Add REST endpoint to get a cache

Change-Id: I09bfa7c052f2b8411b218c77683cda45a0afe844
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

Documentation/rest-api-config.txt

@@ -247,6 +247,44 @@ The entries in the map are sorted by cache name.
   }
 ----
 
+[[get-cache]]
+=== Get Cache
+--
+'GET /config/server/caches/link:#cache-name[\{cache-name\}]'
+--
+
+Retrieves information about a cache.
+
+The caller must be a member of a group that is granted the
+link:access-control.html#capability_viewCaches[View Caches] capability
+or the link:access-control.html#capability_administrateServer[
+Administrate Server] capability.
+
+As result a link:#cache-info[CacheInfo] entity is returned.
+
+.Request
+----
+  GET /config/server/caches/projects HTTP/1.0
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Type: application/json;charset=UTF-8
+
+  )]}'
+  {
+    "name": "projects",
+    "entries": {
+      "mem": 35
+    },
+    "average_get": " 8.6ms",
+    "hit_ratio": {
+      "mem": 99
+    }
+  }
+----
+
 [[list-capabilities]]
 === List Capabilities
 --
@@ -393,6 +431,20 @@ link:#top-menu-entry-info[TopMenuEntryInfo] entities is returned.
 ----
 
 
+[[ids]]
+== IDs
+
+[[cache-name]]
+=== \{cache-name\}
+The name of the cache.
+
+If the cache is defined by a plugin the cache name must include the
+plugin name: "<plugin-name>-<cache-name>".
+
+Gerrit core caches can optionally be prefixed with "gerrit":
+"gerrit-<cache-name>".
+
+
 [[json-entities]]
 == JSON Entities
 

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/GetCacheIT.java

@@ -0,0 +1,74 @@
+// Copyright (C) 2014 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.acceptance.rest.config;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.RestResponse;
+import com.google.gerrit.server.config.ListCaches.CacheInfo;
+
+import org.apache.http.HttpStatus;
+import org.junit.Test;
+
+import java.io.IOException;
+
+public class GetCacheIT extends AbstractDaemonTest {
+
+  @Test
+  public void getCache() throws IOException {
+    RestResponse r = adminSession.get("/config/server/caches/accounts");
+    assertEquals(HttpStatus.SC_OK, r.getStatusCode());
+    CacheInfo result = newGson().fromJson(r.getReader(), CacheInfo.class);
+
+    assertEquals("accounts", result.name);
+    assertNull(result.type);
+    assertEquals(1, result.entries.mem.longValue());
+    assertNotNull(result.averageGet);
+    assertTrue(result.averageGet.endsWith("s"));
+    assertNull(result.entries.disk);
+    assertNull(result.entries.space);
+    assertTrue(result.hitRatio.mem >= 0);
+    assertTrue(result.hitRatio.mem <= 100);
+    assertNull(result.hitRatio.disk);
+
+    userSession.get("/config/server/version").consume();
+    r = adminSession.get("/config/server/caches/accounts");
+    assertEquals(HttpStatus.SC_OK, r.getStatusCode());
+    result = newGson().fromJson(r.getReader(), CacheInfo.class);
+    assertEquals(2, result.entries.mem.longValue());
+  }
+
+  @Test
+  public void getCache_Forbidden() throws IOException {
+    RestResponse r = userSession.get("/config/server/caches/accounts");
+    assertEquals(HttpStatus.SC_FORBIDDEN, r.getStatusCode());
+  }
+
+  @Test
+  public void getCache_NotFound() throws IOException {
+    RestResponse r = adminSession.get("/config/server/caches/nonExisting");
+    assertEquals(HttpStatus.SC_NOT_FOUND, r.getStatusCode());
+  }
+
+  @Test
+  public void getCacheWithGerritPrefix() throws IOException {
+    RestResponse r = adminSession.get("/config/server/caches/gerrit-accounts");
+    assertEquals(HttpStatus.SC_OK, r.getStatusCode());
+  }
+}

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

@@ -14,10 +14,36 @@
 
 package com.google.gerrit.server.config;
 
+import com.google.common.cache.Cache;
 import com.google.gerrit.extensions.restapi.RestView;
+import com.google.inject.Provider;
 import com.google.inject.TypeLiteral;
 
 public class CacheResource extends ConfigResource {
   public static final TypeLiteral<RestView<CacheResource>> CACHE_KIND =
       new TypeLiteral<RestView<CacheResource>>() {};
+
+  private final String name;
+  private final Provider<Cache<?, ?>> cacheProvider;
+
+  public CacheResource(String pluginName, String cacheName, Provider<Cache<?, ?>> cacheProvider) {
+    this.name = cacheNameOf(pluginName, cacheName);
+    this.cacheProvider = cacheProvider;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public Cache<?, ?> getCache() {
+    return cacheProvider.get();
+  }
+
+  public static String cacheNameOf(String plugin, String name) {
+    if ("gerrit".equals(plugin)) {
+      return name;
+    } else {
+      return plugin + "-" + name;
+    }
+  }
 }

