etcd

Helm chart for coreos etcd 3.4+

Overview

This is a chart based on the incubator chart from helm/charts. Dusted off to function with etcd 3.4 and updated for helm3. It also adds support for:

• Restore from snapshot
• CronJob to make snapshots
• Prometheus operator support

Configuration

The following table lists the configurable parameters of the etcd chart and their default values.

Parameter	Description	Default
image.repository	Container image repository	quay.io/coreos/etcd
image.tag	Container image tag	v3.4.15
image.pullPolicy	Container pull policy	IfNotPresent
replicas	k8s statefulset replicas	3
resources	container required resources	{}
clientPort	k8s service port	2379
peerPorts	Container listening port	2380
storage	Persistent volume size	1Gi
storageClass	Persistent volume storage class	anything
affinity	affinity settings for pod assignment	{}
nodeSelector	Node labels for pod assignment	{}
tolerations	Toleration labels for pod assignment	[]
extraEnv	Optional environment variables	[]
memoryMode	Using memory as backend storage	false
auth.client.enableAuthentication	Enables host authentication using TLS certificates. Existing secret is required.	false
auth.client.secureTransport	Enables encryption of client communication using TLS certificates	false
auth.peer.useAutoTLS	Automatically create the TLS certificates	false
auth.peer.secureTransport	Enables encryption peer communication using TLS certificates (At the moment works only with Auto TLS)	false
auth.peer.enableAuthentication	Enables host authentication using TLS certificates. Existing secret required	false
serviceAccount.create	Create serviceaccount	true
podMonitor.enabled	Enable podMonitor	false
prometheusRules.enabled	Enable prometheusRules	false
snapshot.restore.enabled	Enabled restore from snapshot	false
snapshot.restore.claimName	PVC claim name where snapshot is stored	""
snapshot.restore.fileName	Snapshot filename to restore from on PVC	""
snapshot.backup.enabled	Enable CronJob to make snapshots and save to PVC	""
snapshot.backup.schedule	Snapshot schedule	0/30 * * * *
snapshot.backup.historyLimit	Snapshot job history	1
snapshot.backup.snapshotHistoryLimit	Snapashot file history limit	1
snapshot.backup.claimName	Existing claim name name	""
snapshot.backup.size	Create pvc with size	10Gi
snapshot.backup.storageClassName	Create pvc storageclass	default
snapshot.backup.resources	Snapshot CronJob resources	{}

Specify each parameter using the --set key=value[,key=value] argument to helm install.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

$ helm install --name my-release -f values.yaml path/to/etcd

Tip: You can use the default values.yaml

To install the chart with secure transport enabled

First you must create a secret which would contain the client certificates: cert, key and the CA which was to used to sign them. Create the secret using this command:

$ kubectl create secret generic etcd-client-certs --from-file=ca.crt=path/to/ca.crt --from-file=cert.pem=path/to/cert.pem --from-file=key.pem=path/to/key.pem

Deploy the chart with the following flags enabled:

$ helm install --name my-release --set auth.client.secureTransport=true --set auth.client.enableAuthentication=true --set auth.client.existingSecret=etcd-client-certs --set auth.peer.useAutoTLS=true path/to/etcd

Reference to how to generate the needed certificate:

Ref: https://coreos.com/os/docs/latest/generate-self-signed-certificates.html

Deep dive

Cluster Health

$ for i in <0..n>; do kubectl exec <release-podname-$i> -- sh -c 'etcdctl endpoint health'; done

eg.

$ for i in {0..2}; do kubectl -n ops exec named-lynx-etcd-$i -- sh -c 'etcdctl endpoint health'; done
127.0.0.1:2379 is healthy: successfully committed proposal: took = 2.880348ms
127.0.0.1:2379 is healthy: successfully committed proposal: took = 2.616944ms
127.0.0.1:2379 is healthy: successfully committed proposal: took = 3.2329ms

Failover

If any etcd member fails it gets re-joined eventually. You can test the scenario by killing process of one of the replicas:

$ ps aux | grep etcd-1
$ kill -9 ETCD_1_PID

$ kubectl get pods -l "app.kubernetes.io/instance=${RELEASE-NAME},app.kubernetes.io/name=etcd"
NAME                 READY     STATUS        RESTARTS   AGE
etcd-0               1/1       Running       0          54s
etcd-2               1/1       Running       0          51s

After a while:

$ kubectl get pods -l "app.kubernetes.io/instance=${RELEASE-NAME},app.kubernetes.io/name=etcd"
NAME                 READY     STATUS    RESTARTS   AGE
etcd-0               1/1       Running   0          1m
etcd-1               1/1       Running   0          20s
etcd-2               1/1       Running   0          1m

You can check state of re-joining from etcd-1's logs:

$ kubectl logs etcd-1
Waiting for etcd-0.etcd to come up
Waiting for etcd-1.etcd to come up
ping: bad address 'etcd-1.etcd'
Waiting for etcd-1.etcd to come up
Waiting for etcd-2.etcd to come up
Re-joining etcd member
Updated member with ID 7fd61f3f79d97779 in cluster
2016-06-20 11:04:14.962169 I | etcdmain: etcd Version: 2.2.5
2016-06-20 11:04:14.962287 I | etcdmain: Git SHA: bc9ddf2
...

Scaling using kubectl

This is for reference. Scaling should be managed by helm upgrade

The etcd cluster can be scale up by running kubectl patch or kubectl edit. For instance,

$ kubectl get pods -l "app.kubernetes.io/instance=${RELEASE-NAME},app.kubernetes.io/name=etcd"
NAME      READY     STATUS    RESTARTS   AGE
etcd-0    1/1       Running   0          7m
etcd-1    1/1       Running   0          7m
etcd-2    1/1       Running   0          6m

$ kubectl patch statefulset/etcd -p '{"spec":{"replicas": 5}}'
"etcd" patched

$ kubectl get pods -l "app.kubernetes.io/instance=${RELEASE-NAME},app.kubernetes.io/name=etcd"
NAME      READY     STATUS    RESTARTS   AGE
etcd-0    1/1       Running   0          8m
etcd-1    1/1       Running   0          8m
etcd-2    1/1       Running   0          8m
etcd-3    1/1       Running   0          4s
etcd-4    1/1       Running   0          1s

Scaling-down is similar. For instance, changing the number of replicas to 4:

$ kubectl edit statefulset/etcd
statefulset "etcd" edited

$ kubectl get pods -l "app.kubernetes.io/instance=${RELEASE-NAME},app.kubernetes.io/name=etcd"
NAME      READY     STATUS    RESTARTS   AGE
etcd-0    1/1       Running   0          8m
etcd-1    1/1       Running   0          8m
etcd-2    1/1       Running   0          8m
etcd-3    1/1       Running   0          4s

Once a replica is terminated (either by running kubectl delete pod etcd-ID or scaling down), content of /var/run/etcd/ directory is cleaned up. If any of the etcd pods restarts (e.g. caused by etcd failure or any other), the directory is kept untouched so the pod can recover from the failure.