Simplify Change

19 files changed, 159 insertions, 222 deletions

diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/Application.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/Application.java
index abfd94f87a2..e47f5519fae 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/Application.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/Application.java
@@ -13,7 +13,6 @@ import com.yahoo.vespa.hosted.controller.api.integration.organization.IssueId;
 import com.yahoo.vespa.hosted.controller.application.ApplicationRotation;
 import com.yahoo.vespa.hosted.controller.application.ApplicationVersion;
 import com.yahoo.vespa.hosted.controller.application.Change;
-import com.yahoo.vespa.hosted.controller.application.Change.VersionChange;
 import com.yahoo.vespa.hosted.controller.application.Deployment;
 import com.yahoo.vespa.hosted.controller.application.DeploymentJobs;
 import com.yahoo.vespa.hosted.controller.rotation.RotationId;
@@ -152,10 +151,7 @@ public class Application {
 
     /** Returns the version a new deployment to this zone should use for this application */
     public Version deployVersionIn(ZoneId zone, Controller controller) {
-        if (deploying() instanceof VersionChange)
-            return ((Change.VersionChange) deploying()).version();
-
-        return versionIn(zone, controller);
+        return deploying.platform().orElse(versionIn(zone, controller));
     }
 
     /** Returns the current version this application has, or if none; should use, in the given zone */
@@ -166,8 +162,8 @@ public class Application {
 
     /** Returns the application version a deployment to this zone should use, or empty if we don't know */
     public Optional<ApplicationVersion> deployApplicationVersionIn(ZoneId zone) {
-        if (deploying() instanceof Change.ApplicationChange) {
-            ApplicationVersion version = ((Change.ApplicationChange) deploying()).version();
+        if (deploying().application().isPresent()) {
+            ApplicationVersion version = deploying().application().get();
             if (version == ApplicationVersion.unknown)
                 return Optional.empty();
             else
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/ApplicationController.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/ApplicationController.java
index dc39268c48d..fed70b8d175 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/ApplicationController.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/ApplicationController.java
@@ -39,7 +39,6 @@ import com.yahoo.vespa.hosted.controller.api.integration.routing.RoutingGenerato
 import com.yahoo.vespa.hosted.controller.api.integration.zone.ZoneId;
 import com.yahoo.vespa.hosted.controller.application.ApplicationPackage;
 import com.yahoo.vespa.hosted.controller.application.ApplicationVersion;
-import com.yahoo.vespa.hosted.controller.application.Change;
 import com.yahoo.vespa.hosted.controller.application.Deployment;
 import com.yahoo.vespa.hosted.controller.application.DeploymentJobs;
 import com.yahoo.vespa.hosted.controller.application.DeploymentJobs.JobReport;
@@ -323,8 +322,8 @@ public class ApplicationController {
 
             // TODO: Remove after introducing new application version number
             if ( ! options.deployCurrentVersion && applicationPackageFromDeployer.isPresent()) {
-                if (application.deploying() instanceof Change.ApplicationChange) {
-                    application = application.withDeploying(Change.ApplicationChange.of(applicationVersion));
+                if (application.deploying().application().isPresent()) {
+                    application = application.withDeploying(application.deploying().with(applicationVersion));
                 }
                 if (!canDeployDirectlyTo(zone, options) && jobType.isPresent()) {
                     // Update with (potentially) missing information about what we triggered:
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/ApplicationList.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/ApplicationList.java
index dd7c238053c..fe085a6bfa4 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/ApplicationList.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/ApplicationList.java
@@ -54,7 +54,7 @@ public class ApplicationList {
 
     /** Returns the subset of applications which are currently upgrading (to any version) */
     public ApplicationList upgrading() {
-        return listOf(list.stream().filter(ApplicationList::isUpgrading));
+        return listOf(list.stream().filter(application -> application.deploying().platform().isPresent()));
     }
 
     /** Returns the subset of applications which are currently upgrading to the given version */
@@ -170,16 +170,8 @@ public class ApplicationList {
 
     // ----------------------------------- Internal helpers
 
-    private static boolean isUpgrading(Application application) {
-        if ( ! (application.deploying().isPresent()) ) return false;
-        if ( ! (application.deploying() instanceof Change.VersionChange) ) return false;
-        return true;
-    }
-
     private static boolean isUpgradingTo(Version version, Application application) {
-        if ( ! (application.deploying().isPresent()) ) return false;
-        if ( ! (application.deploying() instanceof Change.VersionChange) ) return false;
-        return ((Change.VersionChange)application.deploying()).version().equals(version);
+        return application.deploying().platform().equals(Optional.of(version));
     }
 
     private static boolean failingOn(Version version, Application application) {
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/Change.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/Change.java
index 5e3952f5ad7..7c1049da587 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/Change.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/Change.java
@@ -6,125 +6,93 @@ import com.yahoo.config.application.api.DeploymentSpec;
 
 import java.time.Instant;
 import java.util.Objects;
+import java.util.Optional;
 
