Re: [PATCH v2 1/3] t/lib-httpd: dynamically detect httpd and modules path

On Wed, Nov 08, 2023 at 11:54:26AM -0500, Jeff King wrote:

On Wed, Nov 08, 2023 at 03:57:19PM +0100, Patrick Steinhardt wrote:

quoted

While it is possible to specify these paths via `LIB_HTTPD_PATH` and
`LIB_HTTPD_MODULE_PATH`, it is not a nice experience for the developer
to figure out how to set those up. And in fact we can do better by
dynamically detecting both httpd and its module path at runtime:

    - The httpd binary can be located via PATH.

    - The module directory can (in many cases) be derived via the
      `HTTPD_ROOT` compile-time variable.

Amend the code to do so. The new runtime-detected paths will only be
used in case none of the hardcoded paths are usable.

If these improve detection on your platform, I think that is a good
thing and they are worth doing. But as a generic mechanism, I have two
comments:

quoted

-for DEFAULT_HTTPD_PATH in '/usr/sbin/httpd' '/usr/sbin/apache2'
+for DEFAULT_HTTPD_PATH in '/usr/sbin/httpd' '/usr/sbin/apache2' "$(command -v httpd)"
 do
 	if test -x "$DEFAULT_HTTPD_PATH"
 	then

The binary goes under the name "httpd", but also "apache2". But the PATH
search only looks for "httpd". Should we check "command -v apache2" as
well?

Doesn't hurt to do it.

This also means we may run "test -x" on an empty string, but that is
probably OK in practice (we could guard it with "test -n", though).

Fair, will do.

quoted

+if test -x "$DEFAULT_HTTPD_PATH"
+then
+	DETECTED_HTTPD_ROOT="$("$DEFAULT_HTTPD_PATH" -V | sed -n 's/^ -D HTTPD_ROOT="\(.*\)"$/\1/p')"
+fi

I was really pleased to see this and hoped it could replace the
kitchen-sink list of paths in the hunk below. But sadly I think it
depends on having a configured apache setup. On my Debian system, for
example, I have the "apache2-bin" package installed but not "apache"
(because only the latter actually sets up a system apache daemon, which
I don't want). And thus there is no config:

  $ /usr/sbin/apache2 -D HTTPD_ROOT
  apache2: Could not open configuration file /etc/apache2/apache2.conf: No such file or directory

So without a system config file to act as a template for our custom
config, I think we are stuck with guessing where the installer might
have put them.

Indeed. Also, paths like `/usr/libexec/apache2` wouldn't be possible to
be discovered via `${HTTPD_ROOT}/modules` anyway. It's kind of a shame
that there is no way (or at least no way I know of) to portably discover
the default modules directory used by httpd.

Patrick