Prometheus Monitoring
Each Rook Ceph cluster has some built in metrics collectors/exporters for monitoring with Prometheus.
If you do not have Prometheus running, follow the steps below to enable monitoring of Rook. If your cluster already contains a Prometheus instance, it will automatically discover Rook's scrape endpoint using the standard prometheus.io/scrape
and prometheus.io/port
annotations.
Attention
This assumes that the Prometheus instances is searching all your Kubernetes namespaces for Pods with these annotations. If prometheus is already installed in a cluster, it may not be configured to watch for third-party service monitors such as for Rook. Normally you should be able to add the prometheus annotations prometheus.io/scrape=true
and prometheus.io/port={port}
and prometheus would automatically configure the scrape points and start gathering metrics. If prometheus isn't configured to do this, see the prometheus operator docs.
Prometheus Operator¶
First the Prometheus operator needs to be started in the cluster so it can watch for our requests to start monitoring Rook and respond by deploying the correct Prometheus pods and configuration. A full explanation can be found in the Prometheus operator repository on GitHub, but the quick instructions can be found here:
This will start the Prometheus operator, but before moving on, wait until the operator is in the Running
state:
Once the Prometheus operator is in the Running
state, proceed to the next section to create a Prometheus instance.
Prometheus Instances¶
With the Prometheus operator running, we can create service monitors that will watch the Rook cluster.
There are two sources for metrics collection:
- Prometheus manager module: It is responsible for exposing all metrics other than ceph daemons performance counters.
- Ceph exporter: It is responsible for exposing only ceph daemons performance counters as prometheus metrics.
From the root of your locally cloned Rook repo, go the monitoring directory:
Create the service monitor as well as the Prometheus server pod and service:
Ensure that the Prometheus server pod gets created and advances to the Running
state before moving on:
Dashboard config¶
Configure the Prometheus endpoint so the dashboard can retrieve metrics from Prometheus with two settings: - prometheusEndpoint
: The url of the Prometheus instance - prometheusEndpointSSLVerify
: Whether SSL should be verified if the Prometheus server is using https
The following command can be used to get the Prometheus url:
Following is an example to configure the Prometheus endpoint in the CephCluster CR.
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Note
It is not recommended to consume storage from the Ceph cluster for Prometheus. If the Ceph cluster fails, Prometheus would become unresponsive and thus not alert you of the failure.
Prometheus Web Console¶
Once the Prometheus server is running, you can open a web browser and go to the URL that is output from this command:
You should now see the Prometheus monitoring website.
Click on Graph
in the top navigation bar.
In the dropdown that says insert metric at cursor
, select any metric you would like to see, for example ceph_cluster_total_used_bytes
Click on the Execute
button.
Below the Execute
button, ensure the Graph
tab is selected and you should now see a graph of your chosen metric over time.
Prometheus Consoles¶
You can find Prometheus Consoles for and from Ceph here: GitHub ceph/cephmetrics - dashboards/current directory.
A guide to how you can write your own Prometheus consoles can be found on the official Prometheus site here: Prometheus.io Documentation - Console Templates.
Prometheus Alerts¶
To enable the Ceph Prometheus alerts via the helm charts, set the following properties in values.yaml:
- rook-ceph chart:
monitoring.enabled: true
- rook-ceph-cluster chart:
monitoring.enabled: true
monitoring.createPrometheusRules: true
Alternatively, to enable the Ceph Prometheus alerts with example manifests follow these steps:
-
Create the RBAC and prometheus rules:
-
Make following changes to your CephCluster object (e.g.,
cluster.yaml
). -
Deploy or update the CephCluster object.
Note
This expects the Prometheus Operator and a Prometheus instance to be pre-installed by the admin.
Customize Alerts¶
The Prometheus alerts can be customized with a post-processor using tools such as Kustomize. For example, first extract the helm chart:
Now create the desired customization configuration files. This simple example will show how to update the severity of a rule, add a label to a rule, and change the for
time value.
Create a file named kustomization.yaml:
Create a file named modifications.yaml
Finally, run kustomize to update the desired prometheus rules:
Grafana Dashboards¶
The dashboards have been created by @galexrt. For feedback on the dashboards please reach out to him on the Rook.io Slack.
Note
The dashboards are only compatible with Grafana 7.2.0 or higher. Also note that the dashboards are updated from time to time, to fix issues and improve them.
The following Grafana dashboards are available:
Updates and Upgrades¶
When updating Rook, there may be updates to RBAC for monitoring. It is easy to apply the changes with each update or upgrade. This should be done at the same time you update Rook common resources like common.yaml
.
Hint
This is updated automatically if you are upgrading via the helm chart
Teardown¶
To clean up all the artifacts created by the monitoring walk-through, copy/paste the entire block below (note that errors about resources "not found" can be ignored):
Then the rest of the instructions in the Prometheus Operator docs can be followed to finish cleaning up.
Special Cases¶
Tectonic Bare Metal¶
Tectonic strongly discourages the tectonic-system
Prometheus instance to be used outside their intentions, so you need to create a new Prometheus Operator yourself. After this you only need to create the service monitor as stated above.
CSI Liveness¶
To integrate CSI liveness and grpc into ceph monitoring we will need to deploy a service and service monitor.
This will create the service monitor to have prometheus monitor CSI
Collecting RBD per-image IO statistics¶
RBD per-image IO statistics collection is disabled by default. This can be enabled by setting enableRBDStats: true
in the CephBlockPool spec. Prometheus does not need to be restarted after enabling it.
Using custom label selectors in Prometheus¶
If Prometheus needs to select specific resources, we can do so by injecting labels into these objects and using it as label selector.
Horizontal Pod Scaling using Kubernetes Event-driven Autoscaling (KEDA)¶
Using metrics exported from the Prometheus service, the horizontal pod scaling can use the custom metrics other than CPU and memory consumption. It can be done with help of Prometheus Scaler provided by the KEDA. See the KEDA deployment guide for details.
Following is an example to autoscale RGW:
Warning
During reconciliation of a CephObjectStore
, the Rook Operator will reset the replica count for RGW which was set by horizontal pod scaler. The horizontal pod autoscaler will change the again once it re-evaluates the rule. This can result in a performance hiccup of several seconds after a reconciliation. This is briefly discussed (here)[https://github.com/rook/rook/issues/10001]