 /**
- * A change to an application
+ * The changes to an application we currently wish to complete deploying.
+ * A goal of the system is to deploy platform and application versions separately.
+ * However, this goal must some times be traded against others, so a change can
+ * consist of both an application and platform version change.
+ *
+ * This is immutable.
  *
  * @author bratseth
  */
-public abstract class Change {
-
-    private static NoChange none = new NoChange();
-
-    /** Returns true if this change is blocked by the given spec at the given instant */
-    public abstract boolean blockedBy(DeploymentSpec deploymentSpec, Instant instant);
-
-    public abstract boolean isPresent();
-
-    public static Change empty() { return none; }
-
-    public static class NoChange extends Change {
+public final class Change {
 
-        private NoChange() { }
+    private static Change empty = new Change(Optional.empty(), Optional.empty());
 
-        @Override
-        public boolean isPresent() { return false; }
+    /** The platform version we are upgrading to, or empty if none */
+    private final Optional<Version> platform;
 
-        @Override
-        public boolean blockedBy(DeploymentSpec deploymentSpec, Instant instant) {
-            return false;
-        }
+    /** The application version we are changing to, or empty if none */
+    private final Optional<ApplicationVersion> application;
 
+    private Change(Optional<Version> platform, Optional<ApplicationVersion> application) {
+        Objects.requireNonNull(platform, "platform cannot be null");
+        Objects.requireNonNull(application, "application cannot be null");
+        this.platform = platform;
+        this.application = application;
     }
 
-    /** A change to the application package version of an application */
-    public static class ApplicationChange extends Change {
-
-        private final ApplicationVersion version;
-
-        private ApplicationChange(ApplicationVersion version) {
-            Objects.requireNonNull(version, "version cannot be null");
-            this.version = version;
-        }
-
-        @Override
-        public boolean isPresent() { return true; }
-
-        /** The application package version in this change, or empty if not known yet */
-        public ApplicationVersion version() { return version; }
-
-        @Override
-        public boolean blockedBy(DeploymentSpec deploymentSpec, Instant instant) {
-            return ! deploymentSpec.canChangeRevisionAt(instant);
-        }
-
-        @Override
-        public int hashCode() { return version.hashCode(); }
-
-        @Override
-        public boolean equals(Object other) {
-            if (this == other) return true;
-            if ( ! (other instanceof ApplicationChange)) return false;
-            return ((ApplicationChange)other).version.equals(this.version);
-        }
-
-        /**
-         * Creates an application change which we don't know anything about.
-         * We are notified that a change has occurred by completion of the component job
-         * but do not get to know about what the change is until a subsequent deployment
-         * happens.
-         */
-        public static ApplicationChange unknown() {
-            return new ApplicationChange(ApplicationVersion.unknown);
-        }
-
-        public static ApplicationChange of(ApplicationVersion version) {
-            return new ApplicationChange(version);
-        }
-
-        @Override
-        public String toString() {
-            return "application change to " + version;
-        }
-
+    /** Returns true if this change is blocked by the given spec at the given instant */
+    public boolean blockedBy(DeploymentSpec deploymentSpec, Instant instant) {
+        if (platform.isPresent() && ! deploymentSpec.canUpgradeAt(instant)) return true;
+        if (application.isPresent() && ! deploymentSpec.canChangeRevisionAt(instant)) return true;
+        return false;
     }
 
-    /** A change to the Vespa version running an application */
-    public static class VersionChange extends Change {
-
-        private final Version version;
+    /** Returns whether a change shoudl currently be deployed */
+    public boolean isPresent() {
+        return platform.isPresent() || application.isPresent();
+    }
 
-        public VersionChange(Version version) {
-            Objects.requireNonNull(version, "version cannot be null");
-            this.version = version;
-        }
+    /** Returns the platform version change which should currently be deployed, if any */
+    public Optional<Version> platform() { return platform; }
 
-        @Override
-        public boolean isPresent() { return true; }
+    /** Returns the application version change which should currently be deployed, if any */
+    public Optional<ApplicationVersion> application() { return application; }
 
-        /** The Vespa version this changes to */
-        public Version version() { return version; }
+    /** Returns an instance representing no change */
+    public static Change empty() { return empty; }
 
-        @Override
-        public boolean blockedBy(DeploymentSpec deploymentSpec, Instant instant) {
-            return ! deploymentSpec.canUpgradeAt(instant);
-        }
+    /** Returns a version of this change which replaces or adds this application change */
+    public Change with(ApplicationVersion applicationVersion) {
+        return new Change(platform, Optional.of(applicationVersion));
+    }
 
-        @Override
-        public int hashCode() { return version.hashCode(); }
+    @Override
+    public int hashCode() { return Objects.hash(platform, application); }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) return true;
+        if ( ! (other instanceof Change)) return false;
+        Change o = (Change)other;
+        if ( ! o.platform.equals(this.platform)) return false;
+        if ( ! o.application.equals(this.application)) return false;
+        return true;
+    }
 
-        @Override
-        public boolean equals(Object other) {
-            if (this == other) return true;
-            if ( ! (other instanceof VersionChange)) return false;
-            return ((VersionChange)other).version.equals(this.version);
-        }
+    @Override
+    public String toString() {
+        String platformString = platform.map(v -> "upgrade to " + v).orElse(null);
+        String applicationString = application.map(v -> "application change to " + v).orElse(null);
+        if (platformString != null && applicationString != null)
+            return platformString + " and " + applicationString;
+        if (platformString != null)
+            return platformString;
+        if (applicationString != null)
+            return applicationString;
+        return "no change";
+    }
 
