Replace OsVersion.Node with NodeVersion

11 files changed, 187 insertions, 177 deletions

diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgrader.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgrader.java
index 60bc3d15ec6..93d1dac7382 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgrader.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgrader.java
@@ -61,7 +61,7 @@ public class OsUpgrader extends InfrastructureUpgrader {
         // Return target if we have nodes in this cloud on a lower version
         return controller().osVersion(cloud)
                            .filter(target -> controller().osVersionStatus().nodesIn(cloud).stream()
-                                                         .anyMatch(node -> node.version().isBefore(target.version())))
+                                                         .anyMatch(node -> node.currentVersion().isBefore(target.version())))
                            .map(OsVersion::version);
     }
 
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/CuratorDb.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/CuratorDb.java
index b22b8845c24..dbd52fc6d02 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/CuratorDb.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/CuratorDb.java
@@ -89,7 +89,7 @@ public class CuratorDb {
     private final ApplicationSerializer applicationSerializer = new ApplicationSerializer();
     private final RunSerializer runSerializer = new RunSerializer();
     private final OsVersionSerializer osVersionSerializer = new OsVersionSerializer();
-    private final OsVersionStatusSerializer osVersionStatusSerializer = new OsVersionStatusSerializer(osVersionSerializer);
+    private final OsVersionStatusSerializer osVersionStatusSerializer = new OsVersionStatusSerializer(osVersionSerializer, nodeVersionSerializer);
     private final RoutingPolicySerializer routingPolicySerializer = new RoutingPolicySerializer();
     private final AuditLogSerializer auditLogSerializer = new AuditLogSerializer();
     private final NameServiceQueueSerializer nameServiceQueueSerializer = new NameServiceQueueSerializer();
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/NodeVersionSerializer.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/NodeVersionSerializer.java
index d0e785198b1..4b6e997241d 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/NodeVersionSerializer.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/NodeVersionSerializer.java
@@ -1,6 +1,7 @@
 // Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.hosted.controller.persistence;
 
+import com.google.common.collect.ImmutableMap;
 import com.yahoo.component.Version;
 import com.yahoo.config.provision.HostName;
 import com.yahoo.config.provision.zone.ZoneId;
@@ -8,13 +9,9 @@ import com.yahoo.slime.ArrayTraverser;
 import com.yahoo.slime.Cursor;
 import com.yahoo.slime.Inspector;
 import com.yahoo.vespa.hosted.controller.versions.NodeVersion;
+import com.yahoo.vespa.hosted.controller.versions.NodeVersions;
 
 import java.time.Instant;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-import java.util.Optional;
 
 /**
  * Serializer for {@link com.yahoo.vespa.hosted.controller.versions.NodeVersion}.
@@ -32,37 +29,50 @@ public class NodeVersionSerializer {
 
     private static final String hostnameField = "hostname";
     private static final String zoneField = "zone";
-    private static final String currentVersionField = "currentVersion";
     private static final String wantedVersionField = "wantedVersion";
     private static final String changedAtField = "changedAt";
 
-    public void nodeVersionsToSlime(Collection<NodeVersion> nodeVersions, Cursor array, boolean writeCurrentVersion) {
-        for (var nodeVersion : nodeVersions) {
+    // Legacy fields
+    private static final String environmentField = "environment";
+    private static final String regionField = "region";
+
+    public void nodeVersionsToSlime(NodeVersions nodeVersions, Cursor array) {
+        for (var nodeVersion : nodeVersions.asMap().values()) {
             var nodeVersionObject = array.addObject();
             nodeVersionObject.setString(hostnameField, nodeVersion.hostname().value());
             nodeVersionObject.setString(zoneField, nodeVersion.zone().value());
-            if (writeCurrentVersion) {
-                nodeVersionObject.setString(currentVersionField, nodeVersion.currentVersion().toFullString());
-            }
             nodeVersionObject.setString(wantedVersionField, nodeVersion.wantedVersion().toFullString());
             nodeVersionObject.setLong(changedAtField, nodeVersion.changedAt().toEpochMilli());
         }
     }
 
