Don't store full bundle objects in cluster state history

Bundles have a lot of sub-objects per state, so in systems with a
high amount of node entries, this adds unnecessary pressure on the
heap. Instead, store the string representations of the bundle and
the string representation of the diff to the previous state version
(if any). This is also inherently faster than computing the diffs
on-demand on every status page render.

Also remove mutable `official` field from `ClusterState`. Not worth
violating immutability of an object just to get some prettier (but
with high likelihood actually more confusing) status page rendering.

1 files changed, 23 insertions, 9 deletions

diff --git a/clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/StateVersionTrackerTest.java b/clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/StateVersionTrackerTest.java
index 83bdbfa0213..496d2a3b29a 100644
--- a/clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/StateVersionTrackerTest.java
+++ b/clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/StateVersionTrackerTest.java
@@ -180,8 +180,13 @@ public class StateVersionTrackerTest {
         assertTrue(versionTracker.getClusterStateHistory().isEmpty());
     }
 
-    private static ClusterStateHistoryEntry historyEntry(final String state, final long time) {
-        return new ClusterStateHistoryEntry(stateBundleWithoutAnnotations(state), time);
+    private static ClusterStateHistoryEntry historyEntry(String state, long time) {
+        return ClusterStateHistoryEntry.makeFirstEntry(stateBundleWithoutAnnotations(state), time);
+    }
+
+    private static ClusterStateHistoryEntry historyEntry(String state, String prevState, long time) {
+        return ClusterStateHistoryEntry.makeSuccessor(stateBundleWithoutAnnotations(state),
+                                                      stateBundleWithoutAnnotations(prevState), time);
     }
 
     @Test
@@ -191,12 +196,16 @@ public class StateVersionTrackerTest {
         updateAndPromote(versionTracker, stateWithoutAnnotations("distributor:3 storage:3"), 200);
         updateAndPromote(versionTracker, stateWithoutAnnotations("distributor:4 storage:4"), 300);
 
+        String s4 = "version:4 distributor:4 storage:4";
+        String s3 = "version:3 distributor:3 storage:3";
+        String s2 = "version:2 distributor:2 storage:2";
+
         // Note: newest entry first
         assertThat(versionTracker.getClusterStateHistory(),
                 equalTo(Arrays.asList(
-                         historyEntry("version:4 distributor:4 storage:4", 300),
-                         historyEntry("version:3 distributor:3 storage:3", 200),
-                         historyEntry("version:2 distributor:2 storage:2", 100))));
+                         historyEntry(s4, s3, 300),
+                         historyEntry(s3, s2, 200),
+                         historyEntry(s2, 100))));
     }
 
     @Test
@@ -208,17 +217,22 @@ public class StateVersionTrackerTest {
         updateAndPromote(versionTracker, stateWithoutAnnotations("distributor:3 storage:3"), 200);
         updateAndPromote(versionTracker, stateWithoutAnnotations("distributor:4 storage:4"), 300);
 
+        String s5 = "version:5 distributor:5 storage:5";
+        String s4 = "version:4 distributor:4 storage:4";
+        String s3 = "version:3 distributor:3 storage:3";
+        String s2 = "version:2 distributor:2 storage:2";
+
         assertThat(versionTracker.getClusterStateHistory(),
                 equalTo(Arrays.asList(
-                        historyEntry("version:4 distributor:4 storage:4", 300),
-                        historyEntry("version:3 distributor:3 storage:3", 200))));
+                        historyEntry(s4, s3, 300),
+                        historyEntry(s3, s2, 200))));
 
         updateAndPromote(versionTracker, stateWithoutAnnotations("distributor:5 storage:5"), 400);
 
         assertThat(versionTracker.getClusterStateHistory(),
                 equalTo(Arrays.asList(
-                        historyEntry("version:5 distributor:5 storage:5", 400),
-                        historyEntry("version:4 distributor:4 storage:4", 300))));
+                        historyEntry(s5, s4, 400),
+                        historyEntry(s4, s3, 300))));
     }
 
     @Test