Allocation consistency between model versions

20 files changed, 121 insertions, 76 deletions

diff --git a/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java b/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java
index 215aa6c2f7f..1f52d9db818 100644
--- a/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java
+++ b/config-model/src/main/java/com/yahoo/vespa/model/VespaModelFactory.java
@@ -34,7 +34,7 @@ import java.util.logging.Logger;
 /**
  * Factory for creating {@link VespaModel} instances.
  *
- * @author lulf
+ * @author Ulf Lilleengen
  */
 public class VespaModelFactory implements ModelFactory {
 
diff --git a/config-provisioning/src/main/java/com/yahoo/config/provision/ProvisionInfo.java b/config-provisioning/src/main/java/com/yahoo/config/provision/ProvisionInfo.java
index 4506f52e085..a09e198dbf1 100644
--- a/config-provisioning/src/main/java/com/yahoo/config/provision/ProvisionInfo.java
+++ b/config-provisioning/src/main/java/com/yahoo/config/provision/ProvisionInfo.java
@@ -9,6 +9,7 @@ import com.yahoo.slime.Slime;
 import com.yahoo.vespa.config.SlimeUtils;
 
 import java.io.IOException;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Optional;
diff --git a/config-provisioning/src/main/java/com/yahoo/config/provision/Provisioner.java b/config-provisioning/src/main/java/com/yahoo/config/provision/Provisioner.java
index 980cd4a00b9..6be1d49ebd3 100644
--- a/config-provisioning/src/main/java/com/yahoo/config/provision/Provisioner.java
+++ b/config-provisioning/src/main/java/com/yahoo/config/provision/Provisioner.java
@@ -9,8 +9,7 @@ import java.util.List;
 /**
  * Interface used by the config system to acquire hosts.
  *
- * @author lulf
- * @since 5.11
+ * @author Ulf Lilleengen
  */
 public interface Provisioner {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java b/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java
index 1bda8dcb69a..4f26cfa265b 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/GlobalComponentRegistry.java
@@ -19,8 +19,7 @@ import java.util.Optional;
 /**
  * Interface representing all global config server components used within the config server.
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 public interface GlobalComponentRegistry {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java b/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java
index f88a0ef1a2d..fa5224732f6 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/InjectedGlobalComponentRegistry.java
@@ -22,8 +22,7 @@ import java.util.Optional;
 /**
  * Registry containing all the "static"/"global" components in a config server in one place.
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 public class InjectedGlobalComponentRegistry implements GlobalComponentRegistry {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java b/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
index 94abbc10046..0435c8e59db 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
@@ -9,8 +9,7 @@ import java.util.List;
 /**
  * The applications of a tenant
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 public interface TenantApplications {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/application/ZKTenantApplications.java b/configserver/src/main/java/com/yahoo/vespa/config/server/application/ZKTenantApplications.java
index ac318aba8e8..5260dd9228c 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/application/ZKTenantApplications.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/application/ZKTenantApplications.java
@@ -29,8 +29,7 @@ import java.util.logging.Logger;
  * Each application is stored as a single file, named the same as the application id and containing the id
  * of the session storing the content of the application.
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 // TODO: Merge into interface and separate out curator layer instead
 public class ZKTenantApplications implements TenantApplications, PathChildrenCacheListener {
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 86187a08d17..3c26ce1b76b 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
@@ -48,7 +48,6 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
     private final long appGeneration;
     private final SessionZooKeeperClient zkClient;
     private final Optional<PermanentApplicationPackage> permanentApplicationPackage;
-    private final Optional<com.yahoo.config.provision.Provisioner> hostProvisioner;
     private final ConfigserverConfig configserverConfig;
     private final ConfigDefinitionRepo configDefinitionRepo;
     private final Metrics metrics;
@@ -57,7 +56,8 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
     private final DeployLogger logger;
 
