Rename MutableStatusService to ApplicationLock

The result of acquiring the application lock in the status service is now named
ApplicationLock instead of MutableStatusService.

15 files changed, 136 insertions, 158 deletions

diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/OrchestratorImpl.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/OrchestratorImpl.java
index 964d2875496..be1f83da094 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/OrchestratorImpl.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/OrchestratorImpl.java
@@ -34,7 +34,7 @@ import com.yahoo.vespa.orchestrator.status.ApplicationInstanceStatus;
 import com.yahoo.vespa.orchestrator.status.HostInfo;
 import com.yahoo.vespa.orchestrator.status.HostInfos;
 import com.yahoo.vespa.orchestrator.status.HostStatus;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 import com.yahoo.vespa.orchestrator.status.StatusService;
 
 import java.io.IOException;
@@ -74,14 +74,16 @@ public class OrchestratorImpl implements Orchestrator {
                             ConfigserverConfig configServerConfig,
                             FlagSource flagSource)
     {
-        this(new HostedVespaPolicy(new HostedVespaClusterPolicy(), clusterControllerClientFactory, new ApplicationApiFactory(configServerConfig.zookeeperserver().size())),
-             clusterControllerClientFactory,
-             statusService,
-             instanceLookupService,
-             orchestratorConfig.serviceMonitorConvergenceLatencySeconds(),
-             Clock.systemUTC(),
-             new ApplicationApiFactory(configServerConfig.zookeeperserver().size()),
-             flagSource);
+        this(new HostedVespaPolicy(new HostedVespaClusterPolicy(),
+                                   clusterControllerClientFactory,
+                                   new ApplicationApiFactory(configServerConfig.zookeeperserver().size())),
+                clusterControllerClientFactory,
+                statusService,
+                instanceLookupService,
+                orchestratorConfig.serviceMonitorConvergenceLatencySeconds(),
+                Clock.systemUTC(),
+                new ApplicationApiFactory(configServerConfig.zookeeperserver().size()),
+                flagSource);
     }
 
     public OrchestratorImpl(Policy policy,
@@ -127,17 +129,17 @@ public class OrchestratorImpl implements Orchestrator {
 
     @Override
     public Function<HostName, Optional<HostInfo>> getHostResolver() {
-        return hostName -> instanceLookupService.findInstanceByHost(hostName)
-                                                .map(application -> statusService.getHostInfo(application.reference(), hostName));
+        return hostName -> instanceLookupService
+                .findInstanceByHost(hostName)
+                .map(application -> statusService.getHostInfo(application.reference(), hostName));
     }
 
     @Override
     public void setNodeStatus(HostName hostName, HostStatus status) throws OrchestrationException {
         ApplicationInstanceReference reference = getApplicationInstance(hostName).reference();
         OrchestratorContext context = OrchestratorContext.createContextForSingleAppOp(clock);
-        try (MutableStatusService statusRegistry = statusService
-                .lockApplication(context, reference)) {
-            statusRegistry.setHostState(hostName, status);
+        try (ApplicationLock lock = statusService.lockApplication(context, reference)) {
+            lock.setHostState(hostName, status);
         }
     }
 
@@ -165,9 +167,8 @@ public class OrchestratorImpl implements Orchestrator {
         ApplicationInstance appInstance = getApplicationInstance(hostName);
 
         OrchestratorContext context = OrchestratorContext.createContextForSingleAppOp(clock);
-        try (MutableStatusService statusRegistry = statusService
-                .lockApplication(context, appInstance.reference())) {
-            HostStatus currentHostState = statusRegistry.getHostInfos().getOrNoRemarks(hostName).status();
+        try (ApplicationLock lock = statusService.lockApplication(context, appInstance.reference())) {
+            HostStatus currentHostState = lock.getHostInfos().getOrNoRemarks(hostName).status();
             if (currentHostState == HostStatus.NO_REMARKS) {
                 return;
             }
@@ -178,11 +179,11 @@ public class OrchestratorImpl implements Orchestrator {
             //  2. The whole application is down: the content cluster states are set to maintenance,
             //     and the host may be taken down manually at any moment.
             if (currentHostState == HostStatus.PERMANENTLY_DOWN ||
-                    statusRegistry.getStatus() == ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN) {
+                    lock.getApplicationInstanceStatus() == ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN) {
                 return;
             }
 
