feat(grafana-loki): init (#626)

Adds Grafana Loki as a service.

https://grafana.com/oss/loki/

Author: kashw2

doc/loki.md

@@ -0,0 +1,36 @@
+# Grafana Loki
+
+[Grafana Loki](https://grafana.com/docs/loki/latest/) is a log aggregation system designed to store and query logs from all your applications and infrastructure.
+
+## Getting Started
+
+```nix
+# In `perSystem.process-compose.<name>`
+{
+  services.loki."tp1".enable = true;
+}
+```
+
+{#tips}
+## Tips & Tricks
+
+{#usage-with-grafana}
+### Usage with Grafana
+
+To add loki as a datasource to #[[grafana]], we can use the following config:
+
+```nix
+{
+  services.loki.tp1.enable = true;
+  services.grafana.gf1 = {
+    enable = true;
+    datasources = with config.services.loki.tp1; [{
+      name = "Loki";
+      type = "loki";
+      access = "proxy";
+      url = "http://${httpAddress}:${builtins.toString httpPort}";
+    }];
+  };
+  settings.processes."gf1".depends_on."tp1".condition = "process_healthy";
+}
+```

doc/services.md

@@ -11,6 +11,7 @@ short-title: Services
 - [[elasticsearch]]#
 - [[grafana]]#
   - [[tempo]]
+  - [[loki]]
 - [[memcached]]#
 - [[minio]]#
 - [[mongodb]]#

nix/services/default.nix

@@ -28,6 +28,7 @@ in
     ./weaviate.nix
     ./searxng.nix
     ./tika.nix
+    ./loki.nix
     ./phpfpm.nix
     ./pubsub-emulator.nix
   ]) ++ [

nix/services/loki.nix

@@ -0,0 +1,123 @@
+{ pkgs
+, lib
+, name
+, config
+, ...
+}:
+let
+  inherit (lib) types;
+  yamlFormat = pkgs.formats.yaml { };
+in
+{
+  options = {
+    package = lib.mkPackageOption pkgs "grafana-loki" { };
+
+    httpAddress = lib.mkOption {
+      type = types.str;
+      description = "Which address to access loki from.";
+      default = "localhost";
+    };
+
+    httpPort = lib.mkOption {
+      type = types.port;
+      description = "Which HTTP port to loki should listen on.";
+      default = 3100;
+    };
+
+    grpcPort = lib.mkOption {
+      type = types.port;
+      description = "Which gRPC port to run loki should listen on.";
+      default = 9096;
+    };
+
+    extraConfig = lib.mkOption {
+      type = yamlFormat.type;
+      default = { };
+      description = ''
+        Specify the configuration for Loki in Nix.
+
+        See https://grafana.com/docs/loki/latest/configuration/ for available options.
+      '';
+    };
+
+    extraFlags = lib.mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      example = lib.literalExpression ''
+        [ "-config.expand-env=true" ]
+      '';
+      description = ''
+        Additional flags to pass to loki.
+      '';
+    };
+  };
+
+  config = {
+    outputs = {
+      settings = {
+        processes."${name}" =
+          let
+            lokiConfig = lib.recursiveUpdate
+              {
+                server = {
+                  http_listen_port = config.httpPort;
+                  grpc_listen_port = config.grpcPort;
+                };
+                common = {
+                  instance_addr = config.httpAddress;
+                  path_prefix = "${config.dataDir}/";
+                  storage = {
+                    filesystem = {
+                      chunks_directory = "${config.dataDir}/chunks";
+                      rules_directory = "${config.dataDir}/rules";
+                    };
+                  };
+                  replication_factor = 1;
+                  ring = {
+                    kvstore = {
+                      store = "inmemory";
+                    };
+                  };
+                };
+                schema_config = {
+                  configs = [
+                    {
+                      from = "2020-10-24";
+                      store = "tsdb";
+                      object_store = "filesystem";
+                      schema = "v13";
+                      index = {
+                        prefix = "index_";
+                        period = "24h";
+                      };
+                    }
+                  ];
+                };
+              }
+              config.extraConfig;
+            lokiConfigYaml = yamlFormat.generate "loki.yaml" lokiConfig;
+          in
+          {
+            command = "${config.package}/bin/loki --config.file=${lokiConfigYaml} ${lib.escapeShellArgs config.extraFlags}";
+            readiness_probe = {
+              http_get = {
+                host = config.httpAddress;
+                scheme = "http";
+                port = config.httpPort;
+                path = "/ready";
+              };
+              initial_delay_seconds = 15;
+              period_seconds = 10;
+              timeout_seconds = 2;
+              success_threshold = 1;
+              failure_threshold = 5;
+            };
+            availability = {
+              restart = "on_failure";
+              max_restarts = 5;
+            };
+          };
+      };
+    };
+  };
+}

nix/services/loki_test.nix

@@ -0,0 +1,26 @@
+{ pkgs, config, ... }:
+{
+  services.loki."tp1" = {
+    enable = true;
+  };
+
+  settings.processes.test =
+    let
+      cfg = config.services.loki."tp1";
+    in
+    {
+      command = pkgs.writeShellApplication {
+        runtimeInputs = [
+          cfg.package
+          pkgs.gnugrep
+          pkgs.curl
+        ];
+        text = ''
+          ROOT_URL="http://${cfg.httpAddress}:${builtins.toString cfg.httpPort}";
+          curl -sSfN $ROOT_URL/ready | grep "ready"
+        '';
+        name = "loki-test";
+      };
+      depends_on."tp1".condition = "process_healthy";
+    };
+}

test/flake.nix

@@ -60,6 +60,7 @@
             "${inputs.services-flake}/nix/services/redis-cluster_test.nix"
             "${inputs.services-flake}/nix/services/searxng_test.nix"
             "${inputs.services-flake}/nix/services/tempo_test.nix"
+            "${inputs.services-flake}/nix/services/loki_test.nix"
             "${inputs.services-flake}/nix/services/tika_test.nix"
             "${inputs.services-flake}/nix/services/weaviate_test.nix"
             "${inputs.services-flake}/nix/services/zookeeper_test.nix"