net.core.somaxconn not set automatically for Redis
In https://gitlab.com/gitlab-com/production/issues/431#note_96968283, we discovered that Redis is showing warnings:
# WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
It turns out the default value of 128 isn't changed:
# sudo sysctl -a | grep maxconn
net.core.somaxconn = 128
This value is altered for Unicorn but not for Redis: https://gitlab.com/gitlab-org/omnibus-gitlab/blob/144ce62c6b540dd40a4302aa1cf8f4f42d43f493/files/gitlab-cookbooks/gitlab/recipes/unicorn.rb#L29-31
It seems to make sense to make this a default for Redis as well?