-    public List<NodeVersion> nodeVersionsFromSlime(Inspector object, Optional<Version> version) {
-        var nodeVersions = new ArrayList<NodeVersion>();
-        object.traverse((ArrayTraverser) (i, entry) -> {
+    public NodeVersions nodeVersionsFromSlime(Inspector array, Version version) {
+        var nodeVersions = ImmutableMap.<HostName, NodeVersion>builder();
+        array.traverse((ArrayTraverser) (i, entry) -> {
             var hostname = HostName.from(entry.field(hostnameField).asString());
-            // TODO(mpolden): Make non-optional after September 2019
-            var zone = Serializers.optionalString(entry.field(zoneField))
-                                  .map(ZoneId::from)
-                                  .orElseGet(ZoneId::defaultId);
-            var currentVersion = version.orElseGet(() -> Version.fromString(entry.field(currentVersionField).asString()));
-            var wantedVersion = Version.fromString(entry.field(wantedVersionField).asString());
-            var changedAt = Instant.ofEpochMilli(entry.field(changedAtField).asLong());
-            nodeVersions.add(new NodeVersion(hostname, zone, currentVersion, wantedVersion, changedAt));
+            var zone = zoneFromSlime(entry);
+            // TODO(mpolden): Make the following fields non-optional after September 2019
+            var wantedVersion = Serializers.optionalString(entry.field(wantedVersionField))
+                                           .map(Version::fromString)
+                                           .orElse(Version.emptyVersion);
+            var changedAt = Serializers.optionalInstant(entry.field(changedAtField)).orElse(Instant.EPOCH);
+            nodeVersions.put(hostname, new NodeVersion(hostname, zone, version, wantedVersion, changedAt));
         });
-        return Collections.unmodifiableList(nodeVersions);
+        return new NodeVersions(nodeVersions.build());
+    }
+
+    // TODO(mpolden): Simplify and in-line after September 2019
+    private ZoneId zoneFromSlime(Inspector object) {
+        var zoneInspector = object.field(zoneField);
+        if (zoneInspector.valid()) {
+            return ZoneId.from(zoneInspector.asString());
+        }
+        var regionInspector = object.field(regionField);
+        var environmentInspector = object.field(environmentField);
+        if (regionInspector.valid() && environmentInspector.valid()) {
+            return ZoneId.from(environmentInspector.asString(), regionInspector.asString());
+        }
+        return ZoneId.defaultId();
     }
 
 }
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java
index 88805f54d65..fa29969f166 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializer.java
@@ -1,23 +1,19 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.hosted.controller.persistence;
 
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSortedMap;
 import com.yahoo.component.Version;
-import com.yahoo.config.provision.Environment;
-import com.yahoo.config.provision.HostName;
-import com.yahoo.config.provision.RegionName;
 import com.yahoo.slime.ArrayTraverser;
 import com.yahoo.slime.Cursor;
 import com.yahoo.slime.Inspector;
 import com.yahoo.slime.Slime;
+import com.yahoo.vespa.hosted.controller.versions.NodeVersion;
+import com.yahoo.vespa.hosted.controller.versions.NodeVersions;
 import com.yahoo.vespa.hosted.controller.versions.OsVersion;
 import com.yahoo.vespa.hosted.controller.versions.OsVersionStatus;
 
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
 import java.util.Objects;
-import java.util.TreeMap;
 
 /**
  * Serializer for {@link OsVersionStatus}.
@@ -39,11 +35,14 @@ public class OsVersionStatusSerializer {
     private static final String hostnameField = "hostname";
     private static final String regionField = "region";
     private static final String environmentField = "environment";
+    private static final String nodeVersionsField = "nodeVersions";
 
     private final OsVersionSerializer osVersionSerializer;
+    private final NodeVersionSerializer nodeVersionSerializer;
 
-    public OsVersionStatusSerializer(OsVersionSerializer osVersionSerializer) {
+    public OsVersionStatusSerializer(OsVersionSerializer osVersionSerializer, NodeVersionSerializer nodeVersionSerializer) {
         this.osVersionSerializer = Objects.requireNonNull(osVersionSerializer, "osVersionSerializer must be non-null");
+        this.nodeVersionSerializer = Objects.requireNonNull(nodeVersionSerializer, "nodeVersionSerializer must be non-null");
     }
 
     public Slime toSlime(OsVersionStatus status) {
@@ -53,6 +52,8 @@ public class OsVersionStatusSerializer {
         status.versions().forEach((version, nodes) -> {
             Cursor object = versions.addObject();
             osVersionSerializer.toSlime(version, object);
+            nodeVersionSerializer.nodeVersionsToSlime(nodes, object.setArray(nodeVersionsField));
+            // TODO(mpolden): Stop writing this after September 2019
             nodesToSlime(nodes, object.setArray(nodesField));
         });
         return slime;
@@ -62,40 +63,33 @@ public class OsVersionStatusSerializer {
         return new OsVersionStatus(osVersionsFromSlime(slime.get().field(versionsField)));
     }
 
