Varnish-Cache
We were playing around with the automation around famous Varnish-Cache service and stumbled upon something... the silent killer style of Varnish Cache.
The automated naming was such that it was appending different specific service-node host-names and service-names to form backends and then load balance onto them using "director ... round-robin" configuration. It was creating names that way to avoid name collision for same service running on different nodes load-balanced by Varnish-Cache.
We checked for the configuration correctness
It passed.
We started the Varnish service
It started.
We tried accessing the services via Varnish.
It failed saying there no http service running at Varnish machine:port.
Now what. Can't figure out anything wrong in configuration VCL. So, start looking at logs.
Tried starting varnishlog service
This failed giving error about _.vsm being not present, which was actually present and with right user permissions.
Then a colleague of mine suggests he has faced such issue before due to extremely long backend names.
I extremely shortened the backend name and it started working.
So, the length there does effect but the VCL gives no error when starting Varnish-Cache.
BTW, from the checks performed... the maximum character backend name working for the configuration was 44 Character long.
We were playing around with the automation around famous Varnish-Cache service and stumbled upon something... the silent killer style of Varnish Cache.
The automated naming was such that it was appending different specific service-node host-names and service-names to form backends and then load balance onto them using "director ... round-robin" configuration. It was creating names that way to avoid name collision for same service running on different nodes load-balanced by Varnish-Cache.
We checked for the configuration correctness
$ varnishd -C -f /my/varnish/config/file
It passed.
We started the Varnish service
$ /etc/init.d/varnish start
It started.
We tried accessing the services via Varnish.
It failed saying there no http service running at Varnish machine:port.
Now what. Can't figure out anything wrong in configuration VCL. So, start looking at logs.
Tried starting varnishlog service
$ service varnishlog start
This failed giving error about _.vsm being not present, which was actually present and with right user permissions.
Then a colleague of mine suggests he has faced such issue before due to extremely long backend names.
I extremely shortened the backend name and it started working.
So, the length there does effect but the VCL gives no error when starting Varnish-Cache.
BTW, from the checks performed... the maximum character backend name working for the configuration was 44 Character long.
