Pass wanted node Vespa version around

16 files changed, 127 insertions, 108 deletions

diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/ServerCache.java b/configserver/src/main/java/com/yahoo/vespa/config/server/ServerCache.java
index 59cb7b63114..6d2567f711a 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/ServerCache.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/ServerCache.java
@@ -68,4 +68,5 @@ public class ServerCache {
     public int checkSumElems() {
         return md5Sums.size();
     }
+
 }
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ModelContextImpl.java b/configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ModelContextImpl.java
index 7f26795a003..5fac9f61b4b 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ModelContextImpl.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ModelContextImpl.java
@@ -1,13 +1,13 @@
 // Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.deploy;
 
+import com.yahoo.component.Version;
 import com.yahoo.config.model.api.*;
 import com.yahoo.config.application.api.ApplicationPackage;
 import com.yahoo.config.application.api.DeployLogger;
 import com.yahoo.config.application.api.FileRegistry;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.Rotation;
-import com.yahoo.config.provision.Version;
 import com.yahoo.config.provision.Zone;
 
 import java.io.File;
@@ -31,7 +31,18 @@ public class ModelContextImpl implements ModelContext {
     private final Optional<HostProvisioner> hostProvisioner;
     private final ModelContext.Properties properties;
     private final Optional<File> appDir;
-    Optional<Version> vespaVersion;
+    
+    /** The version of Vespa we are building a model for */
+    private final Version modelVespaVersion;
+
+    /**
+     * The Version of Vespa this model should specify that nodes should use. Note that this
+     * is separate from the version of this model, as upgrades are not immediate.
+     * We may build a config model of Vespa version "a" which specifies that nodes should
+     * use Vespa version "b". The "a" model will then be used by nodes who have not yet
+     * upgraded to version "b".
+     */
+    private final Version wantedNodeVespaVersion;
 
     public ModelContextImpl(ApplicationPackage applicationPackage,
                             Optional<Model> previousModel,
@@ -42,7 +53,8 @@ public class ModelContextImpl implements ModelContext {
                             Optional<HostProvisioner> hostProvisioner,
                             ModelContext.Properties properties,
                             Optional<File> appDir,
-                            Optional<Version> vespaVersion) {
+                            Version modelVespaVersion,
+                            Version wantedNodeVespaVersion) {
         this.applicationPackage = applicationPackage;
         this.previousModel = previousModel;
         this.permanentApplicationPackage = permanentApplicationPackage;
@@ -52,7 +64,8 @@ public class ModelContextImpl implements ModelContext {
         this.hostProvisioner = hostProvisioner;
         this.properties = properties;
         this.appDir = appDir;
-        this.vespaVersion = vespaVersion;
+        this.modelVespaVersion = modelVespaVersion;
+        this.wantedNodeVespaVersion = wantedNodeVespaVersion;
     }
 
     @Override
@@ -101,7 +114,10 @@ public class ModelContextImpl implements ModelContext {
     }
 
     @Override
-    public Optional<Version> vespaVersion() { return vespaVersion; }
+    public Version modelVespaVersion() { return modelVespaVersion; }
+
+    @Override
+    public Version wantedNodeVespaVersion() { return wantedNodeVespaVersion; }
 
     /**
     * @author lulf
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ActivatedModelsBuilder.java b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ActivatedModelsBuilder.java
index 3b15da0fbea..70c855f064c 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ActivatedModelsBuilder.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ActivatedModelsBuilder.java
@@ -72,10 +72,10 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
 
