gerrit-server/src/main/java/com/google/gerrit/server/util/PluginLogFile.java

// 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.util;

import com.google.gerrit.extensions.events.LifecycleListener;
import com.google.gerrit.extensions.systemstatus.ServerInformation;
import com.google.inject.Inject;

import org.apache.log4j.AsyncAppender;
import org.apache.log4j.Layout;
import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;

public abstract class PluginLogFile implements LifecycleListener {

  private final SystemLog systemLog;
  private final ServerInformation serverInfo;
  private final String logName;
  private final Layout layout;

  @Inject
  public PluginLogFile(SystemLog systemLog,
      ServerInformation serverInfo,
      String logName,
      Layout layout) {
    this.systemLog = systemLog;
    this.serverInfo = serverInfo;
    this.logName = logName;
    this.layout = layout;
  }

  @Override
  public void start() {
    AsyncAppender asyncAppender =
        systemLog.createAsyncAppender(logName, layout);
    Logger logger = LogManager.getLogger(logName);
    logger.removeAppender(logName);
    logger.addAppender(asyncAppender);
    logger.setAdditivity(false);
  }

  @Override
  public void stop() {
    // stop is called when plugin is unloaded or when the server shutdown.
    // Only clean up when the server is shutting down to prevent issue when a
    // plugin is reloaded. The issue is that gerrit load the new plugin and then
    // unload the old one so because loggers are static, the unload of the old
    // plugin would remove the appenders just created by the new plugin.
    if (serverInfo.getState() == ServerInformation.State.SHUTDOWN) {
      LogManager.getLogger(logName).removeAllAppenders();
    }
  }
}