Replace memberlist service in favor of cortex provided service

[periklis]

What this PR does / why we need it:
This PR addresses the wiring work needed to use the non-experimental version of memberlist as provided by: cortexproject/cortex#2638

Which issue(s) this PR fixes:

Special notes for your reviewer:

Checklist

• Documentation added
• Tests updated

cc @cyriltovena @pstibrany

[pstibrany]

LGTM, thank you!

[periklis]

@pstibrany I believe it's time to give documentation also some love regarding memberlist. I can add an example configuration with a reference to a headless k8s service.

[pstibrany]

@pstibrany I believe it's time to give documentation also some love regarding memberlist. I can add an example configuration with a reference to a headless k8s service.

That's a great idea. We have some documentation in Cortex, but nothing in Loki.

• https://cortexmetrics.io/docs/getting-started/getting-started-with-gossiped-ring/
• https://cortexmetrics.io/docs/configuration/arguments/#memberlist

[codecov-commenter]

Codecov Report

Merging #2224 into master will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #2224      +/-   ##
==========================================
- Coverage   62.09%   62.08%   -0.01%     
==========================================
  Files         156      156              
  Lines       12531    12529       -2     
==========================================
- Hits         7781     7779       -2     
  Misses       4143     4143              
  Partials      607      607              

Impacted Files	Coverage Δ
cmd/querytee/main.go	0.00% <0.00%> (ø)
pkg/loki/loki.go	0.00% <0.00%> (ø)
pkg/loki/modules.go	9.13% <0.00%> (+0.12%)	⬆️
pkg/querier/queryrange/downstreamer.go	95.87% <0.00%> (-2.07%)	⬇️

[periklis]

Hmm... i noticed that we don't expose the memberlist flags for loki. Maybe also a good time to do so. WDYT?

[pstibrany]

Hmm... i noticed that we don't expose the memberlist flags for loki. Maybe also a good time to do so. WDYT?

Interesting, yes, we should do that. Thanks!

[owen-d]

Keeping an eye on this, looks good so far.

[periklis]

@pstibrany @cyriltovena PTAL with the added docs and examples

[pstibrany]

Nice example. Thanks for all your work on this PR!