[jira] [Created] (ZOOKEEPER-1669) Operations to server will be timed-out while thousands of sessions expired same time

["tokoot (JIRA)" <ji...@apache.org>]

tokoot created ZOOKEEPER-1669:
---------------------------------

             Summary: Operations to server will be timed-out while thousands of sessions expired same time
                 Key: ZOOKEEPER-1669
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1669
             Project: ZooKeeper
          Issue Type: Improvement
          Components: server
    Affects Versions: 3.3.5
            Reporter: tokoot


If there are thousands of clients, and most of them disconnect with server same time(client restarted or servers partitioned with clients), the server will busy to close those "connections" and become unavailable. The problem is in following:
  private void closeSessionWithoutWakeup(long sessionId) {
      HashSet<NIOServerCnxn> cnxns;
          synchronized (this.cnxns) {
              cnxns = (HashSet<NIOServerCnxn>)this.cnxns.clone();  // other thread will block because of here
          }
      ...
  }


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