Best Practise Kubernetes

DevOpsDays Amsterdam 2018

Andy Repton, Mission Critical Engineer @ Schuberg Philis

@SethKarlo

arepton@schubergphilis.com

Overview

  • Workshop 1: Installing Helm
  • Workshop 2: HA with K8S: Creating a Wordpress Website
  • Workshop 3: Readiness and Liveness Probes
  • Workshop 4: Quotas and Limits
  • Workshop 5: AuthZ RBAC Challenge
  • Deep Dive Services quiz
  • Questions/Wrap up

Thank you

They have very kindly let us use their AWS account

Please do not abuse it!!

Will this be a serious and sober workshop?

Getting setup

If you do not have kubectl or helm installed already, there is a how-to in the 1-Installing_Helm folder in the repo you just cloned

Link to the repository: https://bit.ly/2KiLT8d

(Please clone this locally)

Number time

Connecting

cd best-practise-kubernetes

./workshop.sh connect user22

mv ~/.kube/config my_kube_config_backup
mv user22.kubeconfig ~/.kube/config

There is a script we'll use called ./workshop.sh

If you feel more comfortable, you can directly download your kubeconfig from this link:

https://s3-eu-west-1.amazonaws.com/devopsdays-ams-public/${cluster_name}.kubeconfig

Connecting

$ kubectl get componentstatus
NAME                 STATUS    MESSAGE              ERROR
scheduler            Healthy   ok
controller-manager   Healthy   ok
etcd-1               Healthy   {"health": "true"}
etcd-0               Healthy   {"health": "true"}

Confirm you can connect to your cluster:

Put your hand up or call out if you cannot connect

Installing

helm init

kubectl create serviceaccount --namespace kube-system tiller

kubectl create clusterrolebinding tiller-cluster-rule\
    --clusterrole=cluster-admin --serviceaccount=kube-system:tiller

kubectl patch deploy --namespace kube-system tiller-deploy \
    -p '{"spec":{"template":{"spec":{"serviceAccount":"tiller"}}}}'

Helm is the Kubernetes Package manager

Confirm it's running:

 $ kubectl -n kube-system get pods | grep tiller
tiller-deploy-7ccf99cd64-89mvb                                        1/1       Running   0          13s

High Availability in Kubernetes

Making a WordPress site

Deployments and Replica Sets

  • Deployments contain Replica Sets
  • Can have multiple versions (Editing the deployment will create a new version)
  • The old replica set will be scaled down and the new one scaled up

Deploying our site

helm install --name first-wordpress --set wordpressBlogName="Andy's blog" \
    stable/wordpress

Wasn't that easy?

$ kubectl get svc first-wordpress-wordpress --namespace default -o wide
NAME                        TYPE           CLUSTER-IP       EXTERNAL-IP                                                               PORT(S)                      AGE       SELECTOR
first-wordpress-wordpress   LoadBalancer   100.70.163.174   a384579b1786911e895d60a0898d90d2-2143390945.eu-west-1.elb.amazonaws.com   80:32756/TCP,443:32656/TCP   1m        app=first-wordpress-wordpress

Grab this and let's open up our shiny new Wordpress website in your browser

Question: Is this HA?

Remember to change the name to your own!

Debugging outages

$ kubectl get events

We can use the 'get events' command to find out more

$ kubectl get events  --sort-by='.metadata.creationTimestamp'  -o 'go-template={{range .items}}{{.involvedObject.name}}{{"\t"}}{{.involvedObject.kind}}{{"\t"}}{{.message}}{{"\t"}}{{.reason}}{{"\t"}}{{.type}}{{"\t"}}{{.firstTimestamp}}{{"\n"}}{{end}}'

###
ip-172-20-63-237.eu-west-1.compute.internal	Node	Node ip-172-20-63-237.eu-west-1.compute.internal has been rebooted, boot id: 4bb677ca-c309-47b1-b5d3-0c1fec21d75a	Rebooted	Warning	2018-06-25T11:20:56Z
###

Or, sorted by timestamp:

We can see our pods got restarted, and our website went down.

