Fix SearchApplication misusing BytesStreamOutput (elastic#127957)

Closing an xcontent builder in general also closes the underlying stream.
The only reason this worked was that we were always using the no-pooling `BigArrays`
which also makes the use of the circuit breaker a noop here.
Found this when trying to optimize the releasable bytes stream and seeing it
break.
=> just move the non-pooled bytes stream to simplify things

Author: original-brownbear

x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/search/SearchApplication.java

@@ -12,11 +12,10 @@
 import org.elasticsearch.TransportVersions;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
-import org.elasticsearch.common.io.stream.ReleasableBytesStreamOutput;
+import org.elasticsearch.common.io.stream.BytesStreamOutput;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
-import org.elasticsearch.common.util.BigArrays;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.Tuple;
@@ -282,15 +281,13 @@ public String toString() {
      * Returns the merged {@link SearchApplication} from the current state and the provided {@param update}.
      * This function returns the current instance if the update is a noop.
      *
-     * @param update The source of the update represented in bytes.
+     * @param update       The source of the update represented in bytes.
      * @param xContentType The format of the bytes.
-     * @param bigArrays The {@link BigArrays} to use to recycle bytes array.
-     *
      * @return The merged {@link SearchApplication}.
      */
-    SearchApplication merge(BytesReference update, XContentType xContentType, BigArrays bigArrays) throws IOException {
+    SearchApplication merge(BytesReference update, XContentType xContentType) throws IOException {
         final Tuple<XContentType, Map<String, Object>> sourceAndContent;
-        try (ReleasableBytesStreamOutput sourceBuffer = new ReleasableBytesStreamOutput(0, bigArrays.withCircuitBreaking())) {
+        try (BytesStreamOutput sourceBuffer = new BytesStreamOutput()) {
             try (XContentBuilder builder = XContentFactory.jsonBuilder(sourceBuffer)) {
                 toXContent(builder, EMPTY_PARAMS);
             }
@@ -305,7 +302,7 @@ SearchApplication merge(BytesReference update, XContentType xContentType, BigArr
             return this;
         }
 
-        try (ReleasableBytesStreamOutput newSourceBuffer = new ReleasableBytesStreamOutput(0, bigArrays.withCircuitBreaking())) {
+        try (BytesStreamOutput newSourceBuffer = new BytesStreamOutput()) {
             try (XContentBuilder builder = XContentFactory.jsonBuilder(newSourceBuffer)) {
                 builder.value(newSourceAsMap);
             }

x-pack/plugin/ent-search/src/test/java/org/elasticsearch/xpack/application/search/SearchApplicationTests.java

@@ -16,7 +16,6 @@
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.util.BigArrays;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.search.SearchModule;
 import org.elasticsearch.test.ESTestCase;
@@ -111,7 +110,7 @@ public void testMerge() throws IOException {
               "updated_at_millis": 12345
             }""";
         SearchApplication app = SearchApplication.fromXContentBytes("my_search_app", new BytesArray(content), XContentType.JSON);
-        SearchApplication updatedApp = app.merge(new BytesArray(update), XContentType.JSON, BigArrays.NON_RECYCLING_INSTANCE);
+        SearchApplication updatedApp = app.merge(new BytesArray(update), XContentType.JSON);
         assertNotSame(app, updatedApp);
         assertThat(updatedApp.indices(), equalTo(new String[] { "my_index", "my_index_2" }));
         assertThat(updatedApp.analyticsCollectionName(), equalTo("my_search_app_analytics"));