Merge "Remove duplicated code to create a log file from a plugin"

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

@@ -0,0 +1,65 @@
+// 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();
+    }
+  }
+}