roles/dockerserver: initial grafana alloy config

roles/dockerserver.nix

@@ -11,6 +11,8 @@ with lib;
 
 let
   cfg = config.dockerserver;
+  refreshInterval = "5s";
+  dockerSocket = "/run/docker.sock";
 in
 {
   options.dockerserver = {
@@ -33,6 +35,43 @@ in
       };
     };
 
+    environment.etc."alloy/docker.alloy".text = ''
+      discovery.docker "docker_containers" {
+      host             = "${dockerSocket}"
+      refresh_interval = "${refreshInterval}"
+      }
+
+      discovery.relabel "docker_relabel" {
+      	targets = []
+
+      	rule {
+      		source_labels = ["__meta_docker_container_name"]
+      		regex         = "/(.*)"
+      		target_label  = "container"
+      	}
+
+      	rule {
+      		source_labels = ["__meta_docker_container_log_stream"]
+      		target_label  = "logstream"
+      	}
+
+      	rule {
+      		source_labels = ["__meta_docker_container_label_logging_jobname"]
+      		target_label  = "job"
+      	}
+      }
+
+      loki.source.docker "docker_logs" {
+      	host             = "${dockerSocket}"
+      	targets          = discovery.docker.docker_containers.targets
+      	forward_to       = [loki.write.default.receiver]
+      	relabel_rules    = discovery.relabel.docker_relabel.rules
+      	refresh_interval = "${refreshInterval}"
+      }
+    '';
+
+    systemd.services.alloy.serviceConfig.SupplementaryGroups = [ "docker" ];
+
     users.users.etorres.extraGroups = [ "docker" ];
   };
 }