DMaaP Edge Deployment

The Dublin 5G Use Case has dependencies on DMaaP services.  The 5G components  (Data File Collector and 3GPP PM Mapper) will be deployed at the Edge, so DMaaP services should be made available to them to avoid a data flow path through the Central Kubernetes cluster.    This 5G Use Case relies on both Data Router and Message Router.

This Use Case will help flesh out the requirements and techniques for DMaaP Edge deployments.

Definitions  

1. Dublin introduces the notion of a multi-cloud deployment consisting of a single "central" kubernetes  High Availablility (HA) installation, and 0 or more "edge" kubernetes installations.  
2. Geo-redundancy applies to a multi-site central k8s deployment.  This shouldn't be confused with a multi-site ONAP deployment consisting of central and edge sites.

Assumptions

1. 1.DMaaP will maintain a single set of Helm Charts in the oom/kubernetes repo.  Said a different way, we will strive to not maintain separate  DMaaP Central charts and DMaaP Edge charts.
   1. The DMaaP Helm charts will continue to be maintained as a single oom kubernetes directory, with sub-directories for each component.
2. 2. The "central" site will always be deployed before any edge sites.
   1. The Edge deployment (and operation) will rely on central ONAP services (e.g. AAF)
   2. This will allow a human (at least) to capture any values representing central deployment details (such as a K8S gateway IP address)
3. All DMaaP components will continue to be deployed in the "central" k8s.  The details of what components will be deployed at any Edge, and how it will be deployed are the subject of this page.
4. An "edge" site can be deployed any time after the "central" site.
5. Not all edge sites need be deployed at the same time.  
6. As a Platform Service, DMaaP will be deployed before any application/microservice.
7. SSL Server Certificates will be created in advance of deployment, and not generated at deployment time.  (This is a feature for El Alto)
8. By convention, the kubernetes cluster name will be used as the name of the site.

Requirements

1. A Central-deployed DMaaP component muse be able to route to an Edge-deployed component, and distinguish between the same component deployed at different Edge sites.  Examples include:
   1. dr-prov periodically sends provisioning info to each dr-node
   2. A centrally-deployed dr-node may transfer a file to an Edge-deployed dr-node for delivery to a subscriber in that Edge, based on an egress rule
   3. A central mirrormaker subscribes to an Edge-deployed message-router kafka
2. An Edge-deployed DMaaP component must be able to route to a central-deployed service.  Examples include:
   1. dr-node periodically syncs with dr-prov
   2. dr-node authenticates publish requests using aaf
   3. message-router authenticates client requests using aaf
   4. dbc-client makes request to dmaap-bc API during post-install provisioning
   5. Edge mirrormaker subscribes to central message-router kafka
3. Localized DR Routing between a Data File Collector (DFC) and a PM Mapper deployed in the same Edge X.
   1. Localized DR Routing means DR Node is deployed in the same Edge site so data doesn't need to leave the site.
   2. DFC will be a publisher to a feed provisioned at deployment time.
   3. PM Mapper will be a subscriber provisioned at deployment time.
   4. The feed should be unique per site so that when there are multiple sites, PM Mapper only receives its locally produced data.
4. Localized messaging from PM Mapper and DFC.  This will signal DFC that a file was processed.
   1. Localized messaging implies a Message Router instance in the same edge location.
   2. PM Mapper will a publisher provisioned at deployment time 
   3. DFC will be a subscriber provisioned at deployment time.
   4. Communication will utilize an authenticated topic in the MR deployed in the same edge site. 
      1. PM Mapper and DFC will use AAF credentials to authenticate.
      2. PM Mapper identity will be authorized to publish on the topic
      3. DFC identity will be authorized to subscribe on the topic
5. Inter-site messaging from PM Mapper to VES perf3gpp
   1. Inter-site messaging means sending a message from an edge location publisher to a central location subscriber.
   2. PM Mapper, deployed at Edge,  will be a publisher using AAF credentials
   3. VES perf3gpp, deployed in Central, will be a subscriber using AAF credentials
   4. Communication will utilize an authenticated topic on the MR deployed in the same edge site.
      1. PM Mapper and DFC will use AAF credentials to authenticate.
      2. PM Mapper identity will be authorized to publish on the topic
      3. VES perf3gpp identity will be authorized to subscribe on the topic
   5. Furthermore, messages on this topic will be replicated to the central MR instance.
   6. Are there any other subscribers?  (esp, are there any other at edge?)

Solution Options for Dublin

This section is based on a discussion with Jack Lucas about possible approaches that we might consider within the Dublin feature set.