-        @Override
-        public String toString() {
-            return "version change to " + version;
-        }
+    public static Change of(ApplicationVersion applicationVersion) {
+        return new Change(Optional.empty(), Optional.of(applicationVersion));
+    }
 
+    public static Change of(Version platformChange) {
+        return new Change(Optional.of(platformChange), Optional.empty());
     }
 
 }
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/DeploymentJobs.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/DeploymentJobs.java
index 542343d66c0..bb7b39eed0f 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/DeploymentJobs.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/DeploymentJobs.java
@@ -75,7 +75,7 @@ public class DeploymentJobs {
             if (job == null) job = JobStatus.initial(jobType);
             return job.withTriggering(version,
                                       applicationVersion,
-                                      change instanceof Change.VersionChange,
+                                      change.platform().isPresent(),
                                       reason,
                                       triggerTime);
         });
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/JobStatus.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/JobStatus.java
index 10463e6d296..e165d3c9fe5 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/JobStatus.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/application/JobStatus.java
@@ -209,12 +209,9 @@ public class JobStatus {
         // TODO: Consider a version and application version for each JobStatus, to compare against a Target (instead of Change, which is, really, a Target).
         /** Returns whether the job last completed for the given change */
         public boolean lastCompletedWas(Change change) {
-            if (change instanceof Change.ApplicationChange) {
-                return ((Change.ApplicationChange) change).version().equals(applicationVersion);
-            } else if (change instanceof Change.VersionChange) {
-                return version().equals(((Change.VersionChange) change).version());
-            }
-            throw new IllegalArgumentException("Unexpected change: " + change.getClass());
+            if (change.platform().isPresent() && ! change.platform().get().equals(version())) return false;
+            if (change.application().isPresent() && ! change.application().get().equals(applicationVersion)) return false;
+            return true;
         }
 
         @Override
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTrigger.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTrigger.java
index 18838f243ad..f3aeeabd3d4 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTrigger.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTrigger.java
@@ -12,7 +12,6 @@ import com.yahoo.vespa.hosted.controller.api.integration.zone.ZoneId;
 import com.yahoo.vespa.hosted.controller.application.ApplicationList;
 import com.yahoo.vespa.hosted.controller.application.ApplicationVersion;
 import com.yahoo.vespa.hosted.controller.application.Change;
-import com.yahoo.vespa.hosted.controller.application.Change.VersionChange;
 import com.yahoo.vespa.hosted.controller.application.Deployment;
 import com.yahoo.vespa.hosted.controller.application.DeploymentJobs.JobError;
 import com.yahoo.vespa.hosted.controller.application.DeploymentJobs.JobReport;
@@ -87,16 +86,11 @@ public class DeploymentTrigger {
                 if (report.jobType() == JobType.component) {
                     if (acceptNewApplicationVersionNow(application)) {
                         // Set this as the change we are doing, unless we are already pushing a platform change
-                        if ( ! ( application.deploying() instanceof Change.VersionChange)) {
-                            Change.ApplicationChange applicationChange = Change.ApplicationChange.unknown();
-                            // TODO: Remove guard when source is always reported by component
-                            if (report.sourceRevision().isPresent()) {
-                                applicationChange = Change.ApplicationChange.of(
-                                        ApplicationVersion.from(report.sourceRevision().get(),
-                                                                report.buildNumber())
-                                );
-                            }
-                            application = application.withDeploying(applicationChange);
+                        if ( ! ( application.deploying().platform().isPresent())) {
+                            ApplicationVersion applicationVersion = ApplicationVersion.unknown;
+                            if (report.sourceRevision().isPresent())
+                                applicationVersion = ApplicationVersion.from(report.sourceRevision().get(), report.buildNumber());
+                            application = application.withDeploying(Change.of(applicationVersion));
                         }
                     }
                     else { // postpone
@@ -140,11 +134,11 @@ public class DeploymentTrigger {
             if (deployment == null) return false;
 
             // Check actual job outcome (the deployment)
-            if (change instanceof VersionChange) {
-                if (((VersionChange)change).version().isAfter(deployment.version())) return false; // later is ok
+            if (change.platform().isPresent()) {
+                if (change.platform().get().isAfter(deployment.version())) return false; // later is ok
             }
-            else if (((Change.ApplicationChange)change).version() != ApplicationVersion.unknown) {
-                if ( ! ((Change.ApplicationChange)change).version().equals(deployment.applicationVersion())) return false;
+            else if (change.application().isPresent() && change.application().get() != ApplicationVersion.unknown) { // TODO: Should not be "else"
+                if ( ! change.application().get().equals(deployment.applicationVersion())) return false;
             }
             else {
                 return false; // If we don't yet know the application version we are deploying, then we are not complete
@@ -172,8 +166,8 @@ public class DeploymentTrigger {
         // Should the first step be triggered?
         if ( ! jobs.isEmpty() && jobs.get(0).equals(JobType.systemTest) ) {
             JobStatus systemTestStatus = application.deploymentJobs().jobStatus().get(JobType.systemTest);
-            if (application.deploying() instanceof Change.VersionChange) {
-                Version target = ((Change.VersionChange) application.deploying()).version();
+            if (application.deploying().platform().isPresent()) {
+                Version target = application.deploying().platform().get();
                 if (systemTestStatus == null
                     || ! systemTestStatus.lastTriggered().isPresent()
                     || ! systemTestStatus.isSuccess()
@@ -219,10 +213,8 @@ public class DeploymentTrigger {
         if ( ! application.deploying().isPresent()) return false;
         if (next == null) return true;
 
