[DRBD-user] the timing of restarting thread

[Lars Ellenberg]

On Fri, Jul 23, 2010 at 06:15:05PM +0900, Junko IKEDA wrote:
> Hi,
> 
> I'm trying the following test.
> 
> (1) start DRBD.
>      node01 is "Primary" and node02 is "Secondary".
> (2) block the replication port on node02.
>      # iptables -A INPUT -i bond0 -p tcp --dport 7790 -j DROP

insufficient.
you have to block OUTPUT as well.

DRBD has _two_ tcp sessions per device,
one end will have a "random high port",
the end the configured port.
There is nothing that guarantees which node ends up with which end,
typically both have one high port, one configured, but that is
by no means necessary, it can just as well end up with
one node having both configured ports, the other both high ports.

> the result is;
> 
> * protocol B,C
> DRBD did nothing.

You _by chance_ only blocked the "data" socket.

> * protocol A
> It seems that DRBD restarted its threads.

You _by chance_ happened to block the "meta" socket.

> Q1, protocol A is only able to restart the threads, right?

wrong question, no answer.

> if so, which parameter handles the timing of restaring, connect-int in drbd.conf?

man drbdsetup.
online: http://www.drbd.org/users-guide/re-drbdsetup.html


> Q2, Both of receiver and asender thread will restart with new PID?
> syslog said;
> 
> Terminating asender thread
> Restarting receiver thread
> Starting asender thread (from drbd0_receiver [27363])

irrelevant.

> --- netstat on node2---
> 
> # date; iptables -A INPUT -i bond1 -p tcp --dport 7790 -j DROP
> 15:36:48 JST

I suggest to prepare it like this:
iptables -N simulbreak
for c in INPUT OUTPUT ; do
    for d in sport dport ; do
  	iptables -I $c -p tcp --$d -j simulbreak
    done
done

then break it with "iptables -I simulbreak -j DROP",
heal it with "iptables -I simulbreak -j ACCEPT".

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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