[pgpool-general: 2839] Re: Issue with pgpool health check timeout

Tatsuo Ishii ishii at postgresql.org
Fri May 16 11:15:40 JST 2014


From: Shyalika Benthotage <shyalika_benthotage at dialog.com.au>
Subject: RE: [pgpool-general: 2835] Issue with pgpool health check timeout
Date: Fri, 16 May 2014 02:11:27 +0000
Message-ID: <0C34193B8C9D1249A95AD902CCF181CF14CB66AD at otwdgmxbox01.dialoggroup.internal>

> Hi Ishii,
> 
> Thanks for the quick reply. I tested the pgpool settings using a DROP rule in iptables. I.e. the DROP rule will silently drop data packets without sending a response to the sender, making the sender to wait and then the request to time out. So I believe in this case the network related system call does not actually return so it should time out. Am I correct?

Yes,correct. More precisely, 

non blocking connect(2) issued then select(2) waits for something comes in:
>> 2014-05-13 12:14:43 DEBUG: pid 15822: health_check: 0 th DB node 

Then select(2) timed out because there is 1 second time out set in the select(2) parameter.
>> 2014-05-13 12:14:44 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...

> Thanks & Regards,
> Shyalika
> 
> -----Original Message-----
> From: Tatsuo Ishii [mailto:ishii at postgresql.org] 
> Sent: Friday, 16 May 2014 10:17 AM
> To: Shyalika Benthotage
> Cc: pgpool-general at pgpool.net
> Subject: Re: [pgpool-general: 2835] Issue with pgpool health check timeout
> 
>> Hi,
>> 
>> We have configured pgpool 3.3 for our PostgreSQL db in aws. And using the healthcheck parameters as below.
>> 
>> health_check_period = 40
>> health_check_timeout = 10
>> health_check_max_retries = 2
>> health_check_retry_delay = 2
>> 
>> I am trying to test this by using an iptables rule in the active server. When I add a drop rule to the PostgreSQL db port it does trigger a timeout but I think it timeout too soon. I.e. according to my understanding it should wait for the time period specified in "health_check_timeout " in this case, but actually times out in less than a second.(Please see the log below). Shouldn't it wait for 10 secs before time out or is my understanding incorrect. 
> 
> No. health_check_timeout is a timeout before network related system calls returns. If any of system calls returns error immediately, it is possible that it detects error less than 10 seconds.
> 
>> Please note that I checked my DROP rule with telnet and it takes 60 seconds to time out.
>> I have restarted pgpool every time I tested this (I know just 
>> reloading would do)
>> 
>> I have enabled debug mode just to check this.
>> 
>> 2014-05-13 12:14:43 DEBUG: pid 15822: health_check: 0 th DB node 
>> status: 1
>> 2014-05-13 12:14:44 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:44 ERROR: pid 15822: connect_inet_domain_socket: 
>> select() timed out
>> 2014-05-13 12:14:44 ERROR: pid 15822: make_persistent_db_connection: 
>> connection to 10.0.0.5(5432) failed
>> 2014-05-13 12:14:44 DEBUG: pid 15822: health_check: 0 th DB node 
>> status: 1
>> 2014-05-13 12:14:45 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:45 ERROR: pid 15822: connect_inet_domain_socket: 
>> select() timed out
>> 2014-05-13 12:14:45 ERROR: pid 15822: make_persistent_db_connection: 
>> connection to 10.0.0.5(5432) failed
>> 2014-05-13 12:14:45 ERROR: pid 15822: health check failed. 0 th host 
>> 10.0.0.5 at port 5432 is down
>> 2014-05-13 12:14:45 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:45 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:45 LOG: pid 15822: health check retry sleep time: 2 
>> second(s)
>> 2014-05-13 12:14:46 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:47 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:47 DEBUG: pid 15822: retrying 1 th health checking
>> 2014-05-13 12:14:47 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:47 DEBUG: pid 15822: health_check: 0 th DB node 
>> status: 1
>> 2014-05-13 12:14:48 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:48 ERROR: pid 15822: connect_inet_domain_socket: 
>> select() timed out
>> 2014-05-13 12:14:48 ERROR: pid 15822: make_persistent_db_connection: 
>> connection to 10.0.0.5(5432) failed
>> 2014-05-13 12:14:48 ERROR: pid 15822: health check failed. 0 th host 
>> 10.0.0.5 at port 5432 is down
>> 2014-05-13 12:14:48 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:48 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:48 LOG: pid 15822: health check retry sleep time: 2 
>> second(s)
>> 2014-05-13 12:14:49 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:50 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:50 DEBUG: pid 15822: retrying 2 th health checking
>> 2014-05-13 12:14:50 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:50 DEBUG: pid 15822: health_check: 0 th DB node 
>> status: 1
>> 2014-05-13 12:14:51 LOG: pid 15857: connect_inet_domain_socket: select() timed out. retrying...
>> 2014-05-13 12:14:51 ERROR: pid 15822: connect_inet_domain_socket: 
>> select() timed out
>> 2014-05-13 12:14:51 ERROR: pid 15822: make_persistent_db_connection: 
>> connection to 10.0.0.5(5432) failed
>> 2014-05-13 12:14:51 ERROR: pid 15822: health check failed. 0 th host 
>> 10.0.0.5 at port 5432 is down
>> 2014-05-13 12:14:51 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:51 DEBUG: pid 15822: health check: clearing alarm
>> 2014-05-13 12:14:51 LOG: pid 15822: set 0 th backend down status
>> 2014-05-13 12:14:51 DEBUG: pid 15822: failover_handler called
>> 2014-05-13 12:14:51 DEBUG: pid 15822: failover_handler: starting to 
>> select new master node
>> 
>> I even tried setting health_check_timeout to 0 to see whether it defaults to TCP/IP timeout. No difference.
>> 
>> Regards,
>> Shyalika
>> 


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