[GitHub] xiangwangcheng commented on issue #515: org.apache.rocketmq.common.stats.StatsItemSet#getAndCreateStatsItem has multi-thread problem

[GitBox <gi...@apache.org>]

xiangwangcheng commented on issue #515: org.apache.rocketmq.common.stats.StatsItemSet#getAndCreateStatsItem has multi-thread problem
URL: https://github.com/apache/rocketmq/issues/515#issuecomment-435057848
 
 
   Use putIfAbsent will solve this problem.
   
   ```
   public StatsItem getAndCreateStatsItem(final String statsKey) {
       StatsItem statsItem = this.statsItemTable.get(statsKey);
       if (null == statsItem) {
           statsItem = new StatsItem(this.statsName, statsKey, this.scheduledExecutorService, this.log);
           StatsItem prev = this.statsItemTable.putIfAbsent(statsKey, statsItem);
   
           if (null != prev) {
               statsItem = prev;
               // statsItem.init();
           }
       }
   
       return statsItem;
   }
   ```

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