The main idea behind that was to be able to do more sophisticated
merging for stuff that goes into `postgresql.conf`:
`shared_preload_libraries` is a comma-separated list in a `types.str`
and thus not mergeable. With this change, the option accepts both a
comma-separated string xor a list of strings.
This can be implemented rather quick using `coercedTo` +
freeform modules. The interface still behaves equally, but it allows to
merge declarations for this option together.
One side-effect was that I had to change the `attrsOf (oneOf ...)` part into
a submodule to allow declaring options for certain things. While at it,
I decided to move `log_line_prefix` and `port` into this structure as
well.
Closes#216989
First of all, a bit of context: in PostgreSQL, newly created users don't
have the CREATE privilege on the public schema of a database even with
`ALL PRIVILEGES` granted via `ensurePermissions` which is how most of
the DB users are currently set up "declaratively"[1]. This means e.g. a
freshly deployed Nextcloud service will break early because Nextcloud
itself cannot CREATE any tables in the public schema anymore.
The other issue here is that `ensurePermissions` is a mere hack. It's
effectively a mixture of SQL code (e.g. `DATABASE foo` is relying on how
a value is substituted in a query. You'd have to parse a subset of SQL
to actually know which object are permissions granted to for a user).
After analyzing the existing modules I realized that in every case with
a single exception[2] the UNIX system user is equal to the db user is
equal to the db name and I don't see a compelling reason why people
would change that in 99% of the cases. In fact, some modules would even
break if you'd change that because the declarations of the system user &
the db user are mixed up[3].
So I decided to go with something new which restricts the ways to use
`ensure*` options rather than expanding those[4]. Effectively this means
that
* The DB user _must_ be equal to the DB name.
* Permissions are granted via `ensureDBOwnerhip` for an attribute-set in
`ensureUsers`. That way, the user is actually the owner and can
perform `CREATE`.
* For such a postgres user, a database must be declared in
`ensureDatabases`.
For anything else, a custom state management should be implemented. This
can either be `initialScript`, doing it manual, outside of the module or
by implementing proper state management for postgresql[5], but the
current state of `ensure*` isn't even declarative, but a convergent tool
which is what Nix actually claims to _not_ do.
Regarding existing setups: there are effectively two options:
* Leave everything as-is (assuming that system user == db user == db
name): then the DB user will automatically become the DB owner and
everything else stays the same.
* Drop the `createDatabase = true;` declarations: nothing will change
because a removal of `ensure*` statements is ignored, so it doesn't
matter at all whether this option is kept after the first deploy (and
later on you'd usually restore from backups anyways).
The DB user isn't the owner of the DB then, but for an existing setup
this is irrelevant because CREATE on the public schema isn't revoked
from existing users (only not granted for new users).
[1] not really declarative though because removals of these statements
are simply ignored for instance: https://github.com/NixOS/nixpkgs/issues/206467
[2] `services.invidious`: I removed the `ensure*` part temporarily
because it IMHO falls into the category "manage the state on your
own" (see the commit message). See also
https://github.com/NixOS/nixpkgs/pull/265857
[3] e.g. roundcube had `"DATABASE ${cfg.database.username}" = "ALL PRIVILEGES";`
[4] As opposed to other changes that are considered a potential fix, but
also add more things like collation for DBs or passwords that are
_never_ touched again when changing those.
[5] As suggested in e.g. https://github.com/NixOS/nixpkgs/issues/206467
conversions were done using https://github.com/pennae/nix-doc-munge
using (probably) rev f34e145 running
nix-doc-munge nixos/**/*.nix
nix-doc-munge --import nixos/**/*.nix
the tool ensures that only changes that could affect the generated
manual *but don't* are committed, other changes require manual review
and are discarded.
the conversion procedure is simple:
- find all things that look like options, ie calls to either `mkOption`
or `lib.mkOption` that take an attrset. remember the attrset as the
option
- for all options, find a `description` attribute who's value is not a
call to `mdDoc` or `lib.mdDoc`
- textually convert the entire value of the attribute to MD with a few
simple regexes (the set from mdize-module.sh)
- if the change produced a change in the manual output, discard
- if the change kept the manual unchanged, add some text to the
description to make sure we've actually found an option. if the
manual changes this time, keep the converted description
this procedure converts 80% of nixos options to markdown. around 2000
options remain to be inspected, but most of those fail the "does not
change the manual output check": currently the MD conversion process
does not faithfully convert docbook tags like <code> and <package>, so
any option using such tags will not be converted at all.
A centralized list for these renames is not good because:
- It breaks disabledModules for modules that have a rename defined
- Adding/removing renames for a module means having to find them in the
central file
- Merge conflicts due to multiple people editing the central file
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
