Helm: Add priorityClassName for Grafana Agent and Loki Canary (#8506)

**What this PR does / why we need it**:

- Allow configuring PriorityClassName for the GrafanaAgent daemonset
- Allow configuring PriorityClassName for the loki canary daemonset
without also configuring for read deployment
- Helpful when an administrator wants to prioritize logging on their
nodes

**Special notes for your reviewer**:

- Used _coalese_ style like it was already in the case of loki canary
- For loki canary, specifying on the canary takes higher precedence than
on the reader, but lower than global
- For grafana agent, global takes precedence over grafana agent to match
the existing style, but maintainers might consider flipping that around
so that most-specific is also most-prioritized

**Checklist**
- [x] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide

---------

Co-authored-by: Michel Hollands <42814411+MichelHollands@users.noreply.github.com>

docs/sources/installation/helm/reference.md

@@ -2428,6 +2428,15 @@ null
 			<td><pre lang="json">
 {}
 </pre>
+</td>
+		</tr>
+		<tr>
+			<td>monitoring.lokiCanary.priorityClassName</td>
+			<td>string</td>
+			<td>The name of the PriorityClass for loki-canary pods</td>
+			<td><pre lang="json">
+null
+</pre>
 </td>
 		</tr>
 		<tr>
@@ -2545,6 +2554,15 @@ true
 			<td><pre lang="json">
 {}
 </pre>
+</td>
+		</tr>
+		<tr>
+			<td>monitoring.selfMonitoring.grafanaAgent.priorityClassName</td>
+			<td>string</td>
+			<td>The name of the PriorityClass for GrafanaAgent pods</td>
+			<td><pre lang="json">
+null
+</pre>
 </td>
 		</tr>
 		<tr>

production/helm/loki/CHANGELOG.md

@@ -13,6 +13,9 @@ Entries should include a reference to the pull request that introduced the chang
 
 [//]: # (<AUTOMATED_UPDATES_LOCATOR> : do not remove this line. This locator is used by the CI pipeline to automatically create a changelog entry for each new Loki release. Add other chart versions and respective changelog entries bellow this line.)
 
+## 5.8.3
+
+- [ENHANCEMENT] Add priorityClassName for Grafana Agent and Loki Canary
 
 ## 5.8.2
 

production/helm/loki/Chart.yaml

@@ -3,7 +3,7 @@ name: loki
 description: Helm chart for Grafana Loki in simple, scalable mode
 type: application
 appVersion: 2.8.2
-version: 5.8.2
+version: 5.8.3
 home: https://grafana.github.io/helm-charts
 sources:
   - https://github.com/grafana/loki

production/helm/loki/README.md

@@ -1,6 +1,6 @@
 # loki
 
-![Version: 5.8.2](https://img.shields.io/badge/Version-5.8.2-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 2.8.2](https://img.shields.io/badge/AppVersion-2.8.2-informational?style=flat-square)
+![Version: 5.8.3](https://img.shields.io/badge/Version-5.8.3-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 2.8.2](https://img.shields.io/badge/AppVersion-2.8.2-informational?style=flat-square)
 
 Helm chart for Grafana Loki in simple, scalable mode
 

production/helm/loki/templates/loki-canary/_helpers.tpl

@@ -30,10 +30,10 @@ Docker image name for loki-canary
 {{- end -}}
 
 {{/*
-canry priority class name
+canary priority class name
 */}}
 {{- define "loki-canary.priorityClassName" -}}
-{{- $pcn := coalesce .Values.global.priorityClassName .Values.read.priorityClassName -}}
+{{- $pcn := coalesce .Values.global.priorityClassName .Values.monitoring.lokiCanary.priorityClassName .Values.read.priorityClassName -}}
 {{- if $pcn }}
 priorityClassName: {{ $pcn }}
 {{- end }}

production/helm/loki/templates/monitoring/_helpers-monitoring.tpl

@@ -35,3 +35,13 @@ Convert a recording rule group to yaml
     {{- toYaml .rules | nindent 4 }}
 {{- end }}
 {{- end }}
+
+{{/*
+GrafanaAgent priority class name
+*/}}
+{{- define "grafana-agent.priorityClassName" -}}
+{{- $pcn := coalesce .Values.global.priorityClassName .Values.monitoring.selfMonitoring.grafanaAgent.priorityClassName -}}
+{{- if $pcn }}
+priorityClassName: {{ $pcn }}
+{{- end }}
+{{- end }}

production/helm/loki/templates/monitoring/grafana-agent.yaml

@@ -16,6 +16,7 @@ metadata:
 spec:
   serviceAccountName: {{ include "loki.fullname" $ }}-grafana-agent
   enableConfigReadAPI: {{ .enableConfigReadAPI }}
+  {{- include "grafana-agent.priorityClassName" $ | nindent 2 }}
   logs:
     instanceSelector:
       matchLabels:

production/helm/loki/values.yaml

@@ -608,6 +608,8 @@ monitoring:
       labels: {}
       # -- Enable the config read api on port 8080 of the agent
       enableConfigReadAPI: false
+      # -- The name of the PriorityClass for GrafanaAgent pods
+      priorityClassName: null
     # PodLogs configuration
     podLogs:
       # -- PodLogs annotations
@@ -645,6 +647,8 @@ monitoring:
     nodeSelector: {}
     # -- Tolerations for canary pods
     tolerations: []
+    # -- The name of the PriorityClass for loki-canary pods
+    priorityClassName: null
     # -- Image to use for loki canary
     image:
       # -- The Docker registry