Stateful Sets

Some applications can't just be scaled up to multiple replicas

 

Stateful Sets guarantee ordering and scheduling of your pods

 

With a database this is important to ensure that replicas are created in a controlled manner.

Clean up our site

$ helm del --purge first-wordpress

MariaDB StatefulSet

$ helm install --name my-wordpress-db
    --set root.password=devopsdays,
    db.user=bn_wordpress,
    db.password=devopsdays,
    db.name=devopsdays,
    slave.replicas=2
  stable/mariadb

helm's --set option

We can use the --set option to overwrite variables in our helm charts on the fly. Here, we've adjusted the database name and the root password

HA WordPress

$ helm install --name my-wordpress
--set wordpressBlogName="Andy's blog",
  mariadb.enabled=false,
  externalDatabase.host=my-wordpress-db-mariadb,
  externalDatabase.password=devopsdays,
  externalDatabase.database=devopsdays,
  externalDatabase.port=3306,
  persistence.accessMode=ReadWriteMany
stable/wordpress
  • We want enough replicas to spread across our nodes.
  • Wordpress is as simple as scaling up the replica set!
  • We'll use a 'ReadWriteMany' disk to share the disk across the replicas. Once again, set your blog name!
$ kubectl get svc -o wide

Once again get the service and open in your browser

Debugging

Debugging

$ kubectl describe pod my-wordpress

Events:
 Type     Reason            Age                From               Message
 ----     ------            ----               ----               -------
 Warning  FailedScheduling  12s (x13 over 2m)  default-scheduler  PersistentVolumeClaim is not bound: "my-wordpress-wordpress" (repeated 3 times)

Using kubectl describe to debug:

Ok, something to do with the pvc:

$ kubectl describe pvc my-wordpress-wordpress

Events:
 Type     Reason              Age                From                         Message
 ----     ------              ----               ----                         -------
 Warning  ProvisioningFailed  11s (x15 over 3m)  persistentvolume-controller  
Failed to provision volume with StorageClass "gp2": invalid AccessModes [ReadWriteMany]: only AccessModes [ReadWriteOnce] are supported

Third time's the charm

$ helm del --purge my-wordpress

Let's clean up once again:

We'll add a basic NFS provisioner to our cluster: 

$ helm install --name my-nfs stable/nfs-server-provisioner

And now we can redeploy WordPress, now using NFS:

$ helm install --name my-wordpress 
--set wordpressBlogName="Andy's blog",
  mariadb.enabled=false,
  externalDatabase.host=my-wordpress-db-mariadb,
  externalDatabase.password=devopsdays,
  externalDatabase.database=devopsdays,
  externalDatabase.port=3306,
  persistence.storageClass=nfs 
stable/wordpress

Confirm our PVC is using NFS:

$ kubectl get pvc my-wordpress-wordpress
NAME                                    STATUS    VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
my-wordpress-wordpress                  Bound     pvc-f80012f7-732b-11e8-926e-0a33561ebb8c   10Gi       RWO            nfs            52s

Scale up!

Now that we have our website running again, let's increase the replica count

$ kubectl scale deployment my-wordpress-wordpress --replicas=3

Confirm our replicas are on different nodes:

$ kubectl get pods -o wide
NAME                                      READY     STATUS    RESTARTS   AGE       IP            NODE
my-wordpress-wordpress-66b7d5b545-cvzqd   0/1       Running   0          31s       100.96.1.10   ip-172-20-43-243.eu-west-1.compute.internal
my-wordpress-wordpress-66b7d5b545-r7cpq   0/1       Running   0          31s       100.96.2.4    ip-172-20-40-196.eu-west-1.compute.internal
my-wordpress-wordpress-66b7d5b545-v6cg2   1/1       Running   0          2m        100.96.2.3    ip-172-20-40-196.eu-west-1.compute.internal

So, we're HA now. Right?

Some things to consider:

  • Pod Anti Affinity to force pods away from each other
  • What happens if the NFS provisioner dies?

