<4> Indicates how many reduction of the results have been performed. If this
+number increases compared to the last retrieved results, you can expect
+additional results included in the search response
+<5> Indicates how many shards have executed the query. Note that in order for
+shard results to be included in the search response, they need to be reduced
+first.
+<6> Partial aggregations results, coming from the shards that have already
 completed the execution of the query.
 
 The `wait_for_completion` parameter, which defaults to `1`, can also be provided

server/src/main/java/org/elasticsearch/action/search/SearchResponse.java

@@ -420,9 +420,7 @@ public Clusters(int total, int successful, int skipped) {
         }
 
         private Clusters(StreamInput in) throws IOException {
-            this.total = in.readVInt();
-            this.successful = in.readVInt();
-            this.skipped = in.readVInt();
+            this(in.readVInt(), in.readVInt(), in.readVInt());
         }
 
         @Override
@@ -434,7 +432,7 @@ public void writeTo(StreamOutput out) throws IOException {
 
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
-            if (this != EMPTY) {
+            if (total > 0) {
                 builder.startObject(_CLUSTERS_FIELD.getPreferredName());
                 builder.field(TOTAL_FIELD.getPreferredName(), total);
                 builder.field(SUCCESSFUL_FIELD.getPreferredName(), successful);

server/src/test/java/org/elasticsearch/action/search/SearchResponseTests.java

@@ -29,6 +29,7 @@
 import org.elasticsearch.common.text.Text;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
 import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.common.xcontent.XContentType;
@@ -292,4 +293,13 @@ public void testSerialization() throws IOException {
         assertEquals(searchResponse.getSkippedShards(), deserialized.getSkippedShards());
         assertEquals(searchResponse.getClusters(), deserialized.getClusters());
     }
+
+    public void testToXContentEmptyClusters() throws IOException {
+        SearchResponse searchResponse = new SearchResponse(InternalSearchResponse.empty(), null, 1, 1, 0, 1,
+            ShardSearchFailure.EMPTY_ARRAY, SearchResponse.Clusters.EMPTY);
+        SearchResponse deserialized = copyWriteable(searchResponse, namedWriteableRegistry, SearchResponse::new, Version.CURRENT);
+        XContentBuilder builder = XContentBuilder.builder(XContentType.JSON.xContent());
+        deserialized.getClusters().toXContent(builder, ToXContent.EMPTY_PARAMS);
+        assertEquals(0, Strings.toString(builder).length());
+    }
 }

x-pack/plugin/async-search/src/main/java/org/elasticsearch/xpack/search/AsyncSearchIndexService.java

@@ -66,14 +66,14 @@ class AsyncSearchIndexService {
     public static final String EXPIRATION_TIME_FIELD = "expiration_time";
     public static final String RESULT_FIELD = "result";
 
-    public static Settings settings() {
+    private static Settings settings() {
         return Settings.builder()
             .put(IndexMetaData.SETTING_NUMBER_OF_SHARDS, 1)
-            .put(IndexMetaData.SETTING_NUMBER_OF_REPLICAS, 1)
+            .put(IndexMetaData.SETTING_AUTO_EXPAND_REPLICAS, "0-1")
             .build();
     }
 
-    public static XContentBuilder mappings() throws IOException {
+    private static XContentBuilder mappings() throws IOException {
         XContentBuilder builder = jsonBuilder()
             .startObject()
                 .startObject(SINGLE_MAPPING_NAME)

x-pack/plugin/async-search/src/main/java/org/elasticsearch/xpack/search/MutableSearchResponse.java

@@ -40,7 +40,6 @@ class MutableSearchResponse {
     private final AtomicArray<ShardSearchFailure> shardFailures;
     private final Supplier<InternalAggregation.ReduceContext> aggReduceContextSupplier;
 
