Cloud Logging lets you analyze or route logs from your workloads according to multiple criteria, such as cluster name, Kubernetes namespace, or Kubernetes Pod labels. Hierarchy Controller extends these criteria to include both hierarchical and abstract namespaces by propagating your cluster's tree labels to your Pods, making them available to Logging.
For example, consider a workload running in a namespace from the example repository.
Hierarchy Controller lets you select logs generated by any workload
that is a descendant of
online, or any other abstract
namespace. This includes not only the workloads in namespaces located in the Git
repository such as
shipping-prod, but also any Hierarchy Controller
subnamespace that you might create as a descendant of those namespaces.
Enabling hierarchical observability
Hierarchical observability is provided by Hierarchy Controller. To enable hierarchical observability, do the following:
In the configuration file for the Config Management Operator, in the
spec.hierarchyControllerobject, set the value of both
# config-management.yaml apiVersion: configmanagement.gke.io/v1 kind: ConfigManagement metadata: name: config-management spec: # Set to true to enable hierarchical namespaces and logging hierarchyController: enabled: true enablePodTreeLabels: true # ...other fields...
Apply the configuration:
kubectl apply -f config-management.yaml
After about a minute, Hierarchy Controller and hierarchical observability become usable on your cluster.
Verifying the installation
When hierarchical observability is enabled, Hierarchy Controller installs a mutating admission webhook to add the tree labels onto the Pods. These labels are then ingested by Cloud Logging and are made available to analyze or route logs. These labels can also be ingested by any other system that understands Kubernetes labels.
To verify that hierarchical logging is enabled:
Start a workload in any namespace, such as the following:
kubectl run websvr --image=nginx -n default --generator=run-pod/v1
Inspect the Pod and verify that it contains the
kubectl describe pod -n default websvr
Name: websvr Namespace: default # ...other fields... Labels: default.tree.hnc.x-k8s.io/depth=0 # This is the Pod tree label run=websvr # ...other fields...
Clean up the workload:
kubectl delete pod -n default websvr
Using hierarchical workload observability
After Pod tree labels are enabled, they can be used to improve hierarchical workload observability both inside clusters and in other Google Cloud products.
Querying Pods by hierarchy
Any Kubernetes operation that includes a label selector can be used to query Pod
tree labels. For example, to view all Pods in all namespaces that are running in
a descendant of the
default namespace, use the following query:
kubectl get pods --all-namespaces -l default.tree.hnc.x-k8s.io/depth
Output based on the previous workload:
NAMESPACE NAME READY STATUS RESTARTS AGE default websvr 1/1 Running 0 70s
Filtering logs by hierarchy
Cloud Logging supports a slightly different format for labels than
Kubernetes. For example, to search for any workload running in a descendant of
default namespace, instead of searching for the Kubernetes label
default.tree.hnc.x-k8s.io/depth, Cloud Logging expects a
query similar to the following in
the Google Cloud Console:
Alternatively, you can use a similar filter in the
gcloud command-line tool:
gcloud logging read "resource.type=k8s_container AND labels.k8s-pod/default_tree_hnc_x-k8s_io/depth!=''"
Limitations of hierarchical monitoring
The following are limitations of hierarchical monitoring.
Changes to the hierarchy are ignored
Pod tree labels are added to Pods when they are created and are not modified after the Pod starts running. This means that Pods that were started before hierarchical monitoring was enabled do not receive Pod tree labels.
In addition, any Pods whose hierarchy changes after the Pod was started—for example, by using Hierarchy Controller to change the parent of a namespace—will not have its labels updated. While hierarchy modifications are typically quite rare, if this situation occurs and is causing a problem, modify the hierarchy and then restart all Pods.
Pods are still created even if labels cannot be applied
Hierarchical monitoring does not apply to Pods running in key system namespaces
hnc-system. However, the webhook configuration itself
has no way to exclude these namespaces. Therefore, if Hierarchy Controller
encounters a problem, Pod creation in all namespaces could be impacted.
As a result, rather than risk a cluster-wide outage, if Hierarchy Controller
cannot process a Pod within two seconds, the webhook fails and allows the Pod to
be created without the labels. Such webhook failures can be monitored via the
Kubernetes API server
by looking for failures of the
podlabel.hierarchycontroller.configmanagement.gke.io mutating admission
- Learn more about common tasks that you might want to use HNC to accomplish in the HNC User Guide: How-to.