Configserver flags REST API

Adds a new ZooKeeper backed flag source. It is defined in a new module
configserver-flags to allow as many as possible config server modules to depend
on it by minimizing dependencies.

The content of the ZK backed flag source can be viewed and modified through
REST API on the config server/controller. The data stored per flag looks like

  {
    "rules": [
      {
        "conditions": [
          { "type": "whitelist", "dimension": "hostname", "values": ["host1"] }
        ],
        "value": true
      }
    ]
  }

typical for enabling a feature flag on host1.

2 types of conditions are so far supported: whitelist and blacklist. All the
conditions must match in order for the value to apply. If the value is null (or
absent), the default value will be used. At the time the flag's value is
retrieved, it is resolved against the conditions with the current zone,
hostname, and/or application.

The same data structure is used for FileFlagSource for files in
/etc/vespa/flags with the ".2" extension.

The FlagSource component injected in the config server is changed to:
 1. Return the flag value if specified in /etc/vespa/flags, or otherwise
 2. return flag value from ZooKeeper (same as REST API)

The current flags (module) is also changed:
 - All flags must be defined in com.yahoo.vespa.flags.Flags. This allows the ZK
   backed flag source additional sanity checking when modifying flags.
 - If it makes sense to have different flag value depending on e.g. the
   application, then at some point before the value is retrieved, one has to
   bind the flag to that application (using with() to set up the fetch vector).

Future changes would be to 0. make a merged FlagSource in host admin, 1. add
support for viewing and modifying feature flags in dashboard, 2. in hv tool.

3 files changed, 14 insertions, 16 deletions

diff --git a/service-monitor/src/main/java/com/yahoo/vespa/service/duper/DuperModelManager.java b/service-monitor/src/main/java/com/yahoo/vespa/service/duper/DuperModelManager.java
index e0e2b64bdae..57c206ee570 100644
--- a/service-monitor/src/main/java/com/yahoo/vespa/service/duper/DuperModelManager.java
+++ b/service-monitor/src/main/java/com/yahoo/vespa/service/duper/DuperModelManager.java
@@ -10,8 +10,8 @@ import com.yahoo.config.model.api.SuperModelProvider;
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.config.provision.HostName;
 import com.yahoo.log.LogLevel;
-import com.yahoo.vespa.flags.FeatureFlag;
 import com.yahoo.vespa.flags.FlagSource;
+import com.yahoo.vespa.flags.Flags;
 import com.yahoo.vespa.service.monitor.DuperModelInfraApi;
 import com.yahoo.vespa.service.monitor.InfraApplicationApi;
 
@@ -59,12 +59,8 @@ public class DuperModelManager implements DuperModelInfraApi {
     @Inject
     public DuperModelManager(ConfigserverConfig configServerConfig, FlagSource flagSource, SuperModelProvider superModelProvider) {
         this(
-                // Whether to include activate infrastructure applications (except from controller/config apps - see below).
-                new FeatureFlag("dupermodel-contains-infra", true, flagSource).value(),
-                // For historical reasons, the ApplicationInfo in the DuperModel for controllers and config servers
-                // is based on the ConfigserverConfig (this flag is true). We want to transition to use the
-                // infrastructure application activated by the InfrastructureProvisioner once that supports health.
-                new FeatureFlag("dupermodel-use-configserverconfig", true, flagSource).value(),
+                Flags.DUPERMODEL_CONTAINS_INFRA.bindTo(flagSource).value(),
+                Flags.DUPERMODEL_USE_CONFIGSERVERCONFIG.bindTo(flagSource).value(),
                 configServerConfig.multitenant(),
                 configServerApplication.makeApplicationInfoFromConfig(configServerConfig),
                 superModelProvider,
diff --git a/service-monitor/src/main/java/com/yahoo/vespa/service/health/HealthMonitorManager.java b/service-monitor/src/main/java/com/yahoo/vespa/service/health/HealthMonitorManager.java
index 2ad37faf593..340d30e9f41 100644
--- a/service-monitor/src/main/java/com/yahoo/vespa/service/health/HealthMonitorManager.java
+++ b/service-monitor/src/main/java/com/yahoo/vespa/service/health/HealthMonitorManager.java
@@ -8,8 +8,9 @@ import com.yahoo.vespa.applicationmodel.ClusterId;
 import com.yahoo.vespa.applicationmodel.ConfigId;
 import com.yahoo.vespa.applicationmodel.ServiceStatus;
 import com.yahoo.vespa.applicationmodel.ServiceType;
-import com.yahoo.vespa.flags.FeatureFlag;
-import com.yahoo.vespa.flags.FileFlagSource;
+import com.yahoo.vespa.flags.Flag;
+import com.yahoo.vespa.flags.FlagSource;
+import com.yahoo.vespa.flags.Flags;
 import com.yahoo.vespa.service.duper.DuperModelManager;
 import com.yahoo.vespa.service.duper.ZoneApplication;
 import com.yahoo.vespa.service.executor.RunletExecutorImpl;
@@ -49,23 +50,23 @@ public class HealthMonitorManager implements MonitorManager {
     private final ConcurrentHashMap<ApplicationId, ApplicationHealthMonitor> healthMonitors = new ConcurrentHashMap<>();
     private final DuperModelManager duperModel;
     private final ApplicationHealthMonitorFactory applicationHealthMonitorFactory;
-    private final FeatureFlag monitorInfra;
+    private final Flag<Boolean> monitorInfra;
 
