/external-resizer

Sidecar container that watches Kubernetes PersistentVolumeClaims objects and triggers controller side expansion operation against a CSI endpoint

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Build Status

CSI Resizer

The CSI external-resizer is a sidecar container that watches the Kubernetes API server for PersistentVolumeClaim updates and triggers ControllerExpandVolume operations against a CSI endpoint if user requested more storage on PersistentVolumeClaim object.

Overview

A storage provider that allows volume expansion after creation, may choose to implement volume expansion either via a control-plane CSI RPC call or via node CSI RPC call or both as a two step process. The external-resizer is an external-controller that watches Kubernetes API server for PersistentVolumeClaim modifications and triggers CSI calls for control-plane volume-expansion. More details can be found on - CSI Volume expansion

Compatibility

This information reflects the head of this branch.

Compatible with CSI Version Container Image Recommended K8s Version
CSI Spec v1.1.0 quay.io/k8scsi/csi-resizer 1.16

Feature status

Currently all CSI volume expansion features are supported as Beta features by external-resizer.

Usage

It is necessary to create a new service account and give it enough privileges to run the external-resizer, see deploy/kubernetes/rbac.yaml. The resizer is then deployed as single Deployment as illustrated below:

kubectl create deploy/kubernetes/deployment.yaml

The external-resizer may run in the same pod with other external CSI controllers such as the external-attacher, external-snapshotter and/or external-provisioner.

Note that the external-resizer does not scale with more replicas. Only one external-resizer is elected as leader and running. The others are waiting for the leader to die. They re-elect a new active leader in ~15 seconds after death of the old leader.

Command line options

Recommended optional arguments

  • --csi-address <path to CSI socket>: This is the path to the CSI driver socket inside the pod that the external-resizer container will use to issue CSI operations (/run/csi/socket is used by default).

  • --leader-election: Enables leader election. This is mandatory when there are multiple replicas of the same external-resizer running for one CSI driver. Only one of them may be active (=leader). A new leader will be re-elected when current leader dies or becomes unresponsive for ~15 seconds.

  • --leader-election-namespace: Namespace where the leader election resource lives. Defaults to the pod namespace if not set.

  • --csiTimeout <duration>: Timeout of all calls to CSI driver. It should be set to value that accommodates majority of ControllerExpandVolume calls. 15 seconds is used by default.

  • --workers <num>: Number of simultaneously running ControllerExpandVolume operations. Default value is 10.

  • --metrics-address: The TCP network address where the prometheus metrics endpoint will run (example: :8080 which corresponds to port 8080 on local host). The default is empty string, which means metrics endpoint is disabled.

  • --metrics-path: The HTTP path where prometheus metrics will be exposed. Default is /metrics.

Other recognized arguments

  • --kubeconfig <path>: Path to Kubernetes client configuration that the external-resizer uses to connect to Kubernetes API server. When omitted, default token provided by Kubernetes will be used. This option is useful only when the external-resizer does not run as a Kubernetes pod, e.g. for debugging. Either this or --master needs to be set if the external-resizer is being run out of cluster.

  • --master <url>: Master URL to build a client config from. When omitted, default token provided by Kubernetes will be used. This option is useful only when the external-resizer does not run as a Kubernetes pod, e.g. for debugging. Either this or --kubeconfig needs to be set if the external-resizer is being run out of cluster.

  • --version: Prints current external-resizer version and quits.

  • All glog / klog arguments are supported, such as -v <log level> or -alsologtostderr.

Community, discussion, contribution, and support

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Code of conduct

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