-            policy.releaseSuspensionGrant(context.createSubcontextWithinLock(), appInstance, hostName, statusRegistry);
+            policy.releaseSuspensionGrant(context.createSubcontextWithinLock(), appInstance, hostName, lock);
         }
     }
 
@@ -202,10 +203,8 @@ public class OrchestratorImpl implements Orchestrator {
                 .with(FetchVector.Dimension.HOSTNAME, hostName.s())
                 .value();
         OrchestratorContext context = OrchestratorContext.createContextForSingleAppOp(clock, usePermanentlyDownStatus);
-        try (MutableStatusService statusRegistry = statusService
-                .lockApplication(context, appInstance.reference())) {
-            ApplicationApi applicationApi = applicationApiFactory.create(nodeGroup, statusRegistry,
-                                                                         clusterControllerClientFactory);
+        try (ApplicationLock lock = statusService.lockApplication(context, appInstance.reference())) {
+            ApplicationApi applicationApi = applicationApiFactory.create(nodeGroup, lock, clusterControllerClientFactory);
 
             policy.acquirePermissionToRemove(context.createSubcontextWithinLock(), applicationApi);
         }
@@ -220,23 +219,22 @@ public class OrchestratorImpl implements Orchestrator {
     void suspendGroup(OrchestratorContext context, NodeGroup nodeGroup) throws HostStateChangeDeniedException {
         ApplicationInstanceReference applicationReference = nodeGroup.getApplicationReference();
 
-        try (MutableStatusService hostStatusRegistry =
-                     statusService.lockApplication(context, applicationReference)) {
-            ApplicationInstanceStatus appStatus = hostStatusRegistry.getStatus();
+        try (ApplicationLock lock = statusService.lockApplication(context, applicationReference)) {
+            ApplicationInstanceStatus appStatus = lock.getApplicationInstanceStatus();
             if (appStatus == ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN) {
                 return;
             }
 
-            ApplicationApi applicationApi = applicationApiFactory.create(nodeGroup, hostStatusRegistry,
-                                                                         clusterControllerClientFactory);
+            ApplicationApi applicationApi = applicationApiFactory.create(
+                    nodeGroup, lock, clusterControllerClientFactory);
             policy.grantSuspensionRequest(context.createSubcontextWithinLock(), applicationApi);
         }
     }
 
     @Override
     public ApplicationInstanceStatus getApplicationInstanceStatus(ApplicationId appId) throws ApplicationIdNotFoundException {
-        ApplicationInstanceReference appRef = OrchestratorUtil.toApplicationInstanceReference(appId, instanceLookupService);
-        return statusService.getApplicationInstanceStatus(appRef);
+        ApplicationInstanceReference reference = OrchestratorUtil.toApplicationInstanceReference(appId, instanceLookupService);
+        return statusService.getApplicationInstanceStatus(reference);
     }
 
     @Override
@@ -354,17 +352,16 @@ public class OrchestratorImpl implements Orchestrator {
             throws ApplicationStateChangeDeniedException, ApplicationIdNotFoundException{
         OrchestratorContext context = OrchestratorContext.createContextForSingleAppOp(clock);
         ApplicationInstanceReference appRef = OrchestratorUtil.toApplicationInstanceReference(appId, instanceLookupService);
-        try (MutableStatusService statusRegistry =
-                     statusService.lockApplication(context, appRef)) {
+        try (ApplicationLock lock = statusService.lockApplication(context, appRef)) {
 
             // Short-circuit if already in wanted state
-            if (status == statusRegistry.getStatus()) return;
+            if (status == lock.getApplicationInstanceStatus()) return;
 
             // Set content clusters for this application in maintenance on suspend
             if (status == ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN) {
                 ApplicationInstance application = getApplicationInstance(appRef);
 
-                HostInfos hostInfosSnapshot = statusRegistry.getHostInfos();
+                HostInfos hostInfosSnapshot = lock.getHostInfos();
 
                 // Mark it allowed to be down before we manipulate the clustercontroller
                 OrchestratorUtil.getHostsUsedByApplicationInstance(application)
@@ -372,14 +369,14 @@ public class OrchestratorImpl implements Orchestrator {
                         // This filter also ensures host status is not modified if a suspended host
                         // has status != ALLOWED_TO_BE_DOWN.
                         .filter(hostname -> !hostInfosSnapshot.getOrNoRemarks(hostname).status().isSuspended())
-                        .forEach(hostname -> statusRegistry.setHostState(hostname, HostStatus.ALLOWED_TO_BE_DOWN));
+                        .forEach(hostname -> lock.setHostState(hostname, HostStatus.ALLOWED_TO_BE_DOWN));
 
