Support duplicate regions within same global endpoint

To support duplicate regions within a global endpoint we create a combination of
latency and weighted alias targets.

In the following examples an application exists in `us-west-2`, `us-east-1a` and
`us-east-1b`. Before this change global endpoints pointed directly to the
zone endpoint:

```
(latency) ALIAS app1.tenant1.global.vespa.example.com -> app1.tenant1.us-west-2.vespa.example.com
(latency) ALIAS app1.tenant1.global.vespa.example.com -> app1.tenant1.us-east-1a.vespa.example.com
(latency) ALIAS app1.tenant1.global.vespa.example.com -> app1.tenant1.us-east-1b.vespa.example.com
```

After this change we introduce an additional level of names by creating a
weighted record per region:

```
(latency) ALIAS app1.tenant1.global.vespa.example.com -> app1.tenant1.us-west-2-w.vespa.example.com
  |- (weighted) ALIAS app1.tenant1.us-west-2-w.vespa.example.com -> app1.tenant1.us-west-2.vespa.example.com
(latency) ALIAS app1.tenant1.global.vespa.example.com -> app1.tenant1.us-east-1-w.vespa.example.com
  |- (weighted) ALIAS app1.tenant1.us-east-1-w.vespa.example.com -> app1.tenant1.us-east-1a.vespa.example.com
  |- (weighted) ALIAS app1.tenant1.us-east-1-w.vespa.example.com -> app1.tenant1.us-east-1b.vespa.example.com
```

Toggling global routing status now adjusts the weight (`0 = out`) instead of
removing records as this simplified the code.

3 files changed, 21 insertions, 7 deletions

diff --git a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/LatencyAliasTarget.java b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/LatencyAliasTarget.java
index 7bd43ff1dcb..44acf1ab02e 100644
--- a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/LatencyAliasTarget.java
+++ b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/LatencyAliasTarget.java
@@ -44,6 +44,11 @@ public class LatencyAliasTarget extends AliasTarget {
         return Objects.hash(super.hashCode(), zone);
     }
 
+    @Override
+    public String toString() {
+        return "latency target for " + name() + "[id=" + id() + ",dnsZone=" + dnsZone() + "]";
+    }
+
     /** Unpack latency alias from given record data */
     public static LatencyAliasTarget unpack(RecordData data) {
         var parts = data.asString().split("/");
diff --git a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/MemoryNameService.java b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/MemoryNameService.java
index e8688b17347..03b10780e33 100644
--- a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/MemoryNameService.java
+++ b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/MemoryNameService.java
@@ -46,9 +46,10 @@ public class MemoryNameService implements NameService {
                              .map(d -> new Record(Record.Type.ALIAS, name, d.pack()))
                              .collect(Collectors.toList());
         // Satisfy idempotency contract of interface
-        records.stream()
-               .filter(r -> !this.records.contains(r))
-               .forEach(this::add);
+        for (var r1 : records) {
+            this.records.removeIf(r2 -> conflicts(r1, r2));
+        }
+        this.records.addAll(records);
         return records;
     }
 
@@ -115,10 +116,13 @@ public class MemoryNameService implements NameService {
      * most real name services.
      */
     private static boolean conflicts(Record r1, Record r2) {
-        if (!r1.name().equals(r2.name())) return false;               // Distinct names never conflict
-        if (r1.type() == Record.Type.ALIAS && r1.type() == r2.type()) // ALIAS records only require distinct data
-            return r1.data().equals(r2.data());
-        return true;                                                  // Anything else is considered a conflict
+        if (!r1.name().equals(r2.name())) return false;                // Distinct names never conflict
+        if (r1.type() == Record.Type.ALIAS && r1.type() == r2.type()) {
+            AliasTarget t1 = AliasTarget.unpack(r1.data());
+            AliasTarget t2 = AliasTarget.unpack(r2.data());
+            return t1.name().equals(t2.name());                        // ALIAS records require distinct targets
+        }
+        return true;                                                   // Anything else is considered a conflict
     }
 
 }
diff --git a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/WeightedAliasTarget.java b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/WeightedAliasTarget.java
index 9d741cb2dbc..8f81c94257e 100644
--- a/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/WeightedAliasTarget.java
+++ b/controller-api/src/main/java/com/yahoo/vespa/hosted/controller/api/integration/dns/WeightedAliasTarget.java
@@ -47,6 +47,11 @@ public class WeightedAliasTarget extends AliasTarget {
         return Objects.hash(super.hashCode(), weight);
     }
 
+    @Override
+    public String toString() {
+        return "weighted target for " + name() + "[id=" + id() + ",dnsZone=" + dnsZone() + ",weight=" + weight + "]";
+    }
+
     /** Unpack weighted alias from given record data */
     public static WeightedAliasTarget unpack(RecordData data) {
         var parts = data.asString().split("/");