Build DNS changes with HashMap instead of Builder

The existing CloudDnsWriter code uses ImmutableMap.Builder to construct the
map of DNS records to update.  This has been seen to fail on alpha, presumably
in a cases where host records and domain records produce duplicate updates for
a host.

Convert the Builder to a HashMap, allowing us to safely overwrite existing
records in the case of duplicates.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=170103421

java/google/registry/dns/writer/clouddns/CloudDnsWriter.java

@@ -46,6 +46,7 @@
 import java.net.Inet4Address;
 import java.net.Inet6Address;
 import java.net.InetAddress;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -82,8 +83,8 @@ public class CloudDnsWriter extends BaseDnsWriter {
   private final String projectId;
   private final String zoneName;
   private final Dns dnsConnection;
-  private final ImmutableMap.Builder<String, ImmutableSet<ResourceRecordSet>>
-      desiredRecordsBuilder = new ImmutableMap.Builder<>();
+  private final HashMap<String, ImmutableSet<ResourceRecordSet>> desiredRecords =
+      new HashMap<String, ImmutableSet<ResourceRecordSet>>();
 
   @Inject
   CloudDnsWriter(
@@ -121,7 +122,7 @@ public void publishDomain(String domainName) {
     // desiredRecordsBuilder is populated with an empty set to indicate that all existing records
     // should be deleted.
     if (!domainResource.isPresent() || !domainResource.get().shouldPublishToDns()) {
-      desiredRecordsBuilder.put(absoluteDomainName, ImmutableSet.<ResourceRecordSet>of());
+      desiredRecords.put(absoluteDomainName, ImmutableSet.<ResourceRecordSet>of());
       return;
     }
 
@@ -171,7 +172,7 @@ public void publishDomain(String domainName) {
       }
     }
 
-    desiredRecordsBuilder.put(absoluteDomainName, domainRecords.build());
+    desiredRecords.put(absoluteDomainName, domainRecords.build());
     logger.finefmt(
         "Will write %s records for domain %s", domainRecords.build().size(), absoluteDomainName);
   }
@@ -189,7 +190,7 @@ private void publishSubordinateHost(String hostName) {
 
     // Return early if the host is deleted.
     if (!host.isPresent()) {
-      desiredRecordsBuilder.put(absoluteHostName, ImmutableSet.<ResourceRecordSet>of());
+      desiredRecords.put(absoluteHostName, ImmutableSet.<ResourceRecordSet>of());
       return;
     }
 
@@ -227,7 +228,7 @@ private void publishSubordinateHost(String hostName) {
               .setRrdatas(ImmutableList.copyOf(aaaaRrData)));
     }
 
-    desiredRecordsBuilder.put(absoluteHostName, domainRecords.build());
+    desiredRecords.put(absoluteHostName, domainRecords.build());
   }
 
   /**
@@ -273,7 +274,7 @@ public void publishHost(String hostName) {
   @Override
   protected void commitUnchecked() {
     retrier.callWithRetry(
-        getMutateZoneCallback(desiredRecordsBuilder.build()), ZoneStateException.class);
+        getMutateZoneCallback(ImmutableMap.copyOf(desiredRecords)), ZoneStateException.class);
     logger.info("Wrote to Cloud DNS");
   }
 

javatests/google/registry/dns/writer/clouddns/CloudDnsWriterTest.java

@@ -471,4 +471,22 @@ public void testLoadDomain_withPendingDelete() throws Exception {
 
     verifyZone(ImmutableSet.<ResourceRecordSet>of());
   }
+
+  @Test
+  public void testDuplicateRecords() throws Exception {
+    // In publishing DNS records, we can end up publishing information on the same host twice
+    // (through a domain change and a host change), so this scenario needs to work.
+    persistResource(
+            fakeDomain(
+                "example.tld",
+                ImmutableSet.of(persistResource(fakeHost("0.ip4.example.tld", IPv4))),
+                0))
+        .asBuilder()
+        .addSubordinateHost("ns1.example.tld")
+        .build();
+    writer.publishDomain("example.tld");
+    writer.publishHost("0.ip4.example.tld");
+
+    verifyZone(fakeDomainRecords("example.tld", 1, 0, 0, 0));
+  }
 }