                 // If the clustercontroller throws an error the nodes will be marked as allowed to be down
                 // and be set back up on next resume invocation.
                 setClusterStateInController(context.createSubcontextWithinLock(), application, ClusterControllerNodeState.MAINTENANCE);
             }
 
-            statusRegistry.setApplicationInstanceStatus(status);
+            lock.setApplicationInstanceStatus(status);
         }
     }
 
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiFactory.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiFactory.java
index ef14a99d7db..fb52eed2048 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiFactory.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiFactory.java
@@ -2,7 +2,7 @@
 package com.yahoo.vespa.orchestrator.model;
 
 import com.yahoo.vespa.orchestrator.controller.ClusterControllerClientFactory;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 
 /**
  * @author mpolden
@@ -16,9 +16,9 @@ public class ApplicationApiFactory {
     }
 
     public ApplicationApi create(NodeGroup nodeGroup,
-                                 MutableStatusService hostStatusService,
+                                 ApplicationLock lock,
                                  ClusterControllerClientFactory clusterControllerClientFactory) {
-        return new ApplicationApiImpl(nodeGroup, hostStatusService, clusterControllerClientFactory, numberOfConfigServers);
+        return new ApplicationApiImpl(nodeGroup, lock, clusterControllerClientFactory, numberOfConfigServers);
     }
 
 }
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiImpl.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiImpl.java
index 92867cf3258..ccc89fa9191 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiImpl.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/model/ApplicationApiImpl.java
@@ -12,7 +12,7 @@ import com.yahoo.vespa.orchestrator.controller.ClusterControllerClientFactory;
 import com.yahoo.vespa.orchestrator.status.ApplicationInstanceStatus;
 import com.yahoo.vespa.orchestrator.status.HostInfos;
 import com.yahoo.vespa.orchestrator.status.HostStatus;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 
 import java.util.Collection;
 import java.util.Comparator;
@@ -32,19 +32,19 @@ public class ApplicationApiImpl implements ApplicationApi {
 
     private final ApplicationInstance applicationInstance;
     private final NodeGroup nodeGroup;
-    private final MutableStatusService hostStatusService;
+    private final ApplicationLock lock;
     private final List<ClusterApi> clusterInOrder;
     private final HostInfos hostInfos;
 
     public ApplicationApiImpl(NodeGroup nodeGroup,
-                              MutableStatusService hostStatusService,
+                              ApplicationLock lock,
                               ClusterControllerClientFactory clusterControllerClientFactory,
                               int numberOfConfigServers) {
         this.applicationInstance = nodeGroup.getApplication();
         this.nodeGroup = nodeGroup;
-        this.hostStatusService = hostStatusService;
+        this.lock = lock;
         Collection<HostName> hosts = getHostsUsedByApplicationInstance(applicationInstance);
-        this.hostInfos = hostStatusService.getHostInfos();
+        this.hostInfos = lock.getHostInfos();
         this.clusterInOrder = makeClustersInOrder(nodeGroup, hostInfos, clusterControllerClientFactory, numberOfConfigServers);
     }
 
@@ -95,12 +95,12 @@ public class ApplicationApiImpl implements ApplicationApi {
 
     @Override
     public ApplicationInstanceStatus getApplicationStatus() {
-        return hostStatusService.getStatus();
+        return lock.getApplicationInstanceStatus();
     }
 
     @Override
     public void setHostState(OrchestratorContext context, HostName hostName, HostStatus status) {
-        hostStatusService.setHostState(hostName, status);
+        lock.setHostState(hostName, status);
     }
 
     @Override
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/HostedVespaPolicy.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/HostedVespaPolicy.java
index 95ce34a8a61..8b74d8a40ef 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/HostedVespaPolicy.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/HostedVespaPolicy.java
@@ -13,7 +13,7 @@ import com.yahoo.vespa.orchestrator.model.NodeGroup;
 import com.yahoo.vespa.orchestrator.model.StorageNode;
 import com.yahoo.vespa.orchestrator.status.ApplicationInstanceStatus;
 import com.yahoo.vespa.orchestrator.status.HostStatus;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 
 /**
  * @author oyving
@@ -113,9 +113,9 @@ public class HostedVespaPolicy implements Policy {
             OrchestratorContext context,
             ApplicationInstance applicationInstance,
             HostName hostName,
-            MutableStatusService hostStatusService) throws HostStateChangeDeniedException {
+            ApplicationLock lock) throws HostStateChangeDeniedException {
         NodeGroup nodeGroup = new NodeGroup(applicationInstance, hostName);
-        ApplicationApi applicationApi = applicationApiFactory.create(nodeGroup, hostStatusService, clusterControllerClientFactory);
+        ApplicationApi applicationApi = applicationApiFactory.create(nodeGroup, lock, clusterControllerClientFactory);
         releaseSuspensionGrant(context, applicationApi);
     }
 
