Set up a development environment via DevStack

Watcher is currently able to optimize compute resources - specifically Nova compute hosts - via operations such as live migrations. In order for you to fully be able to exercise what Watcher can do, it is necessary to have a multinode environment to use.

You can set up the Watcher services quickly and easily using a Watcher DevStack plugin. See PluginModelDocs for information on DevStack’s plugin model. To enable the Watcher plugin with DevStack, add the following to the [[local|localrc]] section of your controller’s local.conf to enable the Watcher plugin:

enable_plugin watcher

For more detailed instructions, see Detailed DevStack Instructions. Check out the DevStack documentation for more information regarding DevStack.

Quick Devstack Instructions with Datasources

Watcher requires a datasource to collect metrics from compute nodes and instances in order to execute most strategies. To enable this a [[local|localrc]] to setup DevStack for some of the supported datasources is provided. These examples specify the minimal configuration parameters to get both Watcher and the datasource working but can be expanded is desired.


With the Gnocchi datasource most of the metrics for compute nodes and instances will work with the provided configuration but metrics that require Ironic such as host_airflow and host_power will still be unavailable as well as instance_l3_cpu_cache:

enable_plugin watcher

enable_plugin watcher-dashboard

enable_plugin ceilometer

enable_plugin aodh
enable_plugin panko


Detailed DevStack Instructions

  1. Obtain N (where N >= 1) servers (virtual machines preferred for DevStack). One of these servers will be the controller node while the others will be compute nodes. N is preferably >= 3 so that you have at least 2 compute nodes, but in order to stand up the Watcher services only 1 server is needed (i.e., no computes are needed if you want to just experiment with the Watcher services). These servers can be VMs running on your local machine via VirtualBox if you prefer. DevStack currently recommends that you use Ubuntu 16.04 LTS. The servers should also have connections to the same network such that they are all able to communicate with one another.

  2. For each server, clone the DevStack repository and create the stack user:

    sudo apt-get update
    sudo apt-get install git
    git clone
    sudo ./devstack/tools/

    Now you have a stack user that is used to run the DevStack processes. You may want to give your stack user a password to allow SSH via a password:

    sudo passwd stack
  3. Switch to the stack user and clone the DevStack repo again:

    sudo su stack
    cd ~
    git clone
  4. For each compute node, copy the provided local.conf.compute example file to the compute node’s system at ~/devstack/local.conf. Make sure the HOST_IP and SERVICE_HOST values are changed appropriately - i.e., HOST_IP is set to the IP address of the compute node and SERVICE_HOST is set to the IP address of the controller node.

    If you need specific metrics collected (or want to use something other than Ceilometer), be sure to configure it. For example, in the local.conf.compute example file, the appropriate ceilometer plugins and services are enabled and disabled. If you were using something other than Ceilometer, then you would likely want to configure it likewise. The example file also sets the compute monitors nova configuration option to use the CPU virt driver. If you needed other metrics, it may be necessary to configure similar configuration options for the projects providing those metrics.

  5. For the controller node, copy the provided local.conf.controller example file to the controller node’s system at ~/devstack/local.conf. Make sure the HOST_IP value is changed appropriately - i.e., HOST_IP is set to the IP address of the controller node.

    Note: if you want to use another Watcher git repository (such as a local one), then change the enable plugin line:

    enable_plugin watcher <your_local_git_repo> [optional_branch]

    If you do this, then the Watcher DevStack plugin will try to pull the python-watcherclient repo from <your_local_git_repo>/../, so either make sure that is also available or specify WATCHERCLIENT_REPO in the local.conf file.

    Note: if you want to use a specific branch, specify WATCHER_BRANCH in the local.conf file. By default it will use the master branch.

    Note: watcher-api will default run under apache/httpd, set the variable WATCHER_USE_MOD_WSGI=FALSE if you do not wish to run under apache/httpd. For development environment it is suggested to set WATHCER_USE_MOD_WSGI to FALSE. For Production environment it is suggested to keep it at the default TRUE value.

  6. Start stacking from the controller node:

  7. Start stacking on each of the compute nodes using the same command.

  8. Configure the environment for live migration via NFS. See the Multi-Node DevStack Environment section for more details.

Multi-Node DevStack Environment

Since deploying Watcher with only a single compute node is not very useful, a few tips are given here for enabling a multi-node environment with live migration.

Configuring NFS Server

If you would like to use live migration for shared storage, then the controller can serve as the NFS server if needed:

sudo apt-get install nfs-kernel-server
sudo mkdir -p /nfs/instances
sudo chown stack:stack /nfs/instances

Add an entry to /etc/exports with the appropriate gateway and netmask information:

/nfs/instances <gateway>/<netmask>(rw,fsid=0,insecure,no_subtree_check,async,no_root_squash)

Export the NFS directories:

sudo exportfs -ra

Make sure the NFS server is running:

sudo service nfs-kernel-server status

If the server is not running, then start it:

sudo service nfs-kernel-server start

Configuring NFS on Compute Node

Each compute node needs to use the NFS server to hold the instance data:

sudo apt-get install rpcbind nfs-common
mkdir -p /opt/stack/data/instances
sudo mount <nfs-server-ip>:/nfs/instances /opt/stack/data/instances

If you would like to have the NFS directory automatically mounted on reboot, then add the following to /etc/fstab:

<nfs-server-ip>:/nfs/instances /opt/stack/data/instances nfs auto 0 0

Edit /etc/libvirt/libvirtd.conf to make sure the following values are set:

listen_tls = 0
listen_tcp = 1
auth_tcp = "none"

Edit /etc/default/libvirt-bin:

libvirtd_opts="-d -l"

Restart the libvirt service:

sudo service libvirt-bin restart

Setting up SSH keys between compute nodes to enable live migration

In order for live migration to work, SSH keys need to be exchanged between each compute node:

  1. The SOURCE root user’s public RSA key (likely in /root/.ssh/ needs to be in the DESTINATION stack user’s authorized_keys file (~stack/.ssh/authorized_keys). This can be accomplished by manually copying the contents from the file on the SOURCE to the DESTINATION. If you have a password configured for the stack user, then you can use the following command to accomplish the same thing:

    ssh-copy-id -i /root/.ssh/ stack@DESTINATION
  2. The DESTINATION host’s public ECDSA key (/etc/ssh/ needs to be in the SOURCE root user’s known_hosts file (/root/.ssh/known_hosts). This can be accomplished by running the following on the SOURCE machine (hostname must be used):

    ssh-keyscan -H DEST_HOSTNAME | sudo tee -a /root/.ssh/known_hosts

In essence, this means that every compute node’s root user’s public RSA key must exist in every other compute node’s stack user’s authorized_keys file and every compute node’s public ECDSA key needs to be in every other compute node’s root user’s known_hosts file.

Disable serial console

Serial console needs to be disabled for live migration to work.

On both the controller and compute node, in /etc/nova/nova.conf

[serial_console] enabled = False

Alternatively, in devstack’s local.conf:

[[post-config|$NOVA_CONF]] [serial_console] #enabled=false

VNC server configuration

The VNC server listening parameter needs to be set to any address so that the server can accept connections from all of the compute nodes.

On both the controller and compute node, in /etc/nova/nova.conf

vncserver_listen =

Alternatively, in devstack’s local.conf:


Environment final checkup

If you are willing to make sure everything is in order in your DevStack environment, you can run the Watcher Tempest tests which will validate its API but also that you can perform the typical Watcher workflows. To do so, have a look at the Tempest tests section which will explain to you how to run them.