util: SocketAddress.toString() cannot be used for equality

Some addresses are equal even though their toString is different
(InetSocketAddress ignores the hostname when it has an address). And
some addresses are not equal even though their toString might be the
same (AnonymousInProcessSocketAddress doesn't override toString()).

InetSocketAddress/InetAddress do not cache the toString() result. Thus,
even in the worst case that uses a HashSet, this should use less memory
than the earlier approach, as no strings are formatted. It probably also
significantly improves performance in the reasonably common case when an
Endpoint is created just for looking up a key, because the string
creation in the constructor isn't then amorized.
updateChildrenWithResolvedAddresses(), for example, creates n^2 Endpoint
objects for lookups.

util/src/main/java/io/grpc/util/MultiChildLoadBalancer.java

@@ -37,10 +37,10 @@
 import io.grpc.internal.PickFirstLoadBalancerProvider;
 import java.net.SocketAddress;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -494,25 +494,27 @@ protected Helper delegate() {
 
   /**
    * Endpoint is an optimization to quickly lookup and compare EquivalentAddressGroup address sets.
-   * Ignores the attributes, orders the addresses in a deterministic manner and converts each
-   * address into a string for easy comparison.  Also caches the hashcode.
-   * Is used as a key for ChildLbState for most load balancers (ClusterManagerLB uses a String).
+   * It ignores the attributes. Is used as a key for ChildLbState for most load balancers
+   * (ClusterManagerLB uses a String).
    */
   protected static class Endpoint {
-    final String[] addrs;
+    final Collection<SocketAddress> addrs;
     final int hashCode;
 
     public Endpoint(EquivalentAddressGroup eag) {
       checkNotNull(eag, "eag");
 
-      addrs = new String[eag.getAddresses().size()];
-      int i = 0;
+      if (eag.getAddresses().size() < 10) {
+        addrs = eag.getAddresses();
+      } else {
+        // This is expected to be very unlikely in practice
+        addrs = new HashSet<>(eag.getAddresses());
+      }
+      int sum = 0;
       for (SocketAddress address : eag.getAddresses()) {
-        addrs[i++] = address.toString();
+        sum += address.hashCode();
       }
-      Arrays.sort(addrs);
-
-      hashCode = Arrays.hashCode(addrs);
+      hashCode = sum;
     }
 
     @Override
@@ -525,24 +527,21 @@ public boolean equals(Object other) {
       if (this == other) {
         return true;
       }
-      if (other == null) {
-        return false;
-      }
 
       if (!(other instanceof Endpoint)) {
         return false;
       }
       Endpoint o = (Endpoint) other;
-      if (o.hashCode != hashCode || o.addrs.length != addrs.length) {
+      if (o.hashCode != hashCode || o.addrs.size() != addrs.size()) {
         return false;
       }
 
-      return Arrays.equals(o.addrs, this.addrs);
+      return o.addrs.containsAll(addrs);
     }
 
     @Override
     public String toString() {
-      return Arrays.toString(addrs);
+      return addrs.toString();
     }
   }
 

util/src/test/java/io/grpc/util/MultiChildLoadBalancerTest.java

@@ -21,7 +21,6 @@
 import static io.grpc.ConnectivityState.READY;
 import static io.grpc.ConnectivityState.SHUTDOWN;
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.AdditionalAnswers.delegatesTo;
@@ -34,6 +33,7 @@
 import static org.mockito.Mockito.verify;
 
 import com.google.common.collect.Lists;
+import com.google.common.testing.EqualsTester;
 import io.grpc.Attributes;
 import io.grpc.ConnectivityState;
 import io.grpc.ConnectivityStateInfo;
@@ -244,37 +244,28 @@ public void testEndpoint_toString() {
 
   @Test
   public void testEndpoint_equals() {
-    assertEquals(
-        createEndpoint(Attributes.EMPTY, "addr1"),
-        createEndpoint(Attributes.EMPTY, "addr1"));
-
-    assertEquals(
-        createEndpoint(Attributes.EMPTY, "addr1", "addr2"),
-        createEndpoint(Attributes.EMPTY, "addr2", "addr1"));
-
-    assertEquals(
-        createEndpoint(Attributes.EMPTY, "addr1", "addr2"),
-        createEndpoint(affinity, "addr2", "addr1"));
-
-    assertEquals(
-        createEndpoint(Attributes.EMPTY, "addr1", "addr2").hashCode(),
-        createEndpoint(affinity, "addr2", "addr1").hashCode());
-
-  }
-
-  @Test
-  public void testEndpoint_notEquals() {
-    assertNotEquals(
-        createEndpoint(Attributes.EMPTY, "addr1", "addr2"),
-        createEndpoint(Attributes.EMPTY, "addr1", "addr3"));
-
-    assertNotEquals(
-        createEndpoint(Attributes.EMPTY, "addr1"),
-        createEndpoint(Attributes.EMPTY, "addr1", "addr2"));
-
-    assertNotEquals(
-        createEndpoint(Attributes.EMPTY, "addr1", "addr2"),
-        createEndpoint(Attributes.EMPTY, "addr1"));
+    new EqualsTester()
+        .addEqualityGroup(
+            createEndpoint(Attributes.EMPTY, "addr1"),
+            createEndpoint(Attributes.EMPTY, "addr1"))
+        .addEqualityGroup(
+            createEndpoint(Attributes.EMPTY, "addr1", "addr2"),
+            createEndpoint(Attributes.EMPTY, "addr2", "addr1"),
+            createEndpoint(affinity, "addr1", "addr2"))
+        .addEqualityGroup(
+            createEndpoint(Attributes.EMPTY, "addr1", "addr3"))
+        .addEqualityGroup(
+            createEndpoint(Attributes.EMPTY, "addr1", "addr2", "addr3", "addr4", "addr5", "addr6",
+              "addr7", "addr8", "addr9", "addr10"),
+            createEndpoint(Attributes.EMPTY, "addr2", "addr1", "addr3", "addr4", "addr5", "addr6",
+              "addr7", "addr8", "addr9", "addr10"))
+        .addEqualityGroup(
+            createEndpoint(Attributes.EMPTY, "addr1", "addr2", "addr3", "addr4", "addr5", "addr6",
+              "addr7", "addr8", "addr9", "addr11"))
+        .addEqualityGroup(
+            createEndpoint(Attributes.EMPTY, "addr1", "addr2", "addr3", "addr4", "addr5", "addr6",
+              "addr7", "addr8", "addr9", "addr10", "addr11"))
+        .testEquals();
   }
 
   private String addressesOnlyString(EquivalentAddressGroup eag) {

util/src/testFixtures/java/io/grpc/util/AbstractTestHelper.java

@@ -276,7 +276,7 @@ public String toString() {
     }
   }
 
-  public static class FakeSocketAddress extends SocketAddress {
+  public static final class FakeSocketAddress extends SocketAddress {
     private static final long serialVersionUID = 0L;
     final String name;
 
@@ -288,6 +288,20 @@ public static class FakeSocketAddress extends SocketAddress {
     public String toString() {
       return "FakeSocketAddress-" + name;
     }
+
+    @Override
+    public boolean equals(Object o) {
+      if (!(o instanceof FakeSocketAddress)) {
+        return false;
+      }
+      FakeSocketAddress that = (FakeSocketAddress) o;
+      return this.name.equals(that.name);
+    }
+
+    @Override
+    public int hashCode() {
+      return name.hashCode();
+    }
   }
 }