Redis¶
This role installs the Redis in-memory data structure store in the latest version provided by NixOS.
Components¶
Redis
Configuration¶
Out of the box, Redis is set up with a couple of common default parameters and listens on the IP-addresses of the loopback (localhost) and ethsrv-interfaces of your VM on port 6379 (See networking for details on this topic).
In previous versions, custom redis configuration could be set
via /etc/local/redis/custom.conf which is not supported anymore.
If you need to change the behaviour of Redis, you define your redis
configuration with the NixOS option services.redis.settings. See the
NixOS manual for further information.
The following NixOS module adds some modules to be loaded by Redis:
# /etc/local/nixos/redis.nix
{ ... }:
{
services.redis.settings = {
loadmodule = [ "/path/to/my_module.so" "/path/to/other_module.so" ];
};
}
See Custom NixOS-native configuration for general information about writing custom NixOS
modules in /etc/local/nixos.
There are also some options under flyingcircus.services.redis, namely
maxmemory, maxmemory-policy, password and listenAddresses.
The following NixOS module sets the listening addresses to 203.0.113.54 and
203.0.113.57 as well as overriding the password to foobarpass. The maximum
memory size is set to 512mb. The exact behavior Redis follows when the maxmemory
limit is reached is configured using the maxmemory-policy configuration directive
and is set to noeviction in this example. Read more at redis topic lru cache <https://redis.io/topics/lru-cache>.
# /etc/local/nixos/redis.nix
{ ... }:
{
flyingcircus.services.redis = {
listenAddresses = [ "203.0.113.54", "203.0.113.57 "];
password = "foobarpass"; # Makes the password world readable, see paragraphs below for information
maxmemory = "512mb";
maxmemory-policy = "noeviction";
};
}
As an alternative to setting the maxmemory by hand you can set a memoryPercentage
option. This will set the memory limit to a percentage of the total memory of the
system.
# /etc/local/nixos/redis.nix
{ ... }:
{
flyingcircus.services.redis = {
memoryPercentage = "50";
};
}
For further information on how to activate changes on our NixOS-environment, please consult Local Configuration.
The authentication password is automatically generated upon installation
and can be read and changed by service users. It can be found in
/etc/local/redis/password. It can also be specified in the
flyingcircus.services.redis.password option where the password
will have a higher priority than the one in the filesystem. Setting
the password option makes the password world-readable to processes
on the VM since it will be stored in the nix store.
Interaction¶
Service users may invoke sudo fc-manage --build to apply service configuration changes and trigger service restarts (if necessary).