     @Override
     protected Application buildModelVersion(ModelFactory modelFactory, ApplicationPackage applicationPackage,
-                                            ApplicationId applicationId) {
-        Version version = modelFactory.getVersion();
+                                            ApplicationId applicationId, com.yahoo.component.Version wantedNodeVespaVersion) {
         log.log(LogLevel.DEBUG, String.format("Loading model version %s for session %s application %s",
-                                              version, appGeneration, applicationId));
+                                              modelFactory.getVersion(), appGeneration, applicationId));
+        ServerCache cache = zkClient.loadServerCache();
         ModelContext modelContext = new ModelContextImpl(
                 applicationPackage,
                 Optional.<Model>empty(),
@@ -86,10 +86,10 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
                 createHostProvisioner(getForVersionOrLatest(applicationPackage.getProvisionInfoMap(), modelFactory.getVersion())),
                 createModelContextProperties(applicationId),
                 Optional.empty(),
-                Optional.empty());
-        ServerCache cache = zkClient.loadServerCache();
+                new com.yahoo.component.Version(modelFactory.getVersion().toString()),
+                wantedNodeVespaVersion);
         MetricUpdater applicationMetricUpdater = metrics.getOrCreateMetricUpdater(Metrics.createDimensions(applicationId));
-        return new Application(modelFactory.createModel(modelContext), cache, appGeneration, version,
+        return new Application(modelFactory.createModel(modelContext), cache, appGeneration, modelFactory.getVersion(),
                                applicationMetricUpdater, applicationId);
     }
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelsBuilder.java b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelsBuilder.java
index 1b32d6bde22..f2b78e9e0dd 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelsBuilder.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelsBuilder.java
@@ -40,7 +40,8 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
         this.modelFactoryRegistry = modelFactoryRegistry;
     }
 
-    public List<MODELRESULT> buildModels(ApplicationId applicationId, ApplicationPackage applicationPackage) {
+    public List<MODELRESULT> buildModels(ApplicationId applicationId, 
+                                         com.yahoo.component.Version wantedNodeVespaVersion, ApplicationPackage applicationPackage) {
         Set<Version> versions = modelFactoryRegistry.allVersions();
 
         // If the application specifies a major, load models only for that
@@ -60,7 +61,7 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
         for (int i = 0; i < majorVersions.size(); i++) {
             try {
                 allApplicationModels.addAll(buildModelVersion(filterByMajorVersion(majorVersions.get(i), versions),
-                                                              applicationId, applicationPackage));
+                                                              applicationId, wantedNodeVespaVersion, applicationPackage));
 
                     // skip old config models after we have found a major version which works
                     if (allApplicationModels.size() > 0 && allApplicationModels.get(0).getModel().skipOldConfigModels())
@@ -82,10 +83,11 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
     }
 
     private List<MODELRESULT> buildModelVersion(Set<Version> versions, ApplicationId applicationId,
+                                                com.yahoo.component.Version wantedNodeVespaVersion, 
                                                 ApplicationPackage applicationPackage) {
         Version latest = findLatest(versions);
         // load latest application version
-        MODELRESULT latestApplicationVersion = buildModelVersion(modelFactoryRegistry.getFactory(latest), applicationPackage, applicationId);
+        MODELRESULT latestApplicationVersion = buildModelVersion(modelFactoryRegistry.getFactory(latest), applicationPackage, applicationId, wantedNodeVespaVersion);
         if (latestApplicationVersion.getModel().skipOldConfigModels()) {
             return Collections.singletonList(latestApplicationVersion);
         }
@@ -94,7 +96,7 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
             allApplicationVersions.add(latestApplicationVersion);
             for (Version version : versions) {
                 if (version.equals(latest)) continue; // already loaded
-                allApplicationVersions.add(buildModelVersion(modelFactoryRegistry.getFactory(version), applicationPackage, applicationId));
+                allApplicationVersions.add(buildModelVersion(modelFactoryRegistry.getFactory(version), applicationPackage, applicationId, wantedNodeVespaVersion));
             }
             return allApplicationVersions;
         }
@@ -114,7 +116,8 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
     }
 
     protected abstract MODELRESULT buildModelVersion(ModelFactory modelFactory, ApplicationPackage applicationPackage,
-                                                     ApplicationId applicationId);
+                                                     ApplicationId applicationId, 
+                                                     com.yahoo.component.Version wantedNodeVespaVersion);
 
     protected ModelContext.Properties createModelContextProperties(ApplicationId applicationId,
                                                                    ConfigserverConfig configserverConfig,
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/PreparedModelsBuilder.java b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/PreparedModelsBuilder.java
index cb2ffe1c2f9..c158f5ab03d 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/PreparedModelsBuilder.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/PreparedModelsBuilder.java
@@ -1,6 +1,7 @@
 // Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.modelfactory;
 
