1 files changed, 262 insertions, 0 deletions
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/externalids/ExternalIdCacheImpl.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/externalids/ExternalIdCacheImpl.java
new file mode 100644
index 0000000000..4b4d060365
--- /dev/null
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/externalids/ExternalIdCacheImpl.java
@@ -0,0 +1,262 @@
+// Copyright (C) 2016 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.account.externalids;
+
+import static com.google.common.collect.ImmutableSetMultimap.toImmutableSetMultimap;
+import static java.util.stream.Collectors.toSet;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Strings;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import com.google.common.collect.Collections2;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableSetMultimap;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.ListMultimap;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.MultimapBuilder;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.function.Consumer;
+import org.eclipse.jgit.lib.ObjectId;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** Caches external IDs of all accounts. The external IDs are always loaded from NoteDb. */
+@Singleton
+class ExternalIdCacheImpl implements ExternalIdCache {
+  private static final Logger log = LoggerFactory.getLogger(ExternalIdCacheImpl.class);
+
+  private final LoadingCache<ObjectId, AllExternalIds> extIdsByAccount;
+  private final ExternalIdReader externalIdReader;
+  private final Lock lock;
+
+  @Inject
+  ExternalIdCacheImpl(ExternalIdReader externalIdReader) {
+    this.extIdsByAccount =
+        CacheBuilder.newBuilder()
+            // The cached data is potentially pretty large and we are always only interested
+            // in the latest value, hence the maximum cache size is set to 1.
+            // This can lead to extra cache loads in case of the following race:
+            // 1. thread 1 reads the notes ref at revision A
+            // 2. thread 2 updates the notes ref to revision B and stores the derived value
+            //    for B in the cache
+            // 3. thread 1 attempts to read the data for revision A from the cache, and misses
+            // 4. later threads attempt to read at B
+            // In this race unneeded reloads are done in step 3 (reload from revision A) and
+            // step 4 (reload from revision B, because the value for revision B was lost when the
+            // reload from revision A was done, since the cache can hold only one entry).
+            // These reloads could be avoided by increasing the cache size to 2. However the race
+            // window between reading the ref and looking it up in the cache is small so that
+            // it's rare that this race happens. Therefore it's not worth to double the memory
+            // usage of this cache, just to avoid this.
+            .maximumSize(1)
+            .build(new Loader(externalIdReader));
+    this.externalIdReader = externalIdReader;
+    this.lock = new ReentrantLock(true /* fair */);
+  }
+
+  @Override
+  public void onCreate(ObjectId oldNotesRev, ObjectId newNotesRev, Collection<ExternalId> extIds)
+      throws IOException {
+    updateCache(
+        oldNotesRev,
+        newNotesRev,
+        m -> {
+          for (ExternalId extId : extIds) {
+            extId.checkThatBlobIdIsSet();
+            m.put(extId.accountId(), extId);
+          }
+        });
+  }
+
+  @Override
+  public void onRemove(ObjectId oldNotesRev, ObjectId newNotesRev, Collection<ExternalId> extIds)
+      throws IOException {
+    updateCache(
+        oldNotesRev,
+        newNotesRev,
+        m -> {
+          for (ExternalId extId : extIds) {
+            m.remove(extId.accountId(), extId);
+          }
+        });
+  }
+
+  @Override
+  public void onUpdate(
+      ObjectId oldNotesRev, ObjectId newNotesRev, Collection<ExternalId> updatedExtIds)
+      throws IOException {
+    updateCache(
+        oldNotesRev,
+        newNotesRev,
+        m -> {
+          removeKeys(m.values(), updatedExtIds.stream().map(e -> e.key()).collect(toSet()));
+          for (ExternalId updatedExtId : updatedExtIds) {
+            updatedExtId.checkThatBlobIdIsSet();
+            m.put(updatedExtId.accountId(), updatedExtId);
+          }
+        });
+  }
+
+  @Override
+  public void onReplace(
+      ObjectId oldNotesRev,
+      ObjectId newNotesRev,
