feat: add exclude-list for logs in /var/log (#216)

* feat: add exclude-list for logs in /var/log

* improve config option docs

* improve config option docs

* rename exclude_files to path_exclude

charmcraft.yaml

@@ -210,3 +210,17 @@ config:
         Ref: https://grafana.com/docs/agent/latest/static/configuration/flags/#report-information-usage
       type: boolean
       default: true
+    path_exclude:
+      description: >
+        Glob for a set of log files present in `/var/log` that should be ignored by Grafana Agent.
+
+        For example, `/var/log/**/{app_one,app_two}.log` will result in the agent ignoring both 
+        `/var/log/app_one.log` and `/var/log/app_two.log`.
+
+        Note that the value you provide here is not interpreted as a path, but rather as a glob matcher.
+        Specifically, if you want to exclude logs in the `/var/log/test` folder, you should set the 
+        config to `/var/log/test/**`.
+
+        Ref (__path_exclude__): https://grafana.com/docs/loki/latest/send-data/promtail/scraping/
+      type: string
+      default: ""

src/charm.py

@@ -474,6 +474,7 @@ def _additional_log_configs(self) -> List[Dict[str, Any]]:
                                 "targets": ["localhost"],
                                 "labels": {
                                     "__path__": "/var/log/**/*log",
+                                    "__path_exclude__": self.model.config.get("path_exclude"),
                                     "job": "varlog",
                                     **self._own_labels,
                                 },