CSI for S3

This is a Container Storage Interface (CSI) for S3 (or S3 compatible) storage. This can dynamically allocate buckets and mount them via a fuse mount into any container.

Status

This is still very experimental and should not be used in any production environment. Unexpected data loss could occur depending on what mounter and S3 storage backend is being used.

Kubernetes installation

Requirements

• Kubernetes 1.10+
• Kubernetes has to allow privileged containers
• Docker daemon must allow shared mounts (systemd flag MountFlags=shared)

1. Create a secret with your S3 credentials

The endpoint is optional if you are using something else than AWS S3. Also the region can be empty if you are using some other S3 compatible storage.

apiVersion: v1
kind: Secret
metadata:
  name: csi-s3-secret
stringData:
  accessKeyID: <YOUR_ACCESS_KEY_ID>
  secretAccessKey: <YOUR_SECRET_ACCES_KEY>
  endpoint: <S3_ENDPOINT_URL
  region: <S3_REGION>
  # specify which mounter to use
  # can be set to s3fs, goofys or s3ql
  mounter: <MOUNTER>
  # Currently only for s3ql
  # If not using s3ql, set it to ""
  encryptionKey: <FS_ENCRYPTION_KEY>

2. Deploy the driver

cd deploy/kubernetes
$ kubectl create -f provisioner.yaml
$ kubectl create -f attacher.yaml
$ kubectl create -f csi-s3-driver.yaml

3. Create the storage class

$ kubectl create -f storageclass.yaml

4. Test the S3 driver

• Create a pvc using the new storage class:

$ kubectl create -f pvc.yaml

• Check if the PVC has been bound:

$ kubectl get pvc csi-s3-pvc
NAME         STATUS    VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
csi-s3-pvc   Bound     pvc-c5d4634f-8507-11e8-9f33-0e243832354b   5Gi        RWX            csi-s3         9s

• Create a test pod which mounts your volume:

$ kubectl create -f poc.yaml

If the pod can start, everything should be working.

• Test the mount

$ kubectl exec -ti csi-s3-test-nginx bash
$ mount | grep fuse
s3fs on /var/lib/www/html type fuse.s3fs (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
$ touch /var/lib/www/html/hello_world

If something does not work as expected, check the troubleshooting section below.

Additional configuration

Mounter

As seen in the deployment example above, the driver can be configured to use one of these mounters to mount buckets:

• s3fs
• goofys
• s3ql
• s3backer

All mounters have different strengths and weaknesses depending on your use case. Here are some characteristics which should help you choose a mounter:

s3fs

• Large subset of POSIX
• Files can be viewed normally with any S3 client
• Does not support appends or random writes

goofys

• Weak POSIX compatibility
• Performance first
• Files can be viewed normally with any S3 client
• Does not support appends or random writes

s3ql

• (Almost) full POSIX compatibility
• Uses its own object format
• Files are not readable with other S3 clients
• Support appends
• Supports compression before upload
• Supports encryption before upload

s3backer

• Represents a block device stored on S3
• Allows to use a real filesystem
• Files are not readable with other S3 clients
• Support appends
• Supports compression before upload (Not yet implemented in this driver)
• Supports encryption before upload (Not yet implemented in this driver)

Limitations

As S3 is not a real file system there are some limitations to consider here. Depending on what mounter you are using, you will have different levels of POSIX compability. Also depending on what S3 storage backend you are using there are not always consistency guarantees. The detailed limitations can be found on the documentation of s3fs and goofys.

Troubleshooting

Issues while creating PVC

• Check the logs of the provisioner:

$ kubectl logs -l app=csi-provisioner-s3 -c s3-csi-driver

Issues creating containers

• Ensure feature gate MountPropagation is not set to false
• Check the logs of the s3-driver:

$ kubectl logs -l app=csi-s3-driver -c csi-s3-driver

Development

This project can be built like any other go application.

$ go get -u github.com/ctrox/csi-s3-driver

Build

$ make build

Tests

Currently the driver is tested by the CSI Sanity Tester. As end-to-end tests require S3 storage and a mounter like s3fs, this is best done in a docker container. A Dockerfile and the test script are in the test directory. The easiest way to run the tests is to just use the make command:

$ make test