+      Account.Id accountId,
+      Collection<ExternalId> toRemove,
+      Collection<ExternalId> toAdd)
+      throws IOException {
+    ExternalIdsUpdate.checkSameAccount(Iterables.concat(toRemove, toAdd), accountId);
+
+    updateCache(
+        oldNotesRev,
+        newNotesRev,
+        m -> {
+          for (ExternalId extId : toRemove) {
+            m.remove(extId.accountId(), extId);
+          }
+          for (ExternalId extId : toAdd) {
+            extId.checkThatBlobIdIsSet();
+            m.put(extId.accountId(), extId);
+          }
+        });
+  }
+
+  @Override
+  public void onReplace(
+      ObjectId oldNotesRev,
+      ObjectId newNotesRev,
+      Collection<ExternalId> toRemove,
+      Collection<ExternalId> toAdd)
+      throws IOException {
+    updateCache(
+        oldNotesRev,
+        newNotesRev,
+        m -> {
+          for (ExternalId extId : toRemove) {
+            m.remove(extId.accountId(), extId);
+          }
+          for (ExternalId extId : toAdd) {
+            extId.checkThatBlobIdIsSet();
+            m.put(extId.accountId(), extId);
+          }
+        });
+  }
+
+  @Override
+  public ImmutableSet<ExternalId> byAccount(Account.Id accountId) throws IOException {
+    return get().byAccount().get(accountId);
+  }
+
+  @Override
+  public ImmutableSetMultimap<Account.Id, ExternalId> allByAccount() throws IOException {
+    return get().byAccount();
+  }
+
+  @Override
+  public ImmutableSetMultimap<String, ExternalId> byEmails(String... emails) throws IOException {
+    AllExternalIds allExternalIds = get();
+    ImmutableSetMultimap.Builder<String, ExternalId> byEmails = ImmutableSetMultimap.builder();
+    for (String email : emails) {
+      byEmails.putAll(email, allExternalIds.byEmail().get(email));
+    }
+    return byEmails.build();
+  }
+
+  @Override
+  public ImmutableSetMultimap<String, ExternalId> allByEmail() throws IOException {
+    return get().byEmail();
+  }
+
+  private AllExternalIds get() throws IOException {
+    try {
+      return extIdsByAccount.get(externalIdReader.readRevision());
+    } catch (ExecutionException e) {
+      throw new IOException("Cannot load external ids", e);
+    }
+  }
+
+  private void updateCache(
+      ObjectId oldNotesRev,
+      ObjectId newNotesRev,
+      Consumer<Multimap<Account.Id, ExternalId>> update) {
+    lock.lock();
+    try {
+      ListMultimap<Account.Id, ExternalId> m;
+      if (!ObjectId.zeroId().equals(oldNotesRev)) {
+        m =
+            MultimapBuilder.hashKeys()
+                .arrayListValues()
+                .build(extIdsByAccount.get(oldNotesRev).byAccount());
+      } else {
+        m = MultimapBuilder.hashKeys().arrayListValues().build();
+      }
+      update.accept(m);
+      extIdsByAccount.put(newNotesRev, AllExternalIds.create(m));
+    } catch (ExecutionException e) {
+      log.warn("Cannot update external IDs", e);
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  private static void removeKeys(Collection<ExternalId> ids, Collection<ExternalId.Key> toRemove) {
+    Collections2.transform(ids, e -> e.key()).removeAll(toRemove);
+  }
+
+  private static class Loader extends CacheLoader<ObjectId, AllExternalIds> {
+    private final ExternalIdReader externalIdReader;
+
+    Loader(ExternalIdReader externalIdReader) {
+      this.externalIdReader = externalIdReader;
+    }
+
+    @Override
+    public AllExternalIds load(ObjectId notesRev) throws Exception {
+      Multimap<Account.Id, ExternalId> extIdsByAccount =
+          MultimapBuilder.hashKeys().arrayListValues().build();
+      for (ExternalId extId : externalIdReader.all(notesRev)) {
+        extId.checkThatBlobIdIsSet();
+        extIdsByAccount.put(extId.accountId(), extId);
+      }
+      return AllExternalIds.create(extIdsByAccount);
+    }
+  }
+
+  @AutoValue
+  abstract static class AllExternalIds {
+    static AllExternalIds create(Multimap<Account.Id, ExternalId> byAccount) {
+      ImmutableSetMultimap<String, ExternalId> byEmail =
+          byAccount.values().stream()
+              .filter(e -> !Strings.isNullOrEmpty(e.email()))
+              .collect(toImmutableSetMultimap(ExternalId::email, e -> e));
+      return new AutoValue_ExternalIdCacheImpl_AllExternalIds(
+          ImmutableSetMultimap.copyOf(byAccount), byEmail);
+    }
+
+    public abstract ImmutableSetMultimap<Account.Id, ExternalId> byAccount();
+
+    public abstract ImmutableSetMultimap<String, ExternalId> byEmail();
+  }
+}