enable reuse port by default

[rajatjindal]

What this PR does / why we need it:

This enables the reuse port by default as https://trac.nginx.org/nginx/ticket/1300 seems to be fixed.

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

N/A

Special notes for your reviewer:

I tested it using steps on the ticket with ingress controller version 0.14.0, with nginx/1.13.12 and it seems to be working fine.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: rajatjindal
To fully approve this pull request, please assign additional approvers.
We suggest the following additional approver: justinsb

Assign the PR to them by writing /assign @justinsb in a comment when ready.

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov-io]

Codecov Report

Merging #2466 into master will decrease coverage by 0.12%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2466      +/-   ##
==========================================
- Coverage   41.75%   41.62%   -0.13%     
==========================================
  Files          74       74              
  Lines        5291     5292       +1     
==========================================
- Hits         2209     2203       -6     
- Misses       2786     2792       +6     
- Partials      296      297       +1

Impacted Files	Coverage Δ
internal/ingress/controller/config/config.go	98.23% <100%> (+0.01%)	⬆️
cmd/nginx/main.go	21.37% <0%> (-4.83%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 87d1b8b...8efb991. Read the comment docs.

[aledbf]

@rajatjindal before a change in this default we need to make sure do not introduce this issue again #1905
So for that, we need some e2e tests that check this.

[JordanP]

Just to make sure, is the e2e test supposed to check whether "reuse" is present in the Nginx conf or do we aim to have a non regression test for https://trac.nginx.org/nginx/ticket/1300 ?

[aledbf]

or do we aim to have a non regression test for https://trac.nginx.org/nginx/ticket/1300 ?

Not sure how we can do that.

I am not sure this PR should be merged. The user must be aware of this potential issue and turn on the feature with the configmap

[JordanP]

I see. The configmap is always a good choice.

But this was a bug in Nginx and this bug is now fixed, so I am not sure what justifies the change in default (from reuse to noreuse) now.

That being said, I still think we should default to noreuse because "it feels" the safest.

[aledbf]

Closing. The side effect of this setting is too high to change the default. This can enabled in the configuration configmap

[rajatjindal]

thanks for the feedback guys, it totally make sense.