     public ActivatedModelsBuilder(TenantName tenant, long appGeneration, SessionZooKeeperClient zkClient, GlobalComponentRegistry globalComponentRegistry) {
-        super(globalComponentRegistry.getModelFactoryRegistry());
+        super(globalComponentRegistry.getModelFactoryRegistry(), 
+              globalComponentRegistry.getHostProvisioner().isPresent());
         this.tenant = tenant;
         this.appGeneration = appGeneration;
         this.zkClient = zkClient;
@@ -65,7 +65,6 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
         this.configserverConfig = globalComponentRegistry.getConfigserverConfig();
         this.configDefinitionRepo = globalComponentRegistry.getConfigDefinitionRepo();
         this.metrics = globalComponentRegistry.getMetrics();
-        this.hostProvisioner = globalComponentRegistry.getHostProvisioner();
         this.curator = globalComponentRegistry.getCurator();
         this.zone = globalComponentRegistry.getZone();
         this.logger = new SilentDeployLogger();
@@ -76,6 +75,7 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
                                             ApplicationPackage applicationPackage,
                                             ApplicationId applicationId, 
                                             com.yahoo.component.Version wantedNodeVespaVersion,
+                                            SettableOptional<ProvisionInfo> ignored, // Ignored since we have this in the app package for activated models
                                             Instant now) {
         log.log(LogLevel.DEBUG, String.format("Loading model version %s for session %s application %s",
                                               modelFactory.getVersion(), appGeneration, applicationId));
@@ -97,17 +97,6 @@ public class ActivatedModelsBuilder extends ModelsBuilder<Application> {
                                applicationMetricUpdater, applicationId);
     }
 
-    private Optional<HostProvisioner> createHostProvisioner(Optional<ProvisionInfo> provisionInfo) {
-        if (hostProvisioner.isPresent() && provisionInfo.isPresent()) {
-            return Optional.of(createStaticProvisioner(provisionInfo.get()));
-        }
-        return Optional.empty();
-    }
-
-    private HostProvisioner createStaticProvisioner(ProvisionInfo provisionInfo) {
-        return new StaticProvisioner(provisionInfo);
-    }
-
     private static <T> Optional<T> getForVersionOrLatest(Map<Version, T> map, Version version) {
         if (map.isEmpty()) {
             return Optional.empty();
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelFactoryRegistry.java b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelFactoryRegistry.java
index ab1c84eb5dd..1c2c9c731d1 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelFactoryRegistry.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/modelfactory/ModelFactoryRegistry.java
@@ -13,7 +13,7 @@ import java.util.*;
  * A registry of model factories. Allows querying for a specific version of a {@link ModelFactory} or
  * simply returning all of them. Keeps track of the latest {@link com.yahoo.config.provision.Version} supported.
  *
- * @author lulf
+ * @author Ulf Lilleengen
  */
 public class ModelFactoryRegistry {
 
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 509a26370ff..84316d0688a 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
@@ -3,16 +3,20 @@ package com.yahoo.vespa.config.server.modelfactory;
 
 import com.yahoo.cloud.config.ConfigserverConfig;
 import com.yahoo.config.application.api.ApplicationPackage;
+import com.yahoo.config.model.api.HostProvisioner;
 import com.yahoo.config.model.api.ModelContext;
 import com.yahoo.config.model.api.ModelFactory;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.OutOfCapacityException;
+import com.yahoo.config.provision.ProvisionInfo;
+import com.yahoo.config.provision.Provisioner;
 import com.yahoo.config.provision.Rotation;
 import com.yahoo.config.provision.Version;
 import com.yahoo.config.provision.Zone;
 import com.yahoo.vespa.config.server.ConfigServerSpec;
 import com.yahoo.vespa.config.server.deploy.ModelContextImpl;
 import com.yahoo.vespa.config.server.http.UnknownVespaVersionException;
+import com.yahoo.vespa.config.server.provision.StaticProvisioner;
 
 import java.time.Instant;
 import java.util.ArrayList;
@@ -38,8 +42,12 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
 
     private final ModelFactoryRegistry modelFactoryRegistry;
 
-    protected ModelsBuilder(ModelFactoryRegistry modelFactoryRegistry) {
+    /** True if we are running in hosted mode */
+    private final boolean hosted;
+
+    protected ModelsBuilder(ModelFactoryRegistry modelFactoryRegistry, boolean hosted) {
         this.modelFactoryRegistry = modelFactoryRegistry;
+        this.hosted = hosted;
     }
 
     public List<MODELRESULT> buildModels(ApplicationId applicationId, 
@@ -53,7 +61,7 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
         if (requestedMajorVersion.isPresent())
             versions = filterByMajorVersion(requestedMajorVersion.get(), versions);
 
