SONAR-7678 server-side stateless settings

* Settings class becomes abstract as multiple implementations
are used. Can't become an interface for binary
backward-compatibility of API

* tests should use MapSettings, an in-memory implementation
of Settings

* web server uses a thread-specific cache of settings when
processing HTTP requests

* web server does not have a cache of settings during startup,
except for the system settings loaded from sonar.properties

* Compute Engine uses a thread-specific cache of settings when
  processing a task. Cache is clear at end of task.

 * some useless methods of PersistentSettings are removed

2 files changed, 12 insertions, 9 deletions

diff --git a/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java b/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java
index fff798be3cf..a6a97ed4abe 100644
--- a/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java
+++ b/server/sonar-ce/src/main/java/org/sonar/ce/container/ComputeEngineContainerImpl.java
@@ -46,7 +46,7 @@ import org.sonar.ce.CeTaskCommonsModule;
 import org.sonar.ce.db.ReadOnlyPropertiesDao;
 import org.sonar.ce.es.EsIndexerEnabler;
 import org.sonar.ce.platform.ComputeEngineExtensionInstaller;
-import org.sonar.ce.settings.ComputeEngineSettings;
+import org.sonar.ce.settings.ProjectSettingsFactory;
 import org.sonar.ce.user.CeUserSession;
 import org.sonar.core.component.DefaultResourceTypes;
 import org.sonar.core.config.CorePropertyDefinitions;
@@ -101,7 +101,6 @@ import org.sonar.server.notification.email.AlertsEmailTemplate;
 import org.sonar.server.notification.email.EmailNotificationChannel;
 import org.sonar.server.platform.DatabaseServerCompatibility;
 import org.sonar.server.platform.DefaultServerUpgradeStatus;
-import org.sonar.server.platform.PersistentSettings;
 import org.sonar.server.platform.ServerFileSystemImpl;
 import org.sonar.server.platform.ServerImpl;
 import org.sonar.server.platform.ServerLifecycleNotifier;
@@ -131,7 +130,9 @@ import org.sonar.server.rule.RuleRepositories;
 import org.sonar.server.rule.index.RuleIndex;
 import org.sonar.server.rule.index.RuleIndexer;
 import org.sonar.server.search.EsSearchModule;
-import org.sonar.server.setting.ProjectSettingsFactory;
+import org.sonar.server.setting.DatabaseSettingLoader;
+import org.sonar.server.setting.DatabaseSettingsEnabler;
+import org.sonar.server.setting.ThreadLocalSettings;
 import org.sonar.server.startup.LogServerId;
 import org.sonar.server.test.index.TestIndexer;
 import org.sonar.server.user.DefaultUserFinder;
@@ -208,11 +209,10 @@ public class ComputeEngineContainerImpl implements ComputeEngineContainer {
   private static Object[] level1Components() {
     Version apiVersion = ApiVersion.load(System2.INSTANCE);
     return new Object[] {
-      ComputeEngineSettings.class,
+      ThreadLocalSettings.class,
       new SonarQubeVersion(apiVersion),
       SonarRuntimeImpl.forSonarQube(ApiVersion.load(System2.INSTANCE), SonarQubeSide.COMPUTE_ENGINE),
       UuidFactoryImpl.INSTANCE,
-      UrlSettings.class,
       ClusterImpl.class,
       DefaultDatabase.class,
       DatabaseChecker.class,
@@ -248,6 +248,10 @@ public class ComputeEngineContainerImpl implements ComputeEngineContainer {
 
   private static Object[] level2Components() {
     return new Object[] {
+      DatabaseSettingLoader.class,
+      DatabaseSettingsEnabler.class,
+      UrlSettings.class,
+
       // add ReadOnlyPropertiesDao at level2 again so that it shadows PropertiesDao
       ReadOnlyPropertiesDao.class,
       DefaultServerUpgradeStatus.class,
@@ -270,7 +274,6 @@ public class ComputeEngineContainerImpl implements ComputeEngineContainer {
   private static Object[] level3Components() {
     return new Object[] {
       new StartupMetadataProvider(),
-      PersistentSettings.class,
       UriReader.class,
       ServerImpl.class
     };
diff --git a/server/sonar-ce/src/test/java/org/sonar/ce/container/ComputeEngineContainerImplTest.java b/server/sonar-ce/src/test/java/org/sonar/ce/container/ComputeEngineContainerImplTest.java
index 98e1ba5c1e9..6bf1b1a3da7 100644
--- a/server/sonar-ce/src/test/java/org/sonar/ce/container/ComputeEngineContainerImplTest.java
+++ b/server/sonar-ce/src/test/java/org/sonar/ce/container/ComputeEngineContainerImplTest.java
@@ -97,15 +97,15 @@ public class ComputeEngineContainerImplTest {
     );
     assertThat(picoContainer.getParent().getComponentAdapters()).hasSize(
       CONTAINER_ITSELF
-        + 4 // level 3
+        + 3 // level 3
     );
     assertThat(picoContainer.getParent().getParent().getComponentAdapters()).hasSize(
       CONTAINER_ITSELF
-        + 11 // level 2
+        + 14 // level 2
     );
     assertThat(picoContainer.getParent().getParent().getParent().getComponentAdapters()).hasSize(
       COMPONENTS_IN_LEVEL_1_AT_CONSTRUCTION
-        + 25 // level 1
+        + 24 // level 1
         + 49 // content of DaoModule
         + 2 // content of EsSearchModule
         + 54 // content of CorePropertyDefinitions