Cloud test -- Java helper classes to write your tests against hosts in the cloud
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A Java library to test against hosts in the cloud.


  • Decouple test and test machine setup.

  • Setup and tear-down for

    • Amazon EC2 hosts (Automatic host creation/destroy)
    • Vagrant hosts (Set up to the running state, tear down to the initial state)
    • VirtualBox hosts (Load snapshot and start, power off)
    • Libvirt managed KVM hosts (Fast clones using backing store, provisioning)
    • Docker containers
    • Tunneled cloud hosts (Reaching target host via ssh tunnel)
  • Provides hostname and port mapping of created host (@see Ec2CloudHost)

  • Caching of provisioned hosts (vagrant and KVM) with expiration checks


  • Virtualbox version >= 4.2
  • Vagrant version >= 1.2.7
  • Qemu/KVM version that supports domain metadata (QEMU-KVM 1.4.2 (Fedora 19), 2.0.0 (Ubuntu LTS 14))
  • Docker >= 1.6


Set up your host

Overcast looks for configuration properties in this order:

  1. System.getProperty()
  • <HOMEDIR>/.overcast/overcast.conf
  • <WORKDIR>/overcast.conf
  • <CLASSPATH>/overcast.conf

Note: The home location takes precedence over the project location. This allows developers to adapt settings to their local setup without changing the project defaults.

The overcast.conf files are in Typesafe Config HOCON syntax; this is a flexible JSON superset that allows comments, substitution, file inclusion, and more.

Common properties

{my-host-label}.hostname - Hostname. If is not set, overcast will try to create host (For Amazon hosts).

Tunneled properties

{my-host-label}.tunnel.username - Tunnel username

{my-host-label}.tunnel.password - Tunnel password

{my-host-label}.tunnel.ports - Tunnel ports. Comma separated.

{my-host-label}.tunnel.setupTimeout - Attempt to set up the tunnel for this many seconds, default 0.

Amazon EC2 properties

{my-host-label}.amiId - Amazon AMI id. E.g.:ami-c1724eb5

{my-host-label}.amiInstanceType - Instance type. E.g.: m1.small

{my-host-label}.amiSecurityGroup - AMI security group

{my-host-label}.amiKeyName - AMI key name

{my-host-label}.amiBootSeconds - How many seconds max do you expect AMI to boot

{my-host-label}.aws.endpoint - [Endpoint URL] (

{my-host-label}.aws.accessKey - Access key

{my-host-label}.aws.secretKey - Secret key

Vagrant host properties

{my-host-label}.vagrantDir - Directory with Vagrantfile

{my-host-label}.vagrantIp - IP address of the Vagrant host

{my-host-label}.vagrantVm - Name of the Vagrant host

{my-host-label}.vagrantOs - OS type of the Vagrant host (WINDOWS, UNIX)

{my-host-label}.vagrantSnapshotExpirationCmd - Command used to expire the snapshot image of the Vagrant host, it will be executed in the vagrantDir.

VirtualBox host properties

{my-host-label}.vboxUuid - UUID of the virtual machine

{my-host-label}.vboxSnapshotUuid - UUID of the snapshot

{my-host-label}.vboxBoxIp - IP address of the virtual machine

Libvirt host properties

{my-host-label}.libvirtURL - URL of libvirt e.g. qemu+ssh://user@linux-box/system

{my-host-label}.libvirtStartTimeout - The libvirt domain must go into running state before this timeout (default: 30)

{my-host-label}.baseDomain - name of the domain to clone

{my-host-label}.network - name of the network device that should be used for IP to MAC lookup. For example br0.

{my-host-label}.ipLookupStrategy - name of a strategy used to figure out the IP of the clone, static or SSH.

{my-host-label}.static.ip - When ipLookupStrategy is static, the static IP the created host is expected to have.

{my-host-label}.SSH.url - URL for overthere to connect to the system that knows about the MAC to IP mapping. For instance: ssh://user@dhcpserver?os=UNIX&connectionType=SFTP&privateKeyFile=/home/user/.ssh/id_rsa&passphrase=bigsecret

{my-host-label}.SSH.command - command to execute on the system to lookup the IP. For example for dnsmasq: grep {0} /var/lib/misc/dnsmasq.leases | cut -d " " -f 3. {0} is expanded to the MAC address.

{my-host-label}.SSH.timeout - number of seconds to try the above command to find the IP.

{my-host-label}.provision.url - URL for overthere to connect to the created system. For instance: ssh://user@{0}?os=UNIX&connectionType=SCP&privateKeyFile="${user.home}"/.ssh/id_rsa&passphrase=bigsecret. {0} will be replaced by the IP the system got.

{my-host-label}.provision.bootDelay - Boot delay to use after the system has been provisioned.

{my-host-label}.provision.startTimeout - After the boot delay the copy and provision commands will be retried until this timeout expires. This allows for more robust startup when startup times vary, without configuring a big bootDelay.