-        // Load models by one major version at the time as new major versions are allowed to be unloadable
+        // Load models by one major version at the time as new major versions are allowed to be non-loadable
         // in the case where an existing application is incompatible with a new major version
         // (which is possible by the definition of major)
         List<Integer> majorVersions = versions.stream()
@@ -62,11 +70,14 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
                                               .sorted(Comparator.reverseOrder())
                                               .collect(Collectors.toList());
 
+        // The newest version (major and minor) (which is loaded first) decides the allocated hosts
+        SettableOptional<ProvisionInfo> allocatedHosts = new SettableOptional();
         List<MODELRESULT> allApplicationModels = new ArrayList<>();
         for (int i = 0; i < majorVersions.size(); i++) {
             try {
                 allApplicationModels.addAll(buildModelVersion(filterByMajorVersion(majorVersions.get(i), versions),
-                                                              applicationId, wantedNodeVespaVersion, applicationPackage, now));
+                                                              applicationId, wantedNodeVespaVersion, applicationPackage, 
+                                                              allocatedHosts, now));
 
                 // skip old config models if requested after we have found a major version which works
                 if (allApplicationModels.size() > 0 && allApplicationModels.get(0).getModel().skipOldConfigModels(now))
@@ -92,6 +103,7 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
     private List<MODELRESULT> buildModelVersion(Set<Version> versions, ApplicationId applicationId,
                                                 com.yahoo.component.Version wantedNodeVespaVersion, 
                                                 ApplicationPackage applicationPackage,
+                                                SettableOptional<ProvisionInfo> allocatedHosts,
                                                 Instant now) {
         Version latest = findLatest(versions);
         // load latest application version
@@ -99,23 +111,33 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
                                                                  applicationPackage, 
                                                                  applicationId, 
                                                                  wantedNodeVespaVersion, 
+                                                                 allocatedHosts,
                                                                  now);
-        if (latestApplicationVersion.getModel().skipOldConfigModels(now)) {
+        if ( ! allocatedHosts.isPresent())
+            allocatedHosts.set(latestApplicationVersion.getModel().provisionInfo());
+        
+        if (latestApplicationVersion.getModel().skipOldConfigModels(now))
             return Collections.singletonList(latestApplicationVersion);
+
+        // load old model versions
+        List<MODELRESULT> allApplicationVersions = new ArrayList<>();
+        allApplicationVersions.add(latestApplicationVersion);
+
+        // TODO: We use the allocated hosts from the newest version when building older model versions.
+        // This is correct except for the case where an old model specifies a cluster which the new version
+        // does not. In that case we really want to extend the set of allocated hosts to include those of that
+        // cluster as well. To do that, create a new provisioner which uses static provisioning for known
+        // clusters and the node repository provisioner as fallback.
+        for (Version version : versions) {
+            if (version.equals(latest)) continue; // already loaded
+            allApplicationVersions.add(buildModelVersion(modelFactoryRegistry.getFactory(version),
+                                                         applicationPackage,
+                                                         applicationId,
+                                                         wantedNodeVespaVersion,
+                                                         allocatedHosts,
+                                                         now));
         }
-        else { // load old model versions
-            List<MODELRESULT> allApplicationVersions = new ArrayList<>();
-            allApplicationVersions.add(latestApplicationVersion);
-            for (Version version : versions) {
-                if (version.equals(latest)) continue; // already loaded
-                allApplicationVersions.add(buildModelVersion(modelFactoryRegistry.getFactory(version), 
-                                                             applicationPackage, 
-                                                             applicationId, 
-                                                             wantedNodeVespaVersion, 
-                                                             now));
-            }
-            return allApplicationVersions;
-        }
+        return allApplicationVersions;
     }
 
     private Set<Version> filterByMajorVersion(int majorVersion, Set<Version> versions) {
@@ -134,6 +156,7 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
     protected abstract MODELRESULT buildModelVersion(ModelFactory modelFactory, ApplicationPackage applicationPackage,
                                                      ApplicationId applicationId, 
                                                      com.yahoo.component.Version wantedNodeVespaVersion,
+                                                     SettableOptional<ProvisionInfo> allocatedHosts,
                                                      Instant now);
 
     protected ModelContext.Properties createModelContextProperties(ApplicationId applicationId,
@@ -148,4 +171,41 @@ public abstract class ModelsBuilder<MODELRESULT extends ModelResult> {
                                                rotations);
     }
 