+import com.yahoo.component.Vtag;
 import com.yahoo.config.application.api.ApplicationPackage;
 import com.yahoo.config.application.api.DeployLogger;
 import com.yahoo.config.model.api.ConfigChangeAction;
@@ -75,17 +76,19 @@ public class PreparedModelsBuilder extends ModelsBuilder<PreparedModelsBuilder.P
     }
 
     @Override
-    protected PreparedModelResult buildModelVersion(ModelFactory modelFactory, ApplicationPackage applicationPackage,
-                                                    ApplicationId applicationId) {
-        Version version = modelFactory.getVersion();
-        log.log(LogLevel.DEBUG, "Start building model for Vespa version " + version);
+    protected PreparedModelResult buildModelVersion(ModelFactory modelFactory, 
+                                                    ApplicationPackage applicationPackage,
+                                                    ApplicationId applicationId, 
+                                                    com.yahoo.component.Version wantedNodeVespaVersion) {
+        Version modelVersion = modelFactory.getVersion();
+        log.log(LogLevel.DEBUG, "Start building model for Vespa version " + modelVersion);
         FileDistributionProvider fileDistributionProvider = fileDistributionFactory.createProvider(
                 context.getServerDBSessionDir(),
                 applicationId);
 
         Optional<HostProvisioner> hostProvisioner = createHostProvisionerAdapter(properties);
         Optional<Model> previousModel = currentActiveApplicationSet
-                .map(set -> set.getForVersionOrLatest(Optional.of(version)).getModel());
+                .map(set -> set.getForVersionOrLatest(Optional.of(modelVersion)).getModel());
         ModelContext modelContext = new ModelContextImpl(
                 applicationPackage,
                 previousModel,
@@ -96,13 +99,14 @@ public class PreparedModelsBuilder extends ModelsBuilder<PreparedModelsBuilder.P
                 hostProvisioner,
                 properties,
                 getAppDir(applicationPackage),
-                Optional.of(version));
+                new com.yahoo.component.Version(modelVersion.toString()),
+                wantedNodeVespaVersion);
 
-        log.log(LogLevel.DEBUG, "Running createAndValidateModel for Vespa version " + version);
+        log.log(LogLevel.DEBUG, "Running createAndValidateModel for Vespa version " + modelVersion);
         ModelCreateResult result =  modelFactory.createAndValidateModel(modelContext, params.ignoreValidationErrors());
         validateModelHosts(context.getHostValidator(), applicationId, result.getModel());
-        log.log(LogLevel.DEBUG, "Done building model for Vespa version " + version);
-        return new PreparedModelsBuilder.PreparedModelResult(version, result.getModel(), fileDistributionProvider, result.getConfigChangeActions());
+        log.log(LogLevel.DEBUG, "Done building model for Vespa version " + modelVersion);
+        return new PreparedModelsBuilder.PreparedModelResult(modelVersion, result.getModel(), fileDistributionProvider, result.getConfigChangeActions());
     }
 
     private Optional<File> getAppDir(ApplicationPackage applicationPackage) {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSession.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSession.java
index a68ce0441ab..fcd10a35f39 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSession.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/LocalSession.java
@@ -1,6 +1,7 @@
 // Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.session;
 
+import com.yahoo.component.Version;
 import com.yahoo.config.application.api.ApplicationFile;
 import com.yahoo.config.application.api.ApplicationPackage;
 import com.yahoo.config.application.api.ApplicationMetaData;
@@ -83,7 +84,7 @@ public class LocalSession extends Session implements Comparable<LocalSession> {
 
     private Transaction setActive() {
         Transaction transaction = createSetStatusTransaction(Status.ACTIVATE);
-        transaction.add(applicationRepo.createPutApplicationTransaction(zooKeeperClient.readApplicationId(getTenant()), getSessionId()).operations());
+        transaction.add(applicationRepo.createPutApplicationTransaction(zooKeeperClient.readApplicationId(), getSessionId()).operations());
         return transaction;
     }
 
@@ -153,6 +154,10 @@ public class LocalSession extends Session implements Comparable<LocalSession> {
         zooKeeperClient.writeApplicationId(applicationId);
     }
 
+    public void setVespaVersion(Version version) {
+        zooKeeperClient.writeVespaVersion(version);
+    }
+
     public enum Mode {
         READ, WRITE
     }
@@ -161,9 +166,9 @@ public class LocalSession extends Session implements Comparable<LocalSession> {
         return applicationPackage.getMetaData();
     }
 
