xds: Implement equals in RingHashConfig

Lack of equals causes cluster_resolver to consider every update a
different configuration and restart itself.

b/430347751

Author: ejona86

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

@@ -51,6 +51,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
 import javax.annotation.Nullable;
@@ -523,6 +524,22 @@ static final class RingHashConfig {
       this.requestHashHeader = requestHashHeader;
     }
 
+    @Override
+    public boolean equals(Object o) {
+      if (!(o instanceof RingHashConfig)) {
+        return false;
+      }
+      RingHashConfig that = (RingHashConfig) o;
+      return this.minRingSize == that.minRingSize
+          && this.maxRingSize == that.maxRingSize
+          && Objects.equals(this.requestHashHeader, that.requestHashHeader);
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(minRingSize, maxRingSize, requestHashHeader);
+    }
+
     @Override
     public String toString() {
       return MoreObjects.toStringHelper(this)

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

@@ -42,6 +42,7 @@
 
 import com.google.common.collect.Iterables;
 import com.google.common.primitives.UnsignedInteger;
+import com.google.common.testing.EqualsTester;
 import io.grpc.Attributes;
 import io.grpc.CallOptions;
 import io.grpc.ConnectivityState;
@@ -1113,6 +1114,19 @@ protected Helper delegate() {
     assertThat(picks).containsExactly(subchannel1);
   }
 
+  @Test
+  public void config_equalsTester() {
+    new EqualsTester()
+        .addEqualityGroup(
+            new RingHashConfig(1, 2, "headerA"),
+            new RingHashConfig(1, 2, "headerA"))
+        .addEqualityGroup(new RingHashConfig(1, 1, "headerA"))
+        .addEqualityGroup(new RingHashConfig(2, 2, "headerA"))
+        .addEqualityGroup(new RingHashConfig(1, 2, "headerB"))
+        .addEqualityGroup(new RingHashConfig(1, 2, ""))
+        .testEquals();
+  }
+
   private List<Subchannel> initializeLbSubchannels(RingHashConfig config,
       List<EquivalentAddressGroup> servers, InitializationFlags... initFlags) {