Comment 10 for bug 1821343
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| Heitor Alves de Siqueira (halves) wrote | #10 |
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(Get the code!)
I've been doing some research on how we could implement a proper systemd unit file for slapd, and came up with interesting results.
There are a number of options that we can pass to the slapd service that will give us lots of troubles on an "idiomatic" service file. To give some examples:
- The PID file can be directly obtained from /etc/default/slapd if set, or it
has to be parsed from /etc/ldap/slapd.d or /etc/ldap/
files don't follow the /etc/default syntax, so we can't just pass them with
"EnvironmentF
as is currently done by the init script.
- slapd has the "-f" and "-F" flags that can be used to specify a config file or
directory, respectively. It does not accept both at the same time, but
SLAPD_CONF in /etc/default/slapd allows either a file or directory. The init
script will figure out which of those is set, and pass the correct flag
accordingly. I don't see a simple way of doing this in systemd without either
polluting the SLAPD_CONF option with the necessary flag, or delegating it to a
helper script which would check whether the option meant a file or a
directory.
- The slapd.conf file is used by other related tools (see slapd.conf(5)), which
prevents us from pulling some of the options to another centralized file
without also updating these tools
I hoped that the upstream package would have some insight on the proper way of writing the service file, but unfortunately it seems that upstream Openldap devs are very much against the idea of shipping them (be they sysv-init or systemd files). There are some discussions on the openldap lists, one of which deals specifically with adding systemd support for slapd [0]. From that discussion, it's clear that upstream openldap is not ready to provide the necessary systemd files out-of-the-box, even when approached with relevant patches.
I also checked how CentOS implement their slapd.service file since they don't seem to run into these problems. They don't use an autogenerated unit file, and have a proper one instead [1]. From what I've checked, this is easier for them for two reasons:
1) The CentOS configs for slapd are much simpler than what we have in Debian/Ubuntu (their defaults don't include most of the options that we do)
2) They use helper scripts for the funky parsing we have in the sysv-init script ("ExecStartPre=
On Debian/Ubuntu, the autogenerated unit file for slapd uses the sysv-init script as a "shim" to manage the service, which makes it possible to keep the whole config-parsing insanity consistent between sysv-init and systemd.
It's not the most elegant solution, but for now I believe it makes sense to include an override file for the "RemainAfterExit=" option until we have a native systemd unit file for slapd (similar to what was done for apache2 in bug 1488962 mentioned by Ryan Tandy).
[0] https:/
[1] https:/