xds: remove GRPC_XDS_EXPERIMENTAL_V3_SUPPORT env flag

xds/src/main/java/io/grpc/xds/BootstrapperImpl.java

@@ -59,9 +59,6 @@ public class BootstrapperImpl implements Bootstrapper {
   static String bootstrapConfigFromSysProp = System.getProperty(BOOTSTRAP_CONFIG_SYS_PROPERTY_VAR);
   private static final String XDS_V3_SERVER_FEATURE = "xds_v3";
   @VisibleForTesting
-  static boolean enableV3Protocol = Boolean.parseBoolean(
-      System.getenv("GRPC_XDS_EXPERIMENTAL_V3_SUPPORT"));
-  @VisibleForTesting
   static final String CLIENT_FEATURE_DISABLE_OVERPROVISIONING =
       "envoy.lb.does_not_support_overprovisioning";
 
@@ -176,8 +173,7 @@ public class BootstrapperImpl implements Bootstrapper {
       List<String> serverFeatures = JsonUtil.getListOfStrings(serverConfig, "server_features");
       if (serverFeatures != null) {
         logger.log(XdsLogLevel.INFO, "Server features: {0}", serverFeatures);
-        useProtocolV3 = enableV3Protocol
-            && serverFeatures.contains(XDS_V3_SERVER_FEATURE);
+        useProtocolV3 = serverFeatures.contains(XDS_V3_SERVER_FEATURE);
       }
       servers.add(new ServerInfo(serverUri, channelCredentials, useProtocolV3));
     }

xds/src/test/java/io/grpc/xds/BootstrapperImplTest.java

@@ -56,7 +56,6 @@ public class BootstrapperImplTest {
   private String originalBootstrapPathFromSysProp;
   private String originalBootstrapConfigFromEnvVar;
   private String originalBootstrapConfigFromSysProp;
-  private boolean originalEnableV3Protocol;
 
   @Before
   public void setUp() {
@@ -69,7 +68,6 @@ public class BootstrapperImplTest {
     originalBootstrapPathFromSysProp = BootstrapperImpl.bootstrapPathFromSysProp;
     originalBootstrapConfigFromEnvVar = BootstrapperImpl.bootstrapConfigFromEnvVar;
     originalBootstrapConfigFromSysProp = BootstrapperImpl.bootstrapConfigFromSysProp;
-    originalEnableV3Protocol = BootstrapperImpl.enableV3Protocol;
   }
 
   @After
@@ -78,7 +76,6 @@ public class BootstrapperImplTest {
     BootstrapperImpl.bootstrapPathFromSysProp = originalBootstrapPathFromSysProp;
     BootstrapperImpl.bootstrapConfigFromEnvVar = originalBootstrapConfigFromEnvVar;
     BootstrapperImpl.bootstrapConfigFromSysProp = originalBootstrapConfigFromSysProp;
-    BootstrapperImpl.enableV3Protocol = originalEnableV3Protocol;
   }
 
   @Test
@@ -567,7 +564,7 @@ public class BootstrapperImplTest {
         + "      \"channel_creds\": [\n"
         + "        {\"type\": \"insecure\"}\n"
         + "      ],\n"
-        + "      \"server_features\": [\"xds_v3\"]\n"
+        + "      \"server_features\": []\n"
         + "    }\n"
         + "  ]\n"
         + "}";
@@ -581,17 +578,7 @@ public class BootstrapperImplTest {
   }
 
   @Test
-  public void supportV3Protocol_disabledByDefault() throws XdsInitializationException {
-    subtestSupportV3Protocol(false);
-  }
-
-  @Test
-  public void supportV3Protocol_enabled() throws XdsInitializationException {
-    BootstrapperImpl.enableV3Protocol = true;
-    subtestSupportV3Protocol(true);
-  }
-
-  private void subtestSupportV3Protocol(boolean enabled) throws XdsInitializationException {
+  public void useV3ProtocolIfV3FeaturePresent() throws XdsInitializationException {
     String rawData = "{\n"
         + "  \"xds_servers\": [\n"
         + "    {\n"
@@ -609,11 +596,7 @@ public class BootstrapperImplTest {
     ServerInfo serverInfo = Iterables.getOnlyElement(info.getServers());
     assertThat(serverInfo.getTarget()).isEqualTo(SERVER_URI);
     assertThat(serverInfo.getChannelCredentials()).isInstanceOf(InsecureChannelCredentials.class);
-    if (enabled) {
-      assertThat(serverInfo.isUseProtocolV3()).isTrue();
-    } else {
-      assertThat(serverInfo.isUseProtocolV3()).isFalse();
-    }
+    assertThat(serverInfo.isUseProtocolV3()).isTrue();
   }
 
   @Test