Add support to retrieve repository statistics for a project via REST

Statistics for a repository can now be retrieved by GET on
'/projects/*/statistics.git'.

To get the statistics for a repository the global capability
'Run Garbage Collection' is required. Normal users should not be
interested in the repository statistics which is why we keep the access
restricted for now.

Change-Id: If5a2def2f840e1b30206a19a923d02e813db4049
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/rest-api-projects.txt

@@ -374,6 +374,40 @@ As response the new ref to which `HEAD` points is returned.
   "refs/heads/stable"
 ----
 
+[[get-repository-statistics]]
+Get Repository Statistics
+~~~~~~~~~~~~~~~~~~~~~~~~~
+[verse]
+'GET /projects/link:#project-name[\{project-name\}]/statistics.git'
+
+Return statistics for the repository of a project.
+
+.Request
+----
+  GET /projects/plugins%2Freplication/statistics.git HTTP/1.0
+----
+
+The repository statistics are returned as a
+link:#repository-statistics-info[RepositoryStatisticsInfo] entity.
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json;charset=UTF-8
+
+  )]}'
+  {
+    "number_of_loose_objects": 127,
+    "number_of_loose_refs": 15,
+    "number_of_pack_files": 15,
+    "number_of_packed_objects": 67,
+    "number_of_packed_refs": 0,
+    "size_of_loose_objects": 29466,
+    "size_of_packed_objects": 9646
+  }
+----
+
 [[dashboard-endpoints]]
 Dashboard Endpoints
 -------------------
@@ -805,6 +839,24 @@ Message that should be used to commit the change of the project parent
 in the `project.config` file to the `refs/meta/config` branch.
 |=============================
 
+[[repository-statistics-info]]
+RepositoryStatisticsInfo
+~~~~~~~~~~~~~~~~~~~~~~~~
+The `RepositoryStatisticsInfo` entity contains information about
+statistics of a Git repository.
+
+[options="header",width="50%",cols="1,6"]
+|======================================
+|Field Name                |Description
+|`number_of_loose_objects` |Number of loose objects.
+|`number_of_loose_refs`    |Number of loose refs.
+|`number_of_pack_files`    |Number of pack files.
+|`number_of_packed_objects`|Number of packed objects.
+|`number_of_packed_refs`   |Number of packed refs.
+|`size_of_loose_objects`   |Size of loose objects in bytes.
+|`size_of_packed_objects`  |Size of packed objects in bytes.
+|======================================
+
 
 GERRIT
 ------

gerrit-server/src/main/java/com/google/gerrit/server/project/GetStatistics.java

@@ -0,0 +1,63 @@
+// Copyright (C) 2013 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.project;
+
+import com.google.gerrit.common.data.GlobalCapability;
+import com.google.gerrit.extensions.annotations.RequiresCapability;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.inject.Inject;
+
+import org.eclipse.jgit.api.GarbageCollectCommand;
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.api.errors.JGitInternalException;
+import org.eclipse.jgit.lib.Repository;
+
+import java.io.IOException;
+import java.util.Properties;
+
+@RequiresCapability(GlobalCapability.RUN_GC)
+public class GetStatistics implements RestReadView<ProjectResource> {
+
+  private final GitRepositoryManager repoManager;
+
+  @Inject
+  GetStatistics(GitRepositoryManager repoManager) {
+    this.repoManager = repoManager;
+  }
+
+  @Override
+  public RepositoryStatistics apply(ProjectResource rsrc)
+      throws ResourceNotFoundException, ResourceConflictException {
+    try {
+      Repository repo = repoManager.openRepository(rsrc.getNameKey());
+      try {
+        GarbageCollectCommand gc = Git.wrap(repo).gc();
+        return new RepositoryStatistics(gc.getStatistics());
+      } catch (GitAPIException e) {
+        throw new ResourceConflictException(e.getMessage());
+      } catch (JGitInternalException e) {
+        throw new ResourceConflictException(e.getMessage());
+      } finally {
+        repo.close();
+      }
+    } catch (IOException e) {
+      throw new ResourceNotFoundException(rsrc.getName());
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/project/Module.java

@@ -43,6 +43,8 @@ public class Module extends RestApiModule {
     get(PROJECT_KIND, "HEAD").to(GetHead.class);
     put(PROJECT_KIND, "HEAD").to(SetHead.class);
 
+    get(PROJECT_KIND, "statistics.git").to(GetStatistics.class);
+
     child(PROJECT_KIND, "dashboards").to(DashboardsCollection.class);
     get(DASHBOARD_KIND).to(GetDashboard.class);
     put(DASHBOARD_KIND).to(SetDashboard.class);

gerrit-server/src/main/java/com/google/gerrit/server/project/RepositoryStatistics.java

@@ -0,0 +1,32 @@
+// Copyright (C) 2013 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.project;
+
+import com.google.common.base.CaseFormat;
+
+import java.util.Map.Entry;
+import java.util.Properties;
+import java.util.TreeMap;
+
+class RepositoryStatistics extends TreeMap<String, Object> {
+  private static final long serialVersionUID = 1L;
+
+  public RepositoryStatistics(Properties p) {
+    for (Entry<Object, Object> e : p.entrySet()) {
+      put(CaseFormat.LOWER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE,
+          e.getKey().toString()), e.getValue());
+    }
+  }
+}