From 7b804450a31610c8d100c70fa9647ba2ac7e67cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torjus=20H=C3=A5kestad?= <torjus@usit.uio.no>
Date: Fri, 13 Feb 2026 23:40:14 +0100
Subject: [PATCH] promtail: add hostname/tier/role labels and journal priority
 level mapping

Align Promtail labels with Prometheus by adding hostname, tier, and role
static labels to both journal and varlog scrape configs. Add pipeline
stages to map journal PRIORITY field to a level label for reliable
severity filtering across the fleet.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 system/monitoring/logs.nix | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/system/monitoring/logs.nix b/system/monitoring/logs.nix
index 2d5c131..68d9cac 100644
--- a/system/monitoring/logs.nix
+++ b/system/monitoring/logs.nix
@@ -1,4 +1,12 @@
-{ config, ... }:
+{ config, lib, ... }:
+let
+  hostLabels = {
+    hostname = config.networking.hostName;
+    tier = config.homelab.host.tier;
+  } // lib.optionalAttrs (config.homelab.host.role != null) {
+    role = config.homelab.host.role;
+  };
+in
 {
   # Configure journald
   services.journald = {
@@ -32,17 +40,26 @@
             json = true;
             labels = {
               job = "systemd-journal";
-            };
+            } // hostLabels;
           };
           relabel_configs = [
             {
               source_labels = [ "__journal__systemd_unit" ];
               target_label = "systemd_unit";
             }
+          ];
+          pipeline_stages = [
+            # Extract PRIORITY from journal JSON
+            { json.expressions.priority = "PRIORITY"; }
+            # Map numeric PRIORITY to level name
             {
-              source_labels = [ "__journal__hostname" ];
-              target_label = "host";
+              template = {
+                source = "priority";
+                template = ''{{ if or (eq .Value "0") (eq .Value "1") (eq .Value "2") }}critical{{ else if eq .Value "3" }}error{{ else if eq .Value "4" }}warning{{ else if eq .Value "5" }}notice{{ else if eq .Value "6" }}info{{ else if eq .Value "7" }}debug{{ end }}'';
+              };
             }
+            # Attach as level label
+            { labels.level = "priority"; }
           ];
         }
         {
@@ -53,8 +70,7 @@
               labels = {
                 job = "varlog";
                 __path__ = "/var/log/**/*.log";
-                hostname = "${config.networking.hostName}";
-              };
+              } // hostLabels;
             }
           ];
         }