Issue 211: Adding annotation to segment store service for external dns

[pbelgundi]

Signed-off-by: pbelgundi [email protected]

Change log description

Added external-dns annotation to segment store external service that can be used by external-dns provider to assign a DNS name to the service.

Purpose of the change

Fixes #211

What the code does

Added domainName to Pravega Cluster Spec, that can be set via manifest to arrive at the FQDN for a single segment store node.
FQDN for segment store pod = SegmentStore_Pod_Name.domainName. ( ends with a . )

Added annotation external-dns.alpha.kubernetes.io/hostname to external service for each segment store container.

If external access=true, but domain name is not set in manifest, it would default to "pravega.io"

How to verify it

1. In Pravega spec set externalaccess=true, and domainName=example.com. 2 kubectl svc pravega-pravega-segmentstore-0 -o yamlshould show : external-dns.alpha.kubernetes.io/hostname: pravega-pravega-segmentstore-0.example.com.`
2. Check External-DNS component creates a DNS record for the segment store.

[pbelgundi]

Service shows annotation set correctly:

$kubectl get svc pravega-pravega-segmentstore-0 -o yaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    external-dns.alpha.kubernetes.io/hostname: pravega-pravega-segmentstore-0.example.com.
    ncp/internal_ip_for_policy: 100.64.65.241
  creationTimestamp: "2019-07-25T12:10:39Z"
 . . .

[pbelgundi]

When external_access = true, but 'domainName' is not set in manifest, external-dns annotation is not added to the service:

$ kubectl get svc pravega-pravega-segmentstore-0 -o yaml
apiVersion: v1
kind: Service
metadata:
  annotations:
    ncp/internal_ip_for_policy: 100.64.192.5
  creationTimestamp: "2019-07-31T10:23:43Z"

[Tristan1900]

LGTM

[EronWright]

In my opinion, the above variables would best be defined within the for loop.

[EronWright]

Looks good, thanks.