VaaS cron jobs

Remember how we wrote that VaaS does not use an agent? That was a lie. VaaS uses old good cron as an agent to perform two simple tasks. We recommend using a configuration management system to configure these jobs on appropriate servers.

Saving backend status to the database

Assuming you followed our quick-start instruction on running VaaS in production, this cron job should run on VaaS application server:

0-58/2 * * * * /home/vagrant/prod-env/bin/backend_statuses

Generating a startup VCL

On each Varnish server controlled by VaaS, run the following job to save running VCL so that it is available immediately after Varnish restarts:

*/5 * * * * bash -c "source /usr/local/bin/ && save_vcl && put_vcl_in_place"

Additionally, you may want to keep a backup of the last known good configuration - in case of an emergency:

* */6 * * * bash -c "source /usr/local/bin/ && rotate_vcls"

Here's what /usr/local/bin/ could look like:


save_vcl () {
  if [ $(pgrep varnishd > /dev/null ; echo $?) -eq 0 ] ; then
    varnishadm $(varnishadm vcl.list | grep active | egrep -o '[^ ]*$') > /etc/varnish/default.vcl_tmp

put_vcl_in_place () {
  if [ $(stat --printf="%s" /etc/varnish/default.vcl_tmp) -gt 0 ]; then
    mv /etc/varnish/default.vcl_tmp /etc/varnish/default.vcl

rotate_vcls () {
  cp /etc/varnish/default.vcl-6h /etc/varnish/default.vcl-12h
  cp /etc/varnish/default.vcl /etc/varnish/default.vcl-6h