Carp and Apache

[DAve]

Danny Howard wrote:
> Dave,
> 
> Yes.

"Yes" both apache servers have the same IP in httpd.conf? or "Yes" I am 
completely off base in my understanding?

Not certain I can go this route right now anyway as I do not have enough 
test boxes to setup a trial. There seems to be a shortage of good docs 
on using CARP outside of using it with PF.

Thanks,

DAve

> 
> The trick with CARP is that it is an IP-level heartbeat, so if you are
> running Apache, you want to "carp up" after you start apache, and "carp
> down" before you stop Apache.
> 
>>From some test boxes, web0:
> ifconfig_fxp1="inet 192.168.1.210 netmask 255.255.255.0"
> defaultrouter="192.168.1.1"
> cloned_interfaces="carp0 carp1"
> 
> Then, web0 application config file:
> export CARP_PASS="mekmitasdigoat"
> # MASTER
> export CARP_carp0_IP=192.168.1.206
> export CARP_carp0_VHID=1
> # SLAVE
> export CARP_carp1_IP=192.168.1.207
> export CARP_carp1_VHID=2
> export CARP_carp1_SKEW=100
> 
> Next, the Application "control" script:
> # CARP
> carp_ifs=`ifconfig -l | tr ' ' '\n' | grep carp`
> 
> # Set up CARP
> for carp_if in $carp_ifs; do
>         eval   carp_ip=\$CARP_${carp_if}_IP
>         eval carp_vhid=\$CARP_${carp_if}_VHID
>         eval carp_skew=\$CARP_${carp_if}_SKEW
> 
>         if [ -n "$carp_vhid" ]; then
>                 carp_vhid="vhid $carp_vhid"
>         fi
>         if [ -n "$carp_skew" ]; then
>                 carp_skew="advskew $carp_skew"
>         fi
> 
>         if [ -n "${carp_ip}" -a -n "${carp_vhid}" ]; then
>                 ifconfig $carp_if pass "$CARP_PASS" $carp_vhid $carp_skew $carp_ip
>                 ifconfig $carp_if down
>         else
>                 echo "WARNING: $carp_if but missing CARP_${carp_if}_IP or CARP_${carp_if}_VHID!"
>         fi
> done
> 
> [... later ...]
> if [ $status -eq 0 ]; then
>   echo "Apache successfully ${cmd}ed"
>   echo "Ready to CARP UP!"
>   if [ -n "${carp_ifs}" ]; then
>         for carp_if in $carp_ifs; do
>                 eval   carp_ip=\$CARP_${carp_if}_IP
>                 eval carp_vhid=\$CARP_${carp_if}_VHID
>                 if [ -n "${carp_ip}" -a -n "${carp_vhid}" ]; then
>                         ifconfig $carp_if up
>                 fi
>         done
>         sysctl net.inet.carp.preempt=1
>   fi
> else
>   echo "Apache failed to $cmd"
>   exit 2
> fi
> 
> 
> Okay, so that's really quite a mess, but basically:
> * Set cloned_interfaces in rc.conf to create carp<n> at boot.
> * One IP alias and VHID per CARP IP.
> * Set up the backup server with higher advskew.
> * For availability, teach you apachectl script to ifconfig the carp
>   interfaces, ifconfig down, start apache, ifconfig up, and ifconfig
>   down before stopping / restarting apache.
> 
> Cheers,
> -danny
>