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

@@ -14,13 +14,17 @@
 
 package com.google.gerrit.server.config;
 
+import com.google.common.cache.Cache;
 import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.extensions.annotations.RequiresCapability;
 import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.ChildCollection;
 import com.google.gerrit.extensions.restapi.IdString;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.RestView;
+import com.google.gerrit.server.AnonymousUser;
+import com.google.gerrit.server.CurrentUser;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
@@ -32,12 +36,17 @@ public class CachesCollection implements
 
   private final DynamicMap<RestView<CacheResource>> views;
   private final Provider<ListCaches> list;
+  private final Provider<CurrentUser> self;
+  private final DynamicMap<Cache<?, ?>> cacheMap;
 
   @Inject
   CachesCollection(DynamicMap<RestView<CacheResource>> views,
-      Provider<ListCaches> list) {
+      Provider<ListCaches> list, Provider<CurrentUser> self,
+      DynamicMap<Cache<?, ?>> cacheMap) {
     this.views = views;
     this.list = list;
+    this.self = self;
+    this.cacheMap = cacheMap;
   }
 
   @Override
@@ -47,8 +56,29 @@ public class CachesCollection implements
 
   @Override
   public CacheResource parse(ConfigResource parent, IdString id)
-      throws ResourceNotFoundException {
-    throw new ResourceNotFoundException(id);
+      throws AuthException, ResourceNotFoundException {
+    CurrentUser user = self.get();
+    if (user instanceof AnonymousUser) {
+      throw new AuthException("Authentication required");
+    } else if (!user.isIdentifiedUser()) {
+      throw new ResourceNotFoundException();
+    } else if (!user.getCapabilities().canViewCaches()) {
+      throw new AuthException("not allowed to view caches");
+    }
+
+    String cacheName = id.get();
+    String pluginName = "gerrit";
+    int i = cacheName.lastIndexOf('-');
+    if (i != -1) {
+      pluginName = cacheName.substring(0, i);
+      cacheName = cacheName.length() > i + 1 ? cacheName.substring(i + 1) : "";
+    }
+
+    Provider<Cache<?, ?>> cacheProvider = cacheMap.byPlugin(pluginName).get(cacheName);
+    if (cacheProvider == null) {
+      throw new ResourceNotFoundException(id);
+    }
+    return new CacheResource(pluginName, cacheName, cacheProvider);
   }
 
   @Override

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

@@ -0,0 +1,28 @@
+// Copyright (C) 2014 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.config;
+
+import com.google.gerrit.extensions.restapi.RestReadView;
+import com.google.gerrit.server.config.ListCaches.CacheInfo;
+import com.google.inject.Singleton;
+
+@Singleton
+public class GetCache implements RestReadView<CacheResource> {
+
+  @Override
+  public CacheInfo apply(CacheResource rsrc) {
+    return new CacheInfo(rsrc.getName(), rsrc.getCache());
+  }
+}

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

@@ -14,6 +14,8 @@
 
 package com.google.gerrit.server.config;
 
+import static com.google.gerrit.server.config.CacheResource.cacheNameOf;
+
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheStats;
 import com.google.gerrit.common.data.GlobalCapability;
@@ -47,14 +49,6 @@ public class ListCaches implements RestReadView<ConfigResource> {
     return cacheInfos;
   }
 
-  private static String cacheNameOf(String plugin, String name) {
-    if ("gerrit".equals(plugin)) {
-      return name;
-    } else {
-      return plugin + "-" + name;
-    }
-  }
-
   public enum CacheType {
     MEM, DISK;
   }
@@ -67,6 +61,12 @@ public class ListCaches implements RestReadView<ConfigResource> {
     public HitRatioInfo hitRatio;
 
     public CacheInfo(Cache<?,?> cache) {
+      this(null, cache);
+    }
+
+    public CacheInfo(String name, Cache<?,?> cache) {
+      this.name = name;
+
       CacheStats stat = cache.stats();
 
       entries = new EntriesInfo();

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

@@ -30,6 +30,7 @@ public class Module extends RestApiModule {
     DynamicMap.mapOf(binder(), CONFIG_KIND);
     DynamicMap.mapOf(binder(), TOP_MENU_KIND);
     child(CONFIG_KIND, "caches").to(CachesCollection.class);
+    get(CACHE_KIND).to(GetCache.class);
     child(CONFIG_KIND, "capabilities").to(CapabilitiesCollection.class);
     child(CONFIG_KIND, "top-menus").to(TopMenuCollection.class);
     get(CONFIG_KIND, "version").to(GetVersion.class);