Export ServerInformation to extensions and plugins

Plugins can take this value by injection and learn the current
server state during their own LifecycleListener. This enables a
plugin to determine if it is loading as part of server startup, or
because it was dynamically installed or reloaded by an administrator.

Change-Id: Iac57e039ed9f9f3ecaf2f384c5a3c6a66223f5e1

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/systemstatus/ServerInformation.java

@@ -0,0 +1,42 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.systemstatus;
+
+/** Exports current server information to an extension. */
+public interface ServerInformation {
+  /** Current state of the server. */
+  public enum State {
+    /**
+     * The server is starting up, and network connections are not yet being
+     * accepted. Plugins or extensions starting during this time are starting
+     * for the first time in this process.
+     */
+    STARTUP,
+
+    /**
+     * The server is running and handling requests. Plugins starting during this
+     * state may be reloading, or being installed into a running system.
+     */
+    RUNNING,
+
+    /**
+     * The server is attempting a graceful halt of operations and will exit (or
+     * be killed by the operating system) soon.
+     */
+    SHUTDOWN;
+  }
+
+  State getState();
+}

gerrit-server/src/main/java/com/google/gerrit/server/plugins/Plugin.java

@@ -19,6 +19,7 @@ import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.registration.ReloadableRegistrationHandle;
+import com.google.gerrit.extensions.systemstatus.ServerInformation;
 import com.google.gerrit.lifecycle.LifecycleListener;
 import com.google.gerrit.lifecycle.LifecycleManager;
 import com.google.inject.AbstractModule;
@@ -165,9 +166,16 @@ public class Plugin {
   }
 
   private Injector newRootInjector(PluginGuiceEnvironment env) {
-    return Guice.createInjector(
+    List<Module> modules = Lists.newArrayListWithCapacity(4);
-        env.getSysModule(),
+    modules.add(env.getSysModule());
-        new AbstractModule() {
+    final ServerInformation srvInfo = env.getServerInformation();
+    modules.add(new AbstractModule() {
+      @Override
+      protected void configure() {
+        bind(ServerInformation.class).toInstance(srvInfo);
+      }
+    });
+    modules.add(new AbstractModule() {
       @Override
       protected void configure() {
         bind(String.class)
@@ -175,6 +183,7 @@ public class Plugin {
           .toInstance(name);
       }
     });
+    return Guice.createInjector(modules);
   }
 
   public void stop() {

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginGuiceEnvironment.java

@@ -24,6 +24,7 @@ import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.extensions.registration.PrivateInternals_DynamicMapImpl;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.registration.ReloadableRegistrationHandle;
+import com.google.gerrit.extensions.systemstatus.ServerInformation;
 import com.google.gerrit.lifecycle.LifecycleListener;
 import com.google.inject.AbstractModule;
 import com.google.inject.Binding;
@@ -56,6 +57,7 @@ import javax.inject.Inject;
 @Singleton
 public class PluginGuiceEnvironment {
   private final Injector sysInjector;
+  private final ServerInformation srvInfo;
   private final CopyConfigModule copyConfigModule;
   private final List<StartPluginListener> onStart;
   private final List<ReloadPluginListener> onReload;
@@ -76,8 +78,12 @@ public class PluginGuiceEnvironment {
   private Map<TypeLiteral<?>, DynamicMap<?>> httpMaps;
 
   @Inject
-  PluginGuiceEnvironment(Injector sysInjector, CopyConfigModule ccm) {
+  PluginGuiceEnvironment(
+      Injector sysInjector,
+      ServerInformation srvInfo,
+      CopyConfigModule ccm) {
     this.sysInjector = sysInjector;
+    this.srvInfo = srvInfo;
     this.copyConfigModule = ccm;
 
     onStart = new CopyOnWriteArrayList<StartPluginListener>();
@@ -90,6 +96,10 @@ public class PluginGuiceEnvironment {
     sysMaps = dynamicMapsOf(sysInjector);
   }
 
+  ServerInformation getServerInformation() {
+    return srvInfo;
+  }
+
   boolean hasDynamicSet(TypeLiteral<?> type) {
     return sysSets.containsKey(type)
         || (sshSets != null && sshSets.containsKey(type))

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginLoader.java

@@ -17,6 +17,7 @@ package com.google.gerrit.server.plugins;
 import com.google.common.base.Strings;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Sets;
+import com.google.gerrit.extensions.systemstatus.ServerInformation;
 import com.google.gerrit.lifecycle.LifecycleListener;
 import com.google.gerrit.server.config.ConfigUtil;
 import com.google.gerrit.server.config.GerritServerConfig;
@@ -59,6 +60,7 @@ public class PluginLoader implements LifecycleListener {
   private final File pluginsDir;
   private final File tmpDir;
   private final PluginGuiceEnvironment env;
+  private final ServerInformationImpl srvInfoImpl;
   private final ConcurrentMap<String, Plugin> running;
   private final Map<String, FileSnapshot> broken;
   private final ReferenceQueue<ClassLoader> cleanupQueue;
@@ -68,10 +70,12 @@ public class PluginLoader implements LifecycleListener {
   @Inject
   public PluginLoader(SitePaths sitePaths,
       PluginGuiceEnvironment pe,
+      ServerInformationImpl sii,
       @GerritServerConfig Config cfg) {
     pluginsDir = sitePaths.plugins_dir;
     tmpDir = sitePaths.tmp_dir;
     env = pe;
+    srvInfoImpl = sii;
     running = Maps.newConcurrentMap();
     broken = Maps.newHashMap();
     cleanupQueue = new ReferenceQueue<ClassLoader>();
@@ -184,7 +188,9 @@ public class PluginLoader implements LifecycleListener {
   @Override
   public synchronized void start() {
     log.info("Loading plugins from " + pluginsDir.getAbsolutePath());
+    srvInfoImpl.state = ServerInformation.State.STARTUP;
     rescan(false);
+    srvInfoImpl.state = ServerInformation.State.RUNNING;
     if (scanner != null) {
       scanner.start();
     }
@@ -195,6 +201,7 @@ public class PluginLoader implements LifecycleListener {
     if (scanner != null) {
       scanner.end();
     }
+    srvInfoImpl.state = ServerInformation.State.SHUTDOWN;
     synchronized (this) {
       boolean clean = !running.isEmpty();
       for (Plugin p : running.values()) {

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginModule.java

@@ -14,11 +14,15 @@
 
 package com.google.gerrit.server.plugins;
 
+import com.google.gerrit.extensions.systemstatus.ServerInformation;
 import com.google.gerrit.lifecycle.LifecycleModule;
 
 public class PluginModule extends LifecycleModule {
   @Override
   protected void configure() {
+    bind(ServerInformationImpl.class);
+    bind(ServerInformation.class).to(ServerInformationImpl.class);
+
     bind(PluginGuiceEnvironment.class);
     bind(PluginLoader.class);
     bind(CopyConfigModule.class);

gerrit-server/src/main/java/com/google/gerrit/server/plugins/ServerInformationImpl.java

@@ -0,0 +1,28 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.plugins;
+
+import com.google.gerrit.extensions.systemstatus.ServerInformation;
+import com.google.inject.Singleton;
+
+@Singleton
+class ServerInformationImpl implements ServerInformation {
+  volatile State state = State.STARTUP;
+
+  @Override
+  public State getState() {
+    return state;
+  }
+}