I wanted to install Prometheus and Grafana on my new Kubernetes cluster, but in order for these packages to work they need someplace to store persistent data. I had run performance and scale tests on Ceph when I was working as a Cloud Architect at Seagate, and I’ve played with Rook during the past year, so I decided to install Rook+Ceph and use that for the Kubernetes cluster’s data storage.
Ceph is a distributed storage system that provides object, file, and block storage. On each storage node you’ll find a file system where Ceph stores objects and a Ceph OSD (Object storage daemon) process. On a Ceph cluster you’ll also find Ceph MON (monitoring) daemons, which ensure that the Ceph cluster remains highly available.
Rook acts as a Kubernetes orchestration layer for Ceph, deploying the OSD and MON processes as POD replica sets. From the Rook README
file:
Rook turns storage software into self-managing, self-scaling, and self-healing storage services. It does this by automating deployment, bootstrapping, configuration, provisioning, scaling, upgrading, migration, disaster recovery, monitoring, and resource management. Rook uses the facilities provided by the underlying cloud-native container management, scheduling and orchestration platform to perform its duties.
https://github.com/rook/rook/blob/master/README.md
When I created the cluster I built VMs with 40GB hard drives, so with 5 Kubernetes nodes that gives me ~200GB of storage on my cluster, most of which I’ll use for Ceph.
Installing Rook+Ceph
Installing Rook+Ceph is pretty straightforward. On my personal cluster I installed Rook+Ceph v0.9.0 by following these steps:
git clone git@github.com:rook/rook.git
cd rook
git checkout v0.9.0
cd cluster/examples/kubernetes/ceph
kubectl create -f operator.yaml
kubectl create -f cluster.yaml
Rook deploys the PODs in two namespaces, rook-ceph-system
and rook-ceph
. On my cluster it took about 2 minutes for the PODs to deploy, initialize, and get to a running state. While I was waiting for everything to finish I checked the POD status with:
$ kubectl -n rook-ceph-system get pod
NAME READY STATUS RESTARTS AGE
rook-ceph-agent-8tsq7 1/1 Running 0 2d20h
rook-ceph-agent-b6mgs 1/1 Running 0 2d20h
rook-ceph-agent-nff8n 1/1 Running 0 2d20h
rook-ceph-agent-vl4zf 1/1 Running 0 2d20h
rook-ceph-agent-vtpbj 1/1 Running 0 2d20h
rook-ceph-agent-xq5dv 1/1 Running 0 2d20h
rook-ceph-operator-85d64cfb99-hrnbs 1/1 Running 0 2d20h
rook-discover-9nqrp 1/1 Running 0 2d20h
rook-discover-b62ds 1/1 Running 0 2d20h
rook-discover-k77gw 1/1 Running 0 2d20h
rook-discover-kqknr 1/1 Running 0 2d20h
rook-discover-v2hhb 1/1 Running 0 2d20h
rook-discover-wbkkq 1/1 Running 0 2d20h
$ kubectl -n rook-ceph get pod
NAME READY STATUS RESTARTS AGE
rook-ceph-mgr-a-7d884ddc8b-kfxt9 1/1 Running 0 2d20h
rook-ceph-mon-a-77cbd865b8-ncg67 1/1 Running 0 2d20h
rook-ceph-mon-b-7cd4b9774f-js8n9 1/1 Running 0 2d20h
rook-ceph-mon-c-86778859c7-x2qg9 1/1 Running 0 2d20h
rook-ceph-osd-0-67fff79666-fcrss 1/1 Running 0 35h
rook-ceph-osd-1-58bd4ccbbf-lsxj9 1/1 Running 1 2d20h
rook-ceph-osd-2-bf99864b5-n4q7v 1/1 Running 0 2d20h
rook-ceph-osd-3-577466c968-j8gjr 1/1 Running 0 2d20h
rook-ceph-osd-4-6856c5c6c9-92tb6 1/1 Running 0 2d20h
rook-ceph-osd-5-8669577f6b-zqrq9 1/1 Running 0 2d20h
rook-ceph-osd-prepare-node1-xfbs7 0/2 Completed 0 2d20h
rook-ceph-osd-prepare-node2-c9f55 0/2 Completed 0 2d20h
rook-ceph-osd-prepare-node3-5g4nc 0/2 Completed 0 2d20h
rook-ceph-osd-prepare-node4-wj475 0/2 Completed 0 2d20h
rook-ceph-osd-prepare-node5-tf5bt 0/2 Completed 0 2d20h
Final tasks
Now I need to do two more things before I can install Prometheus and Grafana:
- I need to make Rook the default storage provider for my cluster.
- Since the Prometheus Helm chart requests volumes formatted with the XFS filesystem, I need to install XFS tools on all of my Ubuntu Kubernetes nodes. (XFS is not yet installed by Kubespray by default, although there’s currently a PR up that addresses that issue.)
Make Rook the default storage provider
To make Rook the default storage provider I just run a kubectl
command:
kubectl patch storageclass rook-ceph-block -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'
That updates the rook-ceph-block
storage class and makes it the default for storage on the cluster. Any applications that I install will use Rook+Ceph for their data storage if they don’t specify a specific storage class.
Install XFS tools
Normally I would not recommend running one-off commands on a cluster. If you want to make a change to a cluster, you should encode the change in a playbook so it’s applied every time you update the cluster or add a new node. That’s why I submitted a PR to Kubespray to address this problem.
However, since my Kubespray PR has not yet merged, and I built the cluster using Kubespray, and Kubespray uses Ansible, one of the easiest ways to install XFS tools on all hosts is by using the Ansible “run a single command on all hosts” feature:
cd kubespray
export ANSIBLE_REMOTE_USER=ansible
ansible kube-node -i inventory/mycluster/hosts.ini \
--become --become-user root \
-a 'apt-get install -y xfsprogs'
Deploy Prometheus and Grafana
Now that XFS is installed I can successfully deploy Prometheus and Grafana using Helm:
helm install --name prometheus stable/prometheus
helm install --name grafana stable/grafana
The Helm charts install Prometheus and Grafana and create persistent storage volumes on Rook+Ceph for Prometheus Server and Prometheus Alert Manager (formatted with XFS).
Prometheus dashboard
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Grafana dashboard
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Rook persistent volume for Prometheus Server
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Want to learn more?
If you’re interested in learning more about Rook, watch these videos from KubeCon 2018:
Introduction to Rook
Rook Deep Dive
Hope you find this useful.