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/Policy.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/Policy.java
index 6e7a3552828..c410cda23a8 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/Policy.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/policy/Policy.java
@@ -5,7 +5,7 @@ import com.yahoo.vespa.applicationmodel.ApplicationInstance;
 import com.yahoo.vespa.applicationmodel.HostName;
 import com.yahoo.vespa.orchestrator.OrchestratorContext;
 import com.yahoo.vespa.orchestrator.model.ApplicationApi;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 
 /**
  * @author oyving
@@ -32,6 +32,6 @@ public interface Policy {
     void releaseSuspensionGrant(
             OrchestratorContext context, ApplicationInstance applicationInstance,
             HostName hostName,
-            MutableStatusService hostStatusService) throws HostStateChangeDeniedException;
+            ApplicationLock hostStatusService) throws HostStateChangeDeniedException;
 
 }
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ApplicationLock.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ApplicationLock.java
new file mode 100644
index 00000000000..4f6c0547ed6
--- /dev/null
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ApplicationLock.java
@@ -0,0 +1,36 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.vespa.orchestrator.status;
+
+import com.yahoo.vespa.applicationmodel.ApplicationInstanceReference;
+import com.yahoo.vespa.applicationmodel.HostName;
+
+/**
+ * The exclusive lock of an application in the status service, and methods to mutate host status
+ * and data structures guarded by such a lock.
+ *
+ * @author oyving
+ * @author Tony Vaagenes
+ * @author bakksjo
+ */
+public interface ApplicationLock extends AutoCloseable {
+
+    /** The reference of the locked application. */
+    ApplicationInstanceReference getApplicationInstanceReference();
+
+    /** Returns all host infos for this application. */
+    HostInfos getHostInfos();
+
+    /** Sets the state for the given host. */
+    void setHostState(HostName hostName, HostStatus status);
+
+    /** Returns the application status. */
+    ApplicationInstanceStatus getApplicationInstanceStatus();
+
+    /** Sets the orchestration status for the application instance. */
+    void setApplicationInstanceStatus(ApplicationInstanceStatus applicationInstanceStatus);
+
+    /** implNote: Must not throw an exception. */
+    @Override
+    void close();
+
+}
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/MutableStatusService.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/MutableStatusService.java
deleted file mode 100644
index ad68652e968..00000000000
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/MutableStatusService.java
+++ /dev/null
@@ -1,36 +0,0 @@
-// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
-package com.yahoo.vespa.orchestrator.status;
-
-import com.yahoo.vespa.applicationmodel.HostName;
-
-/**
- * Registry of the suspension and host statuses for an application instance.
- *
- * @author oyving
- * @author Tony Vaagenes
- * @author bakksjo
- */
-public interface MutableStatusService extends AutoCloseable {
-
-    /** Returns the status of this application. */
-    ApplicationInstanceStatus getStatus();
-
-    /** Returns a snapshot of all host infos for this application. */
-    HostInfos getHostInfos();
-
-    /** Sets the state for the given host. */
-    void setHostState(HostName hostName, HostStatus status);
-
-    /**
-     * Sets the orchestration status for the application instance.
-     */
-    void setApplicationInstanceStatus(ApplicationInstanceStatus applicationInstanceStatus);
-
-    /**
-     * We don't want {@link AutoCloseable#close()} to throw an exception (what to do about it anyway?),
-     * so we override it here to strip the exception from the signature.
-     */
-    @Override
-    void close();
-
-}
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/StatusService.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/StatusService.java
index 346d0523333..0d4076f3d59 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/StatusService.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/StatusService.java
@@ -24,27 +24,8 @@ public interface StatusService {
      * Returns a mutable host status registry for a locked application instance. All operations performed on
      * the returned registry are executed in the context of a lock, including read operations. Hence, multi-step
      * operations (e.g. read-then-write) are guaranteed to be consistent.
-     *
-     * Some limitations/caveats apply for certain implementations, and since clients of this API must be aware of
-     * these limitations/caveats when using those implementations, they are expressed here, at interface level
-     * rather than at implementation level, because the interface represents the lowest common denominator
-     * of guarantees offered by implementations. Specifically, it is the zookeeper-based implementation's semantics
-     * that "leak through" in this spec. Now, to the specific caveats:
-     *
-     * Locking this application instance only guarantees that the holder is the only one that can mutate host statuses
-     * for the application instance.
-     * It is _not_ safe to assume that there is only one entity holding the lock for a given application instance
-     * reference at any given time.
-     *
-     * You cannot have multiple locks in a single thread, even if they are for different application instances,
-     * (i.e. different HostStatusRegistry instances). (This is due to a limitation in SessionFailRetryLoop.)
-     *
-     * While read-then-write-operations are consistent (i.e. the current value doesn't change between the read
-     * and the write), it is possible that the lock is lost before it is explicitly released by the code. In
-     * this case, subsequent mutating operations will fail, but previous mutating operations are NOT rolled back.
-     * This may leave the registry in an inconsistent state (as judged by the client code).
      */
-    MutableStatusService lockApplication(OrchestratorContext context, ApplicationInstanceReference reference)
+    ApplicationLock lockApplication(OrchestratorContext context, ApplicationInstanceReference reference)
             throws UncheckedTimeoutException;
 