Ways to route to a k8s service in another k8s cluster:

1. Extend the configuration of the Jack's proxy to include DMaaP services.  Note: Current capability will route from edge to central. (See Jack's demo)
   1. Include central deployed DMaaP services with existing node ports in proxy config: dr-prov, message-router, dmaap-bc
   2. Expose central deployed DMaaP service on node port and add to proxy configuration: dr-node
   3. NOTE: proxy can subsequently route by FQDN (for HTTP only).  
2. K8S External Service.  Deploy services at Edge which map to central services.
   1. REF: https://cloud.google.com/blog/products/gcp/kubernetes-best-practices-mapping-external-services
3. Add entries for central services into /etc/hosts on Edge pods so they can route properly
4. Provision some external DNS service that is able to resolve to required IP addresses in other k8s cluster
   1. Will require establishing a convention for FQDN.  eg.  <Release>-<service>.<namespace>
   2. Convention should leverage assumptions of using same value for Release and k8s cluster name.
5. Determine how clients can specify FQDN (service name) but designate IP address to use.  
   1. See  --resolve option in curl for example of how this might work.
6. Apply k8s thinking to DMaaP component design:
   1. Abandon the DR publish redirect protocol and simply use dr-node service instead.
      1. if dr-node is local to the cluster, then client will route to local dr-node pod for publishing (which is desired)
      2. if dr-node isn't local to cluster, then client will route to central dr-node via proxy  (fallback)
   2. Change dr-prov algorithm for distributing prov data to dr-node so dr-prov doesn't need to know how to address every pod
      1. consider simple periodic polling by dr-node
      2. consider using an MR topic to trigger dr-node to poll for prov data
   3. migrate to ELK design for logging, removes need for dr-prov to gather logs from each dr-node.  (already in progress)

Open Issues

  dmaap:

    dmaap-message-router:

      enabled: true

    dmaap-bus-controller:

      enabled: false

    dmaap-dr-prov:

      enabled: false

    dmaap-dr-node:

      enabled: true

Development

1. Helm configuration overrides will be collected in a single file (e.g. dmaap-edge.yaml) and delivered to oom/kubernetes/onap/charts/resource/environments.  Examples of what kinds of overrides will be present in this file include:
   1. Setting the standard enabled indicator to true for dmaap, but false for other components.
      

      dmaap:
        enabled: true

   2. Setting an edge indicator to drive any edge-specific logic.  TBD if this is really useful - hopefully other overrides in this file are edge specific.
   3. Setting the values for a central service which may be needed at the edge.  Known examples include:
      1. Message Router must be configured to access the central AAF instance.  (DR Node may have this requirement in the near future)
      2. Data Router Node must be configured to access the central DR Prov
      3. Both MR and DR Node must register with central Bus Controller
   4. Setting scaling values appropriate to the edge.  e.g. perhaps a single kafka broker is appropriate at the edge
2. DMaaP Chart changes
   
   1. Reorder charts:
      1. Bus Controller must be up and running if other components are going to register with it.  Jira to remove any dependencies on MR.
      2. MR
      3. Mirror Maker
      4. DR Prov
      5. DR Node  (DR Prov must be up for Node to retrieve provisioning info)
   2. Post-install hooks:
      1. Bus controller:
         1. POST <central dmaap-bc>/webapi/dmaap
         2. POST <central dmaap-bc>/webapi/dcaeLocation (for central)
      2. MR:
         1. POST <central dmaap-bc>/webapi/mr_clusters  DMAAP-534  Jira to add kafka brokers to endpoint
      3. DR Node
         1. POST <central dmaap-bc>/webapi/dr_node   DMAAP-534

Step-by-step guide

This outlines the approach for solving this Edge deployment, and will undoubtedly be refined over time.

1. Central K8S Deployment
2. Central DMaaP Deployment
   1. Use k8s cluster name as the Release.  e.g. "central"
   2. Deploy aaf
   3. Deploy aai
   4. Deploy dmaap
   5. Deploy dcae
   6. Deploy VES perf3gpp via dcae
3. Edge K8S Deployment
   1. Register Edge K8S deployment in AAI (how?)
   2. Add dcaeLocation (for new Edge K8S) to DMaaP Bus Controller
4. Edge DMaaP Deployment
   1. Update dmaap-edge.yaml configuration override file with values from central
   2. Use k8s cluster name as the Release.  e.g. "edge1"
   3. deploy dmaap
   4. deploy PM Mapper via dcae

 Presentation

The following deck can be used to discuss the concepts on this page.

Related articles

DCAE MultiSite demo

5G Use Case (R4 Dublin)

• Page:
  Deploy OOM and SDC (or ONAP) on a single VM with microk8s - Honolulu Setup
• Page:
  Setup helm3 for oom
• Page:
  model-driven DMaaP Agent
• Page:
  DMaaP Edge Deployment
• Page:
  Cloud Agnostic Intent and Mappings