+    /** 
+     * Returns a host provisioner returning the previously allocated hosts if available and when on hosted Vespa,
+     * returns empty otherwise.
+     */
+    protected Optional<HostProvisioner> createHostProvisioner(Optional<ProvisionInfo> provisionInfo) {
+        if (hosted && provisionInfo.isPresent())
+            return Optional.of(new StaticProvisioner(provisionInfo.get()));
+        return Optional.empty();
+    }
+
+    /** An optional which contains a settable value */
+    protected static final class SettableOptional<T> {
+
+        private T value = null;
+
+        /** Creates a new empty settable optional */
+        private SettableOptional() {}
+
+        /** Creates a new settable optional with the given value */
+        private SettableOptional(T value) { this.value = value; }
+
+        public boolean isPresent() {
+            return value != null;
+        }
+        
+        public T get() {
+            if (value == null)
+                throw new NoSuchElementException("No value present");
+            return value;
+        }
+        
+        public void set(T value) {
+            this.value = value;
+        }
+        
+    }
+
 }
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 98741c631b1..27de7f2b2e1 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
@@ -13,6 +13,7 @@ import com.yahoo.config.model.api.ModelCreateResult;
 import com.yahoo.config.model.api.ModelFactory;
 import com.yahoo.config.model.application.provider.FilesApplicationPackage;
 import com.yahoo.config.provision.ApplicationId;
+import com.yahoo.config.provision.ProvisionInfo;
 import com.yahoo.config.provision.Version;
 import com.yahoo.log.LogLevel;
 import com.yahoo.vespa.config.server.application.ApplicationSet;
@@ -61,7 +62,7 @@ public class PreparedModelsBuilder extends ModelsBuilder<PreparedModelsBuilder.P
                                  PrepareParams params,
                                  Optional<ApplicationSet> currentActiveApplicationSet,
                                  ModelContext.Properties properties) {
-        super(modelFactoryRegistry);
+        super(modelFactoryRegistry, properties.hostedVespa());
         this.permanentApplicationPackage = permanentApplicationPackage;
         this.configDefinitionRepo = configDefinitionRepo;
 
@@ -80,14 +81,19 @@ public class PreparedModelsBuilder extends ModelsBuilder<PreparedModelsBuilder.P
     protected PreparedModelResult buildModelVersion(ModelFactory modelFactory, 
                                                     ApplicationPackage applicationPackage,
                                                     ApplicationId applicationId, 
-                                                    com.yahoo.component.Version wantedNodeVespaVersion, Instant now) {
+                                                    com.yahoo.component.Version wantedNodeVespaVersion,
+                                                    SettableOptional<ProvisionInfo> activatedHosts,
+                                                    Instant now) {
         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);
+        // Use already allocated hosts if available, create connection to a host provisioner otherwise
+        Optional<HostProvisioner> hostProvisioner = 
+                activatedHosts.isPresent() ? createHostProvisioner(Optional.of(activatedHosts.get())) :
+                                             createHostProvisionerAdapter(properties);
         Optional<Model> previousModel = currentActiveApplicationSet
                 .map(set -> set.getForVersionOrLatest(Optional.of(modelVersion), now).getModel());
         ModelContext modelContext = new ModelContextImpl(
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/provision/HostProvisionerProvider.java b/configserver/src/main/java/com/yahoo/vespa/config/server/provision/HostProvisionerProvider.java
index 4cf2204c086..32a641a3bc7 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/provision/HostProvisionerProvider.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/provision/HostProvisionerProvider.java
@@ -13,20 +13,18 @@ import java.util.logging.Logger;
 /**
  * This class is necessary to support both having and not having a host provisioner. We inject
  * a component registry here, which then enables us to check whether or not we have a provisioner available.
+ * We only have a provisioner if we are running in hosted mode.
  *
- * @author lulf
+ * @author Ulf Lilleengen
  */
 public class HostProvisionerProvider {
 