-    public ApplicationId getApplicationId() {
-        return zooKeeperClient.readApplicationId(getTenant());
-    }
+    public ApplicationId getApplicationId() { return zooKeeperClient.readApplicationId(); }
+
+    public Version getVespaVersion() { return zooKeeperClient.readVespaVersion(); }
 
     public ProvisionInfo getProvisionInfo() {
         return zooKeeperClient.getProvisionInfo();
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/PrepareParams.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/PrepareParams.java
index 03a7a3915d3..3890001518a 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/PrepareParams.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/PrepareParams.java
@@ -1,10 +1,10 @@
 // Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.session;
 
+import com.yahoo.component.Version;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.Rotation;
 import com.yahoo.config.provision.TenantName;
-import com.yahoo.config.provision.Version;
 import com.yahoo.container.jdisc.HttpRequest;
 import com.yahoo.vespa.config.server.TimeoutBudget;
 import com.yahoo.vespa.config.server.http.SessionHandler;
@@ -29,7 +29,6 @@ public final class PrepareParams {
     static final String DRY_RUN_PARAM_NAME = "dryRun";
     static final String VESPA_VERSION_PARAM_NAME = "vespaVersion";
     static final String ROTATIONS_PARAM_NAME = "rotations";
-    static final String DOCKER_VESPA_IMAGE_VERSION_PARAM_NAME = "dockerVespaImageVersion";
 
     private final ApplicationId applicationId;
     private final TimeoutBudget timeoutBudget;
@@ -37,18 +36,15 @@ public final class PrepareParams {
     private final boolean dryRun;
     private final Optional<Version> vespaVersion;
     private final Set<Rotation> rotations;
-    private final Optional<Version> dockerVespaImageVersion;
 
     private PrepareParams(ApplicationId applicationId, TimeoutBudget timeoutBudget, boolean ignoreValidationErrors,
-                         boolean dryRun, Optional<Version> vespaVersion, Set<Rotation> rotations,
-                         Optional<Version> dockerVespaImageVersion) {
+                         boolean dryRun, Optional<Version> vespaVersion, Set<Rotation> rotations) {
         this.timeoutBudget = timeoutBudget;
         this.applicationId = applicationId;
         this.ignoreValidationErrors = ignoreValidationErrors;
         this.dryRun = dryRun;
         this.vespaVersion = vespaVersion;
         this.rotations = rotations;
-        this.dockerVespaImageVersion = dockerVespaImageVersion;
     }
 
     public static class Builder {
@@ -58,7 +54,6 @@ public final class PrepareParams {
         private TimeoutBudget timeoutBudget = new TimeoutBudget(Clock.systemUTC(), Duration.ofSeconds(30));
         private Optional<Version> vespaVersion = Optional.empty();
         private Set<Rotation> rotations;
-        private Optional<Version> dockerVespaImageVersion = Optional.empty();
 
         public Builder() { }
 
@@ -102,18 +97,9 @@ public final class PrepareParams {
             return this;
         }
 
-        public Builder dockerVespaImageVersion(String dockerVespaImageVersion) {
-            Optional<Version> version = Optional.empty();
-            if (dockerVespaImageVersion != null && !dockerVespaImageVersion.isEmpty()) {
-                version = Optional.of(Version.fromString(dockerVespaImageVersion));
-            }
-            this.dockerVespaImageVersion = version;
-            return this;
-        }
-
         public PrepareParams build() {
-            return new PrepareParams(applicationId, timeoutBudget, ignoreValidationErrors, dryRun,
-                                     vespaVersion, rotations, dockerVespaImageVersion);
+            return new PrepareParams(applicationId, timeoutBudget, ignoreValidationErrors, dryRun, 
+                                     vespaVersion, rotations);
         }
 
     }
@@ -125,7 +111,6 @@ public final class PrepareParams {
                                           .applicationId(createApplicationId(request, tenant))
                                           .vespaVersion(request.getProperty(VESPA_VERSION_PARAM_NAME))
                                           .rotations(request.getProperty(ROTATIONS_PARAM_NAME))
-                                          .dockerVespaImageVersion(request.getProperty(DOCKER_VESPA_IMAGE_VERSION_PARAM_NAME))
                                           .build();
     }
 
