Convoy

Overview

Convoy is a Docker volume plugin for a variety of storage back-ends. It supports vendor-specific extensions like snapshots, backups, and restores. It's written in Go and can be deployed as a standalone binary.

Why use Convoy?

Convoy makes it easy to manage your data in Docker. It provides persistent volumes for Docker containers with support for snapshots, backups, and restores on various back-ends (e.g. device mapper, NFS, EBS).

For example, you can:

• Migrate volumes between hosts
• Share the same volumes across hosts
• Schedule periodic snapshots of volumes
• Recover a volume from a previous backup

Supported back-ends

• Device Mapper
• Virtual File System (VFS) / Network File System (NFS)
• Amazon Elastic Block Store (EBS)

Quick Start Guide

First, make sure Docker 1.8 or above is running.

docker --version

If not, install the latest Docker daemon as follows:

curl -sSL https://get.docker.com/ | sh

Once the right Docker daemon version is running, install and configure the Convoy volume plugin as follows:

wget https://github.com/rancher/convoy/releases/download/v0.5.2/convoy.tar.gz
tar xvzf convoy.tar.gz
sudo cp convoy/convoy convoy/convoy-pdata_tools /usr/local/bin/
sudo mkdir -p /etc/docker/plugins/
sudo bash -c 'echo "unix:///var/run/convoy/convoy.sock" > /etc/docker/plugins/convoy.spec'

You can use a file-backed loopback device to test and demo Convoy Device Mapper driver. A loopback device, however, is known to be unstable and should not be used in production.

truncate -s 100G data.vol
truncate -s 1G metadata.vol
sudo losetup /dev/loop5 data.vol
sudo losetup /dev/loop6 metadata.vol

Once the data and metadata devices are set up, you can start the Convoy plugin daemon as follows:

sudo convoy daemon --drivers devicemapper --driver-opts dm.datadev=/dev/loop5 --driver-opts dm.metadatadev=/dev/loop6

You can create a Docker container with a convoy volume. As a test, create a file called /vol1/foo in the Convoy volume:

sudo docker run -v vol1:/vol1 --volume-driver=convoy ubuntu touch /vol1/foo

Next, take a snapshot of the convoy volume and backup the snapshot to a local directory: (You can also make backups to an NFS share or S3 object store.)

sudo convoy snapshot create vol1 --name snap1vol1
sudo mkdir -p /opt/convoy/
sudo convoy backup create snap1vol1 --dest vfs:///opt/convoy/

The convoy backup command returns a URL string representing the backup dataset. You can use this URL to recover the volume on another host:

sudo convoy create res1 --backup <backup_url>

The following command creates a new container and mounts the recovered Convoy volume into that container:

sudo docker run -v res1:/res1 --volume-driver=convoy ubuntu ls /res1/foo

You should see the recovered file in /res1/foo.

Installation

Ensure you have Docker 1.8 or above installed.

Download the latest version of Convoy and unzip it. Put the binaries in a directory in the execution $PATH of sudo and root users (e.g. /usr/local/bin).

wget https://github.com/rancher/convoy/releases/download/v0.5.2/convoy.tar.gz
tar xvzf convoy.tar.gz
sudo cp convoy/convoy convoy/convoy-pdata_tools /usr/local/bin/

Run the following commands to set up the Convoy volume plugin for Docker:

sudo mkdir -p /etc/docker/plugins/
sudo bash -c 'echo "unix:///var/run/convoy/convoy.sock" > /etc/docker/plugins/convoy.spec'

Start Convoy Daemon

You need to pass different arguments to the Convoy daemon depending on your choice of back-end implementation.

Device Mapper

If you're running in a production environment with the Device Mapper driver, it's recommended to attach a new, empty block device to the host Convoy is running on. Then you can make two partitions on the device using dm_dev_partition.sh to get two block devices ready for the Device Mapper driver. See Device Mapper Partition Helper for more details.

Device Mapper requires two block devices to create storage pool for all volumes and snapshots. Assuming you have two devices created one data device called /dev/convoy-vg/data and the other metadata device called /dev/convoy-vg/metadata, then run the following command to start the Convoy daemon:

sudo convoy daemon --drivers devicemapper --driver-opts dm.datadev=/dev/convoy-vg/data --driver-opts dm.metadatadev=/dev/convoy-vg/metadata

• The default Device Mapper volume size is 100G. You can override it with the ---driver-opts dm.defaultvolumesize option.
• You can take a look here if you want to know how much storage should be allocated for the metadata device.