     /**
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkMutableStatusService.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkApplicationLock.java
index e855f78a03c..08cbe1f45d7 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkMutableStatusService.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkApplicationLock.java
@@ -10,9 +10,9 @@ import org.apache.zookeeper.KeeperException;
 
 import java.util.logging.Logger;
 
-class ZkMutableStatusService implements MutableStatusService {
+class ZkApplicationLock implements ApplicationLock {
 
-    private static final Logger log = Logger.getLogger(ZkMutableStatusService.class.getName());
+    private static final Logger log = Logger.getLogger(ZkApplicationLock.class.getName());
 
     private final ZkStatusService statusService;
     private final Curator curator;
@@ -21,12 +21,12 @@ class ZkMutableStatusService implements MutableStatusService {
     private final boolean probe;
     private final HostInfosCache hostInfosCache;
 
-    ZkMutableStatusService(ZkStatusService statusService,
-                           Curator curator,
-                           Runnable onClose,
-                           ApplicationInstanceReference reference,
-                           boolean probe,
-                           HostInfosCache hostInfosCache) {
+    ZkApplicationLock(ZkStatusService statusService,
+                      Curator curator,
+                      Runnable onClose,
+                      ApplicationInstanceReference reference,
+                      boolean probe,
+                      HostInfosCache hostInfosCache) {
         this.statusService = statusService;
         this.curator = curator;
         this.onClose = onClose;
@@ -36,7 +36,12 @@ class ZkMutableStatusService implements MutableStatusService {
     }
 
     @Override
-    public ApplicationInstanceStatus getStatus() {
+    public ApplicationInstanceReference getApplicationInstanceReference() {
+        return reference;
+    }
+
+    @Override
+    public ApplicationInstanceStatus getApplicationInstanceStatus() {
         return statusService.getApplicationInstanceStatus(reference);
     }
 
@@ -77,7 +82,7 @@ class ZkMutableStatusService implements MutableStatusService {
             // We may want to avoid logging some exceptions that may be expected, like when session expires.
             log.log(LogLevel.WARNING,
                     "Failed close application lock in " +
-                    ZkMutableStatusService.class.getSimpleName() + ", will ignore and continue",
+                    ZkApplicationLock.class.getSimpleName() + ", will ignore and continue",
                     e);
         }
     }
diff --git a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkStatusService.java b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkStatusService.java
index 4be629c6d21..c1ca04aea75 100644
--- a/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkStatusService.java
+++ b/orchestrator/src/main/java/com/yahoo/vespa/orchestrator/status/ZkStatusService.java
@@ -110,9 +110,9 @@ public class ZkStatusService implements StatusService {
      *     (i.e. the request is for another applicationInstanceReference)
      */
     @Override
-    public MutableStatusService lockApplication(
-            OrchestratorContext context,
-            ApplicationInstanceReference reference) throws UncheckedTimeoutException {
+    public ApplicationLock lockApplication(OrchestratorContext context, ApplicationInstanceReference reference)
+            throws UncheckedTimeoutException {
+
         Runnable onRegistryClose;
 