@@ -153,6 +138,7 @@ public final class PrepareParams {
         return applicationId;
     }
 
+    /** Returns the Vespa version the nodes running the prepared system should have, or empty to use the system version */
     public Optional<Version> vespaVersion() { return vespaVersion; }
 
     public Set<Rotation> rotations() { return rotations; }
@@ -169,15 +155,4 @@ public final class PrepareParams {
         return timeoutBudget;
     }
 
-    public Optional<Version> getVespaVersion() {
-        return vespaVersion;
-    }
-
-    public Set<Rotation> getRotations() {
-        return rotations;
-    }
-
-    public Optional<Version> getDockerVespaImageVersion() {
-        return dockerVespaImageVersion;
-    }
 }
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSession.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSession.java
index ca4fa21f804..72dc4cbb963 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSession.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSession.java
@@ -49,7 +49,8 @@ public class RemoteSession extends Session {
     }
 
     private ApplicationSet loadApplication() {
-        return ApplicationSet.fromList(applicationLoader.buildModels(zooKeeperClient.readApplicationId(getTenant()),
+        return ApplicationSet.fromList(applicationLoader.buildModels(zooKeeperClient.readApplicationId(),
+                                                                     zooKeeperClient.readVespaVersion(),
                                                                      zooKeeperClient.loadApplicationPackage()));
     }
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionFactoryImpl.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionFactoryImpl.java
index 652f27ddaf4..461019439e0 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionFactoryImpl.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionFactoryImpl.java
@@ -115,13 +115,13 @@ public class SessionFactoryImpl implements SessionFactory, LocalSessionLoader {
                                                   TimeoutBudget timeoutBudget) {
         File existingApp = getSessionAppDir(existingSession.getSessionId());
         ApplicationMetaData metaData = FilesApplicationPackage.readMetaData(existingApp);
-        final ApplicationId existingSessionId = existingSession.getApplicationId();
+        ApplicationId existingApplicationId = existingSession.getApplicationId();
 
-
-        final long liveApp = getLiveApp(existingSessionId);
-        logger.log(LogLevel.DEBUG, "Create from existing application id " + existingSessionId + ", live app for it is " + liveApp);
+        long liveApp = getLiveApp(existingApplicationId);
+        logger.log(LogLevel.DEBUG, "Create from existing application id " + existingApplicationId + ", live app for it is " + liveApp);
         LocalSession session = create(existingApp, metaData.getApplicationName(), liveApp, timeoutBudget);
-        session.setApplicationId(existingSessionId);
+        session.setApplicationId(existingApplicationId);
+        session.setVespaVersion(existingSession.getVespaVersion());
         return session;
     }
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionPreparer.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionPreparer.java
index d9f486a5604..cd10b031a93 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionPreparer.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionPreparer.java
@@ -3,6 +3,7 @@ package com.yahoo.vespa.config.server.session;
 
 import com.google.common.collect.ImmutableList;
 import com.yahoo.cloud.config.ConfigserverConfig;
+import com.yahoo.component.Vtag;
 import com.yahoo.config.application.api.ApplicationPackage;
 import com.yahoo.config.application.api.DeployLogger;
 import com.yahoo.config.application.api.FileRegistry;
@@ -91,7 +92,7 @@ public class SessionPreparer {
         try {
             prep.buildModels();
             prep.makeResult();
-            if (!params.isDryRun()) {
+            if ( ! params.isDryRun()) {
                 prep.writeStateZK();
                 prep.writeRotZK();
                 prep.distribute();
@@ -112,6 +113,10 @@ public class SessionPreparer {
         final Optional<ApplicationSet> currentActiveApplicationSet;
         final Path tenantPath;
         final ApplicationId applicationId;
+
+        /** The version of Vespa the application to be prepared specifies for its nodes */
+        final com.yahoo.component.Version vespaVersion;
+
         final Rotations rotations;
         final Set<Rotation> rotationsSet;
         final ModelContext.Properties properties;
@@ -131,6 +136,7 @@ public class SessionPreparer {
             this.tenantPath = tenantPath;
 
             this.applicationId = params.getApplicationId();
+            this.vespaVersion = params.vespaVersion().orElse(Vtag.currentVersion);
             this.rotations = new Rotations(curator, tenantPath);
             this.rotationsSet = getRotations(params.rotations());
             this.properties = new ModelContextImpl.Properties(params.getApplicationId(),
@@ -168,7 +174,7 @@ public class SessionPreparer {
         }
 
         void buildModels() {
-            this.modelResultList = preparedModelsBuilder.buildModels(applicationId, applicationPackage);
+            this.modelResultList = preparedModelsBuilder.buildModels(applicationId, vespaVersion, applicationPackage);
             checkTimeout("build models");
         }
 
