Enable debug globally if enabled in any server config

[olivierlemasle]

1. Why is this pull request needed and what does it do?

Enable debug globally if enabled in any server config. It was currently enabled only if the plugin debug was enabled in the last server config of the Corefile.

This will still disable debug on reload, if debug is no more present.

Example with Corefile:

example.net {
    hosts
    debug
}

. {
    whoami
}

Logs (with debug message):

[DEBUG] plugin/hosts: Parsed hosts file into 0 entries
example.net.:1053
.:1053
CoreDNS-1.7.0
linux/amd64, go1.14.3, 5b4b3569

Remove debug in the Corefile and reload with SIGHUP1:

Logs (with no more debug message):

[INFO] SIGUSR1: Reloading
[INFO] Reloading
[INFO] Reloading complete

2. Which issues (if any) are related?

Fixes #4006

3. Which documentation changes (if any) need to be made?

N/A

4. Does this introduce a backward incompatible change or deprecation?

No

[codecov-commenter]

Codecov Report

Merging #4007 into master will increase coverage by 0.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4007      +/-   ##
==========================================
+ Coverage   56.85%   57.11%   +0.25%     
==========================================
  Files         224      222       -2     
  Lines       11349    11277      -72     
==========================================
- Hits         6453     6441      -12     
+ Misses       4401     4346      -55     
+ Partials      495      490       -5     

Impacted Files	Coverage Δ
core/dnsserver/server.go	13.19% <100.00%> (+2.15%)	⬆️
plugin/metrics/metrics.go	64.06% <0.00%> (-7.94%)	⬇️
plugin/file/reload.go	69.44% <0.00%> (-5.56%)	⬇️
plugin/grpc/grpc.go	63.79% <0.00%> (-1.67%)	⬇️
plugin/trace/trace.go	79.06% <0.00%> (ø)
plugin/backend_lookup.go	0.00% <0.00%> (ø)
plugin/health/overloaded.go	57.89% <0.00%> (ø)
plugin/template/template.go	88.42% <0.00%> (ø)
plugin/kubernetes/metrics.go	100.00% <0.00%> (ø)
plugin/template/metrics.go
... and 13 more

---

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[miekg]

I'm a bit confused the title says 'enable' but the patch only deals with disable?

[olivierlemasle]

@miekg I hope #4006 explains better the issue 😊

The goal is to have the "debug mode" enabled if it is configured in one of the configuration blocks of a Corefile.
Actually, with a Corefile as below, the "debug mode" is currently enabled and then immediately disabled:

example.net {
  # enable debug
  debug
}

. {
  # No "debug"
}

That's the issue I fix with this PR, by disabling "debug" ONLY IF it is not present in any configuration block.

[miekg]

ack ,that explains it better.

Can you think of a test to add?

[miekg]

probably also warrants documentation changes in the debug readme to explain this global behavior

[olivierlemasle]

Ok, I'll add documentation, and I will try to add tests if it makes sense.

[miekg]

any luck?

[olivierlemasle]

Sorry, I guess I will not have the time today, and then I'm in vacation for the next 2 weeks. I'll do it on August 17th.

[miekg]

enjoy your holiday, I might kick off a smaller 1.7.1 release before that though, but then it will be in 1.7.2 or 1.8.0

[olivierlemasle]

@miekg Sorry for the delay; I've finally updated the PR according to your comments.

[miekg]

thanks! And merged!