-    private void nodesToSlime(List<OsVersionStatus.Node> nodes, Cursor array) {
-        nodes.forEach(node -> nodeToSlime(node, array.addObject()));
+    private void nodesToSlime(NodeVersions nodeVersions, Cursor array) {
+        nodeVersions.asMap().values().forEach(node -> nodeToSlime(node, array.addObject()));
     }
 
-    private void nodeToSlime(OsVersionStatus.Node node, Cursor object) {
+    private void nodeToSlime(NodeVersion node, Cursor object) {
         object.setString(hostnameField, node.hostname().value());
-        object.setString(versionField, node.version().toFullString());
-        object.setString(regionField, node.region().value());
-        object.setString(environmentField, node.environment().value());
+        object.setString(versionField, node.currentVersion().toFullString());
+        object.setString(regionField, node.zone().region().value());
+        object.setString(environmentField, node.zone().environment().value());
     }
 
-    private Map<OsVersion, List<OsVersionStatus.Node>> osVersionsFromSlime(Inspector array) {
-        Map<OsVersion, List<OsVersionStatus.Node>> versions = new TreeMap<>();
+    private ImmutableMap<OsVersion, NodeVersions> osVersionsFromSlime(Inspector array) {
+        var versions = ImmutableSortedMap.<OsVersion, NodeVersions>naturalOrder();
         array.traverse((ArrayTraverser) (i, object) -> {
             OsVersion osVersion = osVersionSerializer.fromSlime(object);
-            List<OsVersionStatus.Node> nodes = nodesFromSlime(object.field(nodesField));
-            versions.put(osVersion, nodes);
+            versions.put(osVersion, nodesFromSlime(object, osVersion.version()));
         });
-        return Collections.unmodifiableMap(versions);
+        return versions.build();
     }
 
-    private List<OsVersionStatus.Node> nodesFromSlime(Inspector array) {
-        List<OsVersionStatus.Node> nodes = new ArrayList<>();
-        array.traverse((ArrayTraverser) (i, object) -> nodes.add(nodeFromSlime(object)));
-        return Collections.unmodifiableList(nodes);
-    }
-
-    private OsVersionStatus.Node nodeFromSlime(Inspector object) {
-        return new OsVersionStatus.Node(
-                HostName.from(object.field(hostnameField).asString()),
-                Version.fromString(object.field(versionField).asString()),
-                Environment.from(object.field(environmentField).asString()),
-                RegionName.from(object.field(regionField).asString())
-        );
+    // TODO(mpolden): Simplify and in-line after September 2019
+    private NodeVersions nodesFromSlime(Inspector object, Version version) {
+        var newField = object.field(nodeVersionsField);
+        if (newField.valid()) {
+            return nodeVersionSerializer.nodeVersionsFromSlime(newField, version);
+        }
+        return nodeVersionSerializer.nodeVersionsFromSlime(object.field(nodesField), version);
     }
 
 }
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/VersionStatusSerializer.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/VersionStatusSerializer.java
index fd02546cf58..4373c8977de 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/VersionStatusSerializer.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/VersionStatusSerializer.java
@@ -1,7 +1,6 @@
 // Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.hosted.controller.persistence;
 
-import com.google.common.collect.ImmutableMap;
 import com.yahoo.component.Version;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.HostName;
@@ -10,7 +9,6 @@ import com.yahoo.slime.Cursor;
 import com.yahoo.slime.Inspector;
 import com.yahoo.slime.Slime;
 import com.yahoo.vespa.hosted.controller.versions.DeploymentStatistics;
-import com.yahoo.vespa.hosted.controller.versions.NodeVersion;
 import com.yahoo.vespa.hosted.controller.versions.NodeVersions;
 import com.yahoo.vespa.hosted.controller.versions.VersionStatus;
 import com.yahoo.vespa.hosted.controller.versions.VespaVersion;
@@ -22,7 +20,6 @@ import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Objects;
-import java.util.Optional;
 import java.util.Set;
 