@@ -179,8 +185,13 @@ public class SessionPreparer {
 
         void writeStateZK() {
             log.log(LogLevel.DEBUG, "Writing application package state to zookeeper");
-            writeStateToZooKeeper(context.getSessionZooKeeperClient(), applicationPackage, params, logger,
-                                  prepareResult.getFileRegistries(), prepareResult.getProvisionInfos());
+            writeStateToZooKeeper(context.getSessionZooKeeperClient(), 
+                                  applicationPackage,
+                                  applicationId,
+                                  vespaVersion,
+                                  logger,
+                                  prepareResult.getFileRegistries(), 
+                                  prepareResult.getProvisionInfos());
             checkTimeout("write state to zookeeper");
         }
 
@@ -217,14 +228,16 @@ public class SessionPreparer {
 
     private void writeStateToZooKeeper(SessionZooKeeperClient zooKeeperClient,
                                        ApplicationPackage applicationPackage,
-                                       PrepareParams prepareParams,
+                                       ApplicationId applicationId,
+                                       com.yahoo.component.Version vespaVersion,
                                        DeployLogger deployLogger,
                                        Map<Version, FileRegistry> fileRegistryMap,
                                        Map<Version, ProvisionInfo> provisionInfoMap) {
         ZooKeeperDeployer zkDeployer = zooKeeperClient.createDeployer(deployLogger);
         try {
             zkDeployer.deploy(applicationPackage, fileRegistryMap, provisionInfoMap);
-            zooKeeperClient.writeApplicationId(prepareParams.getApplicationId());
+            zooKeeperClient.writeApplicationId(applicationId);
+            zooKeeperClient.writeVespaVersion(vespaVersion);
         } catch (RuntimeException | IOException e) {
             zkDeployer.cleanup();
             throw new RuntimeException("Error preparing session", e);
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClient.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClient.java
index ecb5d0980bb..9fbd8d539fb 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClient.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClient.java
@@ -1,6 +1,8 @@
 // Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server.session;
 
+import com.yahoo.component.Version;
+import com.yahoo.component.Vtag;
 import com.yahoo.config.application.api.ApplicationPackage;
 import com.yahoo.config.application.api.DeployLogger;
 import com.yahoo.config.provision.ProvisionInfo;
@@ -34,6 +36,7 @@ public class SessionZooKeeperClient {
 
     private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(SessionZooKeeperClient.class.getName());
     static final String APPLICATION_ID_PATH = "applicationId";
+    static final String VERSION_PATH = "version";
     static final String CREATE_TIME_PATH = "createTime";
     private final Curator curator;
     private final ConfigCurator configCurator;
@@ -137,38 +140,36 @@ public class SessionZooKeeperClient {
         return cacheLoader.loadCache();
     }
 
+    private String applicationIdPath() {
+        return rootPath.append(APPLICATION_ID_PATH).getAbsolute();
+    }
+
     public void writeApplicationId(ApplicationId id) {
-        String path = getApplicationIdPath();
-        try {
-            configCurator.putData(path, id.serializedForm());
-        } catch (RuntimeException e) {
-            throw new RuntimeException("Unable to write application id '" + id + "' to '" + path + "'", e);
-        }
+        configCurator.putData(applicationIdPath(), id.serializedForm());
     }
 
-    private String getApplicationIdPath() {
-        return rootPath.append(APPLICATION_ID_PATH).getAbsolute();
+    public ApplicationId readApplicationId() {
+        if ( ! configCurator.exists(applicationIdPath())) return ApplicationId.defaultId();
+        return ApplicationId.fromSerializedForm(configCurator.getData(applicationIdPath()));
     }
 
