Merge pull request #63569 from libander/OBSDOCS-169

OBSDOCS-169 - Loki Tolerations

Author: stevsmit

logging/log_storage/cluster-logging-loki.adoc

@@ -18,6 +18,8 @@ include::modules/logging-loki-restart-hardening.adoc[leveloffset=+1]
 
 include::modules/logging-loki-reliability-hardening.adoc[leveloffset=+1]
 
+include::modules/logging-loki-pod-placement.adoc[leveloffset=+1]
+
 [role="_additional-resources"]
 .Additional resources
 * link:https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.24/#podantiaffinity-v1-core[`PodAntiAffinity` v1 core Kubernetes documentation]

modules/logging-loki-pod-placement.adoc

@@ -0,0 +1,209 @@
+// Module included in the following assemblies:
+// logging/log_storage/cluster-logging-loki.adoc
+
+:_mod-docs-content-type: CONCEPT
+[id="logging-loki-pod-placement_{context}"]
+= Loki pod placement
+You can control which nodes the Loki pods run on, and prevent other workloads from using those nodes, by using tolerations or node selectors on the pods.
+
+You can apply tolerations to the log store pods with the LokiStack custom resource (CR) and apply taints to a node with the node specification. A taint on a node is a `key:value` pair that instructs the node to repel all pods that do not allow the taint. Using a specific `key:value` pair that is not on other pods ensures that only the log store pods can run on that node.
+
+.Example LokiStack with node selectors
+[source,yaml]
+----
+apiVersion: loki.grafana.com/v1
+kind: LokiStack
+metadata:
+  name: logging-loki
+  namespace: openshift-logging
+spec:
+# ...
+  template:
+    compactor: # <1>
+      nodeSelector:
+        node-role.kubernetes.io/infra: "" # <2>
+    distributor:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+    gateway:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+    indexGateway:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+    ingester:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+    querier:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+    queryFrontend:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+    ruler:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+# ...
+----
+
+<1> Specifies the component pod type that applies to the node selector.
+<2> Specifies the pods that are moved to nodes containing the defined label.
+
+In the previous example configuration, all Loki pods are moved to nodes containing the `node-role.kubernetes.io/infra: ""` label.
+
+
+.Example LokiStack CR with node selectors and tolerations
+[source,yaml]
+----
+apiVersion: loki.grafana.com/v1
+kind: LokiStack
+metadata:
+  name: logging-loki
+  namespace: openshift-logging
+spec:
+# ...
+  template:
+    compactor:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    distributor:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    indexGateway:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    ingester:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    querier:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    queryFrontend:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    ruler:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+    gateway:
+      nodeSelector:
+        node-role.kubernetes.io/infra: ""
+      tolerations:
+      - effect: NoSchedule
+        key: node-role.kubernetes.io/infra
+        value: reserved
+      - effect: NoExecute
+        key: node-role.kubernetes.io/infra
+        value: reserved
+# ...
+----
+
+To configure the `nodeSelector` and `tolerations` fields of the LokiStack (CR), you can use the [command]`oc explain` command to view the description and fields for a particular resource:
+
+[source,terminal]
+----
+$ oc explain lokistack.spec.template
+----
+
+.Example output
+[source,text]
+----
+KIND:     LokiStack
+VERSION:  loki.grafana.com/v1
+
+RESOURCE: template <Object>
+
+DESCRIPTION:
+     Template defines the resource/limits/tolerations/nodeselectors per
+     component
+
+FIELDS:
+   compactor	<Object>
+     Compactor defines the compaction component spec.
+
+   distributor	<Object>
+     Distributor defines the distributor component spec.
+...
+----
+
+For more detailed information, you can add a specific field:
+
+[source,terminal]
+----
+$ oc explain lokistack.spec.template.compactor
+----
+
+.Example output
+[source,text]
+----
+KIND:     LokiStack
+VERSION:  loki.grafana.com/v1
+
+RESOURCE: compactor <Object>
+
+DESCRIPTION:
+     Compactor defines the compaction component spec.
+
+FIELDS:
+   nodeSelector	<map[string]string>
+     NodeSelector defines the labels required by a node to schedule the
+     component onto it.
+...
+----