-    private int version;
     private boolean isPartial;
     private boolean isFinalReduce;
     private int successfulShards;
@@ -63,7 +62,6 @@ class MutableSearchResponse {
         this.skippedShards = skippedShards;
         this.clusters = clusters;
         this.aggReduceContextSupplier = aggReduceContextSupplier;
-        this.version = 0;
         this.shardFailures = totalShards == -1 ? null : new AtomicArray<>(totalShards-skippedShards);
         this.isPartial = true;
         this.sections = totalShards == -1 ? null : new InternalSearchResponse(
@@ -83,7 +81,6 @@ synchronized void updatePartialResponse(int successfulShards, SearchResponseSect
             throw new IllegalStateException("received partial response out of order: "
                 + newSections.getNumReducePhases() + " < " + sections.getNumReducePhases());
         }
-        ++ version;
         this.successfulShards = successfulShards;
         this.sections = newSections;
         this.isPartial = true;
@@ -96,7 +93,6 @@ synchronized void updatePartialResponse(int successfulShards, SearchResponseSect
      */
     synchronized void updateFinalResponse(int successfulShards, SearchResponseSections newSections) {
         failIfFrozen();
-        ++ version;
         this.successfulShards = successfulShards;
         this.sections = newSections;
         this.isPartial = false;
@@ -110,7 +106,6 @@ synchronized void updateFinalResponse(int successfulShards, SearchResponseSectio
      */
     synchronized void updateWithFailure(Exception exc) {
         failIfFrozen();
-        ++ version;
         this.isPartial = true;
         this.failure = ElasticsearchException.guessRootCauses(exc)[0];
         this.frozen = true;
@@ -147,7 +142,7 @@ synchronized AsyncSearchResponse toAsyncSearchResponse(AsyncSearchTask task, lon
         } else {
             resp = null;
         }
-        return new AsyncSearchResponse(task.getSearchId().getEncoded(), version, resp, failure, isPartial,
+        return new AsyncSearchResponse(task.getSearchId().getEncoded(), resp, failure, isPartial,
             frozen == false, task.getStartTime(), expirationTime);
     }
 
@@ -159,7 +154,7 @@ private void failIfFrozen() {
 
     private ShardSearchFailure[] buildShardFailures() {
         if (shardFailures == null) {
-            return new ShardSearchFailure[0];
+            return ShardSearchFailure.EMPTY_ARRAY;
         }
         List<ShardSearchFailure> failures = new ArrayList<>();
         for (int i = 0; i < shardFailures.length(); i++) {

x-pack/plugin/async-search/src/test/java/org/elasticsearch/xpack/search/AsyncSearchIndexServiceTests.java

@@ -5,6 +5,10 @@
  */
 package org.elasticsearch.xpack.search;
 
+import org.elasticsearch.action.admin.indices.get.GetIndexRequest;
+import org.elasticsearch.action.admin.indices.get.GetIndexResponse;
+import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.cluster.metadata.IndexMetaData;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
@@ -17,6 +21,7 @@
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.concurrent.ExecutionException;
 
 import static org.elasticsearch.xpack.search.AsyncSearchResponseTests.assertEqualResponses;
 import static org.elasticsearch.xpack.search.AsyncSearchResponseTests.randomAsyncSearchResponse;
@@ -100,4 +105,15 @@ public void testEnsuredAuthenticatedUserIsSame() throws IOException {
         assertFalse(indexService.ensureAuthenticatedUserIsSame(original, runAsDiffType));
         assertFalse(indexService.ensureAuthenticatedUserIsSame(threadContext.getHeaders(), runAsDiffType));
     }
+
+    public void testSettings() throws ExecutionException, InterruptedException {
+        PlainActionFuture<Void> future = PlainActionFuture.newFuture();
+        indexService.createIndexIfNecessary(future);
+        future.get();
+        GetIndexResponse getIndexResponse = client().admin().indices().getIndex(
+            new GetIndexRequest().indices(AsyncSearchIndexService.INDEX)).actionGet();
+        Settings settings = getIndexResponse.getSettings().get(AsyncSearchIndexService.INDEX);
+        assertEquals("1", settings.get(IndexMetaData.SETTING_NUMBER_OF_SHARDS));
+        assertEquals("0-1", settings.get(IndexMetaData.SETTING_AUTO_EXPAND_REPLICAS));
+    }
 }