content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements. See the NOTICE file distributed with this
   * work for additional information regarding copyright ownership. The ASF
   * licenses this file to you 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 org.apache.bookkeeper.stats;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * This class is used to raise alert when we detect an event that should never happen in production.
   */
  public class AlertStatsLogger {
      private static final Logger logger = LoggerFactory.getLogger(AlertStatsLogger.class);
  
      public final String alertStatName;
  
      private final StatsLogger globalStatsLogger;
      private final StatsLogger scopedStatsLogger;
      private final String scope;
      private Counter globalCounter = null;
      private Counter scopedCounter = null;
  
      public AlertStatsLogger(StatsLogger globalStatsLogger, String scope, String alertStatName) {
          this.globalStatsLogger = globalStatsLogger;
          this.scope = scope;
          this.scopedStatsLogger = globalStatsLogger.scope(scope);
          this.alertStatName = alertStatName;
      }
  
      public AlertStatsLogger(StatsLogger globalStatsLogger, String alertStatName) {
          this.globalStatsLogger = globalStatsLogger;
          this.scope = null;
          this.scopedStatsLogger = null;
          this.alertStatName = alertStatName;
      }
  
      private String format(String msg) {
          return msg.startsWith("ALERT!: ") ? msg :
                  ("ALERT!: " + (scope != null ? "(" + scope + "):" : "") + msg);
      }
  
      private void initializeCountersIfNeeded() {
          if (null != globalCounter) {
              return;
          }
  
          globalCounter = globalStatsLogger.getCounter(alertStatName);
  
          if (null != scopedStatsLogger) {
              scopedCounter = scopedStatsLogger.getCounter(alertStatName);
          }
      }
  
      /**
       * Report an alertable condition". Prefixes "ALERT!: " if not already prefixed.
       */
      public void raise(String msg, Object... args) {
          initializeCountersIfNeeded();
          globalCounter.inc();
          if (null != scopedCounter) {
              scopedCounter.inc();
          }
          logger.error(format(msg), args);
          logger.error("fake exception to generate stack trace", new Exception());
      }
  }
  