 /**
@@ -95,7 +92,7 @@ public class VersionStatusSerializer {
     }
 
     private void nodeVersionsToSlime(NodeVersions nodeVersions, Cursor array) {
-        nodeVersionSerializer.nodeVersionsToSlime(nodeVersions.asMap().values(), array, false);
+        nodeVersionSerializer.nodeVersionsToSlime(nodeVersions, array);
     }
 
     private void deploymentStatisticsToSlime(DeploymentStatistics statistics, Cursor object) {
@@ -123,19 +120,11 @@ public class VersionStatusSerializer {
                                 object.field(isControllerVersionField).asBool(),
                                 object.field(isSystemVersionField).asBool(),
                                 object.field(isReleasedField).asBool(),
-                                nodeVersionsFromSlime(object.field(nodeVersionsField), deploymentStatistics.version()),
+                                nodeVersionSerializer.nodeVersionsFromSlime(object.field(nodeVersionsField), deploymentStatistics.version()),
                                 VespaVersion.Confidence.valueOf(object.field(confidenceField).asString())
         );
     }
 
-    private NodeVersions nodeVersionsFromSlime(Inspector object, Version version) {
-        var nodeVersions = ImmutableMap.<HostName, NodeVersion>builder();
-        for (var nodeVersion : nodeVersionSerializer.nodeVersionsFromSlime(object, Optional.of(version))) {
-            nodeVersions.put(nodeVersion.hostname(), nodeVersion);
-        }
-        return new NodeVersions(nodeVersions.build());
-    }
-
     private Set<HostName> configServersFromSlime(Inspector array) {
         Set<HostName> configServerHostnames = new LinkedHashSet<>();
         array.traverse((ArrayTraverser) (i, entry) -> configServerHostnames.add(HostName.from(entry.asString())));
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/os/OsApiHandler.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/os/OsApiHandler.java
index 450f4481c5f..c168a057bfb 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/os/OsApiHandler.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/os/OsApiHandler.java
@@ -160,17 +160,17 @@ public class OsApiHandler extends AuditLoggingRequestHandler {
         Set<OsVersion> osVersions = controller.osVersions();
 
         Cursor versions = root.setArray("versions");
-        controller.osVersionStatus().versions().forEach((osVersion, nodes) -> {
+        controller.osVersionStatus().versions().forEach((osVersion, nodeVersions) -> {
             Cursor currentVersionObject = versions.addObject();
             currentVersionObject.setString("version", osVersion.version().toFullString());
             currentVersionObject.setBool("targetVersion", osVersions.contains(osVersion));
             currentVersionObject.setString("cloud", osVersion.cloud().value());
             Cursor nodesArray = currentVersionObject.setArray("nodes");
-            nodes.forEach(node -> {
+            nodeVersions.asMap().values().forEach(nodeVersion -> {
                 Cursor nodeObject = nodesArray.addObject();
-                nodeObject.setString("hostname", node.hostname().value());
-                nodeObject.setString("environment", node.environment().value());
-                nodeObject.setString("region", node.region().value());
+                nodeObject.setString("hostname", nodeVersion.hostname().value());
+                nodeObject.setString("environment", nodeVersion.zone().environment().value());
+                nodeObject.setString("region", nodeVersion.zone().region().value());
             });
         });
 
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/versions/OsVersionStatus.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/versions/OsVersionStatus.java
index a73a20198f0..d5e83d99cdd 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/versions/OsVersionStatus.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/versions/OsVersionStatus.java
@@ -4,9 +4,7 @@ package com.yahoo.vespa.hosted.controller.versions;
 import com.google.common.collect.ImmutableMap;
 import com.yahoo.component.Version;
 import com.yahoo.config.provision.CloudName;
-import com.yahoo.config.provision.Environment;
 import com.yahoo.config.provision.HostName;
-import com.yahoo.config.provision.RegionName;
 import com.yahoo.config.provision.zone.ZoneApi;
 import com.yahoo.vespa.hosted.controller.Controller;
 import com.yahoo.vespa.hosted.controller.application.SystemApplication;
@@ -14,11 +12,11 @@ import com.yahoo.vespa.hosted.controller.maintenance.OsUpgrader;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -29,25 +27,25 @@ import java.util.stream.Collectors;
  */
 public class OsVersionStatus {
 