         // A multi-application operation, aka batch suspension, will first issue a probe
@@ -131,7 +131,7 @@ public class ZkStatusService implements StatusService {
         }
 
         try {
-            return new ZkMutableStatusService(
+            return new ZkApplicationLock(
                     this,
                     curator,
                     onRegistryClose,
@@ -145,8 +145,7 @@ public class ZkStatusService implements StatusService {
         }
     }
 
-    private Runnable acquireLock(OrchestratorContext context,
-                                 ApplicationInstanceReference reference)
+    private Runnable acquireLock(OrchestratorContext context, ApplicationInstanceReference reference)
             throws UncheckedTimeoutException {
         ApplicationId applicationId = OrchestratorUtil.toApplicationId(reference);
         String app = applicationId.application().value() + "." + applicationId.instance().value();
diff --git a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/OrchestratorImplTest.java b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/OrchestratorImplTest.java
index 3f560a3e274..f7c5ab15927 100644
--- a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/OrchestratorImplTest.java
+++ b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/OrchestratorImplTest.java
@@ -27,7 +27,7 @@ import com.yahoo.vespa.orchestrator.policy.HostStateChangeDeniedException;
 import com.yahoo.vespa.orchestrator.policy.HostedVespaClusterPolicy;
 import com.yahoo.vespa.orchestrator.policy.HostedVespaPolicy;
 import com.yahoo.vespa.orchestrator.status.HostStatus;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 import com.yahoo.vespa.orchestrator.status.StatusService;
 import com.yahoo.vespa.orchestrator.status.ZkStatusService;
 import com.yahoo.vespa.service.model.ServiceModelCache;
@@ -336,13 +336,12 @@ public class OrchestratorImplTest {
         var clusterControllerClientFactory = mock(ClusterControllerClientFactory.class);
         var clock = new ManualClock();
         var applicationApiFactory = mock(ApplicationApiFactory.class);
-        var hostStatusRegistry = mock(MutableStatusService.class);
+        var lock = mock(ApplicationLock.class);
 
         when(instanceLookupService.findInstanceByHost(any())).thenReturn(Optional.of(applicationInstance));
         when(applicationInstance.reference()).thenReturn(applicationInstanceReference);
-        when(zookeeperStatusService.lockApplication(any(), any()))
-                .thenReturn(hostStatusRegistry);
-        when(hostStatusRegistry.getStatus()).thenReturn(NO_REMARKS);
+        when(zookeeperStatusService.lockApplication(any(), any())).thenReturn(lock);
+        when(lock.getApplicationInstanceStatus()).thenReturn(NO_REMARKS);
 
         var orchestrator = new OrchestratorImpl(
                 policy,
@@ -372,17 +371,17 @@ public class OrchestratorImplTest {
         verify(applicationApiFactory, times(2)).create(any(), any(), any());
         verify(policy, times(2)).grantSuspensionRequest(any(), any());
         verify(instanceLookupService, atLeastOnce()).findInstanceByHost(any());
-        verify(hostStatusRegistry, times(2)).getStatus();
+        verify(lock, times(2)).getApplicationInstanceStatus();
 
         // Each zookeeperStatusService that is created, is closed.
         verify(zookeeperStatusService, times(2)).lockApplication(any(), any());
-        verify(hostStatusRegistry, times(2)).close();
+        verify(lock, times(2)).close();
 
         verifyNoMoreInteractions(
                 policy,
                 clusterControllerClientFactory,
                 zookeeperStatusService,
-                hostStatusRegistry,
+                lock,
                 instanceLookupService,
                 applicationApiFactory);
     }
diff --git a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/model/ModelTestUtils.java b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/model/ModelTestUtils.java
index b37d3fc3850..24a85bfa244 100644
--- a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/model/ModelTestUtils.java
+++ b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/model/ModelTestUtils.java
@@ -29,7 +29,7 @@ import com.yahoo.vespa.orchestrator.policy.HostedVespaPolicy;
 import com.yahoo.vespa.orchestrator.status.HostInfo;
 import com.yahoo.vespa.orchestrator.status.HostInfos;
 import com.yahoo.vespa.orchestrator.status.HostStatus;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 import com.yahoo.vespa.orchestrator.status.StatusService;
 import com.yahoo.vespa.orchestrator.status.ZkStatusService;
 import com.yahoo.vespa.service.model.ServiceModelCache;
@@ -114,10 +114,10 @@ class ModelTestUtils {
             ApplicationInstance applicationInstance,
             HostName... hostnames) {
         NodeGroup nodeGroup = new NodeGroup(applicationInstance, hostnames);
-        MutableStatusService registry = statusService.lockApplication(
+        ApplicationLock lock = statusService.lockApplication(
                 OrchestratorContext.createContextForSingleAppOp(Clock.systemUTC()),
                 applicationInstance.reference());
-        return applicationApiFactory().create(nodeGroup, registry, clusterControllerClientFactory);
+        return applicationApiFactory().create(nodeGroup, lock, clusterControllerClientFactory);
     }
 
