dnsdist: add support for user defined metrics

[chbruyand]

Short description

This PR adds a few functions to declare and manipulate user-defined metrics. Currently supports gauge and counter types with set, increment and decrement operations.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[github-actions]

@check-spelling-bot Report

Unrecognized words, please review:

• custommetrics

Previously acknowledged words that are now absent

AUTHIP dnsheader pieter

To accept these unrecognized words as correct (and remove the previously acknowledged and now absent words), run the following commands

... in a clone of the git@github.com:chbruyand/pdns.git repository
on the dnsdist-custom-metrics branch:

update_files() {
perl -e '
my @expect_files=qw('".github/actions/spell-check/expect.txt"');
@ARGV=@expect_files;
my @stale=qw('"$patch_remove"');
my $re=join "|", @stale;
my $suffix=".".time();
my $previous="";
sub maybe_unlink { unlink($_[0]) if $_[0]; }
while (<>) {
if ($ARGV ne $old_argv) { maybe_unlink($previous); $previous="$ARGV$suffix"; rename($ARGV, $previous); open(ARGV_OUT, ">$ARGV"); select(ARGV_OUT); $old_argv = $ARGV; }
next if /^(?:$re)(?:(?:\r|\n)*$| .*)/; print;
}; maybe_unlink($previous);'
perl -e '
my $new_expect_file=".github/actions/spell-check/expect.txt";
use File::Path qw(make_path);
use File::Basename qw(dirname);
make_path (dirname($new_expect_file));
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"$patch_add"');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a)."-".$a cmp lc($b)."-".$b} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;
system("git", "add", $new_expect_file);
'
}

comment_json=$(mktemp)
curl -L -s -S \
  --header "Content-Type: application/json" \
  "https://api.github.com/repos/PowerDNS/pdns/issues/comments/1144691493" > "$comment_json"
comment_body=$(mktemp)
jq -r .body < "$comment_json" > $comment_body
rm $comment_json

patch_remove=$(perl -ne 'next unless s{^</summary>(.*)</details>$}{$1}; print' < "$comment_body")
  

patch_add=$(perl -e '$/=undef;
$_=<>;
s{<details>.*}{}s;
s{^#.*}{};
s{\n##.*}{};
s{(?:^|\n)\s*\*}{}g;
s{\s+}{ }g;
print' < "$comment_body")
  
update_files
rm $comment_body
git add -u

If the flagged items do not appear to be text

If items relate to a ...

• well-formed pattern.

  If you can write a pattern that would match it,
  try adding it to the patterns.txt file.

  Patterns are Perl 5 Regular Expressions - you can test yours before committing to verify it will match your lines.

  Note that patterns can't match multiline strings.

• binary file.

  Please add a file path to the excludes.txt file matching the containing file.

  File paths are Perl 5 Regular Expressions - you can test yours before committing to verify it will match your files.

  ^ refers to the file's path from the root of the repository, so ^README\.md$ would exclude README.md (on whichever branch you're using).

[rgacogne]

Looks good, thanks! A couple things need to be tied up but the general logic looks great.

[rgacogne]

I cannot reproduce the CI failure locally, though :-/

[Habbie]

I cannot reproduce the CI failure locally, though :-/

Me neither :(

[github-actions]

@check-spelling-bot Report

Unrecognized words, please review:

• custommetrics

Previously acknowledged words that are now absent

AUTHIP dnsheader pieter

To accept these unrecognized words as correct (and remove the previously acknowledged and now absent words), run the following commands

... in a clone of the git@github.com:chbruyand/pdns.git repository
on the dnsdist-custom-metrics branch:

update_files() {
perl -e '
my @expect_files=qw('".github/actions/spell-check/expect.txt"');
@ARGV=@expect_files;
my @stale=qw('"$patch_remove"');
my $re=join "|", @stale;
my $suffix=".".time();
my $previous="";
sub maybe_unlink { unlink($_[0]) if $_[0]; }
while (<>) {
if ($ARGV ne $old_argv) { maybe_unlink($previous); $previous="$ARGV$suffix"; rename($ARGV, $previous); open(ARGV_OUT, ">$ARGV"); select(ARGV_OUT); $old_argv = $ARGV; }
next if /^(?:$re)(?:(?:\r|\n)*$| .*)/; print;
}; maybe_unlink($previous);'
perl -e '
my $new_expect_file=".github/actions/spell-check/expect.txt";
use File::Path qw(make_path);
use File::Basename qw(dirname);
make_path (dirname($new_expect_file));
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"$patch_add"');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a)."-".$a cmp lc($b)."-".$b} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;
system("git", "add", $new_expect_file);
'
}

comment_json=$(mktemp)
curl -L -s -S \
  --header "Content-Type: application/json" \
  "https://api.github.com/repos/PowerDNS/pdns/issues/comments/1144935403" > "$comment_json"
comment_body=$(mktemp)
jq -r .body < "$comment_json" > $comment_body
rm $comment_json

patch_remove=$(perl -ne 'next unless s{^</summary>(.*)</details>$}{$1}; print' < "$comment_body")
  

patch_add=$(perl -e '$/=undef;
$_=<>;
s{<details>.*}{}s;
s{^#.*}{};
s{\n##.*}{};
s{(?:^|\n)\s*\*}{}g;
s{\s+}{ }g;
print' < "$comment_body")
  
update_files
rm $comment_body
git add -u

If the flagged items do not appear to be text

If items relate to a ...

• well-formed pattern.

  If you can write a pattern that would match it,
  try adding it to the patterns.txt file.

  Patterns are Perl 5 Regular Expressions - you can test yours before committing to verify it will match your lines.

  Note that patterns can't match multiline strings.

• binary file.

  Please add a file path to the excludes.txt file matching the containing file.

  File paths are Perl 5 Regular Expressions - you can test yours before committing to verify it will match your files.

  ^ refers to the file's path from the root of the repository, so ^README\.md$ would exclude README.md (on whichever branch you're using).

[rgacogne]

Looks good to me, I'll do more tests once the CI is green 👍

[chbruyand]

Thanks for the comprehensive review!