-    public static final OsVersionStatus empty = new OsVersionStatus(Collections.emptyMap());
+    public static final OsVersionStatus empty = new OsVersionStatus(ImmutableMap.of());
 
-    private final Map<OsVersion, List<Node>> versions;
+    private final Map<OsVersion, NodeVersions> versions;
 
     /** Public for serialization purpose only. Use {@link OsVersionStatus#compute(Controller)} for an up-to-date status */
-    public OsVersionStatus(Map<OsVersion, List<Node>> versions) {
+    public OsVersionStatus(ImmutableMap<OsVersion, NodeVersions> versions) {
         this.versions = ImmutableMap.copyOf(Objects.requireNonNull(versions, "versions must be non-null"));
     }
 
     /** All known OS versions and their nodes */
-    public Map<OsVersion, List<Node>> versions() {
+    public Map<OsVersion, NodeVersions> versions() {
         return versions;
     }
 
     /** Returns nodes eligible for OS upgrades that exist in given cloud */
-    public List<Node> nodesIn(CloudName cloud) {
+    public List<NodeVersion> nodesIn(CloudName cloud) {
         return versions.entrySet().stream()
                        .filter(entry -> entry.getKey().cloud().equals(cloud))
-                       .flatMap(entry -> entry.getValue().stream())
+                       .flatMap(entry -> entry.getValue().asMap().values().stream())
                        .collect(Collectors.toUnmodifiableList());
     }
 
@@ -61,28 +59,52 @@ public class OsVersionStatus {
 
     /** Compute the current OS versions in this system. This is expensive and should be called infrequently */
     public static OsVersionStatus compute(Controller controller) {
-        Map<OsVersion, List<Node>> versions = new HashMap<>();
-
-        // Always include all target versions
-        controller.osVersions().forEach(osVersion -> versions.put(osVersion, new ArrayList<>()));
-
-        for (SystemApplication application : SystemApplication.all()) {
-            if (!application.isEligibleForOsUpgrades()) {
-                continue; // Avoid querying applications that are not eligible for OS upgrades
-            }
-            for (ZoneApi zone : zonesToUpgrade(controller)) {
-                controller.serviceRegistry().configServer().nodeRepository().list(zone.getId(), application.id()).stream()
+        var osVersionStatus = controller.osVersionStatus();
+        var osVersions = new HashMap<OsVersion, List<NodeVersion>>();
+        var now = controller.clock().instant();
+        controller.osVersions().forEach(osVersion -> osVersions.put(osVersion, new ArrayList<>()));
+
+        for (var application : SystemApplication.all()) {
+            if (!application.isEligibleForOsUpgrades()) continue;
+            for (var zone : zonesToUpgrade(controller)) {
+                var targetOsVersion = controller.serviceRegistry().configServer().nodeRepository()
+                                                .targetVersionsOf(zone.getId())
+                                                .osVersion(application.nodeType())
+                                                .orElse(Version.emptyVersion);
+                controller.serviceRegistry().configServer().nodeRepository()
+                          .list(zone.getId(), application.id()).stream()
                           .filter(node -> OsUpgrader.eligibleForUpgrade(node, application))
-                          .map(node -> new Node(node.hostname(), node.currentOsVersion(), zone.getEnvironment(), zone.getRegionName()))
-                          .forEach(node -> {
-                              var version = new OsVersion(node.version(), zone.getCloudName());
-                              versions.putIfAbsent(version, new ArrayList<>());
-                              versions.get(version).add(node);
+                          .map(node -> new NodeVersion(node.hostname(), zone.getId(), node.currentOsVersion(), targetOsVersion, now))
+                          .forEach(nodeVersion -> {
+                              var newNodeVersion = osVersionStatus.of(nodeVersion.hostname())
+                                                                  .map(nv -> nv.withCurrentVersion(nodeVersion.currentVersion(), now)
+                                                                               .withWantedVersion(nodeVersion.wantedVersion()))
+                                                                  .orElse(nodeVersion);
+                              var version = new OsVersion(newNodeVersion.currentVersion(), zone.getCloudName());
+                              osVersions.putIfAbsent(version, new ArrayList<>());
+                              osVersions.get(version).add(newNodeVersion);
                           });
             }
         }
 
