Prometheus exporters
Prometheus exporters provide metrics for the
prometheus monitoring system.
Configuration
One of the most common exporters is the
node
exporter, it provides hardware and OS metrics from the host it's
running on. The exporter could be configured as follows:
services.prometheus.exporters.node = {
enable = true;
enabledCollectors = [
"logind"
"systemd"
];
disabledCollectors = [
"textfile"
];
openFirewall = true;
firewallFilter = "-i br0 -p tcp -m tcp --dport 9100";
};
It should now serve all metrics from the collectors that are explicitly
enabled and the ones that are
enabled
by default, via http under /metrics. In this
example the firewall should just allow incoming connections to the
exporter's port on the bridge interface br0 (this would
have to be configured seperately of course). For more information about
configuration see man configuration.nix or search through
the
available
options.
Adding a new exporter
To add a new exporter, it has to be packaged first (see
nixpkgs/pkgs/servers/monitoring/prometheus/ for
examples), then a module can be added. The postfix exporter is used in this
example:
Some default options for all exporters are provided by
nixpkgs/nixos/modules/services/monitoring/prometheus/exporters.nix:
enableportlistenAddressextraFlagsopenFirewallfirewallFilterusergroup
As there is already a package available, the module can now be added. This
is accomplished by adding a new file to the
nixos/modules/services/monitoring/prometheus/exporters/
directory, which will be called postfix.nix and contains all exporter
specific options and configuration:
# nixpgs/nixos/modules/services/prometheus/exporters/postfix.nix
{ config, lib, pkgs, options }:
with lib;
let
# for convenience we define cfg here
cfg = config.services.prometheus.exporters.postfix;
in
{
port = 9154; # The postfix exporter listens on this port by default
# `extraOpts` is an attribute set which contains additional options
# (and optional overrides for default options).
# Note that this attribute is optional.
extraOpts = {
telemetryPath = mkOption {
type = types.str;
default = "/metrics";
description = ''
Path under which to expose metrics.
'';
};
logfilePath = mkOption {
type = types.path;
default = /var/log/postfix_exporter_input.log;
example = /var/log/mail.log;
description = ''
Path where Postfix writes log entries.
This file will be truncated by this exporter!
'';
};
showqPath = mkOption {
type = types.path;
default = /var/spool/postfix/public/showq;
example = /var/lib/postfix/queue/public/showq;
description = ''
Path at which Postfix places its showq socket.
'';
};
};
# `serviceOpts` is an attribute set which contains configuration
# for the exporter's systemd service. One of
# `serviceOpts.script` and `serviceOpts.serviceConfig.ExecStart`
# has to be specified here. This will be merged with the default
# service confiuration.
serviceOpts = {
serviceConfig = {
ExecStart = ''
${pkgs.prometheus-postfix-exporter}/bin/postfix_exporter \
--web.listen-address ${cfg.listenAddress}:${toString cfg.port} \
--web.telemetry-path ${cfg.telemetryPath} \
${concatStringsSep " \\\n " cfg.extraFlags}
'';
};
};
}
This should already be enough for the postfix exporter. Additionally one
could now add assertions and conditional default values. This can be done
in the 'meta-module' that combines all exporter definitions and generates
the submodules:
nixpkgs/nixos/modules/services/prometheus/exporters.nixUpdating an exporter module
Should an exporter option change at some point, it is possible to add
information about the change to the exporter definition similar to
nixpkgs/nixos/modules/rename.nix:
{ config, lib, pkgs, options }:
with lib;
let
cfg = config.services.prometheus.exporters.nginx;
in
{
port = 9113;
extraOpts = {
# additional module options
# ...
};
serviceOpts = {
# service configuration
# ...
};
imports = [
# 'services.prometheus.exporters.nginx.telemetryEndpoint' -> 'services.prometheus.exporters.nginx.telemetryPath'
(mkRenamedOptionModule [ "telemetryEndpoint" ] [ "telemetryPath" ])
# removed option 'services.prometheus.exporters.nginx.insecure'
(mkRemovedOptionModule [ "insecure" ] ''
This option was replaced by 'prometheus.exporters.nginx.sslVerify' which defaults to true.
'')
({ options.warnings = options.warnings; })
];
}