Cleanup

Before we move on let's clean up ready for Workshop 3. The script will do this for you:

$ ./workshop.sh workshop2-cleanup
Cleaning up Workshop2, this will take a couple of minutes
deployment "my-wordpress-wordpress" scaled
release "my-wordpress" deleted
release "my-nfs" deleted
release "my-wordpress-db" deleted
persistentvolumeclaim "data-first-wordpress-mariadb-0" deleted
persistentvolumeclaim "data-my-wordpress-db-mariadb-master-0" deleted
persistentvolumeclaim "data-my-wordpress-db-mariadb-slave-0" deleted
persistentvolumeclaim "data-my-wordpress-db-mariadb-slave-1" deleted
persistentvolumeclaim "first-wordpress-wordpress" deleted

Readiness and Liveness probes

Running an image

Using kubectl run, we can quickly create a new deployment

$ kubectl run devopsdays --image sethkarlo/nginx:dod-first

Especially for DevOpsDays, I've created a custom nginx image for us

Then use the very helpful port-forward to check our webpage

$ kubectl port-forward devopsdays-7f9bdcc9c5-nm7ch 8080:80

Get the name of your pod:

$ kubectl get pods
NAME                          READY     STATUS    RESTARTS   AGE
devopsdays-7f9bdcc9c5-hwbnh   1/1       Running   0          2m

Readiness Probes

Once we've all opened the site and given it the proper admiration, let's upgrade

$ kubectl patch deployment devopsdays -p '{"spec":{"template":{"spec":{"containers":[{"name":"devopsdays","image":"sethkarlo/nginx:dod-second"}]}}}}'

Patch is a very useful command to quickly update deployments.

Let's check our new image:

$ kubectl get pods
NAME                                      READY     STATUS        RESTARTS   AGE
devopsdays-86945768c-49pvf                1/1       Running       0          18s

$ kubectl port-forward devopsdays-86945768c-49pvf 8080:80
Forwarding from 127.0.0.1:8080 -> 80
Handling connection for 8080

Probes continued

$ kubectl logs devopsdays-86945768c-vr57m
I'm pretending to be a veeeeeery slow to start up Java app. Back in 5 minutes

This is what Readiness Probes are for

Let's find out what's going wrong

Probes continued

A readiness probe will stop a pod from being entered into Service until it's ready

Some examples include:

readinessProbe:
      exec:
        command:
        - grep 'alive'
        - /var/log/application.log
 readinessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: X-Custom-Header
          value: DevOpsDays
readinessProbe:
  tcpSocket:
    port: 8080
  initialDelaySeconds: 15
  periodSeconds: 20
ports:
- name: liveness-port
  containerPort: 8080
  hostPort: 8080

livenessProbe:
  httpGet:
    path: /healthz
    port: liveness-port

Probes continued

$ kubectl apply -f readiness_patch.yml

We can add a readiness probe using the yaml file located in the repo

$ kubectl get pods
NAME                                      READY     STATUS        RESTARTS   AGE
devopsdays-b5bd6ff4d-nxgrr                0/1       Running       0          40s

And we can now see that our pod remains 'unready', so it won't be added to services

Liveness Probes

$ kubectl apply -f liveness_patch.yml

Used to restart a pod when it's 'dead'

$ kubectl get pods
NAME                                      READY     STATUS        RESTARTS   AGE
devopsdays-86945768c-49pvf                1/1       Running       0          40s

$ kubectl port-forward 8080:80
Forwarding from 127.0.0.1:8080 -> 80
Handling connection for 8080

Now we can port-forward once again and see our final image

For example:

  • An application that crashes
  • A dependency on a file or process

Quotas and Limits

Requests

(Canadian pods are very polite)

spec:
  containers:
    resources:
      requests:
        memory: "64Mi"
        cpu: "250m"
  • Requests are the pod asking for a certain amount of RAM and CPU to be available
  • The scheduler uses this to place the pod

Pod will remain pending until space becomes available (also how the cluster autoscaler works)

Limits

spec:
  containers:
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"
  • Limits are a hard limit on the resources the pod is allowed
  • These are passed directly to the container runtime, so usually this is docker

If the pod goes over its limit it'll be restarted

Quotas

apiVersion: v1
kind: ResourceQuota
metadata:
  name: devopsdays-demo
  namespace: devopsdays-demo
spec:
  hard:
    requests.cpu: "2"
    requests.memory: 2Gi
    limits.cpu: "2"
    limits.memory: 2Gi
  • Quotas limit total resources allowed
  • Quotas are assigned to namespaces

Developer:

Cluster Admin:

Using Quotas

$ kubectl create namespace devopsdays-demo

Let's start with a namespace

We'll use the quota from above:

$ kubectl create -f quota.yml

And now let's try and roll out 100 replicas of nginx:

$ kubectl -n devopsdays-demo run nginx --image=nginx:stable --replicas=100

And now we check if the quota worked

Quotas continued

$ kubectl -n devopsdays-demo get pods
No resources found.

