Re: [pve-devel] [PATCH v4 pve-storage 05/16] cephconfig: align our parser more with Ceph's parser

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

On March 5, 2024 4:07 pm, Max Carrara wrote:
>  1. Comments, irrespective of whether they start with '#' or ';' are
>     now treated the same. Otherwise, sections and key-value pairs with
>     a trailing comment starting with ';' are still parsed. Consider
>     this example:
> 
>       [some.section] # inline comment after section
>       foo = bar ; inline comment after value
> 
>      The '[some.section]' section in the example above would otherwise
>      not be parsed at all, while in the key-value definition 'foo'
>      parses as the key, which is correct, but 'bar ; inline comment
>      after value' parses as value, which is incorrect according to
>      Ceph's grammar [0][1].
> 
>  2. Sections may now contain any character, including whitespace, but
>     not '\n' or a comment literal '#' or ';'. The case for comment
>     literals is handled in 1. above.
> 
>  3. Instead of treating '-', '_' and ' ' as the same, only '_' and ' '
>     are treated the same, like in Ceph's parser [2].
> 
>  4. Although not crucial for Ceph, our parser now also supports empty
>     sections. When a section header is successfully parsed, it gets
>     added to the configuration hash and the parser continues operating
>     on the next line.
> 
> [0]: https://git.proxmox.com/?p=ceph.git;a=blob;f=ceph/src/common/ConfUtils.cc;h=2f78fd02bf9e27467275752e6f3bca0c5e3946ce;hb=refs/heads/master#l178
> [1]: https://git.proxmox.com/?p=ceph.git;a=blob;f=ceph/src/common/ConfUtils.cc;h=2f78fd02bf9e27467275752e6f3bca0c5e3946ce;hb=refs/heads/master#l194
> [2]: https://git.proxmox.com/?p=ceph.git;a=blob;f=ceph/src/common/ConfUtils.cc;h=2f78fd02bf9e27467275752e6f3bca0c5e3946ce;hb=refs/heads/master#l294
> 
> Signed-off-by: Max Carrara <m.carrara@proxmox.com>
> ---
> Changes v1 --> v2:
>   * new
> Changes v2 --> v3:
>   * support comment literals (4.)
> Changes v3 --> v4:
>   * support empty sections
>   * fix and move support for comment literals to separate patch
> 
>  src/PVE/CephConfig.pm | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/src/PVE/CephConfig.pm b/src/PVE/CephConfig.pm
> index 6b10d46..74a92eb 100644
> --- a/src/PVE/CephConfig.pm
> +++ b/src/PVE/CephConfig.pm
> @@ -10,6 +10,8 @@ cfs_register_file('ceph.conf',
>  		  \&parse_ceph_config,
>  		  \&write_ceph_config);
>  
> +# For more details on how Ceph's config parser works, see:
> +# https://git.proxmox.com/?p=ceph.git;a=blob;f=ceph/src/common/ConfUtils.cc;h=2f78fd02bf9e27467275752e6f3bca0c5e3946ce;hb=refs/heads/master
>  sub parse_ceph_config {
>      my ($filename, $raw) = @_;
>  
> @@ -20,14 +22,18 @@ sub parse_ceph_config {
>  
>      my $section;
>  
> -    foreach my $line (@lines) {
> -	$line =~ s/#.*$//;
> +    for my $line (@lines) {
> +	$line =~ s/(?<!\\)(#|;).*$//;

nit: [#;] instead of the group works as well, and is a bit more
idiomatic IMHO.

so this seems to agree with the parser grammar, but it kind of disagrees
with the docs that for example state:

> mon_host
> 
> This is a list of IP addresses or hostnames that are separated by commas, whitespace, or semicolons. 

https://docs.ceph.com/en/latest/rados/configuration/ceph-conf/#confval-mon_host

well, they don't mention there that you need to escape the `;` for that
to work, else only the first "entry" takes, and the rest is silently
interpreted as comment. if you quote the "list", then it's even a parse
error since the closing quote is interpreted as part of the comment ;)

but unfortunately there is one more issue:

\\;

still marks the start of a comment (since it's the backlash that is
being escaped) in ceph's parser (same applies to '#' as well).

what a mess this file format is..

>  	$line =~ s/^\s+//;
> -	$line =~ s/^;.*$//;
>  	$line =~ s/\s+$//;
>  	next if !$line;
>  
> -	$section = $1 if $line =~ m/^\[(\S+)\]$/;
> +	if ($line =~ m/^\[(.+)\]$/) {
> +	    $section = $1;
> +	    $cfg->{$section} = {} if !exists($cfg->{$section});
> +	    next;
> +	}
> +
>  	if (!$section) {
>  	    warn "no section - skip: $line\n";
>  	    next;
> @@ -35,11 +41,12 @@ sub parse_ceph_config {
>  
>  	if ($line =~ m/^(.*?\S)\s*=\s*(\S.*)$/) {
>  	    my ($key, $val) = ($1, $2);
> -	    # ceph treats ' ', '_' and '-' in keys the same, so lets do too
> -	    $key =~ s/[-\ ]/_/g;
> +	    # ceph treats ' ' and '_' in keys the same, so lets do too
> +	    $key =~ s/ /_/g;
>  	    $cfg->{$section}->{$key} = $val;
> -	}
>  
> +	    next;

this next serves no purpose? (ah, it does with one of the later patches
that adds code below, so please move this to that patch!)

> +	}
>      }
>  
>      return $cfg;
> -- 
> 2.39.2