Previously, the e2e test was overriding the plugins socket directory to
"/var/lib/kubelet/plugins_registry". This seems wrong, and with that
setting the e2e test was already failing, because the registration
process was timing out, in turn because the kubelet was trying to call
back the device plugin in the wrong place (see below for details).
I can't explain why it worked before - or it if worked at all - but
it really seems that `pluginapi.DevicePluginPath` is the right
setting here.
+++
In a nutshell, the device plugin registration process works like this:
1. The kubelet runs and creates the device plugin socket registration
endpoint:
KubeletSocket = DevicePluginPath + "kubelet.sock"
DevicePluginPath = "/var/lib/kubelet/device-plugins/"
2. Each device plugin will listen to an ENDPOINT the kubelet will connect
backk to. IOW the kubelet will act like a client to each device plugin,
to perform allocation requests (and more)
Each device plugin will serve from a endpoint.
The endpoint name is plugin-specific, but they all must be inside a
well-known directory: pluginapi.DevicePluginPath
3. The kubelet creates the device plugin pod, like any other pod
4. During the startup, each device plugin wants to register itself in the
kubelet. So it sends a request through
the registration endpoint. Key details:
grpc.Dial(kubelet registration socket)
registration request
reqt := &pluginapi.RegisterRequest{
Version: pluginapi.Version,
Endpoint: endpointSocket, <- socket relative to pluginapi.DevicePluginPath
ResourceName: resourceName, <- resource name to be exposed
}
5. While handling the registration request, kubelet dial back the
device plugin on socketDir + req.Endpoint.
But socketDir is hardcoded in the device manager code to
pluginapi.KubeletSocket
Signed-off-by: Francesco Romani <fromani@redhat.com>
98eb6db7c0