[Pacemaker] Arp and configuration advice

[E-Blokos]

----- Original Message ----- 
From: <Darren.Mansell at opengi.co.uk>
To: <pacemaker at clusterlabs.org>
Sent: Wednesday, September 09, 2009 10:39 AM
Subject: Re: [Pacemaker] Arp and configuration advice


>> Greetings,
>> 
>> I have a two webserver/two database server clustered setup. I've got
>> ldirector and LVS managed by pacemaker and configured to be able to
> run
>> on either database machine.
>> 
>> I know how to disable ARP for the machine not running ldirector,
>> unfortunately I'm not sure how to dynamically get the webservers to
>> update their ARP cache when ldirector gets moved upon failure.
>> 
>> Is it possible to set up a service for the two web servers to delete
>> the
>> ARP cache for the VIP on the event that ldirector gets moved?
> 
> The IPaddr2 RA runs send_arp when the start action is called I believe:
> 
> 
> #
> # Run send_arp to note peers about new mac address
> #
> run_send_arp() {
>        ARGS="-i $ARP_INTERVAL_MS -r $ARP_REPEAT -p $SENDARPPIDFILE $NIC
> $BASEIP auto not_used not_used"
>        if [ "x$IP_CIP" = "xyes" ] ; then
>            if [ x = "x$IF_MAC" ] ; then
>                MY_MAC=auto
>            else
>                MY_MAC=`echo ${IF_MAC} | sed -e 's/://'`
>            fi
>            ARGS="-i $ARP_INTERVAL_MS -r $ARP_REPEAT -p $SENDARPPIDFILE
> $NIC $BASEIP $MY_MAC not_used not_used"
>        fi
>        ocf_log info "$SENDARP $ARGS"
>        case $ARP_BACKGROUND in
>        yes)
>                ($SENDARP $ARGS || ocf_log err "Could not send
> gratuitous arps" &) >&2
>                ;;
>        *)
>                $SENDARP $ARGS || ocf_log err "Could not send gratuitous
> arps"
>                ;;
>        esac
> }
> 
> 
> So when the VIP is started on another node, other nodes should be
> notified the IP has changed hosts. Doesn't it work for you?
> 
>> 
>> I can build my own OCF script to update the arp cache, that's not an
>> issue. I simply don't know how to configure pacemaker to say "Oop. db2
>> died. Move ldirector to db1 and tell the webservers to update their
> ARP
>> cache".
>> 
>> Any suggestions?
>> 
>> Thanks in advance!
>> 
>> Justin
>> 
> 
> Regards,
> Darren

I have also this kind of problem months ago,
ARP was not really updating well I don't know why...


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