Hi all, We're experimenting with running Moodle in Azure. We're using a Redis PaaS instance for our application cache. Since php_redis doesn't support SSL, we're looking at stunnel as a solution to encrypt connections to the cache.
The connections work, but we've found that having stunnel in the mix seriously impacts the capacity of the server. We're seeing it able to handle about 2/3 as many requests per second, with a slower response time. It appears that this is due to stunnel consuming a lot of CPU resources as load ramps up, leaving less available for the web server processess.
I realise we're not going to get encryption for free, but this seems to be a much larger overhead that I expcted. Does anyone have any suggestions for how we might improve the performance with stunnel?