-    public ApplicationId readApplicationId(TenantName tenant) {
-        String path = getApplicationIdPath();
-        try {
-            // Fallback for cases where id never existed.
-            if ( ! configCurator.exists(path)) {
-                // TODO: DEBUG LOG
-                log.log(LogLevel.INFO, "Unable to locate application id at '" + path + "', returning default");
-                return ApplicationId.defaultId();
-            }
-            return ApplicationId.fromSerializedForm(configCurator.getData(path));
-        } catch (RuntimeException e) {
-            throw new RuntimeException("Unable to read application id from '" + path + "'", e);
-        }
+    private String versionPath() {
+        return rootPath.append(VERSION_PATH).getAbsolute();
+    }
+
+    public void writeVespaVersion(Version version) {
+        configCurator.putData(versionPath(), version.toString());
+    }
+
+    public Version readVespaVersion() {
+        if ( ! configCurator.exists(versionPath())) return Vtag.currentVersion;
+        return new Version(configCurator.getData(versionPath()));
     }
 
     // in seconds
     public long readCreateTime() {
         String path = getCreateTimePath();
-        if (!configCurator.exists(path)) return 0l;
+        if ( ! configCurator.exists(path)) return 0L;
         return Long.parseLong(configCurator.getData(path));
     }
 
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/ModelContextImplTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/ModelContextImplTest.java
index 0352f2c9f3e..74f030919ec 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/ModelContextImplTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/ModelContextImplTest.java
@@ -1,6 +1,7 @@
 // Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.config.server;
 
+import com.yahoo.component.Version;
 import com.yahoo.config.model.api.ModelContext;
 import com.yahoo.config.model.application.provider.BaseDeployLogger;
 import com.yahoo.config.model.application.provider.MockFileRegistry;
@@ -48,7 +49,8 @@ public class ModelContextImplTest {
                         Zone.defaultZone(),
                         rotations),
                 Optional.empty(),
-                Optional.empty());
+                new Version(6), 
+                new Version(6));
         assertTrue(context.applicationPackage() instanceof MockApplicationPackage);
         assertFalse(context.hostProvisioner().isPresent());
         assertFalse(context.permanentApplicationPackage().isPresent());
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/deploy/DeployTester.java b/configserver/src/test/java/com/yahoo/vespa/config/server/deploy/DeployTester.java
index 07fb3cd51c7..8e20f190c5b 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/deploy/DeployTester.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/deploy/DeployTester.java
@@ -115,14 +115,14 @@ public class DeployTester {
     /**
      * Do the initial "deploy" with the existing API-less code as the deploy API doesn't support first deploys yet.
      */
-    public ApplicationId deployApp(String appName, Optional<String> dockerVespaImageVersion)  {
+    public ApplicationId deployApp(String appName, Optional<String> vespaVersion)  {
         final Tenant tenant = tenant();
         LocalSession session = tenant.getSessionFactory().createSession(testApp, appName, new TimeoutBudget(Clock.systemUTC(), Duration.ofSeconds(60)));
         ApplicationId id = ApplicationId.from(tenant.getName(), ApplicationName.from(appName), InstanceName.defaultName());
         PrepareParams.Builder paramsBuilder = new PrepareParams.Builder()
                 .applicationId(id);
-        if (dockerVespaImageVersion.isPresent())
-            paramsBuilder.dockerVespaImageVersion(dockerVespaImageVersion.get());
+        if (vespaVersion.isPresent())
+            paramsBuilder.vespaVersion(vespaVersion.get());
         session.prepare(new SilentDeployLogger(),
                         paramsBuilder.build(),
                         Optional.empty(),
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/PrepareParamsTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/PrepareParamsTest.java
index d91fff41f2e..b8ea8b5a4f9 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/PrepareParamsTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/PrepareParamsTest.java
@@ -34,9 +34,9 @@ public class PrepareParamsTest {
         assertThat(prepareParams.getApplicationId(), is(ApplicationId.defaultId()));
         assertFalse(prepareParams.isDryRun());
         assertFalse(prepareParams.ignoreValidationErrors());
-        assertThat(prepareParams.getVespaVersion(), is(Optional.<String>empty()));
+        assertThat(prepareParams.vespaVersion(), is(Optional.<String>empty()));
         assertTrue(prepareParams.getTimeoutBudget().hasTimeLeft());
-        assertThat(prepareParams.getRotations().size(), is(0));
+        assertThat(prepareParams.rotations().size(), is(0));
     }
 
