Implement weighted round robin load balancing strategy about k8gb HOT 8 CLOSED

@kuritka Yep, so my point is that by using percentages we're forcing users to think in % and keep the "100% in total" rule in mind.
Whereas when we use just numbers and calculate resulting weights as a proportion of the total sum, we give more flexibility.
This approach still allows using percentages as well, as you've shown in the examples above.
And we don't have to provide a complex validation in this case, we might just limit the max weight to some sensible value, like 1000

from k8gb.

Hi @ytsarev , sure we can. I supposed it's already closed

from k8gb.

The round robin is taken care of by our library https://github.com/k8gb-io/go-weight-shuffling, which shuffles the indexes in the array according to the predefined weights.

The library would run in the new CoreDNS external plugin within https://github.com/k8gb-io/coredns-crd-plugin. Data will be fed into this plugin from annotation within external DNS endpoints. The CoreDNS - external DNS plugin will read these annotations and arrange itself accordingly.

One cluster can have a number of IP addresses that can change from time to time. The N% weight is set per cluster (region), so I need IP addresses X Region X weight. The annotation is string, so I can annotate by json:

[
  {region: "eu", weightPercent: 20, targets:["172.18.0.5","172.18.0.6"]}, 
  {region: "us", weightPercent:80, targets:["172.18.0.1","172.18.0.2"]}
]

apiVersion: externaldns.k8s.io/v1alpha1
kind: DNSEndpoint
metadata:
  annotations:
    k8gb.absa.oss/dnstype: local
    k8gb.absa.oss/weight-round-robin: '[{"region":"eu","weightPercent":20,"targets":["172.18.0.5","172.18.0.6"]},{"region":"us","weightPercent":80,"targets":["172.18.0.1","172.18.0.2"]}]'
  name: k8gb-ns-extdns
  namespace: k8gb

from k8gb.

@kuritka sorry if I'm coming late to the party, but I've tried to check settings for different implementations of WRR, and in most cases, WRR weights are provided as positive integer instead of percentage:

https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/routing-policy-weighted.html
https://cloud.google.com/dns/docs/zones/manage-routing-policies
https://en.wikipedia.org/wiki/Weighted_round_robin
https://en.wikipedia.org/wiki/SRV_record

The resulting percentage for a particular member can be calculated as a proportion of the total weight of all the members in the WRR group.

This way users also don't have to keep in mind the rule of having 100% of weights in total across n clusters.

from k8gb.

It's more about the point of view. The change is a little more extensive, but not complex. Currently it works with percentages and accept values values like "100", "100%",100,100%

But I can change it so that the results are equivalent

# current
weight:
  us: 50%
  eu: 30%
  za: 20
  uk: 0%

# new alternative (integers distribution) 
weight:
  us: 50
  eu: 30
  za: 20
  uk: 0

weight:
  us: 5
  eu: 3
  za: 2
  uk: 0

weight:
  us: 64
  eu: 38
  za: 26
  uk: 0

from k8gb.

ok, will keep it consistent with route53 style and refactor k8gb controller to integers.

from k8gb.

@kuritka as WRR is implemented, can we close this issue?

from k8gb.

WRR was released in https://github.com/k8gb-io/k8gb/releases/tag/v0.11.1. Closing

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