     ApplicationInstance createApplicationInstance(
diff --git a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/resources/HostResourceTest.java b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/resources/HostResourceTest.java
index df5f31c8e47..9133a3bbf2c 100644
--- a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/resources/HostResourceTest.java
+++ b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/resources/HostResourceTest.java
@@ -39,7 +39,7 @@ import com.yahoo.vespa.orchestrator.restapi.wire.PatchHostResponse;
 import com.yahoo.vespa.orchestrator.restapi.wire.UpdateHostResponse;
 import com.yahoo.vespa.orchestrator.status.HostInfo;
 import com.yahoo.vespa.orchestrator.status.HostStatus;
-import com.yahoo.vespa.orchestrator.status.MutableStatusService;
+import com.yahoo.vespa.orchestrator.status.ApplicationLock;
 import com.yahoo.vespa.orchestrator.status.StatusService;
 import com.yahoo.vespa.orchestrator.status.ZkStatusService;
 import org.junit.Before;
@@ -134,7 +134,7 @@ public class HostResourceTest {
         public void releaseSuspensionGrant(
                 OrchestratorContext context, ApplicationInstance applicationInstance,
                 HostName hostName,
-                MutableStatusService hostStatusRegistry) {
+                ApplicationLock hostStatusRegistry) {
         }
     }
 
@@ -236,7 +236,7 @@ public class HostResourceTest {
         public void releaseSuspensionGrant(
                 OrchestratorContext context, ApplicationInstance applicationInstance,
                 HostName hostName,
-                MutableStatusService hostStatusRegistry) throws HostStateChangeDeniedException {
+                ApplicationLock hostStatusRegistry) throws HostStateChangeDeniedException {
             doThrow();
         }
 
diff --git a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusService2Test.java b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusService2Test.java
index 10556a15c51..c5d390050ee 100644
--- a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusService2Test.java
+++ b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusService2Test.java
@@ -50,7 +50,7 @@ public class ZkStatusService2Test {
 
         when(context.getTimeLeft()).thenReturn(Duration.ofSeconds(12));
 
-        try (MutableStatusService registry = zkStatusService.lockApplication(context, reference)) {
+        try (ApplicationLock lock = zkStatusService.lockApplication(context, reference)) {
             // nothing
         }
 
@@ -65,7 +65,7 @@ public class ZkStatusService2Test {
 
         when(context.isProbe()).thenReturn(false);
 
-        try (MutableStatusService registry = zkStatusService.lockApplication(context, reference)) {
+        try (ApplicationLock lock = zkStatusService.lockApplication(context, reference)) {
             // nothing
         }
 
@@ -88,7 +88,7 @@ public class ZkStatusService2Test {
 
         when(context.getTimeLeft()).thenReturn(Duration.ofSeconds(12));
 
-        try (MutableStatusService registry = zkStatusService.lockApplication(context, reference)) {
+        try (ApplicationLock lock = zkStatusService.lockApplication(context, reference)) {
             // nothing
         }
 
@@ -105,7 +105,7 @@ public class ZkStatusService2Test {
         when(context.hasLock(any())).thenReturn(true);
         when(context.registerLockAcquisition(any(), any())).thenReturn(false);
 
-        try (MutableStatusService registry = zkStatusService.lockApplication(context, reference)) {
+        try (ApplicationLock lock = zkStatusService.lockApplication(context, reference)) {
             // nothing
         }
 
diff --git a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusServiceTest.java b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusServiceTest.java
index 48d50946e51..a6d7f09d69b 100644
--- a/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusServiceTest.java
+++ b/orchestrator/src/test/java/com/yahoo/vespa/orchestrator/status/ZkStatusServiceTest.java
@@ -107,17 +107,14 @@ public class ZkStatusServiceTest {
                 Instant.ofEpochMilli((3)),
                 Instant.ofEpochMilli(6));
 