-    private static final Logger log = Logger.getLogger(HostProvisionerProvider.class.getName());
     private final Optional<Provisioner> hostProvisioner;
 
     public HostProvisionerProvider(ComponentRegistry<Provisioner> hostProvisionerRegistry, ConfigserverConfig configserverConfig) {
         if (hostProvisionerRegistry.allComponents().isEmpty() || ! configserverConfig.hostedVespa()) {
-            log.info("Host provisioner is missing, provisioner component count: " + hostProvisionerRegistry.allComponents().size() + ", is hosted Vespa: " + configserverConfig.hostedVespa());
             hostProvisioner = Optional.empty();
         } else {
-            log.log(LogLevel.DEBUG, "Host provisioner injected. Will be used for all deployments");
             hostProvisioner = Optional.of(hostProvisionerRegistry.allComponents().get(0));
         }
     }
@@ -35,6 +33,7 @@ public class HostProvisionerProvider {
         this(componentRegistry, new ConfigserverConfig(new ConfigserverConfig.Builder()));
     }
 
+    /** Returns the host provisioner, or empty if we are not in hosted mode */
     public Optional<Provisioner> getHostProvisioner() {
         return hostProvisioner;
     }
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 c20f6e0b853..d5ed84f44f0 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
@@ -19,8 +19,7 @@ import java.util.logging.Logger;
  * A RemoteSession represents a session created on another config server. This session can
  * be regarded as read only, and this interface only allows reading information about a session.
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 public class RemoteSession extends Session {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionFactory.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionFactory.java
index 0f1e65aaf2b..298acaca901 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionFactory.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/RemoteSessionFactory.java
@@ -12,8 +12,7 @@ import com.yahoo.vespa.curator.Curator;
 import java.time.Clock;
 
 /**
- * @author lulf
- * @since 5.1.24
+ * @author Ulf Lilleengen
  */
 public class RemoteSessionFactory {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionContext.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionContext.java
index a840e5d5a97..323c2667d30 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionContext.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionContext.java
@@ -12,8 +12,7 @@ import java.io.File;
 /**
  * The dependencies needed for a local session to be edited and prepared.
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 public class SessionContext {
 
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 19651041ea4..c2655d1a1b3 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
@@ -170,7 +170,8 @@ public class SessionFactoryImpl implements SessionFactory, LocalSessionLoader {
                                                                             defRepo,
                                                                             serverId,
                                                                             nodeFlavors);
-        SessionContext context = new SessionContext(applicationPackage, sessionZKClient, sessionDir, applicationRepo, hostRegistry, superModelGenerationCounter);
+        SessionContext context = new SessionContext(applicationPackage, sessionZKClient, sessionDir, applicationRepo, 
+                                                    hostRegistry, superModelGenerationCounter);
         return new LocalSession(tenant, sessionId, sessionPreparer, context);
     }
 
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 3b96069c4e7..3dc0eb4f1b5 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
@@ -252,11 +252,8 @@ public class SessionPreparer {
 
         private final ImmutableList<PreparedModelsBuilder.PreparedModelResult> results;
         
-        private final ReconciliatedHostAllocations reconciliatedHostAllocations;
-
         public PrepareResult(List<PreparedModelsBuilder.PreparedModelResult> results) {
             this.results = ImmutableList.copyOf(results);
-            reconciliatedHostAllocations = new ReconciliatedHostAllocations(results);
         }
 
         /** Returns the results for each model as an immutable list */
@@ -264,7 +261,7 @@ public class SessionPreparer {
 
         /** Returns the host allocations resulting from this preparation. */
         public ProvisionInfo getProvisionInfo() {
-            return reconciliatedHostAllocations.allocatedHosts();
+            return results.asList().get(0).getModel().provisionInfo(); // All have the same provision info
         }
 
         public Map<Version, FileRegistry> getFileRegistries() {
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java
index 144bbf10dc6..f4a5e941ac2 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/TenantBuilder.java
@@ -27,8 +27,7 @@ import java.util.concurrent.Executors;
 /**
  * Builder for helping out with tenant creation. Each of a tenants dependencies may be overridden for testing.
  *
- * @author lulf
- * @since 5.1
+ * @author Ulf Lilleengen
  */
 public class TenantBuilder {
 
