gerrit-pgm/src/main/java/com/google/gerrit/pgm/util/PerThreadReviewDbModule.java

// 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.pgm.util;

import com.google.gerrit.extensions.events.LifecycleListener;
import com.google.gerrit.lifecycle.LifecycleModule;
import com.google.gerrit.reviewdb.server.ReviewDb;
import com.google.gwtorm.server.OrmException;
import com.google.gwtorm.server.SchemaFactory;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.ProvisionException;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Module to bind a single {@link ReviewDb} instance per thread.
 * <p>
 * New instances are opened on demand, but are closed only at shutdown.
 */
class PerThreadReviewDbModule extends LifecycleModule {
  private final SchemaFactory<ReviewDb> schema;

  @Inject
  PerThreadReviewDbModule(SchemaFactory<ReviewDb> schema) {
    this.schema = schema;
  }

  @Override
  protected void configure() {
    final List<ReviewDb> dbs = Collections.synchronizedList(
        new ArrayList<ReviewDb>());
    final ThreadLocal<ReviewDb> localDb = new ThreadLocal<>();

    bind(ReviewDb.class).toProvider(new Provider<ReviewDb>() {
      @Override
      public ReviewDb get() {
        ReviewDb db = localDb.get();
        if (db == null) {
          try {
            db = schema.open();
            dbs.add(db);
            localDb.set(db);
          } catch (OrmException e) {
            throw new ProvisionException("unable to open ReviewDb", e);
          }
        }
        return db;
      }
    });
    listener().toInstance(new LifecycleListener() {
      @Override
      public void start() {
        // Do nothing.
      }

      @Override
      public void stop() {
        for (ReviewDb db : dbs) {
          db.close();
        }
      }
    });
  }
}