Provide a data directory to plugins on demand

If a plugin requests a data directory with a @PluginData File
dependency, a data directory will be created automatically by the
server in $site_path/data/$plugin_name and passed to the plugin.

Plugins can use this to store any data they want.

Change-Id: I98de44a033889740cafc8a3d72c582c0e99b7ffd

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/annotations/PluginData.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.annotations;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import com.google.inject.BindingAnnotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Local path where a plugin can store its own private data.
+ * <p>
+ * A plugin or extension may receive this string by Guice injection to discover
+ * a directory where it can store configuration or other data that is private:
+ *
+ * <pre>
+ * @Inject
+ * MyType(@PluginData java.io.File myDir) {
+ *   new FileInputStream(new File(myDir, &quot;my.config&quot;));
+ * }
+ * </pre>
+ */
+@Target({ElementType.PARAMETER, ElementType.FIELD})
+@Retention(RUNTIME)
+@BindingAnnotation
+public @interface PluginData {
+}

gerrit-pgm/src/main/java/com/google/gerrit/pgm/init/SitePathInitializer.java

@@ -72,6 +72,7 @@ public class SitePathInitializer {
     mkdir(site.mail_dir);
     mkdir(site.static_dir);
     mkdir(site.plugins_dir);
+    mkdir(site.data_dir);
 
     for (InitStep step : steps) {
       step.run();

gerrit-server/src/main/java/com/google/gerrit/server/config/SitePaths.java

@@ -31,6 +31,7 @@ public final class SitePaths {
   public final File tmp_dir;
   public final File logs_dir;
   public final File plugins_dir;
+  public final File data_dir;
   public final File mail_dir;
   public final File hooks_dir;
   public final File static_dir;
@@ -66,6 +67,7 @@ public final class SitePaths {
     lib_dir = new File(site_path, "lib");
     tmp_dir = new File(site_path, "tmp");
     plugins_dir = new File(site_path, "plugins");
+    data_dir = new File(site_path, "data");
     logs_dir = new File(site_path, "logs");
     mail_dir = new File(etc_dir, "mail");
     hooks_dir = new File(site_path, "hooks");

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

@@ -16,6 +16,7 @@ package com.google.gerrit.server.plugins;
 
 import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
+import com.google.gerrit.extensions.annotations.PluginData;
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.extensions.registration.ReloadableRegistrationHandle;
@@ -26,6 +27,8 @@ import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
 import com.google.inject.Module;
+import com.google.inject.Provider;
+import com.google.inject.ProvisionException;
 
 import org.eclipse.jgit.storage.file.FileSnapshot;
 
@@ -51,6 +54,7 @@ public class Plugin {
   private final FileSnapshot snapshot;
   private final JarFile jarFile;
   private final Manifest manifest;
+  private final File dataDir;
   private final ClassLoader classLoader;
   private Class<? extends Module> sysModule;
   private Class<? extends Module> sshModule;
@@ -67,6 +71,7 @@ public class Plugin {
       FileSnapshot snapshot,
       JarFile jarFile,
       Manifest manifest,
+      File dataDir,
       ClassLoader classLoader,
       @Nullable Class<? extends Module> sysModule,
       @Nullable Class<? extends Module> sshModule,
@@ -76,6 +81,7 @@ public class Plugin {
     this.snapshot = snapshot;
     this.jarFile = jarFile;
     this.manifest = manifest;
+    this.dataDir = dataDir;
     this.classLoader = classLoader;
     this.sysModule = sysModule;
     this.sshModule = sshModule;
@@ -181,6 +187,27 @@ public class Plugin {
         bind(String.class)
           .annotatedWith(PluginName.class)
           .toInstance(name);
+
+        bind(File.class)
+          .annotatedWith(PluginData.class)
+          .toProvider(new Provider<File>() {
+            private volatile boolean ready;
+
+            @Override
+            public File get() {
+              if (!ready) {
+                synchronized (dataDir) {
+                  if (!dataDir.exists() && !dataDir.mkdirs()) {
+                    throw new ProvisionException(String.format(
+                        "Cannot create %s for plugin %s",
+                        dataDir.getAbsolutePath(), name));
+                  }
+                  ready = true;
+                }
+              }
+              return dataDir;
+            }
+          });
       }
     });
     return Guice.createInjector(modules);

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

@@ -58,6 +58,7 @@ public class PluginLoader implements LifecycleListener {
   static final Logger log = LoggerFactory.getLogger(PluginLoader.class);
 
   private final File pluginsDir;
+  private final File dataDir;
   private final File tmpDir;
   private final PluginGuiceEnvironment env;
   private final ServerInformationImpl srvInfoImpl;
@@ -73,6 +74,7 @@ public class PluginLoader implements LifecycleListener {
       ServerInformationImpl sii,
       @GerritServerConfig Config cfg) {
     pluginsDir = sitePaths.plugins_dir;
+    dataDir = sitePaths.data_dir;
     tmpDir = sitePaths.tmp_dir;
     env = pe;
     srvInfoImpl = sii;
@@ -343,7 +345,7 @@ public class PluginLoader implements LifecycleListener {
       return new Plugin(name,
           srcJar, snapshot,
           jarFile, manifest,
-          pluginLoader,
+          new File(dataDir, name), pluginLoader,
           sysModule, sshModule, httpModule);
     } finally {
       if (!keep) {