Upgrade openresty/lua-resty-balancer

[ArchangelSDY]

What this PR does / why we need it:

This fixes bug in chash:reinit which prevents endpoints from being updated correctly.

See openresty/lua-resty-balancer#25

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

[aledbf]

@ArchangelSDY please increase the version to 0.79 in images/nginx/Makefile

[ArchangelSDY]

@aledbf updated.

[aledbf]

/lgtm
/approve

[aledbf]

@ArchangelSDY thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, ArchangelSDY

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[aledbf]

I will update the ingress controller image after this PR is merged and the new image is available in quay.io

[ArchangelSDY]

Cool, thanks @aledbf !

[ElvinEfendi]

@ArchangelSDY first thanks for fixing this!

Did you see any impact of this on ingress-nginx? I looked into this and only impact I could see is that ingress-nginx would unnecessarily keep calling

ingress-nginx/rootfs/etc/nginx/lua/balancer/resty.lua

Line 22 in 88c2909

self.instance:reinit(nodes)

because

ingress-nginx/rootfs/etc/nginx/lua/balancer/resty.lua

Line 17 in 88c2909

local changed = not util.deep_compare(self.instance.nodes, nodes)

would always be true. But no impact on load balancing logic.

[ArchangelSDY]

@ElvinEfendi Here is the case we encountered:

1. First we have two backends A and B.
2. For some reason B failed readiness probe, so self.instance.nodes != nodes. Then reinit was called correctly.
3. B comes back online afterwards. But now self.instance.nodes == nodes since self.instance.nodes was not correctly updated. So reinit will not be called. B will never be added back.

[ElvinEfendi]

@ArchangelSDY I see, that makes sense. I think this is also the root cause of some session affinity related issues where users were complaining that load balancing is not working.