Re: --debug LEVEL not documented in CLI

[Wilko Meyer <w@wmeyer.eu>]

Hi,
 
"jgart" <jgart@dismail.de> writes:

> What debug LEVEL's are permissible?
>
> For example, is 79 allowed?
>
> Or 5, 4, 3, 2, 1?
>
> What is the difference between the LEVELs? Where is the input LEVEL cutoff? At 6?

The documentation[0] on common build options seems to be a bit more
detailed on this at least on what range is available:

>> Produce debugging output coming from the build daemon. level must be
>> an integer between 0 and 5; higher means more verbose output. Setting
>> a level of 4 or more may be helpful when debugging setup issues with
>> the build daemon.

So a range between 0 and 5 seems to be in use. It's possible to use a
level >5, e.g. 79 or something else, which has the same effect as using
5 as a debug level.

However it's not quite clear from the documentaton itself what the
respective debug levels do. The levels seem to be defined in
nix/libutil/types.hh:

typedef enum {
    lvlError = 0,
    lvlInfo,
    lvlTalkative,
    lvlChatty,
    lvlDebug,
    lvlVomit
} Verbosity;

and all/most(?) levels seem to be in use:

(guix230 (~/devel/guix)) λ rg -cl 'lvl(Error|Info|Talkative|Chatty|Debug|Vomit)'                              
nix/nix-daemon/guix-daemon.cc:6
nix/libutil/serialise.cc:1
nix/libutil/util.hh:1
nix/nix-daemon/nix-daemon.cc:6
nix/libutil/types.hh:6
nix/libutil/util.cc:9
nix/libutil/affinity.cc:3
nix/libstore/sqlite.cc:2
nix/libstore/local-store.cc:18
nix/libstore/globals.cc:1
nix/libstore/optimise-store.cc:15
nix/libstore/pathlocks.cc:2
nix/libstore/build.cc:45
nix/libstore/gc.cc:21
(guix230 (~/devel/guix)) λ rg 'lvl(Error|Info|Talkative|Chatty|Debug|Vomit)' nix/libstore/local-store.cc  
154:        printMsg(lvlError, "waiting for the big store lock...");
829:		if (!err.empty()) printMsg(lvlError, "substitute: " + err);
1240:    printMsg(lvlInfo, format("exporting path `%1%'") % path);
1453:    printMsg(lvlError, format("reading the store..."));
1464:    printMsg(lvlInfo, "checking path existence...");
1477:        printMsg(lvlInfo, "checking hashes...");
1486:                printMsg(lvlTalkative, format("checking contents of `%1%'") % *i);
1490:                    printMsg(lvlError, format("path `%1%' was modified! "
1500:                        printMsg(lvlError, format("fixing missing hash on `%1%'") % *i);
1507:                        printMsg(lvlError, format("updating size field on `%1%' to %2%") % *i % current.second);
1520:                    printMsg(lvlError, format("error: %1%") % e.msg());
1522:                    printMsg(lvlError, format("warning: %1%") % e.msg());
1541:        printMsg(lvlError, format("path `%1%' is not in the store") % path);
1559:            printMsg(lvlError, format("path `%1%' disappeared, removing from database...") % path);
1562:            printMsg(lvlError, format("path `%1%' disappeared, but it still has valid referrers!") % path);
1567:                    printMsg(lvlError, format("warning: %1%") % e.msg());
1584:    printMsg(lvlInfo, format("checking path `%1%'...") % path);
1595:    if (!res) printMsg(lvlError, format("path `%1%' is corrupted or missing!") % path);

judging from my experience, the difference between 0..3 doesn't seem
to be that noticeable in terms of increased verbosity; 4..5
seem to be pretty verbose (whereas the difference between 4 and 5 is
also barely noticeable).

I think it'd be good to update the documention/--help output with a bit
more explanation on this (for this, it'd be probably good to know more
about when to use which level/what the implications of each level are).

[0]: https://guix.gnu.org/manual/en/html_node/Common-Build-Options.html

-- 
Kind regards,

Wilko Meyer
w@wmeyer.eu