Use listeners to manage server startup/shutdown

Instead of enumerating the startup/shutdown sequence inside of the
WebAppInitializer we now use listeners which are bound and managed
by Guice.  The listeners are fired in the order they are registered
within the injector modules.

By using Guice we are more easily able to track the need to start
(or gracefully stop) a component alongside its explicit binding
in the injector.  We can also conditionally include start or stop
rules by controlling which modules are included in the injection.

Change-Id: I93590c666d46e13fdce9aa05100489f9f6d94615
Signed-off-by: Shawn O. Pearce <sop@google.com>

gerrit-server/src/main/java/com/google/gerrit/server/cache/CachePool.java

@@ -17,6 +17,7 @@ package com.google.gerrit.server.cache;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
+import com.google.gerrit.lifecycle.LifecycleListener;
 import com.google.gerrit.server.config.ConfigUtil;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.SitePath;
@@ -43,6 +44,25 @@ import java.util.Map;
 public class CachePool {
   private static final Logger log = LoggerFactory.getLogger(CachePool.class);
 
+  public static class Lifecycle implements LifecycleListener {
+    private final CachePool cachePool;
+
+    @Inject
+    Lifecycle(final CachePool cachePool) {
+      this.cachePool = cachePool;
+    }
+
+    @Override
+    public void start() {
+      cachePool.start();
+    }
+
+    @Override
+    public void stop() {
+      cachePool.stop();
+    }
+  }
+
   private final Config config;
   private final File sitePath;
 
@@ -57,8 +77,7 @@ public class CachePool {
     this.caches = new HashMap<String, CacheProvider<?, ?>>();
   }
 
-  /** Start the cache pool. The pool must be started before any access occurs. */
-  public void start() {
+  private void start() {
     synchronized (lock) {
       if (manager != null) {
         throw new IllegalStateException("Cache pool has already been started");
@@ -71,8 +90,7 @@ public class CachePool {
     }
   }
 
-  /** Stop the cache pool. The pool should be stopped before terminating. */
-  public void stop() {
+  private void stop() {
     synchronized (lock) {
       if (manager != null) {
         manager.shutdown();