     @Inject
-    public HealthMonitorManager(DuperModelManager duperModel, FileFlagSource flagSource) {
+    public HealthMonitorManager(DuperModelManager duperModel, FlagSource flagSource) {
         this(duperModel,
-                new FeatureFlag("healthmonitor-monitorinfra", true, flagSource),
+                Flags.HEALTHMONITOR_MONITOR_INFRA.bindTo(flagSource),
                 new StateV1HealthModel(TARGET_HEALTH_STALENESS, HEALTH_REQUEST_TIMEOUT, KEEP_ALIVE, new RunletExecutorImpl(THREAD_POOL_SIZE)));
     }
 
     private HealthMonitorManager(DuperModelManager duperModel,
-                                 FeatureFlag monitorInfra,
+                                 Flag<Boolean> monitorInfra,
                                  StateV1HealthModel healthModel) {
         this(duperModel, monitorInfra, id -> new ApplicationHealthMonitor(id, healthModel));
     }
 
     HealthMonitorManager(DuperModelManager duperModel,
-                         FeatureFlag monitorInfra,
+                         Flag<Boolean> monitorInfra,
                          ApplicationHealthMonitorFactory applicationHealthMonitorFactory) {
         this.duperModel = duperModel;
         this.monitorInfra = monitorInfra;
diff --git a/service-monitor/src/test/java/com/yahoo/vespa/service/health/HealthMonitorManagerTest.java b/service-monitor/src/test/java/com/yahoo/vespa/service/health/HealthMonitorManagerTest.java
index 86b0ee4a8f3..39147955d4c 100644
--- a/service-monitor/src/test/java/com/yahoo/vespa/service/health/HealthMonitorManagerTest.java
+++ b/service-monitor/src/test/java/com/yahoo/vespa/service/health/HealthMonitorManagerTest.java
@@ -7,7 +7,7 @@ import com.yahoo.vespa.applicationmodel.ClusterId;
 import com.yahoo.vespa.applicationmodel.ConfigId;
 import com.yahoo.vespa.applicationmodel.ServiceStatus;
 import com.yahoo.vespa.applicationmodel.ServiceType;
-import com.yahoo.vespa.flags.FeatureFlag;
+import com.yahoo.vespa.flags.Flag;
 import com.yahoo.vespa.service.duper.ConfigServerApplication;
 import com.yahoo.vespa.service.duper.ControllerHostApplication;
 import com.yahoo.vespa.service.duper.DuperModelManager;
@@ -33,7 +33,8 @@ import static org.mockito.Mockito.when;
 public class HealthMonitorManagerTest {
     private final ConfigServerApplication configServerApplication = new ConfigServerApplication();
     private final DuperModelManager duperModel = mock(DuperModelManager.class);
-    private final FeatureFlag monitorInfra = mock(FeatureFlag.class);
+    @SuppressWarnings("unchecked")
+    private final Flag<Boolean> monitorInfra = (Flag<Boolean>) mock(Flag.class);
     private final ApplicationHealthMonitor monitor = mock(ApplicationHealthMonitor.class);
     private final ApplicationHealthMonitorFactory monitorFactory = mock(ApplicationHealthMonitorFactory.class);
     private final HealthMonitorManager manager = new HealthMonitorManager(duperModel, monitorInfra, monitorFactory);