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenants.java b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenants.java
index 28bae587e2a..377b3997e43 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenants.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/tenant/Tenants.java
@@ -48,12 +48,12 @@ import java.util.logging.Logger;
  * Once a tenant is deleted from zookeeper, the zookeeper watcher thread will get notified on all configservers, and
  * shutdown and delete any per-configserver state.
  *
- * @author vegardh
- * @author lulf
- * @since 5.1.26
+ * @author Vegard Havdal
+ * @author Ulf Lilleengen
  */
 //TODO Rename to TenantRepository
 public class Tenants implements ConnectionStateListener, PathChildrenCacheListener {
+
     public static final TenantName HOSTED_VESPA_TENANT = TenantName.from("hosted-vespa");
     private static final TenantName DEFAULT_TENANT = TenantName.defaultName();
     private static final List<TenantName> SYSTEM_TENANT_NAMES = Arrays.asList(
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/zookeeper/ZKApplicationPackage.java b/configserver/src/main/java/com/yahoo/vespa/config/server/zookeeper/ZKApplicationPackage.java
index 4aa4fc32483..7e82b6bf649 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/zookeeper/ZKApplicationPackage.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/zookeeper/ZKApplicationPackage.java
@@ -2,6 +2,7 @@
 package com.yahoo.vespa.config.server.zookeeper;
 
 import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableSet;
 import com.yahoo.component.Version;
 import com.yahoo.config.application.api.ApplicationMetaData;
 import com.yahoo.config.application.api.ComponentInfo;
@@ -11,6 +12,7 @@ import com.yahoo.config.codegen.DefParser;
 import com.yahoo.config.application.api.ApplicationFile;
 import com.yahoo.config.application.api.ApplicationPackage;
 import com.yahoo.config.model.application.provider.*;
+import com.yahoo.config.provision.HostSpec;
 import com.yahoo.config.provision.NodeFlavors;
 import com.yahoo.config.provision.ProvisionInfo;
 import com.yahoo.io.IOUtils;
@@ -35,7 +37,7 @@ import java.util.Optional;
 /**
  * Represents an application residing in zookeeper.
  *
- * @author tonytv
+ * @author Tony Vaagenes
  */
 public class ZKApplicationPackage implements ApplicationPackage {
 
@@ -62,7 +64,7 @@ public class ZKApplicationPackage implements ApplicationPackage {
         Optional<ProvisionInfo> provisionInfo = readProvisionInfo(allocatedHostsPath, nodeFlavors);
         if ( ! provisionInfo.isPresent()) { // Read from legacy location. TODO: Remove when 6.142 is in production everywhere
             List<String> provisionInfoByVersionNodes = liveApp.getChildren(allocatedHostsPath);
-            provisionInfo = newestOf(readProvisionInfosByVersion(provisionInfoByVersionNodes, nodeFlavors));
+            provisionInfo = merge(readProvisionInfosByVersion(provisionInfoByVersionNodes, nodeFlavors));
         }
         return provisionInfo;
     }
@@ -79,17 +81,16 @@ public class ZKApplicationPackage implements ApplicationPackage {
         return provisionInfoMap;
     }
 
-    private Optional<ProvisionInfo> newestOf(Map<Version, ProvisionInfo> provisionInfoMap) {
+    private Optional<ProvisionInfo> merge(Map<Version, ProvisionInfo> provisionInfoMap) {
+        // Merge the provision infos in any order. This is wrong but preserves current behavior (modulo order differences)
         if (provisionInfoMap.isEmpty()) return Optional.empty();
-        Version newestVersion = null;
-        ProvisionInfo newestInfo = null;
+        
+        Map<String, HostSpec> merged = new HashMap<>();
         for (Map.Entry<Version, ProvisionInfo> entry : provisionInfoMap.entrySet()) {
-            if (newestVersion == null || newestVersion.isBefore(entry.getKey())) {
-                newestVersion = entry.getKey();
-                newestInfo = entry.getValue();
-            }
+            for (HostSpec host : entry.getValue().getHosts())
+                merged.put(host.hostname(), host);
         }
-        return Optional.of(newestInfo);
+        return Optional.of(ProvisionInfo.withHosts(ImmutableSet.copyOf(merged.values())));
     }
 
     /**