fix(google): don't leave orphaned applications in the cache (#4123)

* refactor(google): convert CacheResultBuilderSpec to Java

* test(google): add another test for CacheResultBuilderTest

* refactor(google): keep an empty list around for authoritative types

If a AbstractGoogleServerGroupCachingAgent has some applications stored,
but in the next run it finds no applications, it doesn't put anything
under the "applications" key. DefaultProviderCache then has some weird
behavior where it removes all relationships associated with that
application, but leaves the existing application in the cache. That
means we'll just repeat that behavior again the next time the caching
agent runs. The application data is just orphaned but triggers
relationship evictions every single caching cycle.

Amazon doesn't have this problem because they always stick a
List<CacheData> under the applications key, even if it's empty. This is
enough to tell putCacheResult() to store that empty list, overwriting
whatever was there before.

The orphaned data isn't the cause of spinnaker/spinnaker#4511, but it
dramatically exacerbates that issue. (The real issue is that every
single regional/zonal caching agent asserts ownership over the
application and will happily delete it, which triggers deletions of
relationships that were put there by other caching agents.)

I was working on a larger refactor of CATS to make this bug less likely
to happen, but since we're about to cut a release branch, I'd rather
just check in this smaller fix.

clouddriver-google/src/main/groovy/com/netflix/spinnaker/clouddriver/google/cache/CacheResultBuilder.groovy

@@ -16,11 +16,15 @@
 
 package com.netflix.spinnaker.clouddriver.google.cache
 
+import com.google.common.collect.ImmutableSet
+import com.netflix.spinnaker.cats.agent.AgentDataType
 import com.netflix.spinnaker.cats.agent.DefaultCacheResult
 import com.netflix.spinnaker.cats.cache.CacheData
 import com.netflix.spinnaker.cats.cache.DefaultCacheData
 import groovy.util.logging.Slf4j
 
+import static com.google.common.collect.ImmutableSet.toImmutableSet
+import static com.netflix.spinnaker.cats.agent.AgentDataType.Authority.AUTHORITATIVE
 import static com.netflix.spinnaker.clouddriver.google.cache.Keys.Namespace.ON_DEMAND
 
 @Slf4j
@@ -30,6 +34,27 @@ class CacheResultBuilder {
 
   CacheMutation onDemand = new CacheMutation()
 
+  Set<String> authoritativeTypes = ImmutableSet.of()
+
+  CacheResultBuilder() {}
+
+  /**
+   * Create a CacheResultBuilder for the given dataTypes.
+   *
+   * Any authoritative types in dataTypes are guaranteed to be listed in the
+   * output. If you say you are authoritative for "clusters", but don't include
+   * any data under that namespace, an empty list will be included in the
+   * result. (Whereas if you don't pass dataTypes to the constructor, "clusters"
+   * will just be missing from the result if you don't specify any, and any
+   * existing clusters will remain in the cache).
+   */
+  CacheResultBuilder(Collection<AgentDataType> dataTypes) {
+    authoritativeTypes = dataTypes.stream()
+      .filter({ dataType -> dataType.getAuthority() == AUTHORITATIVE })
+      .map({ dataType -> dataType.getTypeName() })
+      .collect(toImmutableSet())
+  }
+
   Map<String, NamespaceBuilder> namespaceBuilders = [:].withDefault {
     String ns -> new NamespaceBuilder(namespace: ns)
   }
@@ -42,6 +67,9 @@ class CacheResultBuilder {
     Map<String, Collection<CacheData>> keep = [:]
     Map<String, Collection<String>> evict = [:]
 
+    authoritativeTypes.each { namespace ->
+      keep[namespace] = []
+    }
     if (!onDemand.toKeep.empty) {
       keep += [(ON_DEMAND.ns): onDemand.toKeep.values()]
     }

clouddriver-google/src/main/groovy/com/netflix/spinnaker/clouddriver/google/provider/agent/AbstractGoogleServerGroupCachingAgent.java

@@ -150,7 +150,7 @@ abstract class AbstractGoogleServerGroupCachingAgent
   public CacheResult loadData(ProviderCache providerCache) {
 
     try {
-      CacheResultBuilder cacheResultBuilder = new CacheResultBuilder();
+      CacheResultBuilder cacheResultBuilder = new CacheResultBuilder(DATA_TYPES);
       cacheResultBuilder.setStartTime(System.currentTimeMillis());
 
       List<GoogleServerGroup> serverGroups = getServerGroups(providerCache);

clouddriver-google/src/test/groovy/com/netflix/spinnaker/clouddriver/google/cache/CacheResultBuilderTest.java

