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.
Regarding setting the redis password, see the section on redis passwords.
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.
Password¶
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.
Overriding the password
to foobarpass
looks like this:
# /etc/local/nixos/redis.nix
{ ... }:
{
flyingcircus.services.redis = {
password = "foobarpass"; # Makes the password world readable
};
}
Interaction¶
Service users may invoke sudo fc-manage --build to apply service configuration changes and trigger service restarts (if necessary).
Monitoring¶
The default monitoring setup checks that the Redis server is running and is responding to PING.