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prometheus.nix
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prometheus.nix
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# This module deploys a two-tiered Prometheus setup:
#
# - The prometheus-collector discovers compatible endpoints and scrapes all
# metrics from them. It has a short retention time so that the large number
# of ingested metrics does not consume inappropriately large amounts of disk
# storage.
# - The prometheus-persister federates selected metrics from the collector and
# stores them for a long time. This is the datasource of choice for Grafana.
{ config, pkgs, lib, ... }:
with lib;
let
cfg = config.my.services.prometheus;
persisterPort = 9090;
collectorPort = 9091;
serviceDiscoveryPort = config.my.services.monitoring.prometheus.serviceCollectorPort;
serviceDiscoveryPackage = pkgs.callPackage ./pkgs/prometheus-minimum-viable-sd/default.nix {};
collectorRulesYAML = pkgs.writeText "prometheus-collector-rules.yaml" ''
groups:
- name: collector
rules:
- record: node_power_supply_charge_watthours
expr: node_power_supply_charge_ampere * node_power_supply_voltage_volt
'';
collectorConfigYAML = pkgs.writeText "prometheus-collector.yaml" ''
global:
scrape_interval: 60s
evaluation_interval: 60s
scrape_timeout: 5s
rule_files:
- ${collectorRulesYAML}
scrape_configs:
- job_name: prometheus-collector
static_configs:
- targets: ['localhost:${toString collectorPort}']
- job_name: prometheus-persister
static_configs:
- targets: ['localhost:${toString persisterPort}']
- job_name: service-discovery
file_sd_configs:
- files: ['/run/prometheus/services.json']
'';
persisterRulesYAML = pkgs.writeText "prometheus-persister-rules.yaml" ''
groups:
- name: collector
rules:
# This rule tries very hard to continue existing even if the node is down for a bit.
# I collect this to measure uptime percentage.
- record: node_up
expr: (node_load1*0+1) or (min_over_time(node_load1[14d])*0+0)
'';
persisterConfigYAML = pkgs.writeText "prometheus-persister.yaml" ''
global:
scrape_interval: 15s
evaluation_interval: 60s
scrape_timeout: 5s
rule_files:
- ${persisterRulesYAML}
scrape_configs:
- job_name: federate
honor_labels: true
metrics_path: '/federate'
static_configs:
- targets: ['localhost:${toString collectorPort}']
params:
'match[]':
# for the "Node Stats" dashboard
- node_cpu_seconds_total
- node_filesystem_free_bytes
- node_filesystem_size_bytes
- node_load1
- node_load5
- node_memory_MemAvailable_bytes
- node_memory_MemTotal_bytes
- node_memory_SwapFree_bytes
- node_memory_SwapTotal_bytes
- node_network_receive_bytes_total
- node_network_transmit_bytes_total
# other things that interest me
- node_hwmon_temp_celsius
- node_power_supply_charge_ampere
- node_power_supply_charge_watthours
'';
instances = {
prometheus-collector = { port = collectorPort; configYAML = collectorConfigYAML; retention = "1h"; };
prometheus-persister = { port = persisterPort; configYAML = persisterConfigYAML; retention = "365d"; };
};
in {
options.my.services.prometheus.enable = mkEnableOption "prometheus";
config = mkIf cfg.enable {
users.groups.prometheus = {};
users.users.prometheus = {
description = "Prometheus service user";
group = "prometheus";
isSystemUser = true;
home = "/var/empty";
};
# no need to backup ephemeral data that's never more than one hour old
my.services.borgbackup.excludedPaths = [ "/var/lib/prometheus-collector" ];
networking.firewall.interfaces.wg-monitoring.allowedTCPPorts = let
prometheusPorts = map (opts: opts.port) (attrValues instances);
in prometheusPorts ++ [ serviceDiscoveryPort ];
systemd.services = let
prometheusServices = mapAttrs (serviceName: serviceOpts: {
wantedBy = [ "multi-user.target" ];
description = "${serviceName} server";
serviceConfig = {
ExecStart = "${pkgs.prometheus}/bin/prometheus --config.file=${serviceOpts.configYAML} --storage.tsdb.path=/var/lib/${serviceName} --web.listen-address=:${toString serviceOpts.port} --storage.tsdb.retention=${serviceOpts.retention}";
ExecReload = "${pkgs.utillinux}/bin/kill -HUP $MAINPID";
User = "prometheus";
Group = "prometheus";
WorkingDirectory = "/var/lib/${serviceName}";
StateDirectory = serviceName;
};
}) instances;
auxiliaryServices = {
prometheus-minimum-viable-sd-collect = {
wantedBy = [ "multi-user.target" ];
description = "Minimum Viable service discovery for Prometheus";
serviceConfig = {
ExecStart = "${serviceDiscoveryPackage}/bin/prometheus-minimum-viable-sd collect /run/prometheus/services.json :${toString serviceDiscoveryPort}";
Restart = "always";
RestartSec = "10s";
# run under same user/group as prometheus-collector, since prometheus-collector needs to read our runtime directory
User = "prometheus";
Group = "prometheus";
RuntimeDirectory = "prometheus";
RuntimeDirectoryPreserve = "restart";
};
};
};
in mkMerge [ prometheusServices auxiliaryServices ];
my.hardening = let
prometheusHardening = mapAttrs (serviceName: serviceOpts: {
allowInternetAccess = true; # to bind HTTP
allowWriteAccessTo = [ "/var/lib/${serviceName}" ];
}) instances;
auxiliaryHardening = {
prometheus-minimum-viable-sd-collect = {
allowInternetAccess = true; # to bind TCP
};
};
in mkMerge [ prometheusHardening auxiliaryHardening ];
};
}