Prometheus, Grafana, Loki, Promtail on NixOS

configuration.nix

  # MONITORING: services run on loopback interface
  #             nginx reverse proxy exposes services to network
  #             - grafana:3010
  #             - prometheus:3020
  #             - loki:3030
  #             - promtail:3031

  # prometheus: port 3020 (8020)
  #
  services.prometheus = {
    port = 3020;
    enable = true;

    exporters = {
      node = {
        port = 3021;
        enabledCollectors = [ "systemd" ];
        enable = true;
      };
    };

    # ingest the published nodes
    scrapeConfigs = [{
      job_name = "nodes";
      static_configs = [{
        targets = [
          "127.0.0.1:${toString config.services.prometheus.exporters.node.port}"
        ];
      }];
    }];
  };

  # loki: port 3030 (8030)
  #
  services.loki = {
    enable = true;
    configuration = {
      server.http_listen_port = 3030;
      auth_enabled = false;

      ingester = {
        lifecycler = {
          address = "127.0.0.1";
          ring = {
            kvstore = {
              store = "inmemory";
            };
            replication_factor = 1;
          };
        };
        chunk_idle_period = "1h";
        max_chunk_age = "1h";
        chunk_target_size = 999999;
        chunk_retain_period = "30s";
        max_transfer_retries = 0;
      };

      schema_config = {
        configs = [{
          from = "2022-06-06";
          store = "boltdb-shipper";
          object_store = "filesystem";
          schema = "v11";
          index = {
            prefix = "index_";
            period = "24h";
          };
        }];
      };

      storage_config = {
        boltdb_shipper = {
          active_index_directory = "/var/lib/loki/boltdb-shipper-active";
          cache_location = "/var/lib/loki/boltdb-shipper-cache";
          cache_ttl = "24h";
          shared_store = "filesystem";
        };

        filesystem = {
          directory = "/var/lib/loki/chunks";
        };
      };

      limits_config = {
        reject_old_samples = true;
        reject_old_samples_max_age = "168h";
      };

      chunk_store_config = {
        max_look_back_period = "0s";
      };

      table_manager = {
        retention_deletes_enabled = false;
        retention_period = "0s";
      };

      compactor = {
        working_directory = "/var/lib/loki";
        shared_store = "filesystem";
        compactor_ring = {
          kvstore = {
            store = "inmemory";
          };
        };
      };
    };
    # user, group, dataDir, extraFlags, (configFile)
  };

  # promtail: port 3031 (8031)
  #
  services.promtail = {
    enable = true;
    configuration = {
      server = {
        http_listen_port = 3031;
        grpc_listen_port = 0;
      };
      positions = {
        filename = "/tmp/positions.yaml";
      };
      clients = [{
        url = "http://127.0.0.1:${toString config.services.loki.configuration.server.http_listen_port}/loki/api/v1/push";
      }];
      scrape_configs = [{
        job_name = "journal";
        journal = {
          max_age = "12h";
          labels = {
            job = "systemd-journal";
            host = "pihole";
          };
        };
        relabel_configs = [{
          source_labels = [ "__journal__systemd_unit" ];
          target_label = "unit";
        }];
      }];
    };
    # extraFlags
  };

  # grafana: port 3010 (8010)
  #
  services.grafana = {
    port = 3010;
    # WARNING: this should match nginx setup!
    # prevents "Request origin is not authorized"
    rootUrl = "http://192.168.1.10:8010"; # helps with nginx / ws / live

    protocol = "http";
    addr = "127.0.0.1";
    analytics.reporting.enable = false;
    enable = true;

    provision = {
      enable = true;
      datasources = [
        {
          name = "Prometheus";
          type = "prometheus";
          access = "proxy";
          url = "http://127.0.0.1:${toString config.services.prometheus.port}";
        }
        {
          name = "Loki";
          type = "loki";
          access = "proxy";
          url = "http://127.0.0.1:${toString config.services.loki.configuration.server.http_listen_port}";
        }
      ];
    };
  };

  # nginx reverse proxy
  services.nginx = {
    enable = true;
    recommendedProxySettings = true;
    recommendedOptimisation = true;
    recommendedGzipSettings = true;
    # recommendedTlsSettings = true;

    upstreams = {
      "grafana" = {
        servers = {
          "127.0.0.1:${toString config.services.grafana.port}" = {};
        };
      };
      "prometheus" = {
        servers = {
          "127.0.0.1:${toString config.services.prometheus.port}" = {};
        };
      };
      "loki" = {
        servers = {
          "127.0.0.1:${toString config.services.loki.configuration.server.http_listen_port}" = {};
        };
      };
      "promtail" = {
        servers = {
          "127.0.0.1:${toString config.services.promtail.configuration.server.http_listen_port}" = {};
        };
      };
    };

    virtualHosts.grafana = {
      locations."/" = {
        proxyPass = "http://grafana";
        proxyWebsockets = true;
      };
      listen = [{
        addr = "192.168.1.10";
        port = 8010;
      }];
    };

    virtualHosts.prometheus = {
      locations."/".proxyPass = "http://prometheus";
      listen = [{
        addr = "192.168.1.10";
        port = 8020;
      }];
    };

    # confirm with http://192.168.1.10:8030/loki/api/v1/status/buildinfo
    #     (or)     /config /metrics /ready
    virtualHosts.loki = {
      locations."/".proxyPass = "http://loki";
      listen = [{
        addr = "192.168.1.10";
        port = 8030;
      }];
    };

    virtualHosts.promtail = {
      locations."/".proxyPass = "http://promtail";
      listen = [{
        addr = "192.168.1.10";
        port = 8031;
      }];
    };
  };

Thanks for the configuration. I was in the process of doing this piece by piece and this helped a lot.

Small remark though, the current latest schema for loki is v12. So if you're setting this up from scratch, you might want to change it. Personally, I have no clue about the difference between the versions. You can have multiple schemas active depending on the date the data is associated with: https://grafana.com/docs/loki/latest/operations/storage/schema/