Ensure that a selected port is consistent

java/src/org/openqa/selenium/grid/server/BaseServerOptions.java

@@ -41,6 +41,7 @@ public class BaseServerOptions {
 
   private static final Logger LOG = Logger.getLogger(BaseServerOptions.class.getName());
   private final Config config;
+  private int port = -1;
 
   public BaseServerOptions(Config config) {
     this.config = config;
@@ -53,13 +54,17 @@ public Optional<String> getHostname() {
 
   @ManagedAttribute(name = "Port")
   public int getPort() {
-    int port = config.getInt(SERVER_SECTION, "port")
-      .orElseGet(PortProber::findFreePort);
     if (port == -1) {
-      return PortProber.findFreePort();
-    }
-    if (port < 0) {
-      throw new ConfigException("Port cannot be less than 0: " + port);
+      int newPort = config.getInt(SERVER_SECTION, "port")
+        .orElseGet(PortProber::findFreePort);
+      if (newPort == -1) {
+        newPort = PortProber.findFreePort();
+      }
+      if (newPort < 0) {
+        throw new ConfigException("Port cannot be less than 0: " + port);
+      }
+
+      port = newPort;
     }
     return port;
   }

java/test/org/openqa/selenium/grid/server/BUILD.bazel

@@ -5,6 +5,10 @@ java_test_suite(
     name = "MediumTests",
     size = "medium",
     srcs = glob(["*Test.java"]),
+    javacopts = [
+        "--release",
+        "11",
+    ],
     deps = [
         "//java/src/org/openqa/selenium/grid/config",
         "//java/src/org/openqa/selenium/grid/server",

java/test/org/openqa/selenium/grid/server/BaseServerOptionsTest.java

@@ -0,0 +1,39 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.openqa.selenium.grid.server;
+
+import org.junit.Test;
+import org.openqa.selenium.grid.config.MapConfig;
+
+import java.util.Map;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BaseServerOptionsTest {
+
+  @Test
+  public void readingThePortTwiceShouldGiveTheSameResult() {
+    BaseServerOptions options = new BaseServerOptions(new MapConfig(Map.of("server", Map.of("port", -1))));
+
+    int first = options.getPort();
+    int second = options.getPort();
+
+    assertThat(first).isEqualTo(second);
+  }
+
+}