Make keep alive of point in time optional in search (#62184)

A search request should not be required to extend the keep_alive of a point in time. 
This change makes that parameter optional.

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

@@ -75,7 +75,7 @@ public SearchShardIterator(@Nullable String clusterAlias, ShardId shardId,
         this.clusterAlias = clusterAlias;
         this.searchContextId = searchContextId;
         this.searchContextKeepAlive = searchContextKeepAlive;
-        assert (searchContextId == null) == (searchContextKeepAlive == null);
+        assert searchContextKeepAlive == null || searchContextId != null;
     }
 
     /**

server/src/main/java/org/elasticsearch/search/builder/SearchSourceBuilder.java

@@ -1676,33 +1676,35 @@ private static final class XContentParams {
 
         public PointInTimeBuilder(String id, TimeValue keepAlive) {
             this.id = Objects.requireNonNull(id);
-            this.keepAlive = Objects.requireNonNull(keepAlive);
+            this.keepAlive = keepAlive;
         }
 
         public PointInTimeBuilder(StreamInput in) throws IOException {
             id = in.readString();
-            keepAlive = in.readTimeValue();
+            keepAlive = in.readOptionalTimeValue();
         }
 
         @Override
         public void writeTo(StreamOutput out) throws IOException {
             out.writeString(id);
-            out.writeTimeValue(keepAlive);
+            out.writeOptionalTimeValue(keepAlive);
         }
 
         @Override
         public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
             builder.startObject(POINT_IN_TIME.getPreferredName());
             builder.field(ID_FIELD.getPreferredName(), id);
-            builder.field(KEEP_ALIVE_FIELD.getPreferredName(), keepAlive);
+            if (keepAlive != null) {
+                builder.field(KEEP_ALIVE_FIELD.getPreferredName(), keepAlive);
+            }
             builder.endObject();
             return builder;
         }
 
         public static PointInTimeBuilder fromXContent(XContentParser parser) throws IOException {
             final XContentParams params = PARSER.parse(parser, null);
-            if (params.id == null || params.keepAlive == null) {
-                throw new IllegalArgumentException("id and keep_alive must be specified");
+            if (params.id == null) {
+                throw new IllegalArgumentException("point int time id is not provided");
             }
             return new PointInTimeBuilder(params.id, params.keepAlive);
         }

server/src/main/java/org/elasticsearch/search/internal/ShardSearchRequest.java

@@ -175,7 +175,7 @@ private ShardSearchRequest(OriginalIndices originalIndices,
         this.originalIndices = originalIndices;
         this.readerId = readerId;
         this.keepAlive = keepAlive;
-        assert (readerId != null) == (keepAlive != null);
+        assert keepAlive == null || readerId != null : "readerId: " + readerId + " keepAlive: " + keepAlive;
     }
 
     public ShardSearchRequest(StreamInput in) throws IOException {

server/src/test/java/org/elasticsearch/search/builder/SearchSourceBuilderTests.java

@@ -386,17 +386,23 @@ public void testToXContent() throws IOException {
     public void testToXContentWithPointInTime() throws IOException {
         XContentType xContentType = randomFrom(XContentType.values());
         SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
-        searchSourceBuilder.pointInTimeBuilder(new SearchSourceBuilder.PointInTimeBuilder("id", TimeValue.timeValueHours(1)));
+        TimeValue keepAlive = randomBoolean() ? TimeValue.timeValueHours(1) : null;
+        searchSourceBuilder.pointInTimeBuilder(new SearchSourceBuilder.PointInTimeBuilder("id", keepAlive));
         XContentBuilder builder = XContentFactory.contentBuilder(xContentType);
         searchSourceBuilder.toXContent(builder, ToXContent.EMPTY_PARAMS);
         BytesReference bytes = BytesReference.bytes(builder);
         Map<String, Object> sourceAsMap = XContentHelper.convertToMap(bytes, false, xContentType).v2();
         assertEquals(1, sourceAsMap.size());
         @SuppressWarnings("unchecked")
         Map<String, Object> pit = (Map<String, Object>) sourceAsMap.get("pit");
-        assertEquals(2, pit.size());
         assertEquals("id", pit.get("id"));
-        assertEquals("1h", pit.get("keep_alive"));
+        if (keepAlive != null) {
+            assertEquals("1h", pit.get("keep_alive"));
+            assertEquals(2, pit.size());
+        } else {
+            assertNull(pit.get("keep_alive"));
+            assertEquals(1, pit.size());
+        }
     }
 
     public void testParseIndicesBoost() throws IOException {

test/framework/src/main/java/org/elasticsearch/search/RandomSearchRequestGenerator.java

@@ -371,8 +371,8 @@ public static SearchSourceBuilder randomSearchSourceBuilder(
             builder.collapse(randomCollapseBuilder.get());
         }
         if (randomBoolean()) {
-            builder.pointInTimeBuilder(new SearchSourceBuilder.PointInTimeBuilder(randomAlphaOfLengthBetween(3, 10),
-                TimeValue.timeValueMinutes(randomIntBetween(1, 60))));
+            TimeValue keepAlive = randomBoolean() ? TimeValue.timeValueMinutes(randomIntBetween(1, 60)) : null;
+            builder.pointInTimeBuilder(new SearchSourceBuilder.PointInTimeBuilder(randomAlphaOfLengthBetween(3, 10), keepAlive));
         }
         return builder;
     }

x-pack/plugin/src/test/resources/rest-api-spec/test/search/point_in_time.yml

@@ -86,7 +86,6 @@ setup:
           search_after: [24, 172]
           pit:
             id: "$point_in_time_id"
-            keep_alive: 1m
 
   - match: {hits.total: 3 }
   - length: {hits.hits: 1 }
@@ -106,7 +105,6 @@ setup:
           search_after: [18, 42]
           pit:
             id: "$point_in_time_id"
-            keep_alive: 1m
 
   - match: {hits.total: 3}
   - length: {hits.hits: 1 }