{my-host-label}.provision.copy - Files/directories specified here will be copied to the system before provisioning. If the length of the list is even then files/directories are copied pair wise. If the length is odd then everything is copied into the last entry (which should be a directory).

{my-host-label}.provision.cmd - Command to run to provision the system.

{my-host-label}.provision.expirationTag.cmd - Command to run to determine the expiration tag of a cached provisioning operation. Runs locally in the current directory. If an overthere URL is specified it will run the command remotely.

{my-host-label}.provision.expirationTag.url - URL for overthere to connect to a machine hosting the scripts that were used to provision an image.

{my-host-label}.fsMapping.{target}.hostPath - upon cloning create a Filesystem mapping between hostPath and target in the host.

{my-host-label}.fsMapping.{target}.accessMode - Access mode, one of passthrough, mapped, squash (default: passthrough)

{my-host-label}.fsMapping.{target}.readOnly - Whether the mount will be readOnly (default: true)

Docker concepts

During setup(), Overcast will create and start a new Docker container. If the image specified is not available in the local registry, it will be automatically pulled from the central Docker repository.

During teardown(), it will stop the container and optionally remove the container (see remove property).

Calling getHostName() will return the hostname of the Docker Host, assuming the container will run on that host, with the exposed ports accessible on the Docker host.

Calling getPort(port) will translate the internal port (passed as an argument) to the port externally exposed by the Docker Container. The port number is dynamically determined by Docker. The port range used for dynamic allocation is 49153 to 65535 (defined by Docker).

We use the Spotify Docker Client library.

Docker container properties

{my-host-label}.dockerHost - The hostname of the Docker Host. (default: http://localhost:2375). It can also be a unix socket: unix:///var/run/docker.sock.

{my-host-label}.certificates - The certificates to use when connecting to a HTTPS secured docker host. The directory must contain ca.pem, cert.pem and key.pem.

{my-host-label}.dockerImage - The Docker image that will be run. (required)

{my-host-label}.name - The name the container will get. Warning: Docker container names must be unique, even when the container is stopped. Use in combination with remove to make sure you can start a container with the same name again. Also not suitable for parallel testing. (default: random name defined by docker)

{my-host-label}.remove - Boolean. If true, the container will be removed during teardown. (default: false)

{my-host-label}.exposedPorts - List of ports to expose. Use in combination with exposeAllPorts. Must include the protocol. Currently only tcp is supported. For example: ["12345/tcp", "23456/tcp"].

{my-host-label}.exposeAllPorts - Boolean. If true, Docker will expose the ports defined by the Docker image (see EXPOSE), and additionally the ports defined in overcast property exposedPorts. (default: false)

{my-host-label}.command - Command to execute within the container. For example: ["/bin/sh", "-c", "while true; do echo hello world; sleep 1; done"]

{my-host-label}.env - Environment variables that will be exported in the container. For example: ["MYVAR1=AAA", "MYVAR2=BBB", "MYVAR3=CCC"].

Set up and Tear down

public static void doInitHost() {

public static void doTeardownHost() {

Also Overcast is used for integration tests of Overthere.


From maven repo


Note: the libvirt JNA wrapper may require adding the repository to your build:

From sources

gradle build

Notes for setting up test systems


The libvirt implementation uses backing store images. This means that the domain being cloned needs to be shut down. When cloning a system all disks of the base system are cloned using a backing store, and thrown away upon teardown, thus leaving the original system unchanged.

Machines can use static IP's using {host}.ipLookupStrategy=static. It is up to you that you do not start more than one. It is also possible to use DHCP using {host}.ipLookupStrategy=SSH. You have to specify the name of the Virtual Network in libvirt or the name of the bridge the domain is connected to and a command to lookup the IP on the DHCP server giving the system it's IP address. The IP can then be retrieved using the getHostName() method on the CloudHost.

NAT network

Due to the way NAT works the machine would only be accessible from the Libvirt (KVM) host. Example settings for a (NAT) network named my_nat_network:

nat_host {
    SSH {
        command="""grep {0} /var/lib/libvirt/dnsmasq/my_nat_network.leases | cut -d " " -f 3"""
Bridged network

Example settings for a host connected to a bridge named br0. Assuming a DHCP server dhcp-box:

bridged_host {
    SSH {
        command="""grep {0} /var/lib/dnsmasq/dnsmasq.leases | cut -d " " -f 3"""
Routed network

A routed network is similar to a bridged network with the difference that networkDeviceId should be set to the name of the routed network.

File system mapping

With entries in the {host}.fsMapping section it is possible to mount directories from the host in the created domain. For instance like:

my-host {
    fsMapping {
        vagrant { hostPath = ${itest.vagrantDir}"/itest/vagrant", readOnly = true }
        data    { hostPath = ${itest.dataDir}, readOnly = true, accessMode = "mapped" }

These mappings can be mounted on the domain with fstab entries like:

data            /data               9p    ro,trans=virtio
vagrant         /vagrant            9p    ro,trans=virtio

For details on the accessMode variants see:

It may be necessary to add the 9p file system drivers to the initrd image of the base domain image.