Support random see for test purposes.

Author: temawi

core/src/main/java/io/grpc/internal/PickFirstLoadBalancer.java

@@ -31,6 +31,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Random;
 import java.util.concurrent.atomic.AtomicBoolean;
 import javax.annotation.Nullable;
 
@@ -65,7 +66,8 @@ public boolean acceptResolvedAddresses(ResolvedAddresses resolvedAddresses) {
           = (PickFirstLoadBalancerConfig) resolvedAddresses.getLoadBalancingPolicyConfig();
       if (config.shuffleAddressList != null && config.shuffleAddressList) {
         servers = new ArrayList<EquivalentAddressGroup>(servers);
-        Collections.shuffle(servers);
+        Collections.shuffle(servers,
+            config.randomSeed != null ? new Random(config.randomSeed) : new Random());
       }
     }
 
@@ -219,8 +221,16 @@ public static final class PickFirstLoadBalancerConfig {
     @Nullable
     public final Boolean shuffleAddressList;
 
+    // For testing purposes only, not meant to be parsed from a real config.
+    @Nullable final Long randomSeed;
+
     public PickFirstLoadBalancerConfig(@Nullable Boolean shuffleAddressList) {
+      this(shuffleAddressList, null);
+    }
+
+    PickFirstLoadBalancerConfig(@Nullable Boolean shuffleAddressList, @Nullable Long randomSeed) {
       this.shuffleAddressList = shuffleAddressList;
+      this.randomSeed = randomSeed;
     }
   }
 }

core/src/test/java/io/grpc/internal/PickFirstLoadBalancerTest.java

@@ -145,14 +145,16 @@ public void pickAfterResolved() throws Exception {
   public void pickAfterResolved_shuffle() throws Exception {
     loadBalancer.acceptResolvedAddresses(
         ResolvedAddresses.newBuilder().setAddresses(servers).setAttributes(affinity)
-            .setLoadBalancingPolicyConfig(new PickFirstLoadBalancerConfig(true)).build());
+            .setLoadBalancingPolicyConfig(new PickFirstLoadBalancerConfig(true, 123L)).build());
 
     verify(mockHelper).createSubchannel(createArgsCaptor.capture());
     CreateSubchannelArgs args = createArgsCaptor.getValue();
     // We should still see the same set of addresses.
     assertThat(args.getAddresses()).containsExactlyElementsIn(servers);
-    // If the two lists are equal they have maintained order, we don't want that.
-    assertThat(args.getAddresses()).isNotEqualTo(servers);
+    // Because we use a fixed seed, the addresses should always be shuffled in this order.
+    assertThat(args.getAddresses().get(0)).isEqualTo(servers.get(1));
+    assertThat(args.getAddresses().get(1)).isEqualTo(servers.get(0));
+    assertThat(args.getAddresses().get(2)).isEqualTo(servers.get(2));
     verify(mockHelper).updateBalancingState(eq(CONNECTING), pickerCaptor.capture());
     verify(mockSubchannel).requestConnection();