$ kubectl -n devopsdays-demo get deployment
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
nginx     100       0         0            0           41s

First up, let's check for pods

This could be quite confusing if someone didn't know about the quota:

$ kubectl -n devopsdays-demo describe replicasets
Warning  FailedCreate  1m                replicaset-controller  Error creating: pods "nginx-7cc8949494-pm68x" is forbidden: failed quota: devopsdays-demo: must specify limits.cpu,limits.memory,requests.cpu,requests.memory

When a quota is active, all pods must have limits and requests set.

$ kubectl -n devopsdays-demo delete deployment nginx

Now let's clean up and try something a bit more sensible

Adding Requests and Limits

We'll redo our kubectl run command and add the requests and limits in:

$ kubectl -n devopsdays-demo run nginx --image=nginx:stable --requests='cpu=100m,memory=256Mi' --limits='cpu=150m,memory=512Mi' --replicas=10
deployment "nginx" created

And now we can see the quota protected us:

$ kubectl -n devopsdays-demo get pods -o wide
NAME                     READY     STATUS    RESTARTS   AGE       IP             NODE
nginx-6c788db6bd-2qf8n   1/1       Running   0          3s        100.96.1.186   ip-172-20-57-78.eu-west-1.compute.internal
nginx-6c788db6bd-c6w46   1/1       Running   0          3s        100.96.2.161   ip-172-20-59-214.eu-west-1.compute.internal
nginx-6c788db6bd-dkksk   1/1       Running   0          3s        100.96.1.185   ip-172-20-57-78.eu-west-1.compute.internal
nginx-6c788db6bd-lxh2w   1/1       Running   0          3s        100.96.1.184   ip-172-20-57-78.eu-west-1.compute.internal

Let's check on the other 6 pods:

$ kubectl -n devopsdays-demo describe replicasets
Warning  FailedCreate      1m                replicaset-controller  Error creating: pods "nginx-6c788db6bd-cqt4r" is forbidden: exceeded quota: devopsdays-demo, requested: limits.memory=512Mi, used: limits.memory=2Gi, limited: limits.memory=2Gi

What now?

  • With this we can limit namespaces effectively
  • You can set default limits and requests for a namespace, so if it's not set it'll get the default
  • Spending the time early on to get your limits and requests right will pay off in the long run

What's to stop users from simply creating more namespaces, or adjusting the quotas?

AuthZ and RBAC Challenge

What is RBAC?

Role Based Access Control is the successor to ABAC (Attribute Based Access control)

It comprises of Roles and Bindings

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: default
  name: read-only-pods-deploy
rules:
- apiGroups: [""]
  resources: ["pods", "deployments"]
  verbs: ["get", "watch", "list"]
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: read-only-pods-deploy
  namespace: default
subjects:
- kind: Group
  name: managers
  apiGroup: rbac.authorization.k8s.io
- kind: User
  name: yvo
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: Role
  name: read-only-pods-deploy
  apiGroup: rbac.authorization.k8s.io

Roles

kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: default
  name: read-only-pods-deploy
rules:
- apiGroups: [""]
  resources: ["pods", "deployments"]
  verbs: ["get", "watch", "list"]

This is an example of a role that only allows read only access to pods and deployments in the default namespace

Role Bindings

kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: read-only-pods-deploy
  namespace: default
subjects:
- kind: Group
  name: managers
  apiGroup: rbac.authorization.k8s.io
- kind: User
  name: yvo
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: Role
  name: read-only-pods-deploy
  apiGroup: rbac.authorization.k8s.io

Now we can apply this role to the 'managers' group and the user Yvo, to ensure nothing gets broken