-        try (MutableStatusService statusRegistry = zkStatusService
-                .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
+        try (ApplicationLock lock = zkStatusService.lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
 
             //shuffling to catch "clean database" failures for all cases.
             for (HostStatus hostStatus: shuffledList(HostStatus.NO_REMARKS, HostStatus.ALLOWED_TO_BE_DOWN)) {
                 for (int i = 0; i < 2; i++) {
-                    statusRegistry.setHostState(
-                            TestIds.HOST_NAME1,
-                            hostStatus);
+                    lock.setHostState(TestIds.HOST_NAME1, hostStatus);
 
-                    assertThat(statusRegistry.getHostInfos().getOrNoRemarks(TestIds.HOST_NAME1).status(),
+                    assertThat(lock.getHostInfos().getOrNoRemarks(TestIds.HOST_NAME1).status(),
                                is(hostStatus));
                 }
             }
@@ -144,11 +141,11 @@ public class ZkStatusServiceTest {
         ZkStatusService zkStatusService2 = new ZkStatusService(curator, mock(Metric.class), new TestTimer());
 
         final CompletableFuture<Void> lockedSuccessfullyFuture;
-        try (MutableStatusService statusRegistry = zkStatusService
+        try (ApplicationLock lock = zkStatusService
                 .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
 
             lockedSuccessfullyFuture = CompletableFuture.runAsync(() -> {
-                try (MutableStatusService statusRegistry2 = zkStatusService2
+                try (ApplicationLock lock2 = zkStatusService2
                         .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE))
                 {
                 }
@@ -168,7 +165,7 @@ public class ZkStatusServiceTest {
     public void failing_to_get_lock_closes_SessionFailRetryLoop() throws Exception {
         ZkStatusService zkStatusService2 = new ZkStatusService(curator, mock(Metric.class), new TestTimer());
 
-        try (MutableStatusService statusRegistry = zkStatusService
+        try (ApplicationLock lock = zkStatusService
                 .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
 
             //must run in separate thread, since having 2 locks in the same thread fails
@@ -182,7 +179,7 @@ public class ZkStatusServiceTest {
                 killSession(curator.framework(), testingServer);
 
                 //Throws SessionFailedException if the SessionFailRetryLoop has not been closed.
-                statusRegistry.getHostInfos().getOrNoRemarks(TestIds.HOST_NAME1);
+                lock.getHostInfos().getOrNoRemarks(TestIds.HOST_NAME1);
             });
 
             assertThat(resultOfZkOperationAfterLockFailure, notHoldsException());
@@ -244,9 +241,9 @@ public class ZkStatusServiceTest {
                 is(ApplicationInstanceStatus.NO_REMARKS));
 
         // Suspend
-        try (MutableStatusService statusRegistry = zkStatusService
+        try (ApplicationLock lock = zkStatusService
                 .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
-            statusRegistry.setApplicationInstanceStatus(ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN);
+            lock.setApplicationInstanceStatus(ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN);
         }
 
         assertThat(
@@ -255,9 +252,9 @@ public class ZkStatusServiceTest {
                 is(ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN));
 
         // Resume
-        try (MutableStatusService statusRegistry = zkStatusService
+        try (ApplicationLock lock = zkStatusService
                 .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
-            statusRegistry.setApplicationInstanceStatus(ApplicationInstanceStatus.NO_REMARKS);
+            lock.setApplicationInstanceStatus(ApplicationInstanceStatus.NO_REMARKS);
         }
 
         assertThat(
@@ -272,14 +269,14 @@ public class ZkStatusServiceTest {
                 = zkStatusService.getAllSuspendedApplications();
         assertThat(suspendedApps.size(), is(0));
 
-        try (MutableStatusService statusRegistry = zkStatusService
+        try (ApplicationLock statusRegistry = zkStatusService
                 .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE)) {
             statusRegistry.setApplicationInstanceStatus(ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN);
         }
 
-        try (MutableStatusService statusRegistry = zkStatusService
+        try (ApplicationLock lock = zkStatusService
                 .lockApplication(context, TestIds.APPLICATION_INSTANCE_REFERENCE2)) {
-            statusRegistry.setApplicationInstanceStatus(ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN);
+            lock.setApplicationInstanceStatus(ApplicationInstanceStatus.ALLOWED_TO_BE_DOWN);
         }
 
         suspendedApps = zkStatusService.getAllSuspendedApplications();