-        Change change = application.deploying();
-
-        if (change instanceof Change.VersionChange) { // Propagate upgrade while making sure we never downgrade
-            Version targetVersion = ((Change.VersionChange)change).version();
+        if (application.deploying().platform().isPresent()) { // Propagate upgrade while making sure we never downgrade
+            Version targetVersion = application.deploying().platform().get();
 
             if (next.type().isTest()) {
                 // Is it not yet this job's turn to upgrade?
@@ -271,10 +263,9 @@ public class DeploymentTrigger {
                 throw new IllegalArgumentException("Could not start " + change + " on " + application + ": " +
                                                    application.deploying() + " is already in progress");
             application = application.withDeploying(change);
-            if (change instanceof Change.ApplicationChange)
+            if (change.application().isPresent())
                 application = application.withOutstandingChange(false);
-            application = trigger(JobType.systemTest, application, false,
-                                  (change instanceof Change.VersionChange ? "Upgrading to " + ((Change.VersionChange)change).version() : "Deploying " + change));
+            application = trigger(JobType.systemTest, application, false, change.toString());
             applications().store(application);
         });
     }
@@ -381,8 +372,8 @@ public class DeploymentTrigger {
             application.deploying().blockedBy(application.deploymentSpec(), clock.instant())) return false;
 
         // Don't downgrade or redeploy the same version in production needlessly
-        if (application.deploying() instanceof VersionChange &&
-            jobType.isProduction() && alreadyDeployed(((VersionChange) application.deploying()).version(), application, jobType)) return false;
+        if (application.deploying().platform().isPresent() &&
+            jobType.isProduction() && alreadyDeployed((application.deploying().platform().get()), application, jobType)) return false;
 
         if (application.deploymentJobs().isRunning(jobType, jobTimeoutLimit())) return false;
         if  ( ! hasJob(jobType, application)) return false;
@@ -418,7 +409,7 @@ public class DeploymentTrigger {
     private boolean acceptNewApplicationVersionNow(LockedApplication application) {
         if ( ! application.deploying().isPresent()) return true;
 
-        if (application.deploying() instanceof Change.ApplicationChange) return true; // more changes are ok
+        if (application.deploying().application().isPresent()) return true; // more application changes are ok
 
         if (application.deploymentJobs().hasFailures()) return true; // allow changes to fix upgrade problems
 
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployer.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployer.java
index 4485a603f61..0752b90eca9 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployer.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployer.java
@@ -4,17 +4,18 @@ package com.yahoo.vespa.hosted.controller.maintenance;
 import com.yahoo.vespa.hosted.controller.Application;
 import com.yahoo.vespa.hosted.controller.Controller;
 import com.yahoo.vespa.hosted.controller.application.ApplicationList;
+import com.yahoo.vespa.hosted.controller.application.ApplicationVersion;
 import com.yahoo.vespa.hosted.controller.application.Change;
 
 import java.time.Duration;
 
 /**
  * Deploys application changes which have been postponed due to an ongoing upgrade
- * 
+ *
  * @author bratseth
  */
 public class OutstandingChangeDeployer extends Maintainer {
-    
+
     public OutstandingChangeDeployer(Controller controller, Duration interval, JobControl jobControl) {
         super(controller, interval, jobControl);
     }
@@ -25,7 +26,7 @@ public class OutstandingChangeDeployer extends Maintainer {
         for (Application application : applications.asList()) {
             if (application.hasOutstandingChange() &&  ! application.deploying().isPresent())
                 controller().applications().deploymentTrigger().triggerChange(application.id(),
-                                                                              Change.ApplicationChange.unknown());
+                                                                              Change.of(ApplicationVersion.unknown));
         }
     }
 
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/Upgrader.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/Upgrader.java
index 5b87f9eaa86..75f348904dd 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/Upgrader.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/maintenance/Upgrader.java
@@ -20,7 +20,7 @@ import java.util.logging.Logger;
 