Role Bindings apply to a namespace, if you want it for the entire cluster you can use a 'ClusterRoleBinding'

RBAC Challenge

In each of your clusters there is an additional user, named 'devopsandy'. The challenge is:

  1. Using your namespace from Workshop 4 (devopsdays-demo), with the quota
  2. Allow the 'devopsandy' user full permissions to create, edit, view and delete anything inside the 'devopsdays-demo' namespace
  3. Not permit access to any other namespace or any cluster resources

Raise your hand or call out when you've done it and Andy will test from the stage

RBAC Challenge

Answers can be found here:

https://bit.ly/2KiLT8d

Kubernetes Services Deep Dive

Networking without overlay

ip route add 192.168.2.0/24 via 192.168.0.2
ip route add 192.168.1.0/24 via 192.168.0.1

Networking

Does Pod A see the request from:

1. 192.168.0.2 (the node)                      3. Either

2. 192.168.2.88 (Pod B)                          4. Both

What if we add a Service?

1. 192.168.0.2 (the node)                      3. The Service IP

2. 192.168.2.88 (Pod B)                          4. Either

What's going on under the hood?

Chain KUBE-SERVICES (2 references)
 pkts bytes target     prot opt in     out     source               destination
    0     0 KUBE-MARK-MASQ  tcp  --  *      *      !100.96.0.0/11        100.70.163.174       /* default/first-wordpress-wordpress:http cluster IP */ tcp dpt:80
    0     0 KUBE-SVC-F24E2VY7BZETU2MG  tcp  --  *      *       0.0.0.0/0            100.70.163.174       /* default/first-wordpress-wordpress:http cluster IP */ tcp dpt:80
Chain KUBE-SEP-KAC5IFIDSIOQVT7B (1 references)
 pkts bytes target     prot opt in     out     source               destination
    0     0 KUBE-MARK-MASQ  all  --  *      *       100.96.5.8           0.0.0.0/0            /* default/first-wordpress-wordpress:http */
    0     0 DNAT       tcp  --  *      *       0.0.0.0/0            0.0.0.0/0            /* default/first-wordpress-wordpress:http */ tcp to:100.96.5.8:80
Chain KUBE-SVC-F24E2VY7BZETU2MG (2 references)
 pkts bytes target     prot opt in     out     source               destination
    0     0 KUBE-SEP-KAC5IFIDSIOQVT7B  all  --  *      *       0.0.0.0/0            0.0.0.0/0            /* default/first-wordpress-wordpress:http */

IPtables is rewritten by the kube-proxy with the service IP

This goes to it's own chain, that has an entry per pod

Which in turn is redirected to the pod IP

Pod balancing

Chain KUBE-SVC-253L2MOZ6TC5FE7P (1 references)
 pkts bytes target     prot opt in     out     source               destination
    0     0 KUBE-SEP-AL7QVWV4IE7GZBWS  all  --  *      *       0.0.0.0/0            0.0.0.0/0            /* default/nginx1: */ statistic mode random probability 0.33332999982
    0     0 KUBE-SEP-WW7J6EVG3AA3MAGP  all  --  *      *       0.0.0.0/0            0.0.0.0/0            /* default/nginx1: */ statistic mode random probability 0.50000000000
    0     0 KUBE-SEP-AM4GYXY6DIGHHJA3  all  --  *      *       0.0.0.0/0            0.0.0.0/0            /* default/nginx1: */

For a service with 3 endpoints, this now load balances over each pod using statistic probability:

$ kubectl get pods -o wide | grep nginx
nginx1-649d8f4c6-7kcl8                       1/1       Running   0          3m        100.96.5.13   ip-172-20-63-237.eu-west-1.compute.internal
nginx1-649d8f4c6-89tnx                       1/1       Running   0          3m        100.96.4.11   ip-172-20-35-250.eu-west-1.compute.internal
nginx1-649d8f4c6-qdc4z                       1/1       Running   0          3m        100.96.5.14   ip-172-20-63-237.eu-west-1.compute.internal

Here's what those pods look like:

Questions?

Thank you!

Best Practise Kubernetes

By Andy Repton

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