grpclb: internal accessor for balancer address related attribute keys (#6667)

Creates an internal accessor for attribute keys in grpclb package that is used by name resolver implementations to set balancer addresses as name resolution result attributes.

grpclb/build.gradle

@@ -26,3 +26,7 @@ dependencies {
 }
 
 configureProtoCompilation()
+
+javadoc {
+    exclude 'io/grpc/grpclb/Internal*'
+}

grpclb/src/main/java/io/grpc/grpclb/GrpclbConstants.java

@@ -43,7 +43,6 @@ public final class GrpclbConstants {
       Attributes.Key.create("lb-token");
 
   @SuppressWarnings("deprecation")
-  @EquivalentAddressGroup.Attr
   static final Attributes.Key<List<EquivalentAddressGroup>> ATTR_LB_ADDRS =
       io.grpc.internal.GrpcAttributes.ATTR_LB_ADDRS;
 

grpclb/src/main/java/io/grpc/grpclb/GrpclbLoadBalancer.java

@@ -30,7 +30,6 @@ import io.grpc.LoadBalancer;
 import io.grpc.Status;
 import io.grpc.grpclb.GrpclbState.Mode;
 import io.grpc.internal.BackoffPolicy;
-import io.grpc.internal.GrpcAttributes;
 import io.grpc.internal.ServiceConfigUtil;
 import io.grpc.internal.ServiceConfigUtil.LbConfig;
 import io.grpc.internal.TimeProvider;
@@ -92,7 +91,7 @@ class GrpclbLoadBalancer extends LoadBalancer {
   @SuppressWarnings("deprecation")  // TODO(creamsoup) migrate to use parsed service config
   public void handleResolvedAddresses(ResolvedAddresses resolvedAddresses) {
     Attributes attributes = resolvedAddresses.getAttributes();
-    List<EquivalentAddressGroup> newLbAddresses = attributes.get(GrpcAttributes.ATTR_LB_ADDRS);
+    List<EquivalentAddressGroup> newLbAddresses = attributes.get(GrpclbConstants.ATTR_LB_ADDRS);
     if ((newLbAddresses == null || newLbAddresses.isEmpty())
         && resolvedAddresses.getAddresses().isEmpty()) {
       handleNameResolutionError(

grpclb/src/main/java/io/grpc/grpclb/InternalGrpclbConstantsAccessor.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2020 The gRPC Authors
+ *
+ * Licensed 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 io.grpc.grpclb;
+
+import io.grpc.Attributes;
+import io.grpc.EquivalentAddressGroup;
+import io.grpc.Internal;
+import java.util.List;
+
+/**
+ * Internal {@link GrpclbConstants} accessor. This is intended for usage internal to the gRPC
+ * team. If you *really* think you need to use this, contact the gRPC team first.
+ */
+@Internal
+public class InternalGrpclbConstantsAccessor {
+
+  // Prevent instantiation.
+  private InternalGrpclbConstantsAccessor() {
+  }
+
+  /**
+   * Sets attribute for gRPC LB address authority.
+   */
+  public static Attributes setLbAddrAuthorityAttr(
+      @EquivalentAddressGroup.Attr Attributes attrs, String authority) {
+    return attrs.toBuilder().set(GrpclbConstants.ATTR_LB_ADDR_AUTHORITY, authority).build();
+  }
+
+  /**
+   * Sets attribute for gRPC LB addresses.
+   */
+  public static Attributes setLbAddrAttr(Attributes attrs, List<EquivalentAddressGroup> lbAddrs) {
+    return attrs.toBuilder().set(GrpclbConstants.ATTR_LB_ADDRS, lbAddrs).build();
+  }
+}