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Consistent hashing to a subset of nodes. It works like consistent hash,

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but instead of mapping to a single node, we map to a subset of nodes.
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Diego Woitasen 2018-11-10 20:30:06 -03:00
parent 29118750be
commit 60b983503b
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docs/user-guide/nginx-configuration/annotations.md
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@ -186,10 +186,16 @@ nginx.ingress.kubernetes.io/auth-realm: "realm string"
NGINX supports load balancing by client-server mapping based on [consistent hashing](http://nginx.org/en/docs/http/ngx_http_upstream_module.html#hash) for a given key. The key can contain text, variables or any combination thereof. This feature allows for request stickiness other than client IP or cookies. The [ketama](http://www.last.fm/user/RJ/journal/2007/04/10/392555/) consistent hashing method will be used which ensures only a few keys would be remapped to different servers on upstream group changes.
There is a special mode of upstream hashing called subset. In this mode, upstream servers are grouped into subsets, and stickiness works by mapping keys to a subset instead of individual upstream servers. Specific server is chosen uniformly at random from the selected sticky subset. It provides a balance between stickiness and load distribution.
To enable consistent hashing for a backend:
`nginx.ingress.kubernetes.io/upstream-hash-by`: the nginx variable, text value or any combination thereof to use for consistent hashing. For example `nginx.ingress.kubernetes.io/upstream-hash-by: "$request_uri"` to consistently hash upstream requests by the current request URI.
"subset" hashing can be enabled setting `nginx.ingress.kubernetes.io/upstream-hash-by-subset`: "true". This maps requests to subset of nodes instead of a single one. `upstream-hash-by-subset-size` determines the size of each subset (default 3).
Please check the [chashsubset](../../examples/chashsubset/deployment.yaml) example.
### Custom NGINX load balancing
This is similar to [`load-balance` in ConfigMap](./configmap.md#load-balance), but configures load balancing algorithm per ingress.