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diff --git a/nixos/modules/services/monitoring/prometheus/exporters.md b/nixos/modules/services/monitoring/prometheus/exporters.md new file mode 100644 index 000000000000..c085e46d20d7 --- /dev/null +++ b/nixos/modules/services/monitoring/prometheus/exporters.md @@ -0,0 +1,180 @@ +# Prometheus exporters {#module-services-prometheus-exporters} + +Prometheus exporters provide metrics for the +[prometheus monitoring system](https://prometheus.io). + +## Configuration {#module-services-prometheus-exporters-configuration} + +One of the most common exporters is the +[node exporter](https://github.com/prometheus/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; + port = 9100; + 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](https://github.com/prometheus/node_exporter#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 separately of course). For more information about +configuration see `man configuration.nix` or search through +the [available options](https://nixos.org/nixos/options.html#prometheus.exporters). + +Prometheus can now be configured to consume the metrics produced by the exporter: +``` + services.prometheus = { + # ... + + scrapeConfigs = [ + { + job_name = "node"; + static_configs = [{ + targets = [ "localhost:${toString config.services.prometheus.exporters.node.port}" ]; + }]; + } + ]; + + # ... + } +``` + +## Adding a new exporter {#module-services-prometheus-exporters-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`: + + - `enable` + - `port` + - `listenAddress` + - `extraFlags` + - `openFirewall` + - `firewallFilter` + - `user` + - `group` + - 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 configuration. + # Note that by default 'DynamicUser' is 'true'. + serviceOpts = { + serviceConfig = { + DynamicUser = false; + 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.nix` + +## Updating an exporter module {#module-services-prometheus-exporters-update-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; }) + ]; +} +``` |