How does Envoy Load balancing Weighted least request work

[sasinda...@gmail.com]

Does Envoy Loadbalancing "Weighted least request"  work on a global level when there are multiple client envoys accessing same dest service. I mean does each of the clients share information on how many active requests are for each target on a global level, or just know how many active requests are there by self (locally).

It would be nice if the documentation (https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/load_balancing#weighted-least-request) had more info on how envoy does it. 

Thanks

Cheers,

Sasinda.

[Christian Posta]

I believe this is per proxy -- the proxies do not coordinate with each other and try to come to consensus around what the global rates are... at least afaict.

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Christian Posta

twitter: @christianposta

http://blog.christianposta.com

[Matt Klein]

Correct, load balancing is fully distributed. PRs appreciated to the documentation: https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/load_balancing

Thanks,

Matt

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Matt Klein

Software Engineer

mkl...@lyft.com

https://calendly.com/mattklein123

[sasinda rukshan]

Hi Matt, Christian,

Thanks for the info! So there is no global knowledge on which services may be actually getting heavy loads and incurring latencies, under weighted least request.

Also then these load balancing weights coming from SDS, means envoy proxies consider them individually to weight on random selection or round robin etc; isn't it?
SDS, /v1/loadbalancing/:service/:ip_address

{
     "az": "...",
     "region": "...",
     "instance_id": "...",
     "canary": false,
     "load_balancing_weight": 1
  }

Cheers,

Sasinda.

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Best Regards,

Sasinda Rukshan.

[Matt Klein]

Correct, everything is distributed in the current load balancing implementations.