 /**
  * Maintenance job which schedules applications for Vespa version upgrade
- * 
+ *
  * @author bratseth
  * @author mpolden
  */
@@ -39,7 +39,7 @@ public class Upgrader extends Maintainer {
      * Schedule application upgrades. Note that this implementation must be idempotent.
      */
     @Override
-    public void maintain() {        
+    public void maintain() {
         // Determine target versions for each upgrade policy
         Optional<Version> canaryTarget = controller().versionStatus().systemVersion().map(VespaVersion::versionNumber);
         Optional<Version> defaultTarget = newestVersionWithConfidence(VespaVersion.Confidence.normal);
@@ -66,26 +66,25 @@ public class Upgrader extends Maintainer {
         defaultTarget.ifPresent(target -> upgrade(applications().with(UpgradePolicy.defaultPolicy), target));
         conservativeTarget.ifPresent(target -> upgrade(applications().with(UpgradePolicy.conservative), target));
     }
-    
+
     private Optional<Version> newestVersionWithConfidence(VespaVersion.Confidence confidence) {
         return reversed(controller().versionStatus().versions()).stream()
                                                                 .filter(v -> v.confidence().equalOrHigherThan(confidence))
                                                                 .findFirst()
                                                                 .map(VespaVersion::versionNumber);
     }
-    
+
     private List<VespaVersion> reversed(List<VespaVersion> versions) {
         List<VespaVersion> reversed = new ArrayList<>(versions.size());
         for (int i = 0; i < versions.size(); i++)
             reversed.add(versions.get(versions.size() - 1 - i));
         return reversed;
     }
-    
+
     /** Returns a list of all applications */
     private ApplicationList applications() { return ApplicationList.from(controller().applications().asList()); }
-    
+
     private void upgrade(ApplicationList applications, Version version) {
-        Change.VersionChange change = new Change.VersionChange(version);
         applications = applications.notPullRequest(); // Pull requests are deployed as separate applications to test then deleted; No need to upgrade
         applications = applications.hasProductionDeployment();
         applications = applications.onLowerVersionThan(version);
@@ -96,7 +95,7 @@ public class Upgrader extends Maintainer {
         applications = applications.first(numberOfApplicationsToUpgrade()); // throttle upgrades
         for (Application application : applications.asList()) {
             try {
-                controller().applications().deploymentTrigger().triggerChange(application.id(), change);
+                controller().applications().deploymentTrigger().triggerChange(application.id(), Change.of(version));
             } catch (IllegalArgumentException e) {
                 log.log(Level.INFO, "Could not trigger change: " + Exceptions.toMessageString(e));
             }
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializer.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializer.java
index b626fda5be1..41641a59363 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializer.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializer.java
@@ -247,10 +247,10 @@ public class ApplicationSerializer {
         if ( ! deploying.isPresent()) return;
 
         Cursor object = parentObject.setObject(deployingField);
-        if (deploying instanceof Change.VersionChange)
-            object.setString(versionField, ((Change.VersionChange)deploying).version().toString());
-        else if (((Change.ApplicationChange)deploying).version() != ApplicationVersion.unknown)
-            toSlime(((Change.ApplicationChange)deploying).version(), object);
+        if (deploying.platform().isPresent())
+            object.setString(versionField, deploying.platform().get().toString());
+        if (deploying.application().isPresent() && deploying.application().get() != ApplicationVersion.unknown)
+            toSlime(deploying.application().get(), object);
     }
 
     // ------------------ Deserialization
@@ -366,12 +366,14 @@ public class ApplicationSerializer {
     private Change changeFromSlime(Inspector object) {
         if ( ! object.valid()) return Change.empty();
         Inspector versionFieldValue = object.field(versionField);
+        Change change = Change.empty();
         if (versionFieldValue.valid())
-            return new Change.VersionChange(Version.fromString(versionFieldValue.asString()));
-        else if (object.field(applicationPackageHashField).valid())
-            return Change.ApplicationChange.of(applicationVersionFromSlime(object));
-        else
-            return Change.ApplicationChange.unknown();
+            change = Change.of(Version.fromString(versionFieldValue.asString()));
+        if (object.field(applicationPackageHashField).valid())
+            change = change.with(applicationVersionFromSlime(object));
+        if ( ! change.isPresent()) // A deploy object with no fields -> unknown application change
+            change = Change.of(ApplicationVersion.unknown);
+        return change;
     }
 
     private List<JobStatus> jobStatusListFromSlime(Inspector array) {
diff --git a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/application/ApplicationApiHandler.java b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/application/ApplicationApiHandler.java
index 00f1fe3790c..c262782ae37 100644
--- a/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/application/ApplicationApiHandler.java
+++ b/controller-server/src/main/java/com/yahoo/vespa/hosted/controller/restapi/application/ApplicationApiHandler.java
@@ -350,10 +350,10 @@ public class ApplicationApiHandler extends LoggingRequestHandler {
         // Currently deploying change
         if (application.deploying().isPresent()) {
             Cursor deployingObject = object.setObject("deploying");
-            if (application.deploying() instanceof Change.VersionChange)
-                deployingObject.setString("version", ((Change.VersionChange)application.deploying()).version().toString());
-            else if (((Change.ApplicationChange)application.deploying()).version() != ApplicationVersion.unknown)
-                toSlime(((Change.ApplicationChange)application.deploying()).version(), deployingObject.setObject("revision"));
+            application.deploying().platform().ifPresent(v -> deployingObject.setString("version", v.toString()));
+            application.deploying().application()
+                                   .filter(v -> v != ApplicationVersion.unknown)
+                                   .ifPresent(v -> toSlime(v, deployingObject.setObject("revision")));
         }
 
         // Jobs sorted according to deployment spec
@@ -715,7 +715,7 @@ public class ApplicationApiHandler extends LoggingRequestHandler {
                 throw new IllegalArgumentException("Can not start a deployment of " + application + " at this time: " +
                                                            application.deploying() + " is in progress");
 
-            controller.applications().deploymentTrigger().triggerChange(application.id(), new Change.VersionChange(version));
+            controller.applications().deploymentTrigger().triggerChange(application.id(), Change.of(version));
         });
         return new MessageResponse("Triggered deployment of application '" + id + "' on version " + version);
     }
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/ControllerTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/ControllerTest.java
index 3b4c3dda191..8d3fe4dbbfc 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/ControllerTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/ControllerTest.java
@@ -103,12 +103,12 @@ public class ControllerTest {
         tester.notifyJobCompletion(component, app1, true);
         assertEquals("Application version is currently not known",
                      ApplicationVersion.unknown,
-                     ((Change.ApplicationChange)tester.controller().applications().require(app1.id()).deploying()).version());
+                     tester.controller().applications().require(app1.id()).deploying().application().get());
         tester.deployAndNotify(app1, applicationPackage, true, systemTest);
         tester.deployAndNotify(app1, applicationPackage, true, stagingTest);
         assertEquals(4, applications.require(app1.id()).deploymentJobs().jobStatus().size());
 
-        ApplicationVersion applicationVersion = ((Change.ApplicationChange)tester.controller().applications().require(app1.id()).deploying()).version();
+        ApplicationVersion applicationVersion = tester.controller().applications().require(app1.id()).deploying().application().get();
         assertTrue("Application version has been set during deployment", applicationVersion != ApplicationVersion.unknown);
         assertStatus(JobStatus.initial(stagingTest)
                               .withTriggering(version1, applicationVersion, false, "", tester.clock().instant().minus(Duration.ofMillis(1)))
@@ -221,9 +221,9 @@ public class ControllerTest {
         tester.artifactRepository().put(app1.id(), applicationPackage, expectedVersionString);
         tester.notifyJobCompletion(component, app1, Optional.empty(), Optional.of(source), 37);
         ApplicationVersion expectedVersion = ApplicationVersion.from(source, 37);
-        assertEquals(expectedVersionString, ((Change.ApplicationChange) tester.controller().applications()
-                                                                              .require(app1.id())
-                                                                              .deploying()).version().id());
+        assertEquals(expectedVersionString, tester.controller().applications()
+                                                               .require(app1.id())
+                                                               .deploying().application().get().id());
 
         // Deploy without application package
         tester.deployAndNotify(app1, true, systemTest);
@@ -380,8 +380,7 @@ public class ControllerTest {
         assertFalse("Change deployed", app1.deploying().isPresent());
 
         // Version upgrade changes system version
-        Change.VersionChange change = new Change.VersionChange(newSystemVersion);
-        applications.deploymentTrigger().triggerChange(app1.id(), change);
+        applications.deploymentTrigger().triggerChange(app1.id(), Change.of(newSystemVersion));
         tester.deployAndNotify(app1, applicationPackage, true, systemTest);
         tester.deployAndNotify(app1, applicationPackage, true, stagingTest);
         tester.deployAndNotify(app1, applicationPackage, true, productionUsWest1);
@@ -669,13 +668,13 @@ public class ControllerTest {
         Application app = tester.createApplication(tenant, "app1", "default", 1);
 
         tester.controller().applications().lockOrThrow(app.id(), application -> {
-            application = application.withDeploying(new Change.VersionChange(Version.fromString("6.3")));
+            application = application.withDeploying(Change.of(Version.fromString("6.3")));
             applications.store(application);
             try {
                 tester.deploy(app, ZoneId.from("prod", "us-east-3"));
                 fail("Expected exception");
             } catch (IllegalArgumentException e) {
-                assertEquals("Rejecting deployment of application 'tenant1.app1' to zone prod.us-east-3 as version change to 6.3 is not tested", e.getMessage());
+                assertEquals("Rejecting deployment of application 'tenant1.app1' to zone prod.us-east-3 as upgrade to 6.3 is not tested", e.getMessage());
             }
         });
     }
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTester.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTester.java
index 247ec83aff2..dc8bd3e6423 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTester.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTester.java
@@ -94,12 +94,6 @@ public class DeploymentTester {
         return controller().applications().require(application);
     }
 
-    public Optional<Change.VersionChange> versionChange(ApplicationId application) {
-        Change change = application(application).deploying();
-        if (change instanceof Change.VersionChange) return Optional.of((Change.VersionChange)change);
-        return Optional.empty();
-    }
-
     public void updateVersionStatus() {
         controller().updateVersionStatus(VersionStatus.compute(controller(), tester.controller().systemVersion()));
     }
@@ -226,7 +220,7 @@ public class DeploymentTester {
 
     public void completeUpgrade(Application application, Version version, ApplicationPackage applicationPackage) {
         assertTrue(application + " has a deployment", applications().require(application.id()).deploying().isPresent());
-        assertEquals(new Change.VersionChange(version), applications().require(application.id()).deploying());
+        assertEquals(Change.of(version), applications().require(application.id()).deploying());
         completeDeployment(application, applicationPackage, Optional.empty(), true);
     }
 
@@ -240,7 +234,7 @@ public class DeploymentTester {
 
     private void completeUpgradeWithError(Application application, Version version, ApplicationPackage applicationPackage, Optional<JobType> failOnJob) {
         assertTrue(applications().require(application.id()).deploying().isPresent());
-        assertEquals(new Change.VersionChange(version), applications().require(application.id()).deploying());
+        assertEquals(Change.of(version), applications().require(application.id()).deploying());
         completeDeployment(application, applicationPackage, failOnJob, true);
     }
 
