Use Envoy's /ready endpoint for readiness probes

[rochacon]

This PR enables Envoy's 1.11+ /ready endpoint for readiness probes.

Closes #1277

[stevesloka]

Hey thanks for working on this @rochacon! We can also remove the health filter here: https://github.com/heptio/contour/blob/1aaf973e922e1449d107e8e787b04b54058e660f/internal/envoy/stats.go#L76-L88

[ravilr]

we use the envoy.health_check filter today to achieve graceful connection draining during envoy shutdown/rolling deploys, i.e. issue an /healthcheck/fail and then wait for connections to drain.
Does /ready admin endpoint have the same behavior ?

[rochacon]

@stevesloka I've left the filter on purpose, in the intent to use the /ready only for the readinessProbe, but given it is in the same listener it doesn't make sense to keep it. I'll test the change and update the PR later today.

@ravilr yes, both the health check filter and /ready behave quite similar.

[stevesloka]

Thanks @rochacon, I think if we switch to /ready, there's no need for the healthz filter to be applied. One less thing to configure. =)

[youngnick]

LGTM, with the caveat that this will need a section in the upgrade guide for 1.0-beta1 plus all 1.0 releases. I've added a note to #1476

[davecheney]

Nick, would you please merge this for the OP

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On 10 Sep 2019, at 10:02, Nick Young ***@***.***> wrote: @youngnick approved this pull request. LGTM, with the caveat that this will need a section in the upgrade guide for 1.0-beta1 plus all 1.0 releases. I've added a note to #1476 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.