Remove systemPropertiesOverrideTest from 8.19 (#137611)

These tests relate to system properties set only in serverless
Elasticsearch so there's no need for them in the `8.19` branch.
Moreover, as with #137492, this extra Gradle task forces every developer
to make an extra choice when running tests in `:server`. This commit
removes the unnecessary tests, the corresponding Gradle task, and the
now-untested code.

Author: DaveCTurner

server/build.gradle

@@ -147,30 +147,6 @@ if (buildParams.snapshotBuild == false) {
 
 tasks.named("test").configure {
   systemProperty 'es.insecure_network_trace_enabled', 'true'
-  filter {
-    excludeTestsMatching("*.TransportServiceHandshakeTests.testAcceptsMismatchedServerlessBuildHash")
-  }
-  excludes << '**/IndexSettingsOverrideTests.class'
-}
-
-// There are tests rely on system properties to be configured differently. They must run in a separate test job
-// since the default does not work for them and configuring the system properties inside the test class/method
-// is too late because fields based on the system properties are often initialized statically.
-TaskProvider<Test> systemPropertiesOverrideTest = tasks.register("systemPropertiesOverrideTest", Test) {
-  include '**/IndexSettingsOverrideTests.class'
-  include '**/TransportServiceHandshakeTests.class'
-  filter {
-    includeTestsMatching("*.TransportServiceHandshakeTests.testAcceptsMismatchedServerlessBuildHash")
-    includeTestsMatching("*.IndexSettingsOverrideTests.*")
-  }
-  systemProperty 'es.stateless.allow.index.refresh_interval.override', 'true'
-  systemProperty 'es.serverless_transport', 'true'
-  classpath = sourceSets.test.runtimeClasspath
-  testClassesDirs = sourceSets.test.output.classesDirs
-}
-
-tasks.named("check").configure {
-  dependsOn(systemPropertiesOverrideTest)
 }
 
 tasks.named("thirdPartyAudit").configure {

server/src/main/java/org/elasticsearch/index/IndexSettings.java

@@ -303,11 +303,6 @@ public final class IndexSettings {
 
     static class RefreshIntervalValidator implements Setting.Validator<TimeValue> {
 
-        static final String STATELESS_ALLOW_INDEX_REFRESH_INTERVAL_OVERRIDE = "es.stateless.allow.index.refresh_interval.override";
-        private static final boolean IS_OVERRIDE_ALLOWED = Boolean.parseBoolean(
-            System.getProperty(STATELESS_ALLOW_INDEX_REFRESH_INTERVAL_OVERRIDE, "false")
-        );
-
         @Override
         public void validate(TimeValue value) {}
 
@@ -323,18 +318,16 @@ public void validate(final TimeValue value, final Map<Setting<?>, Object> settin
                 && value.compareTo(STATELESS_MIN_NON_FAST_REFRESH_INTERVAL) < 0
                 && indexVersion.after(IndexVersions.V_8_10_0)) {
 
-                if (IS_OVERRIDE_ALLOWED == false) {
-                    throw new IllegalArgumentException(
-                        "index setting ["
-                            + IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getKey()
-                            + "="
-                            + value
-                            + "] should be either "
-                            + TimeValue.MINUS_ONE
-                            + " or equal to or greater than "
-                            + STATELESS_MIN_NON_FAST_REFRESH_INTERVAL
-                    );
-                }
+                throw new IllegalArgumentException(
+                    "index setting ["
+                        + IndexSettings.INDEX_REFRESH_INTERVAL_SETTING.getKey()
+                        + "="
+                        + value
+                        + "] should be either "
+                        + TimeValue.MINUS_ONE
+                        + " or equal to or greater than "
+                        + STATELESS_MIN_NON_FAST_REFRESH_INTERVAL
+                );
             }
         }
 

server/src/main/java/org/elasticsearch/transport/TransportService.java

@@ -37,7 +37,6 @@
 import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.core.AbstractRefCounted;
-import org.elasticsearch.core.Booleans;
 import org.elasticsearch.core.IOUtils;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.Predicates;
@@ -79,15 +78,6 @@ public class TransportService extends AbstractLifecycleComponent
 
     private static final Logger logger = LogManager.getLogger(TransportService.class);
 
-    /**
-     * A feature flag enabling transport upgrades for serverless.
-     */
-    static final String SERVERLESS_TRANSPORT_SYSTEM_PROPERTY = "es.serverless_transport";
-    private static final boolean SERVERLESS_TRANSPORT_FEATURE_FLAG = Booleans.parseBoolean(
-        System.getProperty(SERVERLESS_TRANSPORT_SYSTEM_PROPERTY),
-        false
-    );
-
     public static final String DIRECT_RESPONSE_PROFILE = ".direct";
     public static final String HANDSHAKE_ACTION_NAME = "internal:transport/handshake";
 
@@ -672,7 +662,7 @@ public HandshakeResponse(StreamInput in) throws IOException {
         }
 
         private void maybeThrowOnIncompatibleBuild(@Nullable DiscoveryNode node, @Nullable Exception e) {
-            if (SERVERLESS_TRANSPORT_FEATURE_FLAG == false && isIncompatibleBuild(version, buildHash)) {
+            if (isIncompatibleBuild(version, buildHash)) {
                 throwOnIncompatibleBuild(node, e);
             }
         }

server/src/test/java/org/elasticsearch/index/IndexSettingsOverrideTests.java

@@ -9,7 +9,6 @@
 
 package org.elasticsearch.transport;
 
-import org.elasticsearch.Build;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.Version;
@@ -371,34 +370,6 @@ public void testRejectsMismatchedBuildHash() {
         assertFalse(transportServiceA.nodeConnected(discoveryNode));
     }
 
-    public void testAcceptsMismatchedServerlessBuildHash() {
-        assumeTrue("Current build needs to be a snapshot", Build.current().isSnapshot());
-        final DisruptingTransportInterceptor transportInterceptorA = new DisruptingTransportInterceptor();
-        final DisruptingTransportInterceptor transportInterceptorB = new DisruptingTransportInterceptor();
-        transportInterceptorA.setModifyBuildHash(true);
-        transportInterceptorB.setModifyBuildHash(true);
-        final Settings settings = Settings.builder()
-            .put("cluster.name", "a")
-            .put(IGNORE_DESERIALIZATION_ERRORS_SETTING.getKey(), true) // suppress assertions to test production error-handling
-            .build();
-        final TransportService transportServiceA = startServices(
-            "TS_A",
-            settings,
-            TransportVersion.current(),
-            VersionInformation.CURRENT,
-            transportInterceptorA
-        );
-        final TransportService transportServiceB = startServices(
-            "TS_B",
-            settings,
-            TransportVersion.current(),
-            VersionInformation.CURRENT,
-            transportInterceptorB
-        );
-        AbstractSimpleTransportTestCase.connectToNode(transportServiceA, transportServiceB.getLocalNode(), TestProfiles.LIGHT_PROFILE);
-        assertTrue(transportServiceA.nodeConnected(transportServiceB.getLocalNode()));
-    }
-
     public void testAcceptsMismatchedBuildHashFromDifferentVersion() {
         final DisruptingTransportInterceptor transportInterceptorA = new DisruptingTransportInterceptor();
         final DisruptingTransportInterceptor transportInterceptorB = new DisruptingTransportInterceptor();