-        return new OsVersionStatus(versions);
+        var newOsVersions = ImmutableMap.<OsVersion, NodeVersions>builder();
+        for (var osVersion : osVersions.entrySet()) {
+            var nodeVersions = ImmutableMap.<HostName, NodeVersion>builder();
+            for (var nodeVersion : osVersion.getValue()) {
+                nodeVersions.put(nodeVersion.hostname(), nodeVersion);
+            }
+            newOsVersions.put(osVersion.getKey(), new NodeVersions(nodeVersions.build()));
+        }
+        return new OsVersionStatus(newOsVersions.build());
+    }
+
+    /** Returns version of node identified by given host name */
+    private Optional<NodeVersion> of(HostName hostname) {
+        return versions.values().stream()
+                       .map(nodeVersions -> nodeVersions.asMap().get(hostname))
+                       .map(Optional::ofNullable)
+                       .flatMap(Optional::stream)
+                       .findFirst();
     }
 
     private static List<ZoneApi> zonesToUpgrade(Controller controller) {
@@ -92,52 +114,4 @@ public class OsVersionStatus {
                          .collect(Collectors.toUnmodifiableList());
     }
 
-    /** A node in this system and its current OS version */
-    public static class Node {
-
-        private final HostName hostname;
-        private final Version version;
-        private final Environment environment;
-        private final RegionName region;
-
-        public Node(HostName hostname, Version version, Environment environment, RegionName region) {
-            this.hostname = Objects.requireNonNull(hostname, "hostname must be non-null");
-            this.version = Objects.requireNonNull(version, "version must be non-null");
-            this.environment = Objects.requireNonNull(environment, "environment must be non-null");
-            this.region = Objects.requireNonNull(region, "region must be non-null");
-        }
-
-        public HostName hostname() {
-            return hostname;
-        }
-
-        public Version version() {
-            return version;
-        }
-
-        public Environment environment() {
-            return environment;
-        }
-
-        public RegionName region() {
-            return region;
-        }
-
-        @Override
-        public boolean equals(Object o) {
-            if (this == o) return true;
-            if (o == null || getClass() != o.getClass()) return false;
-            Node node = (Node) o;
-            return Objects.equals(hostname, node.hostname) &&
-                   Objects.equals(version, node.version) &&
-                   environment == node.environment &&
-                   Objects.equals(region, node.region);
-        }
-
-        @Override
-        public int hashCode() {
-            return Objects.hash(hostname, version, environment, region);
-        }
-    }
-
 }
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgraderTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgraderTest.java
index 1af5fafbb79..5e92112d465 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgraderTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsUpgraderTest.java
@@ -12,7 +12,7 @@ import com.yahoo.vespa.hosted.controller.application.SystemApplication;
 import com.yahoo.vespa.hosted.controller.deployment.DeploymentTester;
 import com.yahoo.vespa.hosted.controller.integration.NodeRepositoryMock;
 import com.yahoo.vespa.hosted.controller.integration.ZoneApiMock;
-import com.yahoo.vespa.hosted.controller.versions.OsVersionStatus;
+import com.yahoo.vespa.hosted.controller.versions.NodeVersion;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -111,13 +111,13 @@ public class OsUpgraderTest {
         assertWanted(version1, SystemApplication.tenantHost, zone1.getId(), zone2.getId(), zone3.getId(), zone4.getId());
         statusUpdater.maintain();
         assertTrue("All nodes on target version", tester.controller().osVersionStatus().nodesIn(cloud).stream()
-                                                        .allMatch(node -> node.version().equals(version1)));
+                                                        .allMatch(node -> node.currentVersion().equals(version1)));
     }
 
-    private List<OsVersionStatus.Node> nodesOn(Version version) {
+    private List<NodeVersion> nodesOn(Version version) {
         return tester.controller().osVersionStatus().versions().entrySet().stream()
                      .filter(entry -> entry.getKey().version().equals(version))
-                     .flatMap(entry -> entry.getValue().stream())
+                     .flatMap(entry -> entry.getValue().asMap().values().stream())
                      .collect(Collectors.toList());
     }
 
