Thanks for the pointers.


The details of the Kubernetes plan for DCAE is still work-in-progress.  Here 
are some of highlights for service components.

  1.  Will support Kubernetes based scaling and resilience mechanism for 
dockerized service components.
     *   This implies that the container/containers of a service component will 
be packaged as pod.  The resilience is expected to be provided by Kubernetes 
     *   The Kubernetes based scaling support may need additional support from 
service component developer. For example, if a service component is stateless, 
for which each instance behaves exactly the same as the next, are 
“scaling-ready”.  Load can be distributed to any instance and the result would 
be the same.  However, if the service component keeps states, multiple replicas 
of this service component may have different local states if not handled 
carefully.  The actual mechanism to ensure state synchronization is application 
dependent.  But one typical approach is to push “states” to an external service 
such as a DB, or persistent volume, or a distributed kv store, etc, and states 
are loaded into individual replica when needed (e.g. startup) so different 
replicas get the state view from the same copy.
     *   In terms of multiple replicas subscribing to the same message router 
topic, there is a way to distribute the load.  That is, each replica uses the 
same “groupid” but different “userid”.  Message router will consider a message 
received by a group when it is received by any user of the group.  This way we 
can avoid the same message being delivered to multiple replicas.
  2.  Our goal is to maintain the interfaces that how a service component 
interacts with the rest of DCAE the same, e.g. how your component gets deployed 
and how your component receives configuration updates, etc.
  3.  How the scaling trigger arrives and the actual scaling (i.e. more 
replicas) is handled by external mechanisms.  Service components themselves do 
not need to worry about that.

We hope to have more details to share the next week, and set up focus meeting 
discussing more.


From: Roger Maitland <>
Date: Friday, February 2, 2018 at 1:48 PM
To: "" <>, "JI, LUSHENG 
Cc: "" <>, 
"" <>
Subject: RE: [onap-discuss] [dcae][dcaegen2][holmes] A Question on Auto 
Scailing of DCAE Microservices


I don’t have an answer in the context of the DCAE controller but OOM/Kubernetes 
has facilities to help build a Holmes cluster in the containerized version of 
DCAE (which is being worked on).  The cluster can be static (which is believe 
is what most projects intend for Beijing) or dynamic (the OOM team would love 
to work with you on this). Here are some links I hope you find useful:

  *   OOM Scaling:<>
  *   K8s auto-scaling:<>

Here is a sample of how an auto-scaler is configured:
apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
  name: php-apache
  namespace: default
    apiVersion: apps/v1beta1
    kind: Deployment
    name: php-apache
  minReplicas: 1
  maxReplicas: 10
  - type: Resource
      name: cpu
      targetAverageUtilization: 50
  observedGeneration: 1
  lastScaleTime: <some-time>
  currentReplicas: 1
  desiredReplicas: 1
  - type: Resource
      name: cpu
      currentAverageUtilization: 0
      currentAverageValue: 0

The OOM team would be happy to work with you on implementing this.

[] On Behalf Of
Sent: Friday, February 2, 2018 2:58 AM
Subject: [onap-discuss] [dcae][dcaegen2][holmes] A Question on Auto Scailing of 
DCAE Microservices


The Holmes team is currently working on the auto scaling plans for Holmes. We 
need to confirm something with you.

To my understanding, the microservice should only focus on how to maintain and 
balance its data flow rather than how the docker containers/vms are scaled by 
their controller. As a DCAE application, I think it's DCAE controller's 
responsiblity to determine when and how to scale in or scale out Holmes 
instances. Is that correct?

If what my understanding is correct, does DCAE have any specific requirements 
regarding collecting the status and metrics of its microservices?



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