Amazon redshift AWS红移：致命：超过非引导用户的连接限制“500”

希望你们都没事。 我们经常达到这个极限。我们知道在Redshift中无法达到500个并发用户连接的限制。我们还知道某些视图pg_user_info提供了有关用户实际限制的信息。 我们正在寻找一些在此论坛中找不到的答案，以及基于您经验的任何指导。 问题: 使用更大的EC2实例重新创建集群是否会产生更高的限制值？ 向现有集群添加新节点是否会产生更高的限制值？ 从应用程序开发的角度来看：为了发现或预测达到此极限的情况，您会推荐哪些具体策略/行动？

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Txs-Jimmy

正如你所说，这是红移的一个硬限制，没有办法提高它。Redshift不是高并发/高连接数据库

我希望，如果您需要Redshift的强大数据分析能力，您可以通过连接共享解决这个问题。Pgpool是用于此目的的常用工具

好的，伙计们。 感谢所有回答的人。 我在AWS上贴了一张支持票，这是我的建议，粘贴在这里，虽然很长，但我希望它对很多遇到这个问题的人都有效。这样做的目的是在情况发生之前抓住它：

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您的Amazon Redshift集群是否有500多名并发用户？这些是真人，还是正在连接的应用程序？你真的需要那么多的连接吗？他们都在干什么？

To monitor the number of connections made to the database, you can create a cloudwatch alarm based on the Database connections metrics that will trigger a lambda function when a certain threshold is reached. This lambda function can then terminate idle connections by calling a procedure that terminates idle connections.

Please find the query that creates a procedure to log and terminate long running inactive sessions
:

1. Add view to get all current inactive sessions in the cluster

CREATE OR REPLACE VIEW inactive_sessions as (
    select a.process, 
    trim(a.user_name) as user_name,
    trim(c.remotehost) as remotehost,
    a.usesysid, 
    a.starttime, 
    datediff(s,a.starttime,sysdate) as session_dur, 
    b.last_end, 
    datediff(s,case when b.last_end is not null then b.last_end else a.starttime end,sysdate) idle_dur
        FROM
        (
            select starttime,process,u.usesysid,user_name 
            from stv_sessions s, pg_user u 
            where 
            s.user_name = u.usename 
            and u.usesysid>1
            and process NOT IN (select pid from stv_inflight where userid>1 
            union select pid from stv_recents where status != 'Done' and userid>1)
        ) a 
        LEFT OUTER JOIN (
            select 
            userid,pid,max(endtime) as last_end from svl_statementtext 
            where userid>1 and sequence=0 group by 1,2) b ON a.usesysid = b.userid AND a.process = b.pid

        LEFT OUTER JOIN (
            select username, pid, remotehost from stl_connection_log
            where event = 'initiating session' and username <> 'rsdb') c on a.user_name = c.username AND a.process = c.pid
        WHERE (b.last_end > a.starttime OR b.last_end is null)
        ORDER BY idle_dur
);

2. Add table for logging information about long running transactions that was terminated 

CREATE TABLE IF NOT EXISTS terminated_inactive_sessions (
    process int,
    user_name varchar(50),
    remotehost varchar(50),
    starttime timestamp,
    session_dur int,
    idle_dur int,
    terminated_on timestamp DEFAULT GETDATE()   
);

3. Add procedure to log and terminate any inactive transactions running for longer than 'n' amount of seconds

CREATE OR REPLACE PROCEDURE terminate_and_log_inactive_sessions (n INTEGER) 
AS $$ 
DECLARE
  expired RECORD ; 
BEGIN
FOR expired IN SELECT process, user_name, remotehost, starttime, session_dur, idle_dur FROM inactive_sessions where idle_dur >= n
LOOP
EXECUTE 'INSERT INTO terminated_inactive_sessions (process, user_name, remotehost, starttime, session_dur, idle_dur) values (' || expired.process || ' , ''' || expired.user_name || ''' , ''' || expired.remotehost || ''' , ''' || expired.starttime || ''' , ' || expired.session_dur || ' , ' || expired.idle_dur || ');';
EXECUTE 'SELECT PG_TERMINATE_BACKEND(' || expired.process || ')';
END LOOP ; 

END ; 
$$ LANGUAGE plpgsql;

4. Execute the procedure by running the following command:

  call terminate_and_log_inactive_sessions(100);


Here is a sample lambda function that attempts to close idle connections by querying the view 'inactive_sessions' created above, which you can use as a reference. 

#Current time
now = datetime.datetime.now()

query = "SELECT process, user_name, session_dur, idle_dur FROM inactive_sessions where idle_dur >= %d"

logger = logging.getLogger()
logger.setLevel(logging.INFO)

def lambda_handler(event, context):

   try:
       conn = psycopg2.connect("dbname=" + db_database + " user=" + db_user + " password=" + db_password + " port=" + db_port + " host=" + db_host)
       conn.autocommit = True
   except:
       logger.error("ERROR: Unexpected error: Could not connect to Redshift cluster.")   
       sys.exit()

   logger.info("SUCCESS: Connection to RDS Redshift cluster succeeded")

   with conn.cursor() as cur:
       cur.execute(query % (session_idle_limit))
       row_count = cur.rowcount
       if row_count >=1:
           result = cur.fetchall()
           for row in result:
               print("terminating session with pid %s that has been idle for %d seconds at %s" % (row[0],row[3],now))
              cur.execute("SELECT PG_TERMINATE_BACKEND(%s);" % (row[0]))
           conn.close()
       else:
           conn.close()