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsVersionStatusUpdaterTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsVersionStatusUpdaterTest.java
index fe7f39fd66d..e51fcff33d1 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsVersionStatusUpdaterTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OsVersionStatusUpdaterTest.java
@@ -3,18 +3,15 @@ package com.yahoo.vespa.hosted.controller.maintenance;
 
 import com.yahoo.component.Version;
 import com.yahoo.config.provision.CloudName;
+import com.yahoo.config.provision.zone.UpgradePolicy;
 import com.yahoo.config.provision.zone.ZoneApi;
 import com.yahoo.vespa.hosted.controller.ControllerTester;
-import com.yahoo.config.provision.zone.UpgradePolicy;
-import com.yahoo.config.provision.zone.ZoneId;
 import com.yahoo.vespa.hosted.controller.persistence.MockCuratorDb;
 import com.yahoo.vespa.hosted.controller.versions.OsVersion;
 import com.yahoo.vespa.hosted.controller.versions.OsVersionStatus;
 import org.junit.Test;
 
 import java.time.Duration;
-import java.util.List;
-import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -47,10 +44,10 @@ public class OsVersionStatusUpdaterTest {
         tester.controller().upgradeOsIn(cloud, version1, false);
         statusUpdater.maintain();
 
-        Map<OsVersion, List<OsVersionStatus.Node>> osVersions = tester.controller().osVersionStatus().versions();
+        var osVersions = tester.controller().osVersionStatus().versions();
         assertEquals(2, osVersions.size());
-        assertFalse("All nodes on unknown version", osVersions.get(new OsVersion(Version.emptyVersion, cloud)).isEmpty());
-        assertTrue("No nodes on current target", osVersions.get(new OsVersion(version1, cloud)).isEmpty());
+        assertFalse("All nodes on unknown version", osVersions.get(new OsVersion(Version.emptyVersion, cloud)).asMap().isEmpty());
+        assertTrue("No nodes on current target", osVersions.get(new OsVersion(version1, cloud)).asMap().isEmpty());
     }
 
 }
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializerTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializerTest.java
index 5073f651fd3..c60137e47b4 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializerTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/OsVersionStatusSerializerTest.java
@@ -1,18 +1,23 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.hosted.controller.persistence;
 
+import com.google.common.collect.ImmutableMap;
 import com.yahoo.component.Version;
 import com.yahoo.config.provision.CloudName;
-import com.yahoo.config.provision.Environment;
 import com.yahoo.config.provision.HostName;
-import com.yahoo.config.provision.RegionName;
+import com.yahoo.config.provision.zone.ZoneId;
+import com.yahoo.vespa.config.SlimeUtils;
+import com.yahoo.vespa.hosted.controller.versions.NodeVersion;
+import com.yahoo.vespa.hosted.controller.versions.NodeVersions;
 import com.yahoo.vespa.hosted.controller.versions.OsVersion;
 import com.yahoo.vespa.hosted.controller.versions.OsVersionStatus;
 import org.junit.Test;
 
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.time.Instant;
 import java.util.List;
-import java.util.Map;
-import java.util.TreeMap;
 
 import static org.junit.Assert.assertEquals;
 
@@ -25,22 +30,41 @@ public class OsVersionStatusSerializerTest {
     public void test_serialization() {
         Version version1 = Version.fromString("7.1");
         Version version2 = Version.fromString("7.2");
-        Map<OsVersion, List<OsVersionStatus.Node>> versions = new TreeMap<>();
+        var versions = ImmutableMap.<OsVersion, NodeVersions>builder();
 