NFS

First, mount the NFS share to the root directory used to store volumes. Substitute <vfs_path> with the appropriate directory of your choice:

sudo mkdir <vfs_path>
sudo mount -t nfs <nfs_server>:/path <vfs_path>

The NFS-based Convoy daemon can be started as follows:

sudo convoy daemon --drivers vfs --driver-opts vfs.path=<vfs_path>

EBS

Make sure you're running on an EC2 instance and have already configured AWS credentials correctly.

sudo convoy daemon --drivers ebs

DigitalOcean

Make sure you're running on a DigitalOcean Droplet and that you have the DO_TOKEN environment variable set with your key.

sudo convoy daemon --drivers digitalocean

Volume Commands

Create a Volume

Volumes can be created using the convoy create command:

sudo convoy create volume_name

• Device Mapper: Default volume size is 100G. --size option is supported.
• EBS: Default volume size is 4G. --size and some other options are supported.

You can also create a volume using the docker run command. If the volume does not yet exist, a new volume will be created. Otherwise the existing volume will be used.

sudo docker run -it -v test_volume:/test --volume-driver=convoy ubuntu

Delete a Volume

sudo convoy delete <volume_name>

or

sudo docker rm -v <container_name>

• NFS, EBS and DigitalOcean: The -r/--reference option instructs the convoy delete command to only delete the reference to the volume from the current host and leave the underlying files on NFS server or EBS volume unchanged. This is useful when the volume need to be reused later.
• docker rm -v would be treated as convoy delete with -r/--reference.
• If you use --rm with docker run, all Docker volumes associated with the container would be deleted on container exit with convoy delete --reference. See Docker run reference for details.

List and Inspect a Volume

sudo convoy list
sudo convoy inspect vol1

Take Snapshot of a Volume

sudo convoy snapshot create vol1 --name snap1vol1

Delete a Snapshot

sudo convoy snapshot delete snap1vol1

• Device Mapper: please make sure you keep the latest backed-up snapshot for the same volume available to enable the incremental backup mechanism. Convoy needs it to calculate the differences between snapshots.

Backup a Snapshot

• Device Mapper or VFS: You can backup a snapshot to an NFS mount/local directory or an S3 object store:

sudo convoy backup create snap1vol1 --dest vfs:///opt/backup/

or

sudo convoy backup create snap1vol1 --dest s3://backup-bucket@us-west-2/

or if you want to use a custom S3 endpoint (like Minio)

sudo convoy backup --s3-endpoint http://s3.example.com:9000/ create snap1vol1 --dest s3://backup-bucket@us-west-2/

The backup operation returns a URL string that uniquely identifies the backup dataset.

s3://backup-bucket@us-west-2/?backup=f98f9ea1-dd6e-4490-8212-6d50df1982ea\u0026volume=e0d386c5-6a24-446c-8111-1077d10356b0

If you're using S3, please make sure you have AWS credentials ready either in ~/.aws/credentials or as environment variables, as described here. You may need to put credentials in /root/.aws/credentials or set up sudo environment variables in order to get S3 credentials to work.

• EBS: --dest is not needed. Just do convoy backup create snap1vol1.

Restore a Volume from Backup

sudo convoy create res1 --backup <url>

• EBS: Current host must be in the same region of the backup to be restored.

Mount a Restored Volume into a Docker Container

You can use the standard docker run command to mount the restored volume into a Docker container:

sudo docker run -it -v res1:/res1 --volume-driver convoy ubuntu

Mount an NFS-Backed Volume on Multiple Servers

You can mount an NFS-backed volume on multiple servers. You can use the standard docker run command to mount an existing NFS-backed mount into a Docker container. For example, if you have already created an NFS-based volume vol1 on one host, you can run the following command to mount the existing vol1 volume into a new container:

sudo docker run -it -v vol1:/vol1 --volume-driver=convoy ubuntu

Support and Discussion

If you need any help with Convoy, please join us at either our forum or #rancher IRC channel.

Feel free to submit any bugs, issues, and feature requests to Convoy Issues.

Contribution

Contribution are welcome! Please take a look at Development Guide if you want to how to build Convoy from source or running test cases.

We love to hear new Convoy Driver ideas from you. Implementations are most welcome! Please consider take a look at enhancement ideas if you want contribute.

And of course, bug fixes are always welcome!

References

Convoy Command Line Reference

Using Convoy with Docker

Driver Specific

Device Mapper

Amazon Elastic Block Store

Virtual File System/Network File System