@@ -0,0 +1,123 @@
+/*
+ * Copyright 2019 Google, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.netflix.spinnaker.clouddriver.google.cache;
+
+import static com.google.common.collect.Iterables.getOnlyElement;
+import static com.netflix.spinnaker.cats.agent.AgentDataType.Authority.AUTHORITATIVE;
+import static com.netflix.spinnaker.cats.agent.AgentDataType.Authority.INFORMATIVE;
+import static com.netflix.spinnaker.clouddriver.google.cache.Keys.Namespace.ON_DEMAND;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.netflix.spinnaker.cats.agent.DefaultCacheResult;
+import com.netflix.spinnaker.cats.cache.CacheData;
+import com.netflix.spinnaker.cats.cache.DefaultCacheData;
+import com.netflix.spinnaker.clouddriver.google.cache.CacheResultBuilder.CacheDataBuilder;
+import java.util.Collection;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+import org.junit.platform.runner.JUnitPlatform;
+import org.junit.runner.RunWith;
+
+@RunWith(JUnitPlatform.class)
+final class CacheResultBuilderTest {
+
+  @Test
+  public void testBuild() {
+    CacheResultBuilder cacheResultBuilder = new CacheResultBuilder();
+
+    CacheDataBuilder appBuilder = cacheResultBuilder.namespace("applications").keep("appKey");
+    appBuilder.setAttributes(ImmutableMap.of("santa", "claus"));
+    appBuilder.setRelationships(ImmutableMap.of("clusters", ImmutableList.of("clusterKey")));
+    CacheDataBuilder clusterBuilder = cacheResultBuilder.namespace("clusters").keep("clusterKey");
+    clusterBuilder.setAttributes(ImmutableMap.of("xmen", "wolverine"));
+    clusterBuilder.setRelationships(ImmutableMap.of("foo", ImmutableList.of("bar")));
+
+    Map<String, Collection<CacheData>> cacheResults = cacheResultBuilder.build().getCacheResults();
+
+    assertThat(cacheResults).isNotEmpty();
+    assertThat(cacheResults.get("applications")).hasSize(1);
+    CacheData application = getOnlyElement(cacheResults.get("applications"));
+    assertThat(application.getId()).isEqualTo("appKey");
+    assertThat(application.getAttributes().get("santa")).isEqualTo("claus");
+    assertThat(application.getRelationships().get("clusters")).containsExactly("clusterKey");
+    assertThat(cacheResults.get("clusters")).hasSize(1);
+    CacheData cluster = getOnlyElement(cacheResults.get("clusters"));
+    assertThat(cluster.getId()).isEqualTo("clusterKey");
+    assertThat(cluster.getAttributes().get("xmen")).isEqualTo("wolverine");
+    assertThat(cluster.getRelationships().get("foo")).containsExactly("bar");
+  }
+
+  @Test
+  public void testOnDemandEntries() {
+    CacheResultBuilder cacheResultBuilder = new CacheResultBuilder();
+
+    cacheResultBuilder.getOnDemand().getToEvict().add("evict1");
+    cacheResultBuilder.getOnDemand().getToEvict().add("evict2");
+    cacheResultBuilder
+        .getOnDemand()
+        .getToKeep()
+        .put(
+            "applications",
+            new DefaultCacheData(
+                "appKey",
+                ImmutableMap.of("santa", "claus"),
+                ImmutableMap.of("clusters", ImmutableList.of("clusterKey"))));
+
+    DefaultCacheResult result = cacheResultBuilder.build();
+
+    Map<String, Collection<String>> evictions = result.getEvictions();
+    assertThat(evictions).hasSize(1);
+    assertThat(evictions.get(ON_DEMAND.getNs())).containsExactly("evict1", "evict2");
+
+    Map<String, Collection<CacheData>> cacheResults = result.getCacheResults();
+    assertThat(cacheResults).hasSize(1);
+    assertThat(cacheResults.get(ON_DEMAND.getNs())).hasSize(1);
+    CacheData application = getOnlyElement(cacheResults.get(ON_DEMAND.getNs()));
+    assertThat(application.getId()).isEqualTo("appKey");
+    assertThat(application.getAttributes().get("santa")).isEqualTo("claus");
+    assertThat(application.getRelationships().get("clusters")).containsExactly("clusterKey");
+  }
+
+  @Test
+  public void keepsEmptyListForAuthoritativeTypes() {
+    CacheResultBuilder cacheResultBuilder =
+        new CacheResultBuilder(
+            ImmutableSet.of(
+                AUTHORITATIVE.forType("auth1"),
+                AUTHORITATIVE.forType("auth2"),
+                INFORMATIVE.forType("inf1"),
+                INFORMATIVE.forType("inf2")));
+
+    cacheResultBuilder
+        .namespace("auth2")
+        .keep("id2")
+        .setAttributes(ImmutableMap.of("attr2", "value2"));
+    cacheResultBuilder
+        .namespace("auth3")
+        .keep("id3")
+        .setAttributes(ImmutableMap.of("attr3", "value3"));
+
+    Map<String, Collection<CacheData>> cacheResults = cacheResultBuilder.build().getCacheResults();
+    assertThat(cacheResults.get("auth1")).isEmpty();
+    // Just to make sure the dataTypes constructor doesn't mess anything else up
+    assertThat(cacheResults.get("auth2")).extracting(CacheData::getId).containsExactly("id2");
+    assertThat(cacheResults.get("auth3")).extracting(CacheData::getId).containsExactly("id3");
+  }
+}