-        versions.put(new OsVersion(version1, CloudName.defaultName()), List.of(
-                new OsVersionStatus.Node(HostName.from("node1"), version1, Environment.prod, RegionName.from("us-west")),
-                new OsVersionStatus.Node(HostName.from("node2"), version1, Environment.prod, RegionName.from("us-east"))
-        ));
-        versions.put(new OsVersion(version2, CloudName.defaultName()), List.of(
-                new OsVersionStatus.Node(HostName.from("node3"), version2, Environment.prod, RegionName.from("us-west")),
-                new OsVersionStatus.Node(HostName.from("node4"), version2, Environment.prod, RegionName.from("us-east"))
+        versions.put(new OsVersion(version1, CloudName.defaultName()), NodeVersions.EMPTY.with(List.of(
+                new NodeVersion(HostName.from("node1"), ZoneId.from("prod", "us-west"), version1, version2, Instant.ofEpochMilli(1)),
+                new NodeVersion(HostName.from("node2"), ZoneId.from("prod", "us-east"), version1, version2, Instant.ofEpochMilli(2))
+        )));
+        versions.put(new OsVersion(version2, CloudName.defaultName()), NodeVersions.EMPTY.with(List.of(
+                new NodeVersion(HostName.from("node3"), ZoneId.from("prod", "us-west"), version2, version2, Instant.ofEpochMilli(3)),
+                new NodeVersion(HostName.from("node4"), ZoneId.from("prod", "us-east"), version2, version2, Instant.ofEpochMilli(4))
+        )));
 
-        ));
-
-        OsVersionStatusSerializer serializer = new OsVersionStatusSerializer(new OsVersionSerializer());
-        OsVersionStatus status = new OsVersionStatus(versions);
+        OsVersionStatusSerializer serializer = new OsVersionStatusSerializer(new OsVersionSerializer(), new NodeVersionSerializer());
+        OsVersionStatus status = new OsVersionStatus(versions.build());
         OsVersionStatus serialized = serializer.fromSlime(serializer.toSlime(status));
         assertEquals(status.versions(), serialized.versions());
     }
 
+    @Test
+    public void testLegacySerialization() throws Exception {
+        var data = Files.readAllBytes(Paths.get("src/test/java/com/yahoo/vespa/hosted/controller/persistence/testdata/os-version-status-legacy-format.json"));
+        var serializer = new OsVersionStatusSerializer(new OsVersionSerializer(), new NodeVersionSerializer());
+        var versions = ImmutableMap.of(
+                new OsVersion(Version.fromString("7.42"), CloudName.from("yahoo")),
+                NodeVersions.EMPTY.with(List.of(new NodeVersion(HostName.from("node1"), ZoneId.from("prod", "us-north-1"),
+                                                                Version.fromString("7.42"), Version.emptyVersion, Instant.EPOCH),
+                                                new NodeVersion(HostName.from("node2"), ZoneId.from("prod", "us-north-2"),
+                                                                Version.fromString("7.42"), Version.emptyVersion, Instant.EPOCH))));
+
+        var deserialized = serializer.fromSlime(SlimeUtils.jsonToSlime(data));
+        assertEquals(versions, deserialized.versions());
+
+
+        var serialized = new String(SlimeUtils.toJsonBytes(serializer.toSlime(new OsVersionStatus(versions))), StandardCharsets.UTF_8);
+        assertEquals("{\"versions\":[{\"version\":\"7.42.0\",\"cloud\":\"yahoo\",\"nodeVersions\":[{\"hostname\":\"node1\",\"zone\":\"prod.us-north-1\",\"wantedVersion\":\"0.0.0\",\"changedAt\":0},{\"hostname\":\"node2\",\"zone\":\"prod.us-north-2\",\"wantedVersion\":\"0.0.0\",\"changedAt\":0}],\"nodes\":[{\"hostname\":\"node1\",\"version\":\"7.42.0\",\"region\":\"us-north-1\",\"environment\":\"prod\"},{\"hostname\":\"node2\",\"version\":\"7.42.0\",\"region\":\"us-north-2\",\"environment\":\"prod\"}]}]}",
+                     serialized);
+    }
+
 }
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/testdata/os-version-status-legacy-format.json b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/testdata/os-version-status-legacy-format.json
new file mode 100644
index 00000000000..5a6a864cbf8
--- /dev/null
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/testdata/os-version-status-legacy-format.json
@@ -0,0 +1,22 @@
+{
+  "versions": [
+    {
+      "version": "7.42",
+      "cloud": "yahoo",
+      "nodes": [
+        {
+          "hostname": "node1",
+          "version": "7.42",
+          "region": "us-north-1",
+          "environment": "prod"
+        },
+        {
+          "hostname": "node2",
+          "version": "7.42",
+          "region": "us-north-2",
+          "environment": "test"
+        }
+      ]
+    }
+  ]
+}