openstack/kuryr-kubernetes
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Update the Service Creation Process

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Change-Id: I743e4ef717f5e06932da103c02ef6f07e48fb584
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Sunday Mgbogu 2021-06-08 16:19:47 +01:00
parent 5d2ac1c691
commit 1b6eb50d83
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doc/source/devref/service_support.rst
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@ -88,6 +88,54 @@ LBaaS Driver is added to manage service translation to the LBaaSv2-like API.
It abstracts all the details of service translation to Load Balancer.
LBaaSv2Driver supports this interface by mapping to neutron LBaaSv2 constructs.
Service Creation Process
~~~~~~~~~~~~~~~~~~~~~~~~
What happens when a service gets created by Kubernetes?
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
When a Kubernetes Service and Endpoints are created,the ServiceHandler and
EndpointHandler (at controller/handlers/lbaas.py) are called. When the
ServiceHandler first starts handling the on_present event, it creates the
KuryrLoadBalancer CRD with the Service spec and empty status. When the Endpoints
information is not yet added on the spec by the EndpointHandler, the event reaching
KuryrLoadBalancerHandler is skipped. If the EndpointsHandler starts handling the
on_present event first, the KuryrLoadBalancer CRD is created with the endpoints subsets.
Otherwise, it will update the existing CRD created by the ServiceHandler with the
endpoints subsets.
The KuryrLoadBalancerHandler (at controller/handlers/loadbalancer.py) upon
noticing the KuryrLoadBalancer CRD with the full specification, calls the
appropriate Drivers to handle the openstack resources such as Loadbalancer,
Load Balancer Listeners, Load Balancer Pools, and Load Balancer Members.
It uses the _sync_lbaas_members function to check if Openstack
Loadbalancers are in sync with the kubernetes counterparts.
Service Deletion Process
~~~~~~~~~~~~~~~~~~~~~~~~
What happens when a service gets deleted by Kubernetes?
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
When a Kubernetes Service and Endpoints are deleted, the finalizers which are
added to the service object (and the KLB CRD Object too) and defined during the
KuryrLoadBalancer CRD creation, blocks the removal of the kubernetes object until
the associated OpenStack resources are removed, which also avoids leftovers. When they
are removed, Kubernetes is able to remove the CRD, the service and the endpoints,
hence completing the service removal action.
What happens if the KuryrLoadBalancer CRD status changes?
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
If the members field on the status of the CRD is manually removed or the status is
completely set to an empty object, the KuryrLoadBalancerHandler that is watching these
CRD objects detects this change and confirms that there is no information about the
OpenStack resources on the status and so needs to rediscover or recreate them. It checks
if there are provisioned OpenStack resources (in this case loadbalancers, listeners, pools,
and members) for the service/endpoints defined on the KuryrLoadBalancer CRD spec. If that
is the case, it retrieves their information and puts it back on the CRD status field. If that
is not the case (due to the resources being deleted on the OpenStack side), it will recreate
the resources and write the new information about them on the CRD status field.
.. _Kubernetes service: http://kubernetes.io/docs/user-guide/services/
.. _Kube-Proxy: http://kubernetes.io/docs/admin/kube-proxy/