add loki and promtail for monitoring logs

modules/monitoring.nix

@@ -81,6 +81,109 @@ in
       port = 3001;
     };
 
+    services.loki = {
+      enable = true;
+      dataDir = "/var/lib/loki";
+      configuration = {
+        auth_enabled = false;
+
+        server.http_listen_port = 3002;
+
+        ingester = {
+          lifecycler = {
+            address = "127.0.0.1";
+            ring = {
+              kvstore.store = "inmemory";
+              replication_factor = 1;
+            };
+            final_sleep = "0s";
+          };
+          chunk_idle_period = "5m";
+          chunk_retain_period = "30s";
+        };
+
+        schema_config = {
+          configs = [
+            {
+              from = "2018-04-15";
+              store = "boltdb";
+              object_store = "filesystem";
+              schema = "v9";
+              index.prefix = "index_";
+              index.period = "168h";
+            }
+          ];
+        };
+
+        storage_config = {
+          boltdb.directory = "/tmp/loki/index";
+          filesystem.directory = "/tmp/loki/chunks";
+        };
+
+        limits_config = {
+          enforce_metric_name = false;
+          reject_old_samples = true;
+          reject_old_samples_max_age = "168h";
+        };
+
+        chunk_store_config = {
+          max_look_back_period = 0;
+        };
+
+        table_manager = {
+          chunk_tables_provisioning = {
+            inactive_read_throughput = 0;
+            inactive_write_throughput = 0;
+            provisioned_read_throughput = 0;
+            provisioned_write_throughput = 0;
+          };
+          index_tables_provisioning = {
+            inactive_read_throughput = 0;
+            inactive_write_throughput = 0;
+            provisioned_read_throughput = 0;
+            provisioned_write_throughput = 0;
+          };
+          retention_deletes_enabled = false;
+          retention_period = 0;
+        };
+      };
+    };
+
+    services.promtail = {
+      enable = true;
+      configuration = {
+        server = {
+          http_listen_port = 9080;
+          grpc_listen_port = 0;
+        };
+
+        positions.filename = "/tmp/positions.yaml";
+
+        client.url = "http://localhost:${toString config.services.loki.configuration.server.http_listen_port}/api/prom/push";
+
+        scrape_configs = [
+          {
+            job_name = "systemd";
+            journal = {
+              json = false;
+              max_age = "12h";
+              path = "/var/log/journal";
+              # matches = "_TRANSPORT=kernel";
+              labels = {
+                job = "systemd-journal";
+              };
+            };
+            relabel_configs = [
+              {
+                source_labels = [ "__journal__systemd_unit" ];
+                target_label = "unit";
+              }
+            ];
+          }
+        ];
+      };
+    };
+
     services.nginx = {
       enable = true;