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ovn-fake-multinode

Using this repo, you can leverage nested namespaces to deploy an OVN cluster where outer namespaces represent a compute node -- aka OVN chassis. Inside each of these emulated chassis, we are then able to create inner namespaces to emulate something comparable to ports of a VM in a compute node.

For more details, take a look at this talk from the 2019 OVScon: Deploying multi chassis OVN using docker in docker by Numan Siddique, Red Hat: Slides Video

Steps

Step 1: Build the container images

By default, podman is used (users can control the container runtime through the RUNC_CMD environment variable):

sudo OVN_SRC_PATH=<path_to_ovn_src_folder> OVS_SRC_PATH=<path_to_ovs_src_folder> ./ovn_cluster.sh build

This will create 2 container images

  • ovn/cinc: base image that gives us the nesting capability
  • ovn/ovn-multi-node: built on top of cinc where ovs+ovn is compiled and installed

By default, these container images are built on top of fedora:latest. This behavior can be controlled by two environment variables:

  • OS_IMAGE: URL from which the base OCI image is pulled (default: quay.io/fedora/fedora:latest)
  • OS_BASE: Which OS is used for the base OCI image. Supported values are fedora and ubuntu (default: fedora)

Step 2: Start openvswitch in your host

In order to interconnect the containers that emulate the chassis, we need an underlay network. This step is what provides that.

sudo /usr/share/openvswitch/scripts/ovs-ctl --system-id=testovn start

Step 3: Start the ovn-fake-multinode

sudo ./ovn_cluster.sh start

Step 4: Stop the ovn-fake-multinode and tweak cluster as needed

sudo ./ovn_cluster.sh stop

# look for start-container and configure-ovn functions in
vi ./ovn_cluster.sh

# Go back to step 3 and have fun!

Getting into underlay

A port called ovnfake-ext is created in the fake underlay network as part of ovn_cluster.sh start. You can use that as an easy way of getting inside the cluster (via NAT in OVN). Look for ip netns add ovnfake-ext in ovn_cluster.sh. An example for doing that is shown here:

sudo ip netns exec ovnfake-ext bash
ip a
ip route
ping -i 1 -c 1 -w 1 172.16.0.110 >/dev/null && \
   echo 'happy happy, joy joy' || echo sad panda
exit

Similarly, a port called ovnfake-int is created in the fake node network. It can be used to access the emulated chassis. Here is an example:

sudo ip netns exec ovnfake-int bash
ip a
ping -i 1 -c 1 -w 1 170.168.0.2 >/dev/null && \
   echo 'happy happy, joy joy' || echo sad panda
exit

Pre-provisioning NB and/or SB databases.

It's sometime useful to be able to start up a cluster with pre-existing OVN NB and/or SB databases. For example, when debugging an issue from a real production cluster. In order to achieve that the OVN_NBDB_SRC and OVN_SBDB_SRC` variables can be used:

OVN_NBDB_SRC=some-nb.db OVN_SBDB_SRC=some-sb.db ./ovn_cluster.sh start

Vagrant based VM

To deploy a VM that automatically performs the steps above as part of it's provisioning, consider using Vagrantfile located in this repo.

git clone https://github.com/ovn-org/ovn-fake-multinode.git && \
cd ovn-fake-multinode && vagrant up && vagrant ssh

Vagrant based development

If you would like to use the Vagrant based approach to do OVS and/or kernel development check out the following document. It also has some simple traffic test to see throughput performance.