Re: [PATCH 1/2] nscd: Improved support for tracking startup failure in nscd service (#16639)

[Russ Allbery <eagle at eyrie dot org>]

Siddhesh Poyarekar <siddhesh@redhat.com> writes:

> Currently, the nscd parent process parses commandline options and
> configuration, forks on startup and immediately exits with a success.
> If the child process encounters some error after this, it goes
> undetected and any services started up after it may have to repeatedly
> check to make sure that the nscd service did actually start up and is
> serving requests.

> To make this process more reliable, I have added a pipe between the
> parent and child process, through which the child process sends a
> notification to the parent informing it of its status.  The parent
> waits for this status and once it receives it, exits with the
> corresponding exit code.  So if the child service sends a success
> status (0), the parent exits with a success status.  Similarly for
> error conditions, the child sends the non-zero status code, which the
> parent passes on as the exit code.

> This, along with setting the nscd service type to forking in its
> systemd configuration file, allows systemd to be certain that the nscd
> service is ready and is accepting connections.

> Tested on Fedora by doing the following:

> - Removing the 'nscd' user from /etc/passwd, which results in failure
>   in the child.  This used to be ignored by the forking parent, but is
>   now caught and reported.

> - Added code in the child to segfault at the end of nscd_init.  This
>   was not detected earlier, but is now caught and reported.

Not being a glibc developer, I obviously can't do a formal review, but for
the record I read through this and it looks right to me.  Thank you very
much for working on this, Siddhesh!

-- 
Russ Allbery (eagle@eyrie.org)              <http://www.eyrie.org/~eagle/>