Lazily lookup LDAP group memberships

By deferring LDAP queries until a contains method is called the
server can avoid looking up LDAP group information when only
internal Gerrit groups are used in access rules.

Change-Id: I96ac1894da07e00935ed6182084885a237ac414e

gerrit-server/src/main/java/com/google/gerrit/server/auth/ldap/LdapGroupBackend.java

@@ -31,7 +31,6 @@ import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.account.GroupBackend;
 import com.google.gerrit.server.account.GroupMembership;
-import com.google.gerrit.server.account.ListGroupMembership;
 import com.google.gerrit.server.auth.ldap.Helper.LdapSchema;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.project.ProjectControl;
@@ -60,7 +59,7 @@ import javax.security.auth.login.LoginException;
  * Implementation of GroupBackend for the LDAP group system.
  */
 public class LdapGroupBackend implements GroupBackend {
-  private static final Logger log = LoggerFactory.getLogger(LdapGroupBackend.class);
+  static final Logger log = LoggerFactory.getLogger(LdapGroupBackend.class);
 
   private static final String LDAP_NAME = "ldap/";
   private static final String GROUPNAME = "groupname";
@@ -185,21 +184,7 @@ public class LdapGroupBackend implements GroupBackend {
     if (id == null) {
       return GroupMembership.EMPTY;
     }
-
-    try {
-      final Set<AccountGroup.UUID> groups = membershipCache.get(id);
-      return new ListGroupMembership(groups) {
-        @Override
-        public Set<AccountGroup.UUID> getKnownGroups() {
-          Set<AccountGroup.UUID> g = Sets.newHashSet(groups);
-          g.retainAll(projectCache.guessRelevantGroupUUIDs());
-          return g;
-        }
-      };
-    } catch (ExecutionException e) {
-      log.warn(String.format("Cannot lookup membershipsOf %s in LDAP", id), e);
-      return GroupMembership.EMPTY;
-    }
+    return new LdapGroupMembership(membershipCache, projectCache, id);
   }
 
   private static String findId(final Collection<AccountExternalId> ids) {

gerrit-server/src/main/java/com/google/gerrit/server/auth/ldap/LdapGroupMembership.java

@@ -0,0 +1,76 @@
+// Copyright (C) 2015 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.auth.ldap;
+
+import com.google.common.cache.LoadingCache;
+import com.google.gerrit.reviewdb.client.AccountGroup;
+import com.google.gerrit.server.account.GroupMembership;
+import com.google.gerrit.server.account.ListGroupMembership;
+import com.google.gerrit.server.project.ProjectCache;
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.ExecutionException;
+
+class LdapGroupMembership implements GroupMembership {
+  private final LoadingCache<String, Set<AccountGroup.UUID>> membershipCache;
+  private final ProjectCache projectCache;
+  private final String id;
+  private GroupMembership membership;
+
+  LdapGroupMembership(
+      LoadingCache<String, Set<AccountGroup.UUID>> membershipCache,
+      ProjectCache projectCache,
+      String id) {
+    this.membershipCache = membershipCache;
+    this.projectCache = projectCache;
+    this.id = id;
+  }
+
+  @Override
+  public boolean contains(AccountGroup.UUID groupId) {
+    return get().contains(groupId);
+  }
+
+  @Override
+  public boolean containsAnyOf(Iterable<AccountGroup.UUID> groupIds) {
+    return get().containsAnyOf(groupIds);
+  }
+
+  @Override
+  public Set<AccountGroup.UUID> intersection(Iterable<AccountGroup.UUID> groupIds) {
+    return get().intersection(groupIds);
+  }
+
+  @Override
+  public Set<AccountGroup.UUID> getKnownGroups() {
+    Set<AccountGroup.UUID> g = new HashSet<>(get().getKnownGroups());
+    g.retainAll(projectCache.guessRelevantGroupUUIDs());
+    return g;
+  }
+
+  private synchronized GroupMembership get() {
+    if (membership == null) {
+      try {
+        membership = new ListGroupMembership(membershipCache.get(id));
+      } catch (ExecutionException e) {
+        LdapGroupBackend.log.warn(String.format(
+            "Cannot lookup membershipsOf %s in LDAP", id), e);
+        membership = GroupMembership.EMPTY;
+      }
+    }
+    return membership;
+  }
+}