Revert change to transport protocol (elastic#115009)

Add a new version for reverting the change - in v9, this just adds a boolean. This is so the transport protocol
is the same between 8.x and main, for ease of backports. When the versions are collapsed, this can be removed.

Author: thecoop

server/src/main/java/org/elasticsearch/TransportVersions.java

@@ -175,6 +175,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion ML_INFERENCE_ATTACH_TO_EXISTSING_DEPLOYMENT = def(8_771_00_0);
     public static final TransportVersion CONVERT_FAILURE_STORE_OPTIONS_TO_SELECTOR_OPTIONS_INTERNALLY = def(8_772_00_0);
     public static final TransportVersion REMOVE_MIN_COMPATIBLE_SHARD_NODE = def(8_773_00_0);
+    public static final TransportVersion REVERT_REMOVE_MIN_COMPATIBLE_SHARD_NODE = def(8_774_00_0);
 
     /*
      * STOP! READ THIS FIRST! No, really,

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

@@ -20,6 +20,7 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.index.mapper.SourceLoader;
 import org.elasticsearch.index.query.QueryRewriteContext;
 import org.elasticsearch.index.query.Rewriteable;
@@ -254,8 +255,10 @@ public SearchRequest(StreamInput in) throws IOException {
             finalReduce = true;
         }
         ccsMinimizeRoundtrips = in.readBoolean();
-        if (in.getTransportVersion().before(TransportVersions.REMOVE_MIN_COMPATIBLE_SHARD_NODE) && in.readBoolean()) {
-            Version.readVersion(in); // and drop on the floor
+        if ((in.getTransportVersion().before(TransportVersions.REMOVE_MIN_COMPATIBLE_SHARD_NODE)
+            || in.getTransportVersion().onOrAfter(TransportVersions.REVERT_REMOVE_MIN_COMPATIBLE_SHARD_NODE)) && in.readBoolean()) {
+            @UpdateForV9(owner = UpdateForV9.Owner.CORE_INFRA)  // this can be removed (again) when the v9 transport version can diverge
+            Version v = Version.readVersion(in); // and drop on the floor
         }
         waitForCheckpoints = in.readMap(StreamInput::readLongArray);
         waitForCheckpointsTimeout = in.readTimeValue();
@@ -291,7 +294,8 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeBoolean(finalReduce);
         }
         out.writeBoolean(ccsMinimizeRoundtrips);
-        if (out.getTransportVersion().before(TransportVersions.REMOVE_MIN_COMPATIBLE_SHARD_NODE)) {
+        if (out.getTransportVersion().before(TransportVersions.REMOVE_MIN_COMPATIBLE_SHARD_NODE)
+            || out.getTransportVersion().onOrAfter(TransportVersions.REVERT_REMOVE_MIN_COMPATIBLE_SHARD_NODE)) {
             out.writeBoolean(false);
         }
         out.writeMap(waitForCheckpoints, StreamOutput::writeLongArray);

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

@@ -16,9 +16,12 @@
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.io.stream.BytesStreamOutput;
+import org.elasticsearch.common.io.stream.NamedWriteableAwareStreamInput;
+import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.util.ArrayUtils;
 import org.elasticsearch.core.TimeValue;
+import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.index.query.QueryBuilders;
 import org.elasticsearch.index.query.TermQueryBuilder;
@@ -102,6 +105,23 @@ public void testSerialization() throws Exception {
         assertNotSame(deserializedRequest, searchRequest);
     }
 
+    @UpdateForV9(owner = UpdateForV9.Owner.CORE_INFRA)  // this can be removed when the affected transport version constants are collapsed
+    public void testSerializationConstants() throws Exception {
+        SearchRequest searchRequest = createSearchRequest();
+
+        // something serialized with previous version to remove, should read correctly with the reversion
+        try (BytesStreamOutput output = new BytesStreamOutput()) {
+            output.setTransportVersion(TransportVersionUtils.getPreviousVersion(TransportVersions.REMOVE_MIN_COMPATIBLE_SHARD_NODE));
+            searchRequest.writeTo(output);
+            try (StreamInput in = new NamedWriteableAwareStreamInput(output.bytes().streamInput(), namedWriteableRegistry)) {
+                in.setTransportVersion(TransportVersions.REVERT_REMOVE_MIN_COMPATIBLE_SHARD_NODE);
+                SearchRequest copiedRequest = new SearchRequest(in);
+                assertEquals(copiedRequest, searchRequest);
+                assertEquals(copiedRequest.hashCode(), searchRequest.hashCode());
+            }
+        }
+    }
+
     public void testSerializationMultiKNN() throws Exception {
         SearchRequest searchRequest = createSearchRequest();
         if (searchRequest.source() == null) {