 
@@ -46,8 +46,7 @@ public class PrepareParamsTest {
             PrepareParams.DRY_RUN_PARAM_NAME + "=true&" +
             PrepareParams.IGNORE_VALIDATION_PARAM_NAME + "=false&" +
             PrepareParams.APPLICATION_NAME_PARAM_NAME + "=baz&" +
-            PrepareParams.VESPA_VERSION_PARAM_NAME + "=" + vespaVersion + "&" +
-            PrepareParams.DOCKER_VESPA_IMAGE_VERSION_PARAM_NAME+ "=" + vespaVersion;
+            PrepareParams.VESPA_VERSION_PARAM_NAME + "=" + vespaVersion;
 
     @Test
     public void testCorrectParsingWithRotation() {
@@ -59,12 +58,11 @@ public class PrepareParamsTest {
         assertTrue(prepareParams.isDryRun());
         assertFalse(prepareParams.ignoreValidationErrors());
         final Version expectedVersion = Version.fromString(vespaVersion);
-        assertThat(prepareParams.getVespaVersion().get(), is(expectedVersion));
+        assertThat(prepareParams.vespaVersion().get(), is(expectedVersion));
         assertTrue(prepareParams.getTimeoutBudget().hasTimeLeft());
-        final Set<Rotation> rotations = prepareParams.getRotations();
+        final Set<Rotation> rotations = prepareParams.rotations();
         assertThat(rotations.size(), is(1));
         assertThat(rotations, contains(equalTo(new Rotation(rotation))));
-        assertThat(prepareParams.getDockerVespaImageVersion().get(), is(expectedVersion));
     }
 
     @Test
@@ -74,7 +72,7 @@ public class PrepareParamsTest {
         PrepareParams prepareParams = createParams(request + "&" +
                         PrepareParams.ROTATIONS_PARAM_NAME + "=" + twoRotations,
                 TenantName.from("foo"));
-        final Set<Rotation> rotations = prepareParams.getRotations();
+        final Set<Rotation> rotations = prepareParams.rotations();
         assertThat(rotations, containsInAnyOrder(new Rotation(rotation), new Rotation(rotationTwo)));
     }
 
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java
index ac25cba3b47..1e61e6e9e08 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionPreparerTest.java
@@ -186,7 +186,7 @@ public class SessionPreparerTest extends TestWithCurator {
         preparer.prepare(getContext(getApplicationPackage(testApp)), getLogger(), params, Optional.empty(), tenantPath);
         SessionZooKeeperClient zkc = new SessionZooKeeperClient(curator, appPath);
         assertTrue(configCurator.exists(appPath.append(SessionZooKeeperClient.APPLICATION_ID_PATH).getAbsolute()));
-        assertThat(zkc.readApplicationId(tenant), is(origId));
+        assertThat(zkc.readApplicationId(), is(origId));
     }
 
     @Test
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClientTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClientTest.java
index 4508d8c234f..d4f3665ac6f 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClientTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/session/SessionZooKeeperClientTest.java
@@ -76,7 +76,7 @@ public class SessionZooKeeperClientTest extends TestWithCurator {
 
     @Test
     public void require_that_default_name_is_returned_if_node_does_not_exist() {
-        assertThat(createSessionZKClient("3").readApplicationId(TenantName.defaultName()).application().value(), is("default"));
+        assertThat(createSessionZKClient("3").readApplicationId().application().value(), is("default"));
     }
 
     @Test
@@ -101,7 +101,7 @@ public class SessionZooKeeperClientTest extends TestWithCurator {
         SessionZooKeeperClient zkc = createSessionZKClient(sessionId);
         String path = "/" + sessionId + "/" + SessionZooKeeperClient.APPLICATION_ID_PATH;
         configCurator.putData(path, idString);
-        ApplicationId zkId = zkc.readApplicationId(TenantName.defaultName());
+        ApplicationId zkId = zkc.readApplicationId();
         assertThat(zkId.serializedForm(), is(expectedIdString));
     }