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTriggerTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTriggerTest.java
index 4bc64a8f213..73c6f1c1126 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTriggerTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/deployment/DeploymentTriggerTest.java
@@ -320,7 +320,7 @@ public class DeploymentTriggerTest {
                                                                  new JobControl(tester.controllerTester().curator()));
         LockedApplication app = (LockedApplication)tester.createAndDeploy("default0", 3, "default");
         // Store that we are upgrading but don't start the system-tests job
-        tester.controller().applications().store(app.withDeploying(new Change.VersionChange(Version.fromString("6.2"))));
+        tester.controller().applications().store(app.withDeploying(Change.of(Version.fromString("6.2"))));
         assertEquals(0, tester.buildSystem().jobs().size());
         readyJobsTrigger.run();
         assertEquals(1, tester.buildSystem().jobs().size());
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/FailureRedeployerTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/FailureRedeployerTest.java
index b200e2d7e18..b89fcec11a5 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/FailureRedeployerTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/FailureRedeployerTest.java
@@ -58,7 +58,7 @@ public class FailureRedeployerTest {
         tester.clock().advance(Duration.ofSeconds(1)); // Advance time so that we can detect jobs in progress
         tester.deployAndNotify(app, applicationPackage, false, DeploymentJobs.JobType.productionUsEast3);
         assertEquals("Production job is retried", 1, tester.buildSystem().jobs().size());
-        assertEquals("Application has pending upgrade to " + version, version, tester.versionChange(app.id()).get().version());
+        assertEquals("Application has pending upgrade to " + version, version, tester.application(app.id()).deploying().platform().get());
 
         // Another version is released, which cancels any pending upgrades to lower versions
         version = Version.fromString("5.2");
@@ -66,7 +66,7 @@ public class FailureRedeployerTest {
         tester.deployAndNotify(app, applicationPackage, true, DeploymentJobs.JobType.productionUsEast3); // Finish previous production job.
         tester.upgrader().maintain();
         assertEquals("Application starts upgrading to new version", 1, tester.buildSystem().jobs().size());
-        assertEquals("Application has pending upgrade to " + version, version, tester.versionChange(app.id()).get().version());
+        assertEquals("Application has pending upgrade to " + version, version, tester.application(app.id()).deploying().platform().get());
 
         // Failure redeployer does not retry failing job for prod.us-east-3 as there's an ongoing deployment
         tester.clock().advance(Duration.ofMinutes(1));
@@ -150,7 +150,7 @@ public class FailureRedeployerTest {
         tester.updateVersionStatus(version);
         assertEquals(version, tester.controller().versionStatus().systemVersion().get().versionNumber());
         tester.upgrader().maintain();
-        assertEquals("Application has pending upgrade to " + version, version, tester.versionChange(app.id()).get().version());
+        assertEquals("Application has pending upgrade to " + version, version, tester.application(app.id()).deploying().platform().get());
 
         // system-test fails and exhausts all immediate retries
         tester.deployAndNotify(app, applicationPackage, false, DeploymentJobs.JobType.systemTest);
@@ -164,7 +164,7 @@ public class FailureRedeployerTest {
         tester.updateVersionStatus(version);
         assertEquals(version, tester.controller().versionStatus().systemVersion().get().versionNumber());
         tester.upgrader().maintain();
-        assertEquals("Application has pending upgrade to " + version, version, tester.versionChange(app.id()).get().version());
+        assertEquals("Application has pending upgrade to " + version, version, tester.application(app.id()).deploying().platform().get());
 
         // Consume system-test job for 5.2
         tester.buildSystem().takeJobsToRun();
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployerTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployerTest.java
index d904e1f87c0..690e5c6d512 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployerTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/OutstandingChangeDeployerTest.java
@@ -31,9 +31,9 @@ public class OutstandingChangeDeployerTest {
         tester.createAndDeploy("app2", 22, "default");
 
         Version version = new Version(6, 2);
-        tester.deploymentTrigger().triggerChange(tester.application("app1").id(), new Change.VersionChange(version));
+        tester.deploymentTrigger().triggerChange(tester.application("app1").id(), Change.of(version));
 
-        assertEquals(new Change.VersionChange(version), tester.application("app1").deploying());
+        assertEquals(Change.of(version), tester.application("app1").deploying());
         assertFalse(tester.application("app1").hasOutstandingChange());
         tester.notifyJobCompletion(DeploymentJobs.JobType.component, tester.application("app1"), true);
         assertTrue(tester.application("app1").hasOutstandingChange());
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/UpgraderTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/UpgraderTest.java
index 63043d39b55..c435aed96ee 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/UpgraderTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/maintenance/UpgraderTest.java
@@ -9,7 +9,6 @@ import com.yahoo.vespa.hosted.controller.Application;
 import com.yahoo.vespa.hosted.controller.ControllerTester;
 import com.yahoo.vespa.hosted.controller.api.integration.zone.ZoneId;
 import com.yahoo.vespa.hosted.controller.application.ApplicationPackage;
-import com.yahoo.vespa.hosted.controller.application.Change;
 import com.yahoo.vespa.hosted.controller.application.Deployment;
 import com.yahoo.vespa.hosted.controller.application.DeploymentJobs;
 import com.yahoo.vespa.hosted.controller.deployment.ApplicationPackageBuilder;
@@ -174,11 +173,11 @@ public class UpgraderTest {
         assertEquals(VespaVersion.Confidence.normal, tester.controller().versionStatus().systemVersion().get().confidence());
         tester.upgrader().maintain();
         assertEquals("Upgrade of defaults are scheduled", 5, tester.buildSystem().jobs().size());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default0.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default1.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default2.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default3.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default4.id()).deploying()).version());
+        assertEquals(version54, tester.application(default0.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default1.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default2.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default3.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default4.id()).deploying().platform().get());
         tester.completeUpgrade(default0, version54, "default");
         // State: Default applications started upgrading to 5.4 (and one completed)
         Version version55 = Version.fromString("5.5");
@@ -190,11 +189,11 @@ public class UpgraderTest {
         assertEquals(VespaVersion.Confidence.normal, tester.controller().versionStatus().systemVersion().get().confidence());
         tester.upgrader().maintain();
         assertEquals("Upgrade of defaults are scheduled", 5, tester.buildSystem().jobs().size());
-        assertEquals(version55, ((Change.VersionChange)tester.application(default0.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default1.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default2.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default3.id()).deploying()).version());
-        assertEquals(version54, ((Change.VersionChange)tester.application(default4.id()).deploying()).version());
+        assertEquals(version55, tester.application(default0.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default1.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default2.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default3.id()).deploying().platform().get());
+        assertEquals(version54, tester.application(default4.id()).deploying().platform().get());
         tester.completeUpgrade(default1, version54, "default");
         tester.completeUpgrade(default2, version54, "default");
         tester.completeUpgradeWithError(default3, version54, "default", DeploymentJobs.JobType.stagingTest);
@@ -216,7 +215,7 @@ public class UpgraderTest {
         assertEquals("Upgrade of defaults are scheduled on 5.4 instead, since 5.5 broken: " +
                      "This is default3 since it failed upgrade on both 5.4 and 5.5",
                      1, tester.buildSystem().jobs().size());
-        assertEquals("5.4", ((Change.VersionChange)tester.application(default3.id()).deploying()).version().toString());
+        assertEquals("5.4", tester.application(default3.id()).deploying().platform().get().toString());
     }
 
     @Test
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializerTest.java b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializerTest.java
index f674e7be02e..46389b288c4 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializerTest.java
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/persistence/ApplicationSerializerTest.java
@@ -82,7 +82,7 @@ public class ApplicationSerializerTest {
                                                deploymentSpec,
                                                validationOverrides,
                                                deployments, deploymentJobs,
-                                               new Change.VersionChange(Version.fromString("6.7")),
+                                               Change.of(Version.fromString("6.7")),
                                                true,
                                                Optional.of(IssueId.from("1234")),
                                                new MetricsService.ApplicationMetrics(0.5, 0.9),
@@ -145,18 +145,18 @@ public class ApplicationSerializerTest {
         assertEquals(6, serialized.deployments().get(zone2).metrics().writeLatencyMillis(), Double.MIN_VALUE);
 
         { // test more deployment serialization cases
-            Application original2 = writable(original).withDeploying(Change.ApplicationChange.of(ApplicationVersion.from("hash1")));
+            Application original2 = writable(original).withDeploying(Change.of(ApplicationVersion.from("hash1")));
             Application serialized2 = applicationSerializer.fromSlime(applicationSerializer.toSlime(original2));
             assertEquals(original2.deploying(), serialized2.deploying());
-            assertEquals(((Change.ApplicationChange)serialized2.deploying()).version().source(),
-                         ((Change.ApplicationChange)original2.deploying()).version().source());
+            assertEquals(serialized2.deploying().application().get().source(),
+                         original2.deploying().application().get().source());
 
-            Application original3 = writable(original).withDeploying(Change.ApplicationChange.of(ApplicationVersion.from("hash1",
-                                                                                                                         new SourceRevision("a", "b", "c"))));
+            Application original3 = writable(original).withDeploying(Change.of(ApplicationVersion.from("hash1",
+                                                                                                       new SourceRevision("a", "b", "c"))));
             Application serialized3 = applicationSerializer.fromSlime(applicationSerializer.toSlime(original3));
             assertEquals(original3.deploying(), serialized2.deploying());
-            assertEquals(((Change.ApplicationChange)serialized3.deploying()).version().source(),
-                         ((Change.ApplicationChange)original3.deploying()).version().source());
+            assertEquals(serialized3.deploying().application().get().source(),
+                         original3.deploying().application().get().source());
 
             Application original4 = writable(original).withDeploying(Change.empty());
             Application serialized4 = applicationSerializer.fromSlime(applicationSerializer.toSlime(original4));
diff --git a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/restapi/application/responses/application-deployment-cancelled.json b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/restapi/application/responses/application-deployment-cancelled.json
index d1e1ebe94fd..3b6d8ed71e9 100644
--- a/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/restapi/application/responses/application-deployment-cancelled.json
+++ b/controller-server/src/test/java/com/yahoo/vespa/hosted/controller/restapi/application/responses/application-deployment-cancelled.json
@@ -1 +1 @@
-{"message":"Cancelled version change to 6.1 for application 'tenant1.application1'"}
+{"message":"